Wmi Alhap Final Report 2006

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Alberta Hail Suppression Project 2006 Field Program Final Report Page: 2

Weather Modification Inc. October 2006

ALBERTA HAIL SUPPRESSION PROJECT

FINAL REPORT2006

Terry W. Krauss, [email protected]

Editor

A Program forSeeding Convective Cloudswith Glaciogenic Nuclei to

Mitigate Urban Hail Damage in theProvince of Alberta, Canada

by

Weather Modification Inc.3802 - 20thStreet North

Fargo, North DakotaU.S.A. 58102

www.weathermod.com

for

Alberta Severe Weather Management Society

Calgary, AlbertaCanada

October 2006
mailto:[email protected]:[email protected]


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EXECUTIVE SUMMARY

This report summarizes the activities and data collected during the 2006 field operations of the AlbertaHail Suppression Project. This was the eleventh year of operations by Weather Modification Inc. (WMI)of Fargo, North Dakota under contract with the Alberta Severe Weather Management Society ofCalgary, Alberta. 2006 is the first year of the 3

rd5-year contract cycle for this on-going program. The

program continues to be funded entirely by private insurance companies in Alberta with the sole intentto mitigate the damage to urban property caused by hail. The cloud-seeding project was renewed in2001 because the insurance losses due to hail were approximately 50% less than expected during thefirst five-year contract period 1996-2000. Calgary and Red Deer have seen >30% increases inpopulation in the last 10 years, however, the financial losses caused by hail have been less than the 10year average before the start of the cloud seeding program in 1996. This is in spite of Calgary reachinga population of 1 million this past summer. The project design has remained the same throughout theperiod. The program was operational from June 1

stto September 15

th, 2006 and storms that posed a

hail threat to an urban area, as identified by the projects weather radar situated at the Olds-DidsburyAirport, were seeded. The project target area covers the region from High River in the south toLacombe in the north, with priority given to the two largest cities of Calgary and Red Deer. The targetarea was increased slightly towards the east to include the town of Strathmore and some of the smallertowns east of the QEII highway.

Hail fell within the project area on 35 days. Larger than golf ball size hail fell on July 9thnear HeritagePointe golf course (South of Calgary), and on the afternoon of July 29

thwest of Olds. Golf ball size hail

was reported on three days (July 6thnear Eckville), July 12

thwest of Airdrie, and on August 10

thnear

Markerville and the Red Deer Regional Airport/Springbrook). Walnut size hail was reported on five days(July 17th, 28th, 30th, Aug 3rd, and Aug 9th).

For the entire Province of Alberta, the Alberta Agriculture Financial Services Corporation in Lacombereported hail damage to crops (days with >1 claim) on 67 days (4 days in May, 13 days in June, 23 daysin July, 21 days in August, and 6 days in September). Golf ball size hail was reported on 7 days (June14th, July 5th, 9th, 10th and 12th, and August 9

thand 10

th) this summer in Alberta. Preliminary data

from crop insurance claims indicates that crop damage in 2006 was approximately 7% above the 1986to 1995 average. This was a bad summer for severe weather across the prairies. Environment Canadareported at the end of August that there had been 34 severe hail days in Alberta, 24 severe hail days in

Saskatchewan, and 29 severe hail days in Manitoba. Furthermore, there had been 5 tornados reportedin Alberta, 5 in Saskatchewan, and 9 in Manitoba. A tornado was reported on July 9thnear Pine Lake,and another on August 16thnear Rocky Mountain House. Both tornados were short lived and did notproduce any damage. No tornados were reported from any seeded storms and our pilots spotted none.

Alberta wide, 2006 was an above-average year for the number of hail days and severe hail days. Ingeneral, the weather in the project area this summer was warm and dry, with an above average numberof days with temperatures > 30 deg C.

During this season, there were 92 aircraft flights totaling 190.2 hrs on 39 operational days. A total of 65storms were seeded during 60 seeding flights (162.8 hrs) on 28 days on which seeding took place.There were 13 patrol flights (15.1 hrs) and 13 test flights (10.2 hrs). The amount of silver-iodidenucleating agent dispensed during the 2006 field season totaled 214 kg: consisting of 4929 ejectable(cloud-top) flares (98.6 kg seeding agent), 703 end-burning (cloud-base) flares (105.5 kg seeding

agent), and 145.4 gallons of AgI-acetone solution (9.97 kg seeding agent). There were 6 flights (2.1hrs) for public relations, marketing, or media purposes.

The procedures used in 2006 remained the same as for the previous ten years. Three speciallyequipped cloud seeding aircraft were dedicated to the project. One Piper Cheyenne II and a Cessna340A were based in Calgary, and a Beech King Air C90 was based in Red Deer. The Calgary officeand aircraft were located at the Morgan Air hangar at the Calgary International Airport. A WMI RedDeer office was set up in the former Hillman Air hangar at the Red Deer Regional Airport.

The aircraft and crews provided a 24-hr service, seven days a week throughout the period. Seven full-time pilots and four meteorologists were assigned to the project this year, allowing everyone to follow a


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work schedule and receive some scheduled time-off during the summer. Roger Tilbury, Chief Pilot fromthe WMI Fargo head office conducted training of new pilots during June. There were no changes to thestaff during the summer. Overall, the personnel and equipment performed exceptionally well and therewere no interruptions or missed opportunities in the service.

The TITAN radar images were sent to the WMI web server at 5-min intervals, although there were oftenmissing images in the web archive which were blamed on computer problems and interruptions in themicrowave internet connection at the radar. The microwave modem at the radar was upgraded during

the summer and this provided a slight improvement in August and September. The radar performedvery well but there were two interruptions in service. The radar failed at 2 am on July 24thdue to a

broken wave-guide assembly within the antenna pedestal. Replacement parts had to be ordered fromFargo and the radar was back in service at 8 am on July 26. During this time, the web radar imagesfrom the Environment Canada radars at Strathmore and Carvel were used as guidance for cloudseeding operations. On July 27that 1:27 pm, the radar was again shut down due to a broken piece offlex wave-guide at the pedestal. The flex portion of wave-guide was replaced with a custom built solidmetal wave-guide and the radar was back in operation at 11 am on July 28 th. Fortunately, seedingoperations continued during these periods and all threatening hailstorms were seeded. All of theprojects radar data, meteorological data, and reports have been recorded onto CD-ROM for the AlbertaSevere Weather Management Society. These data include the daily reports, radar maps, aircraft flighttracks, as well as meteorological charts for each day. These data can be made available for outsideresearch purposes through a special request to the Alberta Severe Weather Management Society.

Numerous public relations activities occurred this year. On June 2nd, T. Krauss was interviewed by theOlds radio station CKFM. On June 25th, the Edmonton Journal ran a story about Weather Modificationtitled Scientists Dream of Taming Hurricanes. The story included interview comments and a photo ofT. Krauss at the Olds-Didsbury Airport. On July 6th, David Boucher of Global TV Calgary visited theOlds radar to film and conducted interviews with T. Krauss, J. Renick, and C. Lee (HS2 Crew). Also onJuly 6th, the Calgary Herald interviewed T. Krauss. On July 11th, Jim Renick was interviewed live onCBC Radio for their morning show. On July 12th, T. Krauss was interviewed again by CKFM radio inOlds, about the recent severe storms. On August 2

ndJ. Renick was interviewed by a radio station in

Weyburn SK about cloud seeding for drought relief. On August 23rd, Jim Renick and Dave Johnsonwere interviewed by The Weather Network in Calgary. On August 31st, T. Krauss was interviewed byCindy White of 660AM News radio in Calgary for a story that ran several times on Sept 7about the

Anniversary of the Sept 7, 1991 severe hailstorm. On September 11th, Jacob Siebelink fromReformatorisch-Dagblad, a daily newspaper in the Netherlands, visited the radar and interviewed

project personal. On the same day, about a dozen Mountain View County officials and agriculturespecialists visited the radar in the afternoon for a tour and discussion about the project. Finally onSeptember 14th, a film crew from Toronto called Creative Differences, working for the DiscoveryChannel (U.S.) program Best Evidence, interviewed Terry Krauss at the radar, and then filmed HS3 atthe Red Deer Airport. All of the publicity was positive this year.

