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DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 


Near-surface Measurements In Support of Electromagnetic Wave Propagation 

Study 

Qing Wang 

Meteorology Department, Naval Postgraduate School 
Monterey, CA 93943 

Phone: (831) 656-7716, Fax: (831) 656-3061 email: qwang@nps.edu 
Award # N0001413WX21166 


LONG-TERM GOAL 

The long-term goal of this project is to improve environmental prediction for electromagnetic wave 
propagation forecast. 

OBJECTIVES 

The objectives of this project are 1) to characterize atmospheric conditions resulting in nonstandard 
EM propagation in the atmospheric boundary layer during Trident Warrior 2013 field campaign; 2) to 
support NPS ongoing research on numerical simulations of EM propagation using AREPS and 
COAMPS single column model. 

APPROACH 

Basic approaches of the project involves measurements of the NPS Marine-Air-Sea Flux (MASFlux) 
buoy during Trident Warrior 2013 (TW13) field campaign and analyses of the measurements to reveal 
the interplay between surface fluxes, surface layer mean profiles, surface waves, and upper ocean 
temperature. This analyses will be aided by other measurements from TW13 including rawinsonde 
profiles and measurements from other platforms. 

The TW13 data will be used to initialize/evaluate planned COAMPS single column model simulations 
in an effort to improve predictions of the near surface thermodynamic profiles as input to EM 
propagation modeling. 

Qing Wang is responsible for the overall project and part of the TW13 data analyses. NPS Ph. D 
student, LCDR Corey Cherrett, will make more in-depth data analyses. Mr. Dick Lind was responsible 
for buoy preparation and field deployment. 

WORK COMPLETED 

1. Completion of the Trident Warrior 2013 field experiment in July 2013. NPS team was involved in 
flux buoy deployment, real time AREPS simulation, rawinsonde launches, and kite-based 
measurements (Peter Guest). Real-time data QC and analyses were made to support EM modeling 
and sampling efforts in addition to UAV operation. 


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30 SEP 2013 2 ' REPORT TYPE 

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Near-surface Measurements In Support of Electromagnetic Wave 
Propagation Study 

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Naval Postgraduate School,Department of 

Meteorology,Monterey,CA,93943 

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2. Preliminary data analyses on NPS buoy measurements as well as rawinsonde measurements made 
by NPS (Peter Guest) and NSWC (Kate Horgan). These analyses involves data QC efforts as well 
as efforts to understand the general EM propagation conditions during the TW13 field campaign. 

3. Participated in the TW13 workshop and presented initial results of NPS buoy measurements. Also 
participated in group discussions for plans of future collaborative work. 

RESULTS 

TW13 NPS measurements overview: During TW13, NPS made extensive measurements with flux 
buoys, rawinsondes, and shipboard instruments. Figure 1 summarizes the time periods of these 
measurements together with all rawinsonde soundings and kite soundings made by NSWC (Kate 
Horgan) and NPS (Peter Guest). Three periods of buoy measurements were made on July 14, 15, and 
16, respectively. The locations of the soundings and buoy measurements are given in Figure 2. The 
measurements on July 14 and 16 were very close to the coast of Virginia Beach, while the flux buoy 
was about 50 km offshore on July 15. Figure 3 shows the variations of four levels of temperature 
measurements near the surface and three levels in the water on all three days. The surface layers on 
these three days had rather different thermal stratifications with July 14 and 16 having weakly stable 
and stable conditions, and July 15 having offshore unstable conditions. The table insert shown in 
Figure 3 summaries the air-sea temperature difference from all three periods of measurements to 
quantify the sign and magnitude of the thermo stability. It is also seen from all subplots of Figure 3 
that strong temporal variability was observed on each time period, especially on July 14 and 16, both 
measurements were made close to the coast. Such observed temporal variation is likely a combination 
of temporal and spatial variation as the buoy was also drifting with the current, particularly on July 16. 
Our future analyses will examine how this temporal and spatial variability may affect the surface flux 
parameterization. 

