Magdalena D. Anguelova, Justin P. Bobak, William E. Asher, David J. Dowgiallo, Ben I. Moat, Robin W. Pascal, Margaret J. Yelland 16th Conference on Air-Sea.

Magdalena D. Anguelova, Justin P. Bobak, William E. Asher, David J. Dowgiallo, Ben I. Moat, Robin W. Pascal, Margaret J. Yelland 16th Conference on Air-Sea Interaction 11–15 January 2009, Phoenix, Arizona Validation of satellite-based estimates of whitecap coverage: Approaches and initial results Validation of satellite-based estimates of whitecap coverage: Approaches and initial results Naval Research Laboratory, Washington, DC Applied Physics Laboratory, University of Washington, Seattle, WA National Oceanography Centre, Southampton, UK

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Long-term goal Improve Sea Salt Source Function parameterization by modeling the high variability of whitecap coverage or u – wind speed (u 10 or u * ?)  T – atmospheric stability (= T air – T sea ) X – wind fetch d – wind duration U cur – water currents T s – sea surface temperature S – salinity C k – concentration, type (k) of surface active materials

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. The first step Framework  Improve existing or develop new models;  Extensive database: W + various factors;  Measurements: W + various factors;  Existing W measurements:  Photographs/video images;  Insufficient for extensive database;  Alternative approach: From satellites to get  global coverage;  wide range of meteo & environ conditions; Whitecap variability:

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Daily map of W Daily data (swath) for entire 2006, months of 2007 and 2008

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al.  Retrieving W (changes in T B at microwave frequencies):  Using parts of WindSat forward model (v.1.9.6) ;  Rough surface emissivity, e r ;  Atmospheric variables  atm. correction;  Foam emissivity model, e f ;  Independent sources for the input variables:  T B from WindSat;  V, L from SSM/I or TMI;  U 10 from QuikSCAT, SSM/I, or GDAS;  T s from GDAS;  S = 34 psu;  Improvements over the published feasibility study:  More physical models for e r, e f, and atm. corr.;  Independence of the variables;  Minimization of errors. Satellite-based foam fraction W

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Validation  Insufficient ground truth values:  Data collection:  Slow and expensive;  Sporadic and non-systematic;  Limited range of conditions;  Fewer in situ-satellite matches in time and space;  Different principles of measurement:  Reflectivity in the Visible (photographic/video);  Emissivity in the Microwave (radiometer);  Various approaches to circumvent difficulties.

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Validation approaches  Historical database of in situ values;  Wind speed formula;  Ship-borne measurements;  Air-borne measurements. There are questions and issues with each approach.

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. In situ historical data by type

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. 10 GHz seems good

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. All Frequencies, H pol

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Satellite vs Wind formula  W sat more uniform by latitude;  High lat higher W. March, 2007, 0.5 deg x 0.5 deg Satellite, 18.7 GHz, H pol.  Wind speed formula:  Monahan and O’Muircheartaigh, 1980:  U 10 from QuikSCAT or GDAS;  Time/space matched with WindSat;

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Difference maps  W = W sat – W mod 18H 10H +  W = 0.041% ; -  W = 0.44% +  W = 0.61% ; -  W = 0.63%

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al.  Experiment HiWASE on Polarfront ship positioned at Station M;  UK colleagues: Margaret Yelland, Ben Moat and Robin Pascal;  Long-term (Sep 2006 to Sep 2009) measurements of W and other variables;  In situ data for W;  Two cameras, daylight restrictions (Mar-Oct);  Photographic data processed at 3 intensity thresholds with AWE technique;  Temporally-averaged values in a time window around or close to WindSat pass time;  The effect of time window (minutes to 3 hours) was investigated;  WindSat data for W:  Closest pixel to lat/lon position of each in situ point;  WindSat low resolution (50 km x 71 km);  Three frequencies (10, 18, and 37 GHz), H pol.;  The effect of averaging over NºxNº box (e.g., 1/2ºx1/2º) was investigated;  In situ data for W;  Two cameras, daylight restrictions (Mar-Oct);  Photographic data processed at 3 intensity thresholds with AWE technique;  Temporally-averaged values in a time window around or close to WindSat pass time;  The effect of time window (minutes to 3 hours) was investigated;  WindSat data for W:  Closest pixel to lat/lon position of each in situ point;  WindSat low resolution (50 km x 71 km);  Three frequencies (10, 18, and 37 GHz), H pol.;  The effect of averaging over NºxNº box (e.g., 1/2ºx1/2º) was investigated; Polarfront ship data

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Polarfront to historical in situ

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. WindSat matched to Polarfront

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. In situ and satellite winds 180-min time window

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. RASSI Experiment  RAdiometry and Sea Surface Imagery (2007):  North Atlantic, Gulf of Mexico (Hurricane Dean);  High altitude: 6.7 km (20,000 ft);  Clear sky to partial cloud cover;  Radiometric measurements:  APMIR ( Airborne Polarimetric Microwave Imaging Radiometer )  Channels available (GHz): 37VH34, 19VH34, 6.6VH, 6.8VH, 7.2VH (some data at channels at 10.7 and 22.235);  Footprint roughly 1x2 km from on 19 and 37 GHz;  Video measurements:  High resolution video camera;  Field of view of 159 m by 119 m.