A formal evaluation of the hail suppression program is still not possible without receiving morecomprehensive, detailed, high resolution property insurance claim data. Preliminary assessments usingthe available, published data show a reduction in urban and Provincial agricultural losses after elevenyears, and there appears to be no doubt that the program has been a financial success. The evidencehas been consistently positive, however, the crop-damage data according to municipality does notindicate a reduction in hail for the target area. Rather, the greatest reduction in hail damage hasoccurred south of Calgary and, therefore, is a result of external forces such as climate change or natural

year-to-year variability. Furthermore, there seems to be a trend towards increasing hail within the targetarea and north over the past few years, and this is expected to continue into the near future. The factthat the crop damage data does not show a reduction in crop damage within the target area is notsurprising since not all hailstorms are seeded. Many hailstorms go unseeded if they do not threaten atown or city. Furthermore, small hail may cause significant crop damage without causing propertydamage; therefore, it is not directly correlated to property damage but only an indication of the overallthreat. There are no reasons to change the scientific seeding hypotheses, methodologies, or design ofthe program based on our experiences and results of the past 11 years. The Alberta Hail SuppressionProject continues to be a model operational program, using cloud seeding as a viable technology forreducing the economic impact of hailstorms.


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ACKNOWLEDGMENTS

WMI wishes to acknowledge the kind support of Dave Johnson (President), Jim Renick (ProjectDirector), Catherine Janssen (Chief Financial Officer), and the entire Board of Directors of the AlbertaSevere Weather Management Society (ASWMS). The continued understanding, support, andcooperation of the ASWMS are greatly appreciated.

A number of agencies and people deserve recognition and thanks. The cooperation of Mark McCraeand John Exley of the Air Traffic Control (ATC) Nav-Canada facilities at Calgary and Edmonton, isgratefully acknowledged. The excellent cooperation by the ATC once again, played a very importantrole in allowing the project pilots to treat the threatening storms in an efficient and timely manner asrequired, often directly over the city of Calgary.

Mr. Rob Cruickshank, Agriculture Financial Services Corp. in Lacombe, is thanked for providing thecrop insurance information. Once again, special thanks also goes to Bob Jackson for sharing his officeand hangar at the Olds-Didsbury airport, used for the radar and communications control center. Thecooperation of all these people helped make the project a success and much more enjoyable.

WMI wishes to acknowledge the contributions of the staff who served the project during the summer of2006: meteorologists (Jason Goehring, Dr. Andre Sinkevich, Dr. Viktor Makitov), electronics-radar

technician Harry Ewen, pilots in command (Roger Tilbury, Jayson Bryant, Marshall Makarowski, DanielHaines, and Craig Lee); the co-pilots (Mark Friel, Joel Zimmer, and Daniel Fillion), and the aircraftmaintenance engineers (Gary Hillman and Dale Campbell). The staff performed exceptionally well as ateam. The support of Patrick and James Sweeney, Randy Jenson, Hans Ahlness, Bruce Boe, Dennis

Afseth, Cindy Dobbs, Mark Grove, Erin Fisher, and Mike Clancy in the Fargo head office is alsogratefully acknowledged. As always, the author wishes to thank Jim Renick for his continueddedication, cooperation, support, and guidance during the field operations as well as his contributions tothis final report.


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Figure 1: Jim Renick (Project Director) and Jim Sweeney (WMI Vice President).

Figure 2: Dr. Terry Krauss (WMI VP Meteorology and Project Manager) and Bruce Boe (WMIDirector of Meteorology)


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Figure 3: Meteorologists Dr. Viktor Makitov and Dr. Andre Sinkevich.

Figure 4: Meteorologist Jason Goehring and Electronics Tech Harry Ewen.


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Figure 5: Hans Ahlness (WMI VP Operations) and Roger Tilbury (Chief Pilot).

Figure 6: Pilots Jayson Bryant and Marshall Makarowski.


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Figure 7: Pilots: Daniel Haines and Craig Lee.

Figure 8: Pilots: Mark Friel and Joel Zimmer.


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Figure 9: Pilot Daniel Fillion and Airc raft Engineer Gary Hillman.


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TABLE OF CONTENTS

EXECUTIVE SUMMARY............................................................................................................................... 3

ACKNOWLEDGMENTS ............................................................................................................................... 5

TABLE OF CONTENTS.............................................................................................................................. 11

LIST OF FIGURES...................................................................................................................................... 13

LIST OF TABLES ....................................................................................................................................... 15

INTRODUCTION......................................................................................................................................... 16

THE 2006 FIELD PROGRAM..................................................................................................................... 17

PROJECT OBJECTIVES............................................................................................................................ 19

PRIORITIES................................................................................................................................................ 20

CONCEPTUAL HAIL MODEL.................................................................................................................... 21

HAIL SUPPRESSION HYPOTHESIS ............................................................................................................... 21PRECIPITATION EFFICIENCY ....................................................................................................................... 23

OPERATIONS PLAN .................................................................................................................................. 24

ONSET OF SEEDING................................................................................................................................... 24IDENTIFICATION OF HAIL PRODUCING STORMS ............................................................................................ 24CLOUD SEEDING METHODOLOGY ............................................................................................................... 25NIGHT TIME SEEDING ................................................................................................................................ 26STOPPING SEEDING ................................................................................................................................... 26SEEDING RATES ........................................................................................................................................ 26SEEDING MATERIALS ................................................................................................................................. 27FLARE EFFECTIVENESS TESTS ................................................................................................................... 29

Summary Of CSU Tests ..................................................................................................................... 31

PROGRAM ELEMENTS AND INFRASTRUCTURE.................................................................................. 32

GROUND SCHOOL .................................................................................................................................... 32

PUBLIC RELATIONS ................................................................................................................................. 33

FLIGHT OPERATIONS............................................................................................................................... 33

AIR-TRAFFIC CONTROL.............................................................................................................................. 34CLOUD SEEDINGAIRCRAFT........................................................................................................................ 35

Piper Cheyenne II ............................................................................................................................... 35Beech King-Air C90 ............................................................................................................................ 36C340A Aircraft..................................................................................................................................... 36

Meteorological Aircraft Instrumentation.............................................................................................. 37

RADAR CONTROL AND COMMUNICATIONS CENTER......................................................................... 37

RADAR........................................................................................................................................................ 39

RADAR CALIBRATION CHECKS.................................................................................................................... 40

AIRCRAFT TRACKING GLOBAL POSITIONING SYSTEM (GPS).......................................................... 42

SUMMAR Y OF SEEDING OPERATIONS................................................................................................. 43

FLIGHTS.................................................................................................................................................... 43


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SEEDINGAMOUNTS ................................................................................................................................... 47COMPARISON OF 2006WITH PREVIOUS YEARS.......................................................................................... 47COMPARISON BYAIRCRAFT........................................................................................................................ 47

STORM TRACK MAPS .............................................................................................................................. 49

WEATHER FORECASTING....................................................................................................................... 50

CONVECTIVE DAY CATEGORY (CDC) ......................................................................................................... 50

COORDINATED UNIVERSAL TIME................................................................................................................. 51DAILY BRIEFINGS....................................................................................................................................... 51METEOROLOGICAL STATISTICS................................................................................................................... 51FORECASTING PERFORMANCE ................................................................................................................... 54THE HAILCAST MODEL ............................................................................................................................... 56

LARGE HAIL DAYS SOUNDING COMPARISON..................................................................................... 57

06JULY 2006 ........................................................................................................................................... 5809JULY 2006 ........................................................................................................................................... 5812JULY 2006 ........................................................................................................................................... 5929JULY 2006 ........................................................................................................................................... 60SUMMARY ................................................................................................................................................. 60

THE CALGARY STORM OF JULY 9TH

, 2006............................................................................................ 61

METEOROLOGICAL SITUATION .................................................................................................................... 61SEEDING OPERATIONS............................................................................................................................... 69CONCLUSION............................................................................................................................................. 71

7 JULY 2006 CASE STUDY....................................................................................................................... 71

PILOT REPORT (BY JOEL ZIMMER).............................................................................................................. 73STORM TRACKANALYSIS (BY DR.ANDRE SINKEVICH) ................................................................................. 75

