NAVAL

POSTGRADUATE SCHOOL

MONTEREY, CALIFORNIA

OC3570 PROJECT

ESTIMATING EVAPORATION DUCT HEIGHT BY KITE FLYING RAWINSONDE

by

Kuofeng CHENG

Professor: Peter Guest Professor: Curtis Collins

THIS PAGE INTENTIONALLY LEFT BLANK

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TABLE OF CONTENTS

I. INTRODUCTION........................................................................................................1 A. EVAPORATION DUCT .................................................................................1 B. REFRACTIVITY.............................................................................................2 D. BULK METHOD.............................................................................................2

II. MEASUREMENT DESCRIPTION...........................................................................5 A. OC3570 CRUISE .............................................................................................5 B. MEASUREMENT METHODS ......................................................................5

1. Rawinsonde...........................................................................................5 2. Kite ........................................................................................................6

C. MEASUREMENT INTERVALS ...................................................................6

III. DATA PROCESSING .................................................................................................7 A. SEA SURFACE HEIGHT CORRECTION ..................................................7 B. DATA FILTERING.........................................................................................7 C. AVERAGE PERIOD.......................................................................................8 D. BULK METHOD APPROXIMATION.........................................................8

IV. RESULTS ...................................................................................................................11 A. DATASET ‘060120_1904Z’ ..........................................................................11 B. DATASET ‘060121_1938Z’ ..........................................................................11 C. DATASET ‘060123_2226Z’ ..........................................................................12 D. DATASET ‘060125_2043Z’ ..........................................................................12

V. CONCULSION ..........................................................................................................17

ACKNOWLEDGMENTS .....................................................................................................18

APPENDIX HISTORICAL REVIEW OF SCIENTIFIC KITE ........................19 A. EARLY AGE..................................................................................................19 B. GOLDEN TO ABANDON ............................................................................19 C. RESENT MEASUREMENTS ......................................................................20

LIST OF REFERENCES......................................................................................................21

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LIST OF FIGURES

Figure 1 The cruise report of OC3570 course. (From OC3570 2006.) ...........................5 Figure 2 Kit measurement of sea surface boundary layer. (From Mabey 2002.)............6 Figure 3 Sea surface height correction. ............................................................................7 Figure 4 Data filtering of ‘060120_1904z’ dataset with scenarios (a) only remove

set-up and final stages, and (b) remove the shadow effects of vessel body.......9 Figure 5 Vertical data distribution of same average period with data filtering

scenarios (a) and (b).........................................................................................10 Figure 6 The result of dataset ‘060120_1904z’. (a)-(d) are different average

periods, blue dot indicates in-situ measurement, magenta circle mean value, black solid line the bulk method, and black circle suggests the theoretical evaporation duct height. .................................................................13

Figure 7 The result of dataset ‘060121_1938z’. Similar format as Figure 6. ...............14 Figure 8 The result of dataset ‘060123_2226z’. Similar format as Figure 6. ...............15 Figure 9 The result of dataset ‘060125_2043z’. Similar format as Figure 6. ...............16

Equation Section 1

1

I. INTRODUCTION

Several kite flying rawinsonde have been performed to measure atmospheric

boundary layer profile during the OC3570 cruise from 18 to 26 January 2006. This

project will apply and process these measurements, compare them with theoretical

profiles, and estimate the height of evaporation duct.

Outline of this project report is as following. First, a brief introduction about

evaporation duct and refractivity is reviewed. Part II describes the kite and rawinsonde

measurement. The data processing algorithm is illustrated in part III. Results is shown

and discussed in part IV, and following the conclusion and suggestions in part V.

A. EVAPORATION DUCT The evaporation duct has been recognized as a propagation mechanism that can

substantially increase beyond-horizon radio signals above diffraction levels for high

frequencies. It is a subset of surface ducts and is formed just above the sea surface by

strong vertical humidity gradients. The evaporation duct almost always presents; but its

height is highly variable in space and time (Babin et al. 1997). The height of evaporation

duct could be determined by refraction parameter (Figure 1).

Figure 1 Determining evaporation duct height from modified refractivity. (From Guest

2006.)