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. RASSI Experiment  RAdiometry and Sea Surface Imagery (2007):  North Atlantic, Gulf of Mexico (Hurricane Dean);  High altitude: 6.7 km (20,000 ft);  Clear sky to partial cloud cover;  Radiometric measurements:  NRL’s APMIR ( Airborne Polarimetric Microwave Imaging Radiometer )  Channels available (GHz): 37VH34, 19VH34, 6.6VH, 6.8VH, 7.2VH (some data at channels at 10.7 and 22.235);  Footprint roughly 1x2 km from on 19 and 37 GHz;  Video measurements:  High resolution video camera;  Field of view of 159 m by 119 m.

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. RASSI Experiment  RAdiometry and Sea Surface Imagery (2007):  North Atlantic, Gulf of Mexico (Hurricane Dean);  High altitude: 6.7 km (20,000 ft);  Clear sky to partial cloud cover;  Radiometric measurements:  NRL’s APMIR ( Airborne Polarimetric Microwave Imaging Radiometer )  Channels available (GHz): 37VH34, 19VH34, 6.6VH, 6.8VH, 7.2VH (some data at channels at 10.7 and 22.235);  Footprint roughly 1x2 km from on 19 and 37 GHz;  Video measurements:  UW’s High resolution video camera;  Field of view of 159 m by 119 m.

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Hurricane Dean flight KSYP #6 #7 #42003 #42055 3FPQ9 #1 #2 #3 #4 #5 Buoy Ship RASSI

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. RASSI foam vs historical in situ

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. RASSI vs WindSat pairs Wind dependent AB factor 11 to 15 using Monahan & Woolf (1989) parameterizations for A+B and A

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al.  Difficulties in validating satellite-based foam fraction;  Amount of data;  Conditions covered;  Principle of measurements;  Compensate using different approaches:  Historical in situ data;  Wind speed formula;  Direct validation with APMIR/video data;  Direct validation with ship data;  Results:  Ball-park in magnitude compared to in situ data;  More uniform latitudinally than wind formula;  Direct validation shows:  underestimate at low winds and  over estimate at high winds;  How much of this result is correct?  Future work:  More match-ups of in situ and satellite data;  Indirect validation (with other variables, not directly W);  Tuning of the satellite-based algorithm. Summary  Compensate using different approaches:  Historical in situ data;  Wind speed formula;  Direct validation with ship-borne photographic data;  Direct validation with air-borne video data;  Results:  Ball-park in magnitude compared to in situ data;  More uniform latitudinally than wind formula;  Direct validation shows:  W sat overestimate at low winds and  Relatively good estimate at high winds;  Future work:  More match-ups of in situ and satellite data;  Indirect validation (with other variables, not directly W);  Tuning of the satellite-based algorithm.

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Additional slides

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Match-up issues  Only 4 full swaths:  from GDAS,  Large temporal mismatch for other GDAS match-ups;  Chunks of swaths for most passes:  due to QuikSCAT passes CROSSING the WindSAT passes;  Reflects on the number of samples available for low and high latitudes. Sample count

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Samples available for 1 month Sample count  High latitudes with high winds are under represented.

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Frequency and polarization dependence  Understanding the info each freq and pol gives for W :  Research foam skin depth;  The effect of foam thickness on the skin depth and foam emissivity;  The results could be important for gas exchange (CO 2 and other gases);  Combining suitable freqs and pols in one “oceanographically” representative W;

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Compare to in situ A+B data

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Low freqs close to in situ A+B

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. 18 GHz  Very similar to 23 GHz  Atmosphere influence?

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. All frequencies, V pol

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. All Frequencies, H pol

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Biases  Pair binned data;   W = W sat -W ins ;  Plot bins with high count. Freq (GHz), H pol. 6 10 1823 37

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Satellite vs Wind formula March, 2007 0.5 deg x 0.5 deg Wind speed formula Satellite, 10.7 GHz, H pol.

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Ship cruises  Two ship cruises  in 2006 and 2007  Ian Brooks and Margaret Yelland, UK:  Data for:  Foam fraction – direct validation;  Sea-salt aerosol flux – indirect val.  Matchups with WindSat data  Spatial and temporal;  Video data availability for about 10 points;  Cruise data still processed

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. In situ and satellite winds (raw)

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Binned by wind speed

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Compare in situ – satellite pairs

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. RASSI measuring configuration

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Wind speed conditions

16th Air-Sea Interaction Conference, 14 January, 2009, Anguelova et al. Wind vector field during the flight

Magdalena D. Anguelova, Justin P. Bobak, William E. Asher, David J. Dowgiallo, Ben I. Moat, Robin W. Pascal, Margaret J. Yelland 16th Conference on Air-Sea.

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Presentation on theme: "Magdalena D. Anguelova, Justin P. Bobak, William E. Asher, David J. Dowgiallo, Ben I. Moat, Robin W. Pascal, Margaret J. Yelland 16th Conference on Air-Sea."— Presentation transcript:

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Magdalena D. Anguelova, Justin P. Bobak, William E. Asher, David J. Dowgiallo, Ben I. Moat, Robin W. Pascal, Margaret J. Yelland 16th Conference on Air-Sea.

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Presentation on theme: "Magdalena D. Anguelova, Justin P. Bobak, William E. Asher, David J. Dowgiallo, Ben I. Moat, Robin W. Pascal, Margaret J. Yelland 16th Conference on Air-Sea."— Presentation transcript:

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