CLIMATE PERSPECTIVES........................................................................................................................ 79

PRECIPITATION AT CALGARY AND RED DEER DURING THE SUMMER OF 2006................................................ 79PRECIPITATION AND TEMPERATUREANOMALIES IN CANADA DURING THE SUMMER OF 2006.......................... 80EL NINO .................................................................................................................................................... 82

PROVINCIAL CROP HAIL INSURANCE RESULTS................................................................................. 83

CONCLUSIONS AND RECOMMENDATIONS.......................................................................................... 88

REFERENCES AND RECOMMENDED READING................................................................................... 90

APPENDICES ............................................................................................................................................. 94

A. ORGANIZATIONCHART............................................................................................................... 95B. DAILYWEATHERANDACTIVITIESSUMMARYTABLE2006..................................................... 96C. AIRCRAFTOPERATIONSFLIGHTSUMMARY2006................................................................. 131D. FLIGHTSUMMARYTABLE2006 ................................................................................................ 133E. FORMS......................................................................................................................................... 136F. SPECIFICATIONS FORPIPERCHEYENNEIIAIRCRAFT......................................................... 140G. SPECIFICATIONS FORBEECHCRAFTKINGAIRC90AIRCRAFT........................................... 141H. SPECIFICATIONS FORCESSNAC-340AIRCRAFT.................................................................. 142I. GROUNDSCHOOLAGENDA ..................................................................................................... 143J. WMIAIRBORNEGENERATORSEEDINGSOLUTION .............................................................. 144K. DAILYMETEOROLOGICAL FORECASTSTATISTICS2006 ..................................................... 145L. PROJECTPERSONNELANDTELEPHONELIST...................................................................... 149


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LIST OF FIGURES

Figure 1: Jim Renick (Project Director) and Jim Sweeney (WMI Vice President). ..................................................6

Figure 2: Dr. Terry Krauss (WMI VP Meteorology and Project Manager) and Bruce Boe (WMI Director of

Meteorology) ..............................................................................................................................................................6

Figure 3: Meteorologists Dr. Viktor Makitov and Dr. Andre Sinkevich. ..................................................................7

Figure 4: Meteorologist Jason Goehring and Electronics Tech Harry Ewen...........................................................7

Figure 5: Hans Ahlness (WMI VP Operations) and Roger Tilbury (Chief Pilot). ....................................................8

Figure 6: Pilots Jayson Bryant and Marshall Makarowski. .....................................................................................8

Figure 7: Pilots: Daniel Haines and Craig Lee. .......................................................................................................9Figure 8: Pilots: Mark Friel and Joel Zimmer..........................................................................................................9

Figure 9: Pilot Daniel Fillion and Aircraft Engineer Gary Hillman. :...................................................................10

Figure 10: The average number of hail days per year, based on the 19511980 climate normals of Environment

Canada (1987) and taken from Etkin and Brun (1999)............................................................................................16

Figure 11: Map of southern Alberta showing the project target area (Figure courtesy J. Renick)........................19

Figure 12: The conceptual model of hailstone formation and hail mitigation processes for Alberta (adapted from

WMO, 1995). This schematic figure shows the cloud seeding methodology at cloud-top and cloud-base for a

mature hailstorm.......................................................................................................................................................22

Figure 13: A three-dimensional schematic figure of an Alberta hailstorm, showing the cloud seeding

methodology within the new growth zone.................................................................................................................23

Figure 14: Precipitation efficiency for High Plains convective storms. Known supercell hailstorms are labeled S.

Storms that produced rain only are labeled R (Browning, 1977). ...........................................................................24

Figure 15: A photo of a cloud seeding plane dropping ejectable flares during a cloud seeding penetration (photocourtesy John Ulan)..................................................................................................................................................26

Figure 16: Photograph of a burning BIP flare. ......................................................................................................27

Figure 17: Pilot Joel Zimmer attaching the ejectable flare racks on the belly of the King Air C90 seeding aircraft.

..................................................................................................................................................................................28

Figure 18: Hail Stop 2, C340 aircraft shown seeding with Acetone Solution burners and Burn-In-Place (BIP)

flares. ........................................................................................................................................................................29

Figure 19: Yield of ice crystals (corrected) per gram of pyrotechnic versus cloud supercooling temperature

(T


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Figure 35: Edmonton sounding at 6 pm on July 6, 2006 (red), compared with the ETA model 12 hr forecast

sounding (blue) for Edmonton..................................................................................................................................58

Figure 36: Edmonton sounding at 6 am on July 9, 2006 (red), compared with the ETA model 12 hr forecast






Figure 39: Maximum Reflectivity map for the storms on 9-July-2006. ....................................................................62Figure 40: Aircraft tracks for Hailstop 1(green), 2(white), and 3(blue) on 9-July-2006........................................63

Figure 41: GEM model 12 hr forecast of 500 mb heights and vorticity at 6 pm 9-July-2006 (00Z, 10 July 2006).

..................................................................................................................................................................................64

Figure 42: Jet stream analysis at 6 pm 9-July-2006 (00Z, 10 July 2006)................................................................64

Figure 43: Surface analysis at 18Z (12 pm) on July 9th, 2006. ..............................................................................65

Figure 44: ETA 12 hr forecast atmospheric sounding for Calgary at 6 pm (00UTC) on July 9th2006. Also shown

is the trace for a lifted parcel with Temperature 26C and Dew Point 17C as reported in Calgary at 1 pm. ..........65

Figure 45: Map of surface 3-hr pressure changes and wind vectors at 12 pm (18Z) on July 9th, 2006. ...............66

Figure 46: Map of surface streamlines and equivalent potential temperature (Theta-E) at 12 pm (18Z) on July

9th, 2006...................................................................................................................................................................67

Figure 47: Surface moisture-flux divergence and wind gust map at 18Z (12 pm) on July 9th, 2006. ....................68

Figure 48: Water vapor satellite image at 3 pm (21Z 9 July 2006). ........................................................................68

Figure 49: Water vapor satellite image at 5 pm (23Z 9 July 2006). ........................................................................69Figure 50: Time sequence of radar composite reflectivity displays and aircraft tracks over Calgary on July 9th,

2006. Hailstorms are identified with blue circles and their forecast tracks in 10 min intervals are shown with red

circles. The storm cells are annotated with their top heights in km. The aircraft seeding tracks are shown as

green, white, or blue lines.........................................................................................................................................70

Figure 51: Maximum reflectivity map (top right), maximum vertical-integrated-liquid (VIL) shown in top right

and lower left panels, and aircraft tracks (lower right) for July 9th 2006. VIL shades of green are generally

indicative of hail >1 cm diameter at the surface (graphic courtesy J. Renick). .......................................................71

Figure 52: Maximum radar reflectivity map at 2231Z (top), 2358Z (middle), and max VIL map at 0021Z on July

7, 2006. .....................................................................................................................................................................72

Figure 53: Flight track of Hailstop 3 on July 7, 2006.............................................................................................72

Figure 54: The track of the radar reflectivity centroid as defined by TITAN on July 7, 2006................................76

Figure 55: Time plot of the TITAN cell top height (km) on July 7, 2006. The start and stop times of seeding are

indicated. ..................................................................................................................................................................77

Figure 56: Time plot of the TITAN cell maximum reflectivity on July 7, 2006. The seeding start and stop times

are indicated.............................................................................................................................................................78

Figure 57: Time plot of the TITAN cell vertically integrated hail mass (kg/m2) on July 7, 2006...........................78

Figure 58: Daily and accumulated rainfall for Calgary from Sept. 21, 2005 to Sept. 21, 2006. .............................79

Figure 59: Daily and accumulated rainfall for Red Deer from Sept. 21, 2005 to Sept. 21, 2006............................80

Figure 60: Departures from normal Precipitation during the summer of 2006 in Canada.....................................81

Figure 61: Departures from normal Temperature during the summer of 2006 in Canada. ....................................81

Figure 62: Sea Surface Temerature (SST) anomalies for the 4 Nino regions of the equatorial tropical Pacific over

the period November 2005 to October 2006. ...........................................................................................................82

Figure 63: Pacific Ocean sea surface temperature anomalies for the period November 2005 to October 2006...83

