A New Satellite Wind Climatology from QuikSCAT, WindSat, AMSR-E and SSM/I

Transcription

1 A New Satellite Wind Climatology from QuikSCAT, WindSat, AMSR-E and SSM/I Frank J. Wentz (presenting), Lucrezia Ricciardulli, Thomas Meissner, and Deborah Smith Remote Sensing Systems, Santa Rosa, CA Supported By: NASA s Earth Science Division.Status of RSS s Satellite Inter-Calibration Project.New WindSat Dataset. Climate Trends in Winds Presented at: OVWST Annual Meeting, Annapolis, Maryland, May,

2 Engineering Climate Data Records: The Problem Large Volume: Over satellite-years of observations from Microwave Radiometers Microwave Imagers SSM/I: F, F, F F,F, F SSM/IS: F, F, F TMI AMSR-E and AMSR WindSat Microwave Sounders MSU: Tiros-N, NOAA,,,,,,, and AMSU: NOAA,,, and, Aqua, MetOP A Difficult Calibration: Each sensor has its unique set of problems Sensor pointing and S/C attitude errors Antenna pattern knowledge error Scan-dependent errors Sun intrusion and thermal gradients in Hot Load Emissive Antenna High Precision Required: Climate Variability is typically % of the Mean

3 Distinguishing Sensor Errors from RTM Errors: F GHz Same ΔTa (simulated minus measured) plotted versus different parameters Same color scale: ΔTa goes from -K to +K x Y=Wind, X=SST Sun intruding Into hot load Orbit Position, South Pole to South Poel,xX=Orbit number ( years) - - Sensor Calibration Error Diagnostics.. -. x Y=Vapor, X=SST RTM Error Diagnostics - Y=Wind, X=Vapor Y=Sun Polar Angle, X=Sun Azimuth Angle. x

4 Anomalous Signature in AMSR-E TA_mea minus TA_rtm Plots GHZ, Hpol. -. GHZ, Hpol GHZ, Hpol - GHZ, Hpol -. GHZ, Hpol GHZ, Hpol

5 Megahertz change to AMSR-E. GHz channel (i.e., use. GHz rather than.) GHZ, Hpol GHZ, Hpol. -. GHZ, Hpol GHZ, Hpol WindSat ( MHz) AMSR-E ( MHz) AMSR-E Adjusted - GHZ, Hpol -. GHZ, Hpol

6 WindSat Before Calibration GHZ, Hpol x x GHZ, Hpol x GHZ, Hpol..... x GHZ, Hpol... GHZ, Hpol x

7 WindSat After Calibration GHZ, Hpol x -. x x..... GHZ, Hpol GHZ, Hpol GHZ, Hpol GHZ, Hpol x x

8 Current Status of V Development F SSM/I, AMSR-E, and WindSat DONE!! Sensor Time Period Ascending de Times SSM/I F May v am ± minutes AMSR-E Jun Present : pm ± minutes WindSat Feb Present am ± minutes Remaining SSM/I and the F and F SSM/IS will soon follow New QuikSCAT Geophysical Model Function Incorporates V Calibration Standards F, AMSR-E, WindSat and QuikSCAT form the Backbone for the Satellite Wind CDR All data, both brightness temperature and ocean products, are freely available

9 Remote Sensing Systems WindSat Data Released April SST, different wind products, wind directions, vapor, cloud, and rain rates Wider swaths due to using both fore and aft looks First all-weather winds available

10 WindSat V Ocean Products For combining forward and aft observations: A very elaborate Optimum Interpolation use to directly map swath data to a fixed Earth grid. million pre-computer target weights to avoid in-line matrix inversions / degree (about km) Earth grid (reporting gird, NOT resolution) Resolution + Required Channels Product. GHz km. GHz km. GHz km. GHz km SST Wind speed no rain Wind speed through rain Wind direction Water vapor Liquid cloud water Rain rate

11 Combining Forward & Aft Observation Provides Wider Swath NRL WindSat RSS WindSat

12 New Winds-Through-Rain Product Rain-free WindSat All-weather WindSat Rain rate Satellite BUOY Wind Speed [m/s] Bias Standard Deviation Rain Rate WindSat all-weather algorithm QuikSCAT Ku no rain.... light rain mm/h.... moderate rain mm/h.... heavy rain > mm/h -....

13 Decadal Trends in Wind Speed Calibration methodology is designed to NOT affect trends in the observations Climate studies require an accuracy at the %/decade level or better. It is an outstanding question as to whether this is achievable.

14 Inter-Comparison of Satellite Wind Time Series F-F Wind. -. F-F Wind. -. F-F Wind. F SSM/I Problem -. F-F Wind. -.. F-F Wind F-F Wind F-F Wind F-F Wind F-F Wind F-F Wind F SSMI, F & F SSM/IS, WindSat, and AMSR-E -. Year AMSR-E minus WindSat?? -. Year

15 Inter-Comparison of Satellite Wind Time Series F-QuikSCAT Wind (m/s) F-QuikSCAT Wind (m/s) F-QuikSCAT Wind (m/s) F SSMI and QuikSCAT Ascending and descending? Year Year Year Ascending only Descending only

16 Recent Paper on Satellite Wind Time Series from Altimeters Global Trends in Wind Speed and Wave Height R. Young*, S. Zieger, and A. V. Babanin Science : April Altimeter provides by far (and seemly only) the longest duration record mention of any scatterometer or radiometer results! Geographically patterns similar to those reported by us (Science ) But amplitude of trends (.%/decade) are over twice as high as found by us and others. Winds increasing by.%/decade would have serious implication w.r.t. the global hydrological cycle (big increases in rain). Paper claims that the th percentile winds are increasing by at least.%/decade ( A very gutsy call) Assuming the authors were truly unaware of the existing body of research in this area, this paper provides a valuable independent data point.

17 Summary Satellite Inter-Calibration Project progressing slow but sure V SSM/I F, AMSR-E, and WindSat Completed New QuikSCAT GMF calibrated to V standards Remaining SSM/I and the F and F SSM/IS will soon follow Newly released WindSat Dataset Wider Swath Winds through Rain Multiple, quasi-independent estimates of ocean products Decadal Trends in Winds being Assessed