Improved High Wind Retrievals from ASCAT Wind Vector Measurements

1. CMOD5n B0 Input σ0 values Pre-processing aft EUMETSAT vs wind speed Inversion using CMOD5n GMF Cumulative distribution curve Cumulative distribution curve New B0 mid 2 m/s reference line 2 m/s reference line U10Nsat =61.5 m/s B0 Quality Control 64° 37° New B0 37° 27° fore 52° aft Input NWP collocation (NOAA’s GFS) 27° Operational Users 52° Ambiguity Removal mid 64° Output Wind Vector fore KNMI Research & Validation U10Nsat =61.5 m/s Wind Speed (m/s) Hersbach, et al., J. Geophys. Res. (2007) Fernandez, et al., J. Geophys. Res. (2006) New ASCAT Operational ASCAT B0 vs wind speed Aircraft experiment (IWRAP) Gale-Storm force wind radii (new ASCAT) CMOD5n QuikSCAT Improved High Wind Retrievals from ASCAT Wind Vector Measurements Seubson Soisuvarn1, Zorana Jelenak1, Paul Chang2(GOVERNMENT PRINCIPAL INVESTIGATOR), Qi Zhu3, and Khalil Ahmad3 1UCAR, 2NOAA/NESDIS/STAR, 3Perot Systems Wind speed scatter plot diagram • Requirement: • Weather & Water: • Increase lead-time and accuracy for weather and water warnings and forecasts • Improve predictability of the onset, duration, and impact of hazardous and severe weather and water events • Increase development, application, and transition of advanced science and technology to operations and services • Integrate local, regional, and global observation systems into NOAA’s weather and water services to increase the collaboration between NOAA and external environmental partners • Reduce uncertainty associated with weather and water forecasts and assessments • Enhance environmental literacy and improve understanding, value, and use of weather and water information and services • Marine Transportation: • Support decisions in aviation, marine, and surface navigation • Research, develop, and deploy more accurate and timely information products • Science: • Provide highest quality Satellite Ocean Surface Vector Wind (OSVW) data in near real time (NRT) • Produce QuikSCAT type ocean surface vector wind products from foreign scatterometer measurements • Benefit: • National Weather Service forecasters and their customers: • Emergency planners • General public (recipients of weather warnings)‏ • International users • Marine commerce New ASCAT Operational ASCAT Wind direction scatter plot diagram New ASCAT Operational ASCAT ASCAT Measurement Geometry and Wind Data Processor Wind speed across swath biases Operational ASCAT New ASCAT Wind speed across swath RMS errors Stydy Approach • Scatterometer wind retrievals are dependent on the Geophysical Model Function (GMF) that relates backscatter to ocean surface wind fields • The ASCAT operational GMF (CMOD5n) is written in harmonic terms: • Assumption is that B1 and B2 are modeled correctly. • ASCAT/QuikSCAT match-ups show B0 is biased high at high wind speeds • Aircraft experiment (IWRAP GMF) B0 is written in the form: New ASCAT Operational ASCAT High Wind Speed B0 ; Incidence: 50 deg N-AWIPS Example Conclusions • New ASCAT GMF was developed • B0 was modified for high wind speeds by matching IWRAP GMF high wind trend and correcting for observed B0 biases • New ASCAT high wind speed retrievals compare better to QuikSCAT • Bias and RMS wind speed errors are improved • New ASCAT wind speed retrievals are still biased low but resultant biases are smaller Comparision of B0 http://manati.orbit.nesdis.noaa.gov/cgi-bin/ascatTest_cur_25km.pl Science Challenges:Novel techniques for improving resolution of C-band scatterometer measurements. Next Steps:Transitioning of OSVW measurements from foreign scatterometer missions into operations Transition Path:Experimental version of new STAR ASCAT product will be evaluated by users and disseminated to AWIPS and NAWIPS if approved