Figure 64: Alberta Agriculture Financial Services Corp hail insurance loss-to-risk and claims statistics from

1978 to 2006. ............................................................................................................................................................84

Figure 65: The frequency distribution of loss-to-risk ratio for the Target area before seeding (1981-1995) versusthe seeding period (1996 to 2006)............................................................................................................................85

Figure 66: The frequency distribution of loss-to-risk ratio for the municipalities Downwind of the Target area

before seeding (1981-1995) versus the seeding period (1996 to 2006)....................................................................85

Figure 67: The frequency distribution of loss-to-risk ratio for the municipalities North of the Target area before

seeding (1981-1995) versus the seeding period (1996 to 2006)...............................................................................86

Figure 68: The frequency distribution of loss-to-risk ratio for the municipalities South of the Target area before

seeding (1981-1995) versus the seeding period (1996 to 2006)...............................................................................87

Figure 69: Trend analysis for the period 1981 to 2006 for the Loss-to-Risk ratio for the Target area. ..................88


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INTRODUCTION

Hailstorms pose a serious threat to property and crops in the province of Alberta. Historically, claimsfor agricultural hail damage are received on an average of 50 days each year between 1 June and 10September (Summers and Wojtiw, 1971). The most recent climatology of hail in Canada waspublished by Etkin and Brun (1999) in the International Journal of Climatology. The average number ofhail days per year, based on the 19511980 climate normals (Environment Canada, 1987) is shown inFigure 10. The contours were hand drawn, based primarily upon about 350 weather stations. Thehighest frequency of hail in Canada occurs in Alberta between the North Saskatchewan River and theBow River, immediately downwind of the Rocky Mountain foothills. This region is often referred to ashail alley.

Figure 10: The average number of hail days per year, based on the 19511980 climate normalsof Envi ronment Canada (1987) and taken from Etkin and Brun (1999).

Etkin and Brun (1999) point out that the period 19771993 was associated with substantial increases inhail-observing stations. As the 19511980 hail climatology was mostly based on pre-1977 data, it had a


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relatively coarse resolution in comparison. An updated Alberta hail climatology for 19771993 hassince been completed. It has a greater resolution than the national climatology, and shows theimportance of some topographical features, such as the Rocky Mountains. The influence of localtopographical features on mesoscale hail frequency is a major control. After 1982, hail frequencies in

Alberta showed a significant increase. The City of Calgary is in a region that normally gets between 3and 4 hailstorms each year.

By overlaying the hail frequency map with the population density map, the region of greatest financial

risk to insurance companies covers the area from Calgary to Red Deer and Rocky Mountain House.For this reason, this is the region that was selected as the target area for the hail suppression program.

Insurance claims due to hailstorms in urban areas worldwide have generally escalated over the past 10years. Denver Colorado was pounded by golf-ball to tennis-ball sized hail on July 11, 1990, anddamages reached a record (for the U.S.A. at that time) $625 million. In Canada, the damagesassociated with the severe hailstorm that struck Calgary on September 7, 1991 exceeded $416 million(Insurance Bureau of Canada, 2004). Insured claims from the hailstorm that struck Sydney Australia on

April 14, 1999 were approximately $1.5 billion, making it the most damaging event in Australianinsurance history. A study by Herzog (2002) compiled and summarized the hailstorm damages in theUSA for the period 1994-2000 for the Institute for Business and Home Safety (IBHS). Verified haillosses amounted to $2.5 Billion per year, with the actual amount possibly being 50% higher. Personalbuilding losses totalled $11.5 Billion (66%), commercial building losses totalled $2.7B (15%), and

vehicles accounted for $3.3B (19%). And recently, the most damaging hailstorm ever recorded in theUSA moved from eastern Kansas to southern Illinois on 10 April 2001, depositing 2.5- to 7.5-cm-diameter hailstones along a 585-km path, over portions of the St. Louis and Kansas City urban areascollectively created $1.9 billion in damage claims from a 2-day period, becoming the ninth most costlyweather catastrophe in the United States since property insurance records began in 1949 (Changnonand Burroughs, 2003).

Estimates of the average annual crop loss to hail have also continued to increase with time, from $50million annually in 1975 (Renick, 1975) to more than $150 million annually during the period 1980 -1985 (Alberta Research Council, 1986). Actual insured crop losses are typically in the $80M rangeannually.

The new Alberta Hail Suppression Project was initiated in 1996 as a result of the increased frequency ofdamaging hailstorms in Alberta, compounded by an increasing population inside an area of high storm

frequency. It is the first project of its kind in the World to be entirely funded by private insurancecompanies with the sole objective of reducing the damage to property by hail. At this time, Alberta CropInsurance and the Provincial and Federal Governments do not contribute financially to the project,although they stand to benefit from the seeding.

Weather Modification Inc. (WMI) has been a leader in the field of hail suppression since the early1960's. With extensive knowledge and experience in the cloud seeding industry, WMI is best known forits successful hail suppression operations in the northern great plains and other cloud modificationservices around the world, most recently and notably in Argentina. WMI was awarded the first contractto conduct the Alberta Hail Suppression Project in April 1996 by the Alberta Severe WeatherManagement Society. The project was made an ongoing program of the Alberta insurance industry in2001 because of the drop in hail damage costs in Alberta, counter to the trend in the rest of the countryand the World. The contract calls for the provision of all personnel and equipment for a turnkey system

of cloud seeding and related services for the purpose of reducing hail damage to property insouth-central (Calgary to Red Deer) Alberta. The organization chart of the project is shown in Appendix

A.

THE 2006 FIELD PROGRAM

In 2006, WMI conducted the operational cloud-seeding program from June 1st to September 15th. Theproject is based upon the techniques, methods, and results of the long-term hail research projectconducted by the Alberta Research Council from the late 1960s through 1985 (Alberta ResearchCouncil, 1986) and by WMI in North Dakota (Smith et al, 1997). The present program utilizes the latest


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cloud seeding technology available, incorporating several notable improvements over previous projectsin the province. These improvements include:

New fast-acting, high-yield mixtures for the silver-iodide flares and acetone solution. The flares aremanufactured by Ice Crystal Engineering (ICE) of North Dakota. The new generation ICEpyrotechnics produce >1011ice nuclei per gram of AgI at -4C, and produce between 10 13and 1014ice nuclei per gram of pyrotechnic between -6C and -10C. CSU isothermal cloud chamber testsindicate that at a temperature of -6.3C, 63% of the nuclei are active in


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Figure 11: Map of southern Alberta showing the project target area (Figure courtesy J. Renick).

PROJECT OBJECTIVESThe project has two main objectives:

Conduct cloud seeding using 3 aircraft with experienced crews to suppress hail for the purpose ofreducing damage to property;

Operate a C-band weather radar and collect weather information by skilled professionalmeteorologists and engineers for purposes of storm identification, accurate storm tracking, optimaldirection of aircraft to conduct cloud seeding for hail suppression purposes, and the collection of adata archive that may be used for the scientific assessment of the program's effectiveness.


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Priorities

Table 1 lists the recent census figures obtained via the internet for the cities and towns within theproject area. Priority is given according to population, which is related to the risk of property damage.This list was posted in the radar control room as a constant reminder to the meteorologists of the prioritywhen allocating resources to storms on any given day. The biggest increases in population haveoccurred in Cochrane, Airdrie, and Sylvan Lake. Blackfalds, Crossfield, and Okotoks have also seenlarge increases in population. Project meteorologists made special note of the fact that the combined

population of Turner Valley and Black Diamond is almost as large as Blackfalds or Didsbury. Stormsthat do not threaten a town or city are not likely to be seeded. Also, most storms are not seeded afterthey cross the QEII highway, except for storms east of Airdrie and Calgary that might threatenStrathmore.

Table 1: Census figures (2005 or most recent) for the towns and cit ies in the pro ject area.

