Modelling of MPB Transport and Dispersion using Atmospheric Models

Mountain Pine Beetle Initiative Research Program Update Session April 8, 2004

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Modelling of MPB Transport and Dispersion using Atmospheric

ModelsPeter L. Jackson

Brendan Murphy

UNBC Environmental Science & EngineeringWith assistance from:

Ben Burkholder, Melissa Darney, Brenda Moore

Funded by: NRCan/CFS Mountain Pine Beetle Initiative grant awarded to Jackson, Lindgren and Ackerman


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Outline

1. Introduction / Motivation

2. Objectives / Outcomes

3. Methods

4. Synoptic Climatology Results Highlights

5. Atmospheric Modelling – Test Case (first try)

6. Information Needs…


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Introduction / Motivation

• MBP infestation has reached epidemic proportions in central BC affecting 4.2 million ha and 108 million m3 of timber

• Emergence and flight in summer after 3 days of Tmax > 18 ºC but < 30°C


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• Dispersion is – active by flight over short distances / light wind

(local scale: within stand over a few km)– passive advection due to winds and turbulence

above and within canopy (landscape scale: between stands perhaps 10-100 km)

• Passive transport allows epidemic to spread rapidly over great distances little is known about passive transport and this is the focus of our work


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• MPB fly on hot summer days

• Warmest conditions usually occur under slack synoptic weather conditions

terrain-induced thermal circulations (e.g. mountain/valley winds, anabatic/katabatic flows) and steering of winds by terrain should determine the above-canopy, and the within-canopy air flow


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Objectives

1. Identify synoptic weather patterns present during periods of MPB dispersal

2. Identify fundamental relationships between terrain features, atmospheric flows and MPB fallout zones

3. Assess potential for physics-based meteorological and dispersion models to estimate MPB dispersal from one year to the next


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Methods• The premise behind our work is that passive

transport of MPB is not unlike transport and dispersion of air pollutants

• Techniques exist to model air pollution • Physics-based mesoscale atmospheric

models are well-developed and tested • Models have demonstrated skill

representing and predicting the circulations in complex terrain that are likely important during times of MPB flight


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• Objectives 2 &3 will make use of the CSU Regional Atmospheric Modeling System (RAMS) to simulate the atmosphere (wind, temperature, humidity, pressure, etc. on a nested 3D grid)

• The meteorological fields from RAMS will then drive a Lagrangian Particle Dispersion Model (HYPACT) that will advect and disperse MPB

• Can also calculate forward and backward trajectories from the model wind fields


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• A basic step prior to modelling is to find the average environmental conditions present during MPB flight

• The Synoptic weather pattern determines the atmospheric background conditions in which MPB emerge and move.

• Average weather pattern(s) associated with MPB flight are found using compositing

• This leads to an understanding of regional wind patterns


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Synoptic Climatology• As a surrogate for known dates of MPB flight, we

have defined “Heating Cycle 1” (HC1) as at least 4 consecutive days with the Tmax > 20 oC but < 30 oC

• We use the weather pattern on day 3 to define the composite

• We have identified 3 related map types corresponding to HC1 defining the general weather patterns during emergence and flight


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Distribution of HC1 by month for Prince George 1943-2002 (8.9 cycles/y)

Heating cycle length

Avg length = 5.6 days

Max length = 24 days (1979)


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Distribution of wind speed by hour at Prince George during HC1

Distribution of temperature by hour during HC1


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Peak Emergence

• It is likely that passive transport will be most important when peak emergence is occuring

• Peak emergence is associated with higher temperatures

• Define HC2 as days with Tmax > 25 C, but < 30 C


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500 hPa July & August climate (all days), HC2 composite, anomaly

Sea level July & August climate (all days), HC2 composite, anomaly


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July & August Climatology, HC2 composite and anomaly

for Temperature at surface, and Relative Humidity at 700 hPa (clouds).


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Evolution of 500 hPa composite pattern through HC2 event

• as upper ridge passes atmosphere becomes moderately unstable

• this would result in increased afternoon “thermals”


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Evolution of surface composite pattern through HC2 event

• sea level pressure drops as temperature increases

• pressure drop seems to be consistent across many cases – does MPB emergence and flight respond to pressure as well as temperature?


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Validation of HC2 / Peak Emergence

common features of peak emergence:

• as surface temperatures go up

• sea level pressure drops

• pattern seen in several other cases too…(we need more emergence data at daily resolution)


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(mslp – white

500 hPa – yellow)

Andrew McLellan /CANFOR; Bugbusters,


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Atmospheric Modelling – Test Case (first try)•RAMS run for July 28 -Aug 1 2003

•5 nested grids at 81,27,9,3,1 km horizontal resolution

•30 levels in vertical starting at 25 m resolution


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2003 MPB destinations 2003 MPB source


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Time-height cross section from a location west of the Rockies. Wind (arrows), temperature (contours) and potential temperature (colour)


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Hourly output from RAMS simulation at model level 2 (~40 m AGL), from grid 4 at 3 km horizontal resolution (only every 2nd wind vector shown)

Chetwynd

Burnt R.

North of Monkman Park

MacKenzie


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Trajectories• Three scenarios chosen:

– Two “endpoints” – 2003 green attack east of Rockies– One “starting point” 2003 red on western slope of

Rockies

• Foreword Trajectories in RED starting at 11:00 PDT at 1 hour resolution

• Backward Trajectories in BLACK from 2003 green attack starting at 16:00 PDT at 1 hour resolution

• (there are some problems with the wind simulation that we are working on– so these are far from final results)


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2003 MPB destinations 2003 MPB source


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40 m 105 m

309 m 1288 m


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40 m 105 m

309 m 1288 m


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Kwoen – MWLAP weather station in Burnt River – east of Rockies

• wind speeds OK

• wind directions are poor

• we are looking at why…

MacKenzie – EC weather station

• wind directions west of Rockies slightly better


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Information Needs

• More documented MPB flight / emergence periods, ideally at daily resolution

• MPB time in flight, height of flight – how many fly above the canopy? – working with new MSC doppler radar at Baldy Hughes – pilots?

• More “case studies” of between stand movement for validation (especially isolated populations) – Prince George City


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The End

Documents

Modelling of MPB Transport and Dispersion using Atmospheric Models