Improved High Wind Retrievals from ASCAT Wind Vector

Improved High Wind Retrievals from ASCAT Wind Vector Measurements Seubson Soisuvarn 1, Zorana Jelenak 1, Paul Chang 2 (GOVERNMENT PRINCIPAL INVESTIGATOR), Qi Zhu 3, and Khalil Ahmad 3 1 UCAR, 2 NOAA/NESDIS/STAR, 3 Perot 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 Operational ASCAT Cumulative distribution curve New ASCAT Science: • Provide highest quality Satellite Ocean Surface Vector Wind (OSVW) data in near real time (NRT) • Produce Quik. SCAT type ocean surface vector wind products from foreign scatterometer measurements Wind direction scatter plot diagram Benefit: Operational ASCAT • National Weather Service forecasters and their customers: – Emergency planners – General public (recipients of weather warnings) • International users • Marine commerce Cumulative distribution curve New ASCAT Measurement Geometry and Wind Data Processor Input values Pre-processing σ0 EUMETSAT aft mid 64° Inversion using CMOD 5 n GMF 52° Quality Control 27° 64° 37° fore Wind speed across swath biases aft 27° Input NWP collocation (NOAA’s GFS) Operational Users Ambiguity Removal 52° mid 2 m/s reference line Output Wind Vector KNMI Research & Validation fore 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 (CMOD 5 n) is written in harmonic terms: Assumption is that B 1 and BHersbach, correctly. 2 are modeled et al. , J. Geophys. Res. (2007) ASCAT/Quik. SCAT match-ups show B 0 is biased high at high wind speeds Aircraft experiment (IWRAP GMF) B 0 is written in the form: 2 m/s reference line New ASCAT Operational ASCAT Fernandez, et al. , J. Geophys. Res. (2006) New ASCAT Operational ASCAT High Wind Speed B 0 ; Incidence: 50 deg B 0 vs wind speed Aircraft experiment (IWRAP) Gale-Storm force wind radii (new ASCAT) U 10 Nsat =61. 5 m/s N-AWIPS Example New B 0 CMOD 5 n Quik. SCAT U 10 Nsat =61. 5 m/s Conclusions • New ASCAT GMF was developed Comparision of B 0 CMOD 5 n B 0 • B 0 was modified for high wind speeds by matching IWRAP GMF high wind trend and correcting for observed B 0 biases • New ASCAT high wind speed retrievals compare better to Quik. SCAT • Bias and RMS wind speed errors are improved • New ASCAT wind speed retrievals are still biased low but resultant biases are smaller http: //manati. orbit. nesdis. noaa. gov/cgi-bin/ascat. Test_cur_25 km. pl New B 0 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 Wind Speed (m/s) Center for Satellite Applications and Research (STAR) Review 09 – 11 March 2010