Rank POPULATION 1996 20012005 (or most

recent) % increase

1 Calgary Metropolitan Area 821,628 951,395 1,060,300 29%

2 Calgary 768,000 879,277 991,759 29%

3 Red Deer 60,000 67,707 79,082 32%

4 Airdrie 15,900 20,382 27,069 70%5 Cochrane 7,400 11,798 12,688 71%

6 Okotoks 8,510 11,664 11,664 37%

7 Lacombe 9,384 10,850 16%

8 Strathmore 7,621 9,653 27%

9 High River 7,400 9,345 9,522 29%

10 Sylvan Lake 5,200 7,884 8,504 64%

11 Chestermere 7,904

12 Innisfail 6,100 6,954 7,208 18%

13 Olds 5,800 6,607 6,703 16%

14 Rocky Mountain House 5,800 6,208 6,584 14%

15 Blackfalds 3,042 4,373 44%

16 Didsbury 3,600 3,932 3,932 9%

17Turner Valley/Black

Diamond 3,652

18 Three Hills 3,554

19 Crossfield 1,900 2,389 2,603 37%

20 Carstairs 1,900 2,254 2,501 32%

21 Sundre 2,000 2,267 2,267 13%

22 Penhold 1,625 1,729 1,750 8%23 Bowden 1,000 1,174 17%

24 Irricana 820 1,038 1,104 35%

25 Trochu 1,033

26 Eckville 900 1,019 13%

27 Caroline 470 556 18%

28 Cremona 380 415 9%


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CONCEPTUAL HAIL MODEL

The hail suppression conceptual model is based on the experience of WMI in the USA, Canada,Argentina, and Greece. It involves the use of silver-iodide reagents to seed the developing feederclouds near the -10C level in the upshear, new growth propagation region of hailstorms. The silver-iodide reagents initiate a condensation-freezing process and produce enhanced concentrations of icecrystals that compete for the available, super-cooled liquid water in a storm and help prevent the growthof large damaging hail. The seeding also initiates the precipitation process earlier in a cloud (cell) tospeed up the growth of cloud hydrometeors via an ice-phase (graupel) to rain mechanism instead ofcontinuing to grow to damaging hail.

Hail Suppression Hypothesis

The cloud seeding hypothesis is based on the cloud microphysical concept of "beneficial competition".Beneficial competition is based upon the documented deficiency of natural ice nuclei in the environmentand that the injection of silver iodide (AgI) will result in the production of a significant number of"artificial" ice nuclei. The natural and artificial ice crystals "compete" for the available super-cooled liquidcloud water within the storm. Hence, the hailstones that are formed within the seeded cloud volumeswill be smaller and produce less damage if they should survive the fall to the surface. If sufficient nucleiare introduced into the new growth region of the storm, then the hailstones will be small enough to melt

completely before reaching the ground. Cloud seeding alters the microphysics of the treated clouds,assuming that the present precipitation process is inefficient due to a deficiency of natural ice nuclei.This deficiency of natural ice has been documented in the new growth zone of Alberta storms (Krauss,1981). Cloud seeding does not attempt to compete directly with the energy and dynamics of the storm.

Any alteration of the storm dynamics occurs as a consequence of the increased ice crystalconcentration and initiation of riming and precipitation sized ice particles earlier in the clouds lifetime.

The cloud seeding is based on the conceptual model of Alberta hailstorms which evolved from theexperiments and studies of Chisholm (1970), Chisholm and Renick (1972), Marwitz (1972a,b,c), Bargeand Bergwall (1976), Krauss and Marwitz (1984), and English (1986). Direct observational evidencefrom the instrumented aircraft penetrations of Colorado and Alberta storms in the 1970's and early1980s indicates that hail embryos grow within the time evolving "main" updraft of single cell storms andwithin the updrafts of developing "feeder clouds" or cumulus towers that flank mature "multi-cell" and

"super-cell" storms (see e.g. Foote, 1984; Krauss and Marwitz, 1984). The computation of hail growthtrajectories within the context of measured storm wind fields provided a powerful new tool for integratingcertain parts of hail growth theories, and illustrated a striking complexity in the hail growth process.Some of this complexity is reviewed in the paper of Foote (1985) that classifies a broad spectrum ofstorm types according to both dynamical and microphysical processes thought to be critical to hailproduction. Hail embryo sources identified by Foote (1985) include the following: Embryos from first-ice in a time-developing updraft Embryos from first-ice in the core of a long-lived updraft Embryos from flanking cumulus congestus Embryos from a merging mature cell Embryos from a mature cell positioned upwind Embryos from the edges of the main updraft Embryos created by melting and shedding

Embryos from entrainment of stratiform cloud Embryos from embedded small-scale updrafts and downdrafts Recirculation of embryos that have made a first pass through the updraft core

The growth to large hail is hypothesized to occur primarily along the edges of the main storm updraftwhere the merging feeder clouds interact with the main storm updraft (WMO, 1995). The maturehailstorm may consist of complicated airflow patterns and particle trajectories, therefore, the cloud-seeding cannot hope to affect all embryo sources but attempts to modify the primary hail formationprocess. In other words, the cloud seeding cannot attempt to eliminate all of the hail, but canreduce the size and amount o f hail.


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Figure 13: A three-dimensional schematic figure of an Alberta hailstorm, showing the cloudseeding methodology within the new growth zone.

As mentioned previously, cloud seeding cannot prevent or completely eliminate the occurrence ofdamaging hail. We presently do not have the ability to predict with any certainty exactly the amount andsize of hail that would occur if cloud seeding did not take place. Therefore, we do not have the ability topredict with certainty the net effect of the seeding. Our purpose is to seed the new growth zone ofhailstorms and observe the amount and type of precipitation at the surface, as well as the radarreflectivity characteristics of the storm before, during, and after seeding. We expect that the successfulapplication of the technology will yield a decrease of damaging hail by approximately 50% of theamount that would have occurred if seeding had not taken place. This goal is consistent with the resultsreported in North Dakota (Smith et al, 1997) and in Greece (Rudolph et al, 1994). The decrease in hailcan only be measured as an average over time (e.g. 5 years) and over an area and then compared withthe historical values for the same areas. Because of these uncertainties, the evaluation of any hailmitigation program requires a statistical analysis. Both seeded storms and unseeded storms havevariability and populations of seeded and unseeded storms overlap in all measurements of theircharacteristics.

Precipitation Efficiency

A common question about cloud seeding concerns the effect on the rainfall. Krauss and Santos (2004)analyzed two years of Alberta radar data and concluded that seeded storms produced more rain thannon-seeded storms of the same height. The seeding effect was estimated to increase the mean rainfallvolume (averaged for categories 7.5 to 11.5 km height storms) by a factor of 2.2 with an average 95%confidence interval of 1.4 to 3.4. The seeded storms lived longer (+50%), had greater mean

precipitation rates (+29%), and had greater mean total rain area-time integrals (+54%).

There is a general (yet false) assumption by the public and some scientists that thunderstorms operateat near 100% efficiency in producing rainfall, therefore, any modification of the hail, or causing therainfall to start earlier, may limit the amount of precipitation that can fall later in a storms lifetime, downwind of the project area. There have been numerous studies of the fluxes of air and water vaporthrough convective clouds and these are summarized in Figure 14.

Precipitation efficiencies can vary widely from as little as 2% for storms studied by Marwitz (1972) andDennis et al. (1970) to near 100%. Marwitz (1972) and Foote and Fankhauser (1973) show that in thecase of High Plains storms there is an inverse relation between the precipitation efficiency and the


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environmental wind shear in the cloud-bearing layer. The least efficient storms tend to be supercellhailstorms; the highly efficient storms tend not to produce hail. The average wind shear on hail days in

Alberta is approximately 2.5 x 10-3sec-1. This shear value corresponds to precipitation efficiency near

50%.

It is logical that the production of large, damaging hail is a result of the natural inefficiency of the stormto produce rain. Therefore, the introduction of more precipitation embryos earlier in a clouds lifetime ishighly advantageous to the initiation of precipitation earlier, making the cloud more efficient as a rain

producer, and in the process reducing the amount and size of the hail. Increasing the rainfall from ahailstorm by 20% due to the seeding is a very achievable goal, and means that less water is lost eithervia the entrainment of dry environmental air through the sides and top of the cloud, or water lost to icecrystals that are exhausted out of the anvil at the top of the troposphere and which eventually sublimateback to the vapor phase at high altitudes.