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B. REFRACTIVITY Propagation of microwave and millimeter-wave electromagnetic radiation in the

atmosphere is determined by gradients of the refractive index of air, which could be

further expressed in term of modified refractivity. The gradient of the index of refraction

n is given (Babin et al. 1997; Guest 2006)

cnv

= (1.1)

where c is the speed of light, and v is the speed of the wave front. Since n is very close

to 1, Debye’s theory is used to express the scale quantity, radio refractivity N

6 52( 1) 10 77.6 5.6 3.73 10P e eN n

T T T= − × = − + × (1.2)

where P is atmospheric pressure in hPa, T is the air temperature in K, e is the vapor

pressure in hPa, and z is height above surface in meter.

Consider the curvature of earth, the modified refractivity M is related to N as

6 0.15710e

zM N N zr −= + ≅ +×

(1.3)

where er is the radius of earth (use 66.371 10× m) and z is altitude in meters. This

modified refractivity is used here to estimate the evaporation height.

D. BULK METHOD Fairall (1996) reviewed the bulk parameterization of air-sea fluxes. The turbulent

fluxes of sensible heat sH , latent heat lH , and stress τ are defined by normal Reynolds

averages,

_______

* *

_______

* *_______

2*

' ' ( )

' ' ( )

' '

s a pa a pa a pa h s

l a e a e a e e s

a a

H c w T c u T c C S T

H L w q L u q L C S q q

w u u

ρ ρ ρ θ

ρ ρ ρ

τ ρ ρ

= = = −

= = = −

= = −

(1.4)

The standard bulk expression for the scalar fluxes are

3

( )

( )s a pa h s

l a e e s

H c C S T

H L C S q q

ρ θ

ρ

= −

= − (1.5)

where T is the temperature, θ is the potential temperature, q is the water vapor mixing

ration, w is the vertical wind, u is the stream-wise component of horizontal wind,

respectively. Superscript ' denotes the turbulent fluctuations, while subscript a is the

character of air, s the character of sea surface , and * is the dimensionless parameter. S

is the average value of the wind speed at reference height rz . hC , eC , and dC are the

transfer coefficients for sensible hear, latent heat, and stress.

The water vapor mixing ratio at height q , at sea surface sq , and the potential

temperature θ can be expressed at,

( )

0.98 ( )0.0098

s

s sat s

r

q RHq Tq q T

T zθ

=== +

(1.6)

The transfer coefficients are partitioned into individual profile components,

1/ 2 1/ 2

1/ 2 1/ 2

h T d

e q d

C c c

C c c

=

= (1.7)

furthermore,

1/ 2

1/ 2

1/ 2 1/ 2

( )/ 1log( / ) log( / )

( )/ 1

log( / ) log( / )

( )/ 1log( / ) log( / )

hT

r oT r oT

qq

r oq r oq

ud d

r o r o

acz z z z

acz z z z

aC cz z z z

ξκ

ξκ

ξκ

Ψ= −

Ψ

= −

Ψ= = −

(1.8)

The scale parameters can be computed independently from the above transfer

coefficients

4

1/ 2*

1/ 2*

*

( )

( )T s

q s

d

T c T

q c q q

u C Su

θ= − −

= − −

=

(1.9)

The theoretical temperature and humility profile could be derived form the last

portion of equations (1.4) and (1.5). In this project the bulk method profile is calculated

implicit by a Matlab program given estimated temperature at sea surface, at certain height

(use 20m here), and humility at certain height (20 m).

5

II. MEASUREMENT DESCRIPTION

A. OC3570 CRUISE An operational cruise had been planed as the core project of OC3570 course

March 2006 (Collins and Guest 2006). It was operated from 18 to 26 January 2006 in the

close water of central California. The platform is Research Vessel (R/V) Point Sur under

Moss Landing Marine Laboratory (MLML). The cruise had been divided into three legs,

from MLML to Port San Luis (18 to 22 January), Port San Luis to Port Hueneme (22 to

25 January), and Port Hueneme to San Pedro (26 January). Various instruments were

launched, including CTD, XBT, rawinsonde by balloon, rawinsonde by kite, and

sonobuoy. The cruise information is shown as Figure 2.

Figure 2 The cruise report of OC3570 course. (From Collins and Guest 2006.)

B. MEASUREMENT METHODS

1. Rawinsonde

Vaisala RS80 series GPS Radiosonde is used to measure meteorological

parameters in the OC3570 cruise. Meteorological sensor onboard is so called the PTU

Sensor, which measures pressure, temperature, and humidity. Furthermore, a codeless

GPS receiver is also onboard for positioning, and for computing the wind speed and

direction by differential concept (Vaisala 1999). Radiosonde is carried by balloon as well

as by kite to measure the vertical atmospheric profile.