Near-surface vertical profiles and deviation from Monin-Obukhov similarity: Measurements from 
the NPS flux buoy provided an unique opportunity for examining the vertical profiles of temperature, 
humidity, and wind within several meters of the sea surface. Figure 4 shows the hourly averaged near¬ 
surface profiles from 15 July, 2013 with unstable thermal stratification in the offshore region. The 
potential temperature profile and the top water temperature profiles are plotted on the same figure to 
illustrate the coupled evolution on both sides of the interface. We can clearly see the atmospheric 
adjustment to the changing water temperature from the evolution of both air and water temperature. 

The largest gradient between the warm sea and the relatively cold air appear to be below 0.38 m above 
surface, which is the lowest level of temperature measurements on the buoy mast. We also find that the 
thermo stability appears to be similar between 0.38 m and 1.54 m, but further decrease above 1.54 m. 
Figure 4b shows the wind speed variability with height. Three of the profiles (one-hour average 
centered at 15:16, 16:16, 17:16 UTC time) show signs of wind reversal, where the wind speed at 1.8 m 
is higher than that from 3.5 m, a clear deviation from the log-wind profile or its variations in stability 
affected conditions. The evolution of the moisture profiles in specific humidity and relative humidity 
are shown in Figure 4c and 4d. The strong temporal/spatial variability shown here will be 'blended' 
with the measurements from higher above to provide a full profile for further evaluation of their impact 
on EM propagation. 


IMPACT/APPLICATIONS 

Near-surface temperature and water vapor variability are crucial to EM propagation close to the surface and 
yet is normally not directly sampled from in situ measurements. The NPS MASFlux buoy has the unique 


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capability that provides concurrent measurements of both near-surface profiles and the surface momentum 
flux. With further analyses, this dataset should provide more insights on the flux-profile relationship in the 
lowest several meters over the ocean and insights on flux parameterization in complex coastal regions. 


RELATED PROJECTS 

Related project is the ONR Trident Warrior 2013 exercise. 


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Figure 1. Timeline of all NPS-related TW13 measurements from the R/VKnorr between 14-20 July, 

2013. 


37.2 
37.1 

37 

O 36.9 
S 36.8 

3 

5 36.7 
36.6 
36.5 
36.4 

36.3 

Figure 2. Locations of all soundings and NPS MASFlux buoy during TW13. 


TW13 Soundings and Buoy Locations 



4 























Temperature & SST (°C) Temperature & SST (°C) 


TW13 IMPS Drifting Flux Buoy f 20130716 


TW13 N P S Dr ifti n g FI u x Buoy, 20130714 



_ 29 


s 28 


-T4 {3.07 m) 
-13(1.54 m) 

T2 (0.77 m) 

-T1 (0,33 m) 
SST2 ( -0.16 m) 
SST3 (-0.41 m) 


-L^ /J 


■^A^Kv 




i 


16:00 17:00 

Time UTC) 


TW13NPS Drifting Flux Buoy, 20130716 



Date 

SST 

T-air 

A(SST-air) 

7/14/2013 

25.4 

26 

-0.61 

7/15/2013 

27.4 

25.9 

1.47 

7/16/2013 

24 

25.3 

-1.28 


Figure 3. Variation of air and top water temperature from the three measurement periods of 
MASFlux during TW13. The table insert give a summary of the mean SSTfrom the top water 
sensor at ~3 cm below surface and the mean air temperature from the lowest sensor at 0.38 m above 

water line. 


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Height (m) Helfltrt(m) 


2013071S 


2013071S 



#SSST < K > ws [m s" 1 ) 

2013071S 2013071S 




Figure 4. Hourly averaged near-surface profiles of (a) potential temperature and water 
temperature; (b) wind speed; (c) specific humidity; and (d) relative humidity. The legend shows the 
middle of the hour-long period during which the averages were made. 


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