Figure 14: Precipitation efficiency for High Plains convective storms. Known supercellhailstorms are labeled S. Storms that produced rain only are labeled R (Browning, 1977).

OPERATIONS PLAN

The following guidelines represent the current state of the science of hail suppression operations beingapplied by Weather Modification Inc.

Onset of Seeding

In order for cloud seeding to be successful, it is the goal of the program to seed (inject ice nucleatingagents) the developing "new growth" cloud towers of a hail producing storm, at least 20 minutes beforethe damaging hail falls over a town or city within the target zone. For the Alberta project, the principletargets are the towns and cities within the project area. Since 20 min is the minimum time reasonablyexpected for the seeding material to nucleate, and have the seeded ice crystals grow to sufficient sizeto compete for the available super-cooled liquid water in order to yield positive results, a 30 min leadtime is generally thought to be advisable.

Identification of Hail Producing Storms


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The height of the 45 dBZ contour was a criterion tested in the Swiss hail suppression program. TheSwiss research indicated that all hailstorms had 45 dBZ contours that exceeded the 5C temperaturelevel (Waldvogel, Federer, and Grimm, 1979). There was a False Alarm Rate (FAR) of 50%, largelybecause some strong rainstorms also met the criterion. However, it is preferable to make an error andassume that a heavy rainstorm is going to produce hail than to mistakenly believe that a hailstorm isonly going to produce heavy rain. Studies of Alberta hailstorms also indicated that 50% of all Albertahail storms had a maximum radar reflectivity greater than 45 dBZ, higher than the -5C level(Humphries, English, and Renick, 1987). The Russian criteria for hail identification stated that the height

of the 45 dBZ contour had to exceed the height of the 0C isotherm by more than 2 km (Abshaev,1999). Similarly, the criteria used by the National Hail Research Experiment in the USA 1972-1974 fora declared hail day was defined by radar maximum reflectivity greater than 45 dBZ above the -5C level(Foote and Knight, 1979).

Our experience suggests that the Swiss/Alberta/Russian/USA criterion is reasonable (Makitov, 1999).The physical reasoning behind it is simply that high radar reflectivity implies that significant supercooledliquid water exists at temperatures cold enough for large hail growth.

In Alberta, the TITAN cell identification program was set in 2006 to track any cell having >10 km3of 40dBZ reflectivity, extending above 3 km altitude (MSL). Each cell tracked by TITAN was then consideredto be a potential hail threat, therefore, this represents our seeding criteria. A storm is a seedingcandidate if the storm cell (as defined by TITAN) is moving towards, and is expected to reach, a town orcity within the target area in less than 30 min.

Cloud Seeding Methodology

Radar meteorologists are responsible for making the "seed" decision and directing the cloud seedingmissions, incorporating the visual observations of the pilots into their decisions. Patrol flights are oftenlaunched before clouds within the target area meet the radar reflectivity seeding criteria, especially overthe cities of Calgary and Red Deer. These patrol flights provide a quicker response to developing cells.In general, a patrol is launched in the event of visual reports of vigorous towering cumulus clouds orwhen radar cell tops exceed 25 kft height over the higher terrain along the western border on dayswhen the forecast calls for thunderstorms with large hail potential.

Launches of more than one aircraft are determined by the number of storms, the lead time required for

a seeder aircraft to reach the proper location and altitude, and projected overlap of coverage andon-station time for multiple aircraft missions. In general, only one aircraft can work safely at cloud topand one aircraft at cloud base for a single storm. The operation of three aircraft is used to provideuninterrupted seeding coverage at either cloud-base or cloud-top and/or to seed three stormssimultaneously if required.

Factors that determine cloud top or cloud base seeding are: storm structure, visibility, cloud baseheight, or time available for aircraft to reach seeding altitude. Cloud base seeding is conducted byflying at cloud base within the main inflow of single cell storms, or the inflow associated with the newgrowth zone (shelf cloud) located on the upshear side of multi-cell storms.

Cloud top seeding can be conducted between -8C and -15C. The 20 g pencil flares fall approximately1.5 km (approximately 10C) during their 35-40 s burn time. Figure 15 shows a cloud seeding plane

dropping flares. The seeding aircraft penetrate the up-shear edges of single convective cells meetingthe seed criteria. For multi-cell storms, or storms with feeder clouds, the seeding aircraft penetrate thetops of the developing cumulus towers on the upshear sides of convective cells, as they grow upthrough the -10C flight level.


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per litre averaged over the plume within 2.5 min. This is more than sufficient to deplete the liquid watercontent produced by updrafts up to 10 m/s (2000 ft/min), thereby preventing the growth of hailstoneswithin the seeded cloud volumes (Cooper and Marwitz, 1980). For effective hail suppression, sufficientdispersion of the particles is required for the AgI plume from consecutive flares to overlap by the timethe cloud particles reach hail size. The work by Grandia et al. (1979) based on turbulencemeasurements within Alberta feeder clouds indicated that the time for the diameter of the diffusing lineof AgI to reach the integral length scale (200 m) in the inertial subrange size scales of mixing, is 140seconds. This is insufficient time for ice particles to grow to hail size, therefore, dropping flares at 5 sec

(assuming a true-airspeed of 80 m/s) intervals should provide sufficient nuclei and allow adequatedispersion to effectively deplete the super-cooled liquid water and prevent the growth of hail particles.The use of the 20 gm flares and a frequent drop rate provides better seeding coverage than using largerflares with a greater time/distance spacing between flare drops. In fact, the above calculations areconservative when one considers that the center of the ice crystal plume will have a greaterconcentration of ice crystals.

For cloud base seeding, a seeding rate using two acetone generators or one end-burner flare istypically used, dependent on the updraft velocity at the cloud base. For an updraft >500 ft/min,generators and consecutive flares per seeding run are typically used. Cloud seeding runs are repeateduntil no further inflow is found. Acetone burners are used to provide continuous silver iodide seeding ifextensive regions of weak updraft are found at cloud base and in the shelf cloud region. Base seedingis not conducted if downdrafts only are encountered at cloud base, since this would waste seeding

material.

Seeding Materials

WMI exclusively uses silver-iodide formulation flares manufactured by Ice Crystal Engineering (ICE) ofDavenport, ND. The ejectable flares contain 20 gm of seeding material and burn for approximately 37sec and fall approximately 4000 ft. The end-burning or burn in place (BIP) flares contain 150 gm ofseeding material, and burn for approximately 6 min. A photograph of a burning BIP flare test is shownin Figure 16.

Figure 16: Photograph of a burning BIP flare.

Silver-iodide is dispensed using droppable/ejectable (shown in Figured 15 and 17) and/or end-burningpyrotechnics (Fig. 16) and/or acetone burners (shown in Figure 18). In 2006 the WMI acetonegenerators performed very well and the level of required maintenance decreased significantly. Crewsstill kept a close watch of igniter rods, valves, nozzles, and seals in order that the generators operatedreliably. Details of the silver-iodide acetone solution used in 2006 are given in an Appendix.


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Arrangements were once again made with Solution Blend Services, a Calgary chemical company topre-mix the acetone seeding solution. All required handling, mixing, storage, and labelling requirementswere satisfied.

Figure 17: Pilot Joel Zimmer attaching the ejectable flare racks on the belly o f the King Air C90seeding aircraft.


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Figure 18: Hail Stop 2, C340 aircraft shown seeding with Acetone Solution burners and Burn-In-Place (BIP) flares.

Flare Effectiveness Tests

The Cloud Simulation and Aerosol Laboratory at Colorado State University has performed routinetesting of the ice nucleating ability of aerosols produced from cloud seeding flares for many years(Garvey, 1975). Note: The CSU laboratory has now stopped this service and a new testing facility toconduct these standardized tests is desperately needed for the cloud seeding industry. The new ICEpyrotechnics were tested at CSU in 1999 and the results are reported in DeMott (1999). Aerosols werecollected and tested at nominal temperatures of -4, -6 and -10C. At least two tests at were done ateach temperature, with greater emphasis placed on warmer temperatures. Liquid water content (LWC)was 1.5 g m-3 in most tests, but was altered to 0.5 g m-3 in a few other experiments. In this way,information concerning the rate-dependence on cloud droplet concentration was obtained. The primaryproduct of the laboratory characterization is the "effectiveness plot" for the ice nucleant which gives thenumber of ice crystals formed per gram of nucleant as a function of cloud temperature. Yield results forthe ICE flares at various sets of conditions are shown in Figure 19 and are tabulated in Table 2.