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2. Kite

A common leisure kite is used in this cruise as the platform for rawinsonde to

measure the sea surface boundary layer PTU. The kite is controlled by a fishing stick

with electric motor to arrange the string. The rawinsonde is hanged at a 10-m string from

about 10-m to the kite (see Figure 3). It was flew to 160-200 m in height then steadily

pulled back by the string motor to 1-2 m above sea surface. Latter, a precise release of

string let the kite flying freely and kept at a constant height above the sea surface. Finally

the kite continuous ascended to previous height.

Combined the ascending and the descending paths, each cycle takes about 5

minutes and repeats for a number of times (about 15-20 times in two-hour window).

Further description of the kite settings and operations could be referred to Mabey (2002);

a historical review is also provided in Appendix.

C. MEASUREMENT INTERVALS In OC3570 cruise, kite flying with rawinsonde measurement was taken place for

four times. They were at 1904UTC 20 January on (123.45 Wo , 36.04 No ), 1938UTC 21

January on (122.26 Wo , 34.40 No ), 2233UTC 23 January on (121.60 Wo , 33.39 No ), and

2043UTC 25 January on (119.56 Wo , 33.93 No ); all locations are shown in 0. Each

measurement was continued for about two hours, which included 10 to 20 cycles.

Therefore, there are four datasets available in this study, ‘060120_1904z’,

‘060121_1938z’, ‘060123_2226z’, and ‘060125_2043z’, respectively.

Figure 3 Kit measurement of sea surface boundary layer. (From Mabey 2002.)

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III. DATA PROCESSING

Previously, one set of Matlab codes had been developed to deal with the kite

flying rawinsonde measurement (Mabey 2001; Welsch 2002). It includes the calculation

of modified refractivity and the estimation of bulk method. Professor Guest further

revised it and provided as ‘workingkite_mat2006.m’ here to process these datasets.

A. SEA SURFACE HEIGHT CORRECTION As the kite was freely released near the sea surface, an estimation of rawinsonde

height above the sea surface was recorded along time. This height series is used to

correct the pressure measurement, that is, to refer the vertical distribution of temperature

and humility to the sea surface.

Figure 4 shows the correction of sea surface height for dataset ‘060120_1904z’.

The blue line is the rawinsonde-measured pressure, in term of height, and the magenta

line indicates the sea surface. It is seen that rawinsonde-measured pressure tends to

decrease (heighten) over time.

Figure 4 Sea surface height correction.

B. DATA FILTERING The second step of the Matlab program is to create a bad data file, that is, to filter

out unreasonable measurement. An easy assumption is to see all in-situ measurement

reflecting real atmospheric environment; hence, all measurement would be used except

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the set-up stage (first few minutes) and final stage (last few minutes), which have no sea

surface height record to correct vertical position. On the other hand, Professor Guest

pointed out that the shadow effects of R/V Point Sur body should be important since kite

was flying in downwind portion of R/V Point Sur. Each descending path should be

affected more significantly as closed to vessel.

Here, two scenarios for bad data filtering are applied here (a) only remove first

and last few minutes, and (b) remove every descending path from half way to first few

seconds close to sea surface. Figure 5 shows two different scenarios to remove bad data.

The discontinuity of blue point in Figure 5b indicate the data been filtered.

Figure 6 compares the data distribution of a general case with filtering scenarios

(a) and (b). In Figure 6a, a bunch between 5 to 10 m is clearly observed in the potential

temperature panel; the same feature does not disappeared in Figure 6b with a more proper

data filtering. Furthermore, it is observed in almost every case. This suggests that the

potential temperature bunch just above sea surface is a natural feature according to in-situ

measurement. And, since scenario (b) is a more proper filtering, only the result form

scenario (b) filtering is discussed hereafter.

C. AVERAGE PERIOD

Due to the meteorological variance within one dataset, the data averaging period

should been picked according to the atmosphere condition. This study separates the

average period mainly based on the wind speed and direction; except the dataset

‘060123_2226z’, very dry humility was measured, and additional average period is

selected.

D. BULK METHOD APPROXIMATION

The final step of the Matlab program is to estimate the temperature at sea surface,

at the sea surface layer height, and the humility at the surface layer height for computing

the bulk method. The estimation of humility at sea surface is unnecessary since it was

suggested very close to 100%. According to the hourly bucket measurement of the sea

surface water temperature, the sea surface temperatures for four datasets are 12.8 Co ,

13.9 Co , 13.3 Co , and 13.1 Co , respectively. The constant sea surface height, 20 m, is

used here to estimate the temperature and humility.