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1.00E+10

1.00E+11

1.00E+12

1.00E+13

1.00E+14

1.00E+15

0 5 10 15

Supercooling (C)

Yie

ld(#g

-1p

yro)

ICE Pyro

July 1999

___________

___________

Figure 19: Yield of ice crystals (corrected) per gram of pyrotechnic versus cloud supercooling

temperature (T


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y = 57.483x-1.9653

R2= 0.8298

y = 4.723x-1.1862

R2= 0.8552

0

1

2

3

4

5

6

7

8

9

10

0 2 4 6 8 10 12Supercooling (C)

Time(minutes)

63

9

__________________

Figure 20: Times for 63% (diamond symbols) and 90% (square symbols) ice formation versus

supercooling (T


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Beech King-Air C90

Figure 24: Beech Craft King-Air C90 aircraft (N911FG) designated as Hail-Stop 3 shown at theOlds-Didsbury Airport.

A photo of the Beechcraft King Air C90 designated Hail Stop 3 (N911FG) is shown in Figure 24 at theOlds-Didsbury Airport. The specifications of the King Air C90 are given in an Appendix. The King Airwas similarly equipped as the Cheyenne II. The Cheyenne II and King Air C90 are both high

performance twin-engine turboprop aircraft that have proven themselves during seeding operations.

C340A Aircraft

Cloud seeding was also conducted using one Cessna 340A aircraft equipped with ejectable flare bellyracks, wing mounted flare racks, and acetone burners. The aircraft registered as N457DM wasdesignated as Hail-Stop 2 (shown in Figure 25). The C340A aircraft is a pressurized, twin-engine, sixcylinder, turbocharged and fuel-injected all weather aircraft. The C340 aircraft also has a weatheravoidance radar and GPS navigation system. Complete specifications for the C340 are given in an

Appendix. The C340 aircraft carried 306 20-g pencil flares and 24 150-g end-burning flares and two 7US gallon acetone burners. Although the C340 can seed at cloud top, its performance is rather limitedin known icing conditions. Therefore, the C340 is used primarily as a cloud-base seeder. During 2006,the C340 seeded one day at cloud top. Otherwise it was used exclusively as a cloud-base seeder.


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Figure 25: C340A aircraft (N457DM) designated as Hail-Stop 2 and configured to seed withdroppable flares, end-burning flares, and AgI acetone burners.

Meteorological Aircraft Instrumentation

Each of the cloud seeding aircraft had a temperature and liquid water sensor to help assure that thecloud penetration seeding runs were conducted at known temperature levels and to document the

presence of supercooled liquid cloud water. A radio telemetry system was used to transmit the aircraftdata to the radar communications and control center where it was displayed in real time and recorded at1 sec intervals. These measurements, combined with the recorded radar data, helped assure that theproject is conducted on a sound scientific basis.

All three aircraft performed very reliably with no seeding opportunities were missed due to maintenanceissues.

RADAR CONTROL AND COMMUNICATIONS CENTER

The projects radar control room consists of the Airlink computer with radio telemetry modem for GPStracking information, as well as the TITAN computer and display, and the meteorological dataacquisition (Compaq) computer. Controllers communicated with the seeding aircraft using a VHF radioat 122.95 MHz frequency. The controlling duties were shared by Terry Krauss, Jason Goehring, AndreSinkevich, and Viktor Makitov (shown in Figure 26).

An upgraded TITAN radar display and analysis computer system was installed in 2004 (shown in Figure27). The new TITAN was able to display several new hail parameters that gave the meteorologistsadditional information to improve identification of hailstorms and improved the direction of the aircraft tothe most important hail growth regions of the storm. The TITAN radar images were sent to the WMIweb server at 5-min intervals, although there were often missing images in the web archive which wereblamed on computer problems and interruptions in the microwave internet connection at the radar. Themicrowave modem at the radar was upgraded during the summer and this provided a slightimprovement in August and September. A more reliable radar file transfer routine will be investigated


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The radar antenna was raised 8 ft in 2001 in order to provide more clearance above nearby buildingsthat had been constructed at the Olds-Didsbury Airport. The base elevation radar scan was set to 0.8degrees elevation in order reduce the amount of ground clutter, yet still provide a good viewing angle ofthe low-level precipitation at far ranges, especially over Calgary and Red Deer. The radar transmitter islocated inside a shed built directly under the radar tower (shown in Figure 29). The radar shed isinsulated and air-conditioned. The radome was repainted on August 25th, 2006.

Figure 29: WMI C-band radar at the Olds-Didsbury airport.

The radar data acquisition computer RDAS is programmed to control the radar antenna such that acomplete volume scan of 18 elevation steps, up to 45elevation, was performed about every 4.8 min.The RDAS computer sends the polar coordinate radar data to the TITAN computer via a local areanetwork and the TITAN computer performs the Cartesian transformation and records a permanentarchive of all of the scans. The polar data were stored and displayed on the CIDD computer. All of theTITAN volume-scan radar data collected during 2006 have been recorded on CD-ROM. The GIF PPIpicture files created every 5 min, have been archived onto CD-ROM.

Radar Calibration Checks

The quantitative use of radar requires that various parameters of the system be measured andcalibrated. The WMI WR100 C-band radar located at the Olds-Didsbury Airport is used to direct seedingaircraft in the Alberta Hail Suppression Project. As such, it needs to provide accurate values of radarreflectivity along with range, azimuth and elevation.


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Assuming that all the terms relating to the electrical components and propagation of the radar beam areconstants and if we always assume we are looking at water, a simplified radar equation takes the form(Rinehart, 1997):

z = C prr2

Thus, calculating radar reflectivity factor z is simply a matter of getting the power from a target of knownrange (times a constant). The WR100 parameters and calibration values are shown in Table 4. The

RDAS radar acquisition software performs digital signal processing to simulate a quadratic response ofthe receiver output (Terblanche, 1996) and uses a reference range of 100 km.

Table 4: Radar parameter calibration values for the ALBERTA-WMI WR100.

value Log Db Units

Pulse0.0000033 -5.481 -54.81

Sec

PRF256 2.408 24.08

Sec-1

Freq5.64E+09 9.751 97.51

Sec-1

Duty cycle = Pulse * PRF

-30.73

Minimum detectable signal = -107 DB

Nominal Radar Constant for rangein nmi

(in the RDAS-TITAN convention)

-160.96 DB

The radar was found to be stable from day to day and the radar transmitted power varied by no morethan 0.5 dB over the operational period from June 1 to September 15. The WR100 transmitted powervalues measured during the summer are shown in Table 5.

Table 5: Radar transmitted power calibration values measured during the 2006 season.

DatePower(dBm) Power (kw) Notes

18-May-06 84 251

23-May-06 83.9 245 calibration

1-Jun-06 84 251

7-Jun-06 83.6 229 new crystal detector

12-Jun-06 83.5 224

21-Jun-06 84 251 fan replacement

29-Jun-06 83.8 240 calibration

3-Jul-06 83.8 240

24-Jul-06mechanical failure of crown waveguide

26-Jul-06 83.9 245

27-Jul-06 pedestal flex wave guide fails

28-Jul-06 83.8 240 Replaced power supply.

5-Aug-06 83.9 245

10-Aug-06 83.9 245

14-Aug-06 83.9 245 Calibration using EC attenuator

1-Sep-06 83.9 245

11-Sep-06 83.8 240


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Figure 30: Radar calibration of RDAS digital counts to equivalent radar reflectivity power (dBZ)for the WMI radar at Olds-Didsbury during the 2006 field season.