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Figure 5 Data filtering of ‘060120_1904z’ dataset with scenarios (a) only remove set-up

and final stages, and (b) remove the shadow effects of vessel body.

(b)

(a)

10

Figure 6 Vertical data distribution of same average period with data filtering scenarios (a)

and (b).

(b)

(a)

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IV. RESULTS

A. DATASET ‘060120_1904Z’ The rawinsonde measurement of this dataset is from 1916UTC to 2057UTC 20

January 2006. At that time, the meteorological condition was relatively stable.

Temperature remained constant above 20 m, while humility slightly decreased as higher.

The wind direction consisted at 330 degree, and the wind speed changed between 8 m/s.

Hence, in this dataset, the average periods were divided according to wind speed.

The result from the data processing of Part III is shown as Figure 7. The upper

panel displays the PTU measurement against wind condition for whole dataset. The

vertical lines separate the average periods. Figure 7a-d show the measured temperature

and humility and the computation of modified refractivity for each average period. The

solid line suggests the bulk method approximation.

Compared with bulk method, the temperature profile is generally in a good

agreement with the exponential approximation, except the bunch around 5-10 m, as

mentioned earlier. On the other hand, the humility profile does not agree well with the

bulk method suggestion because of the high humility close to sea surface is rare

measured.

The bulk method suggests that the evaporation duct is at around 12 m for all four

average periods. But according to in-situ measurement, no strong evidence shows there

were a evaporation duct existed. It is also evident that the wind speed has no significant

effect on the evaporation duct height.

B. DATASET ‘060121_1938Z’ This result (see Figure 8) is in a very similar meteorological condition as previous

dataset. The wind speed is higher at 8 to 12 m/s, and the wind direction changes between

320 to 340 degrees. The average periods are selected based on the wind direction.

Again, temperature profiles agree better than humility profiles; the sea surface

temperature bunch is still observed.

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However, it is weak evident that there was evaporation duct in Figure 8a and

Figure 8b. Although, the surface duct height should be at 4 m, which was lower than

suggested 9 m.

C. DATASET ‘060123_2226Z’ The dataset of 23 January is the most interesting measurement among all.

Increasing temperature and very dry humility was measured above 100 m. Moreover, the

air temperature was significantly higher than the bucket measured sea surface

temperature, which was 13.3 Co .

The result is shown as Figure 9. Different from other figures, the height axis was

set to 180 m in order to display the atmospheric features above 100 m. Depending on the

humility time series, the average periods were selected as small variances and large

variances. The temperature profiles fit properly. The sea surface temperature bunch is

still seen. Only Figure 9d, the extreme humility variance average period, had a better

agreement in humility profile.

Figure 9a and Figure 9b obviously suggested no evaporation duct. On the other

hand, Figure 9b had a very strange modified refractivity profile from 0 to 20 m. There

seems to be an evaporation duct from 8 to 14 m, but not under 8 m. Figure 9d had no

surface duct, but it showed a different duct type from 80 to 150 m, which was not

discussed in this study.

D. DATASET ‘060125_2043Z’ On 25 January, the sea surface temperature was still lower than the air

temperature at 13.1 Co (see Figure 10) as well as previous dataset, ‘060123_2226z’. It

was hard to tell this feature was cause by local weather system or the lower latitude.

The significant result here is Figure 10d. A strange shift below 10 m in both

temperature and humility, and caused an evaporation duct-like shape in modified

refractivity profile, which agreed with bulk method suggested height. This high

temperature, low humility feature seems be consisted with the wind direction shift at a

sea surface measurement period.

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Figure 7 The result of dataset ‘060120_1904z’. (a)-(d) are different average periods, blue

dot indicates in-situ measurement, magenta circle mean value, black solid line the bulk method, and black circle suggests the theoretical evaporation duct height.

(b)(a) (d)(c)

(a) (b)

(c) (d)

14

Figure 8 The result of dataset ‘060121_1938z’. Similar format as Figure 7.

(c) (d)(a) (b)

(a) (b)

(c) (d)

15

Figure 9 The result of dataset ‘060123_2226z’. Similar format as Figure 7.

(c) (d)(a) (b)

(a) (b)

(c) (d)

16

Figure 10 The result of dataset ‘060125_2043z’. Similar format as Figure 7.

(c) (d) (a) (b)

(a) (b)

(c) (d)

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V. CONCULSION

The objective of this study was to analyze the kite flying rawinsonde dataset to

estimate the evaporation duct height. Compared the in-situ measurements and theoretical

suggestions, several features were shown. First, the temperature profile tended to agree

with bulk method better than humility. Temperature bunch below 10m was observed

almost everywhere. And no humility was measured higher than 85%; the higher humility

was seen at the high altitude instead of at sea surface.

Theoretical estimations of duct height were 13 m, 9 m, 20 m, 10 m, respectively.

There was no significant variance within each 2-hr dataset, except the dry air case (Figure

9b). Unfortunately, most in-situ observations did not claim the existence of evaporation

duct, which was opposite to general acceptance. Only few examples showed weak

evidence of evaporation duct height, but at least one of them might be resulted from bad

data. The observed evaporation duct might suggest that bulk method could overestimate

the evaporation duct height.

The main factor of this failure in field measurement should come from the

measurement disability or inexistence of increasing to saturated humility near sea surface.

Furthermore, the surface temperature bunch was shown from time to time. Hence, a

question rises here. Would this vertical structure of temperature and humility from 0 to 5

m be real? If not, what factors cause this surface features?

Several points should be considered for further studies. First, the accuracy of

visual estimation is relatively low. It is generally accepted that this accuracy is only

within the order of 10 m. Hence, current sea surface height correction might not a good

approach. As been suggested, the result shows that the setting of flying kite with

rawinsonde sensor could not a good method to measure the near sea surface PTU (Lana

2004; Kuehn 2002). New measurement method should be developed. One possible

imagination here was to determine the evaporation duct directly, which to measure PTU

indirectly. That was, it might be possible to apply portable microwave sensor to measure

the evaporation duct height analogous to applying sonar to determine the acoustics sea

surface duct depth.

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ACKNOWLEDGMENTS

I would like to thank Professor Guest for his effort on revising the Matlab

program, and kindly providing it for this project application. He also carefully reviewed

the project results and discussed them with me in person. Further thanks must to be

extended to previous projects in kite flying topic. They were well produced and provided

good trail to follow and refer.

I also appreciate Professor Collins for his lead during the operational cruise. I am

grateful to Lt Young and LT Vancas for being on watch, and to LT Long for shearing a

cabin in cruise. All these sum to a wonderful learning experience for OC3570.

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APPENDIX HISTORICAL REVIEW OF SCIENTIFIC KITE

Opposite to my previous proposal, kite flight had been utilized in Meteorological

research quite frequently and for more than 200 years. A timeline of scientific kite flight

is summarized as following. It is referred to various sources (Blair 1909; Gregg 1927;

Ealsley et al. 1998; Robinson 2003).

A. EARLY AGE 206 B. C. Han Sin, a Chinese general in Han Dynasty, was considered as the first

made and flew the kite.

1749 Alexander Wilson and Thomas Melville, students of University of Glasgow, Scotland, first flew kite for weather experiments; it was 30 years before the first balloon flight, and 150 years before the first aeroplane.

1752 Benjamin Franklin, at Philadelphia, PA, first flew kite for atmospheric electricity experiment.

1822-7 Captain Sir William E. Parry and Reverend George Fisher, near Igloolik in the Canadian Arctic, measured the lapse rate using a paper kite with thermometer.

1825 Professor Alexander Wilson, in England, recalled and published the first kite experiment (1749) after almost 70 years.

1835 Franklin Kite Club, Philadelphia, was formed in the purpose of flying kites for scientific experiments; it included many scientists, such as James P. Espy, Sir Francis Reynolds, W. R. Birt, etc.

1836-7 Admiral Black, from HMS Terror, raised a kite to 1200 feet and obtained free air temperatures over the ocean.

1847 Sir Francis Reynolds and W. R. Birt, the Kew Gardens Observatory, England, developed a six-sided meteorological kite to raise and lower weather instruments using a pulley system.

1883 E. D. Archibald, British Meteorologist, studied the mechanics of kite flight and introduced the use of high-tensile piano wire lines to replace kite string.

1887 E. D. Archibald first flew kite to take aerial photographs.

B. GOLDEN TO ABANDON 1893 Ballonsondes was first used to carry recording instruments into the stratosphere.

1893 Lawrence Hargrave, Australia, invented the box (cellular) kite; Charles F. Marvine studied the mechanics and equilibrium of kite flight and modified the box kite to the Marvine-Hargrave kite, which was also called ‘workhorse’.