When a radar is modified or repaired, it is important to check and/or recalibrate the RDAS computerwhich converts the raw radar video signal into a digital value (i.e.; number of RDAS counts)representing a known power (i.e.; equivalent dBZ value at 100 km range). The output power of thetransmitter was measured regularly. The RDAS calibration curve was checked for accuracy at the start,mid-season, and again at the end of the season. The calibration tests measured during the summer of2006 are shown in Figure 30. The calibrations show a change of approximately 5 dB between the earlycalibrations and the August 14

th calibration. A special piece of test equipment (attenuator) wasborrowed from Environment Canada for the August 14th calibration. This allowed a constant signalgenerator setting to be used, and the attenuator was used to reduce the power for the calibration. The

August 14thcalibration is thought to be more accurate, therefore, the radar reflectivity values prior toAugust 14thare likely to have been 5 db too low.

The final calibration check for a radar system is a measurement of the pointing accuracy of the antenna.To check the antenna alignment and accuracy, the dish is pointed at the sun and its positioncoordinates in azimuth and elevation are cross-referenced to the accurate, known position of the sun atthat exact time of day. The exact position of the sun can be determined using a computer programdesigned for that specific purpose. The pointing accuracy of the system was also verified numerous

times by confirming the position of the aircraft relative to the position of an isolated echo.

AIRCRAFT TRACKING GLOBAL POSITIONING SYSTEM (GPS)

The WMI weather radar control and communications center was equipped to receive and record datafrom the aircraft GPS position telemetry system. The GPS system displays the exact position of theaircraft superimposed on the radar PPI display to enable the controller to accurately direct the seedingaircraft to optimum seeding locations within the storm system. The colour coded aircraft position on thePPI display enabled radar controllers to discriminate between each project aircraft. The Airlink tracking


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percentile for landings is approximately 6 pm. The convective storms in Alberta have a strong diurnalcycle associated with the period of daily maximum temperature. In Alberta, the temperature usuallycools off sufficiently when the sun goes down to prevent continued deep convection. Occasionally,however, a passing cold-front or upper-level disturbance is strong enough to trigger evening convection,therefore, nocturnal storms cannot be ruled out. This is in contrast to the storms and experiences ofWMI in Mendoza, Argentina where half the storms occurred after sunset.

Figure 32: The frequency of occurrence and cumulative distributions of aircraft take-off andlanding times for all flights as a function on time during 2006.

Figure 33: Amount of seeding material dispensed per operational day in 2006.


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Seeding Amounts

The amount of seeding material dispensed on each day of operations in 2006 is shown in Figure 33.There were 8 days on which >10 kg of seeding material was dispensed during 2006. In comparison,there were 6 days during 2003 and 2005 on which >10 kg was dispensed, and 16 days >10 kg during2004. The eight greatest seed days in 2006 were: July 9

th (21.4 kg), August 3

rd (19.5 kg), July 17

th

(16.8 kg), June 21st (16.4 kg), July 1st(15.8 kg), June 30th(13.8 kg), August 9th(10.9 kg), and July 6th(10.4 kg).

Comparison Of 2006 With Previous Years

Table 6 gives a list of the operational statistics for the past eleven years of the Alberta Hail SuppressionProject. These statistics can be useful for planning purposes. This summer had an average number ofstorm days, aircraft missions, and flight hours. However, the total amount of seeding was greater, andthere was an above average amount of seeding per day, per hour, and per storm. This supports oursubjective impression that the storms during 2006 tended to be more severe and longer lived thanaverage. The greater seeding material and flight hours could also be due in part to the expandedproject area.

The best seeding coverage is achieved by seeding simultaneously at cloud base and cloud top thedeveloping feeder clouds along the upwind side of a mature storm. The Cheyenne II and King Airaircraft have proven themselves as excellent cloud-top seeders. The seeding strategy has been tostagger the launch of the seeding aircraft, and use one aircraft to seed at cloud base and one aircraft atcloud top when the storm is over the highest priority areas. However, if multiple storms threaten threeareas at the same time, generally only one aircraft is used on each storm, or the aircraft areconcentrated on the highest population area around Calgary. This happened on August 10

thwhen only

Hailstop 3 was used to seed the storm that caused considerable damage at Springbrook, south of RedDeer, because Hailstop 2 was seeding storms near High River and Hailstop 1 was used to seed stormsnear Calgary.

Comparison by Aircraft

A summary of the flare usage according to aircraft during the past 11 years is given in Table 7. TheCessna 340 (Hailstop 2) has been primarily used as a cloud base seeding aircraft because it has lessperformance than the other two prop-jet aircraft. Nevertheless, Hailstop 2 seeded effectively at cloudtop on July 12th and served a very useful purpose seeding for long periods, continuously at cloud baseusing a combination of BIP flares and acetone generators. Hailstop 1 in Calgary has been a PiperCheyenne II for all 11 years, and Hailstop 2 in Calgary has been a Cessna 340A for all 11 years.Hailstop 3 in Red Deer was a C340 for 4 years (1996-99), a Cheyenne II from 2000 to 2003, and 2005,and a Beech King Air C90 in 2004 and 2006. The advantages of the C90 are that it has slightly longerendurance for increased seeding time, and good performance for reaching the far western regions ofthe target area near Rocky Mountain House in a reasonable amount of time (e.g.


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2006 54.0 3217 top, 179base

70.2 72 top, 248 base,58.2 hr

66.0 1640 top, 276 base

C90 King Air

2005 49.1 2750 top, 169base

44.8 0 top, 121 base,37.7 hr

63.9 1020 top, 225 base

Cheyenne II

2004 83.2 5574 top, 359base

62.2 0 top, 196 base,53.1 hr

82.1 939 top, 322 base

C90 King Air

2003 63.9 3598 top, 250base

54.2 0 top, 130 base,37.1 hr

45.5 867 top, 138 base

Cheyenne II

2002 57.1 1994 top, 163base

49.3 2 top, 73 base, 32.1hr

51.0 1112 top, 141 base

Cheyenne II

2001 62.4 3174 top, 216base

74.8 4 top, 215 base, 56.3hr

68.1 2093 top, 102 base

Cheyenne II

2000 89.5 4755 top, 379base

77.4 164 top, 193 base,56.5 hr

97.4 4734 top, 368 baseCheyenne II

1999 91.3 3795 top, 313base

81.4 244 top, 197 base,59.6 hr

78.6 400 top, 180 base,59.4 hr

C340

1998 62.2 1880 top, 107base

68.4 134 top, 199 base,29.2 hr

59.4 9 top, 190 base, 48.3hr

C340

1997 70.2 1828 top, 62base 58.0 264 top, 128 base,25.9hr 60.0 284 top, 166 base,31.8 hr

C340

1996 61.6 2128 top, 143base

45.8 895 top, 192 base,9.4 hr

51.7 794 top, 207 base,22.8 hr

C340


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WEATHER FORECASTING

The daily forecast for the hail project was routinely prepared each morning by one of the meteorologistsat the Radar, and presented at the weather briefing telephone conference call at 12 noon. The forecasttime period for verification was considered to be 24 hrs, spanning the period from 6am to 6 am. Theprimary input data used for the forecast included the following: Regional analyses at 250 mb, 500 mb, 700 mb. Upper air sounding data from Edmonton or Kelowna ETA model forecast soundings for Calgary, Red Deer, Sundre, and Rocky Mtn. House. Public and Aviation Forecasts Severe weather charts Numerical model forecasts (GEM, ETA/NAM) Satellite pictures Radar pictures from Environment Canada facilities at Strathmore and Carvel.

All of the meteorological data downloaded via the internet during the field season have been stored onCD-ROM for future reference purposes.

Convective Day Category (CDC)

After the weather forecast is produced, a Convective Day Category (CDC) is selected that bestdescribes the conditions that are expected for the day. The CDC (Strong, 1979) is an index that givesthe potential for hailstorm activity and seeding operations. A description of the weather conditions foreach CDC is given in Table 8. The distinction between the -2 and -1 category is sometimes difficult,since overcast or prolonged rain eventually breaks up into scattered showers. The maximum VIL pixelvalues were used for forecast verification purposes of hail size in the absence of surface hail reports.Radar VIL values were used within the project area or buffer zones on the north, east, and south sides(not including the western buffer zone). This may have increased the number of hail days from theearly years, which relied on a human report of hail fall at the surface; however, it is believed to be amore realistic measure of hail. There were a few days when pea size hail was reported and the VILwas < 10 kg/m2. The

Documents

Wmi Alhap Final Report 2006