1894 William A. Eddy invented the Eddy kite, which was original from a Malay kite and was modified to equal dimensions; latter, in the Blue Hill Observatory, Boston, he succeeded to launch the first automatic recording thermograph using kite.

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1895 William A. Eddy, in the Blue Hill Observatory, Boston, succeeded to launch the first automatic recording meteorograph (temperature, pressure, and humidity) using kite.

1896 The International Conference on Aeronautics, in Paris, established ‘international days’, usually the first Thursday of every month, to coordinate kite and balloon flights in all countries.

1898 The Weather Bureau of U.S. Agricultural Department established 17 sites in east of the Rocky Mountains to fly kites on a daily basis until 1933; under these operations, government specifications for the kite design, materials used, launching and land, sites for launching, etc., were developed.

1898 At the Blue Hill Observatory, Boston, MA, the highest single kite altitude record (3,812 m) was established.

1898-1903 W. H. Dines, off the west coast of Scotland, provided strong impetus for the kites-from-boats technology and for studying the atmosphere over the ocean.

1906 George R. Lawrence, in San Francisco, CA, took the photo ‘San Francisco in Ruins’ by a ‘captive airship’, which was actually a set of kites.

1913 Sir G. I. Taylor, from the streamer ‘Scotia’, flew kites to study the generation of the intense fog banks off the coasts of Newfoundland and Nova Scotia in the northern Atlantic.

1919 At the Lindenberg Observatory, Germany, the highest multiple kite (a train of eight kites) altitude record (9,740 m) was made.

1933 The systemic kite measurements were ended due to the drawback of labor intensive and expensive, as well as the advent of inexpensive balloonsondes and aircraft.

C. RESENT MEASUREMENTS 1980s late The Cooperative Institute for Research in the Environmental Sciences of

the University of Colorado started to use kites for atmospheric research again.

1998 A state-of-the-art kite measurement was reported by Balsley et al. (1998).

21

LIST OF REFERENCES

Babin, S. M., G. S. Young, and J. A. Carton, 1997: A new model of the oceanic evaporation duct. J. Appl. Meteorol., 36, 193-204.

Balsley, B. B., M. L. Jensen, and R. G. Frehlich, 1998: The use of state-of-the-art kites for profiling the lower atmosphere. Boundary-Layer Meteorology, Dordrecht, The Netherlands, 87, 1-25.

Blair, W. R., 1909: The exploration of the upper air by means of kites and balloons. Proc. Am. Philos. Soc., 48, 8-33.

Collins, C. A., P. Guest, cited 2006: OC/MR 3570 Operational oceanography. [Available online at http://nps.blackboard.com/webapps/portal/frameset.jsp?tab=courses&url=/bin/common/course.pl?course_id=_2478_1.]

Fairall, C. W., E. F. Bradley, D. P. Rogers, J. B. Edson, and G. S. Young, 1996: Bulk parameterization of air-sea fluxes for Tropical Ocean-Global Atmosphere Coupled-Ocean Atmosphere Response Experiment. J. Geophys. Res. (C Oceans), 101, 3747-3764.

Gregg, W. R., 1927: Meteorology and its application to flying. Ann. Am. Acad. Pol. Soc. Sci., 131, 107-117.

Guest, P., 2006: The evaporation duct. MR3419 Class Note, 31 pp.

Kuehn, D., 2002: Evaporation duct heights derived from rawinsonde kite profiles and the bulk method. NPS OC3570 Project Report, 12 pp.

Lana, A. D., 2004: Evaporation duct height calculations using experimental radiosonde configuration to collect near surface humility, temperature, and pressure data. NPS OC3570 Project Report, 11 pp.

Mabey, D. L., 2001: Evaporation duct profile comparisons using kites and bulk methods. NPS OC3570 Project Report, 12 pp.

______, 2002: Variability of refractivity in the surface layer. M.S. thesis, Dept. of Oceano., Naval Postgraduate School, 66 pp.

Robinson, M., cited 2003: Meteorological Kites: Scientific Kites of the Industrial Revolution. [Available online at http://mysite.verizon.net/~vze26db3/Miscellaneous/meteorological_kites.htm.]

Vaisala, 1998: Technical information – RS80 radiosonde. [Available online at http://www.vaisala.com/DynaGen_attachments/Att2745/2745.pdf.]

Welsch, C. A., 2002: Evaporation duct: A comparison study between bulk methods and kite profiles. NPS OC3570 Project Report, 9 pp.