Impact Experiments on GMAO Data Assimilation and Forecast Systems with

MODIS winds during MOWSAP

Lars Peter Riishojgaard and Yanqiu Zhu

Global Modeling and Assimilation Office, NASA/GSFC, Greenbelt, Maryland

Outline

• Overview of MODIS winds• MOWSAP: MODIS winds Special

Acquisition Period• GMAO experiment results• Timeliness of MODIS winds

Overview of MODIS winds• MODIS winds coverage and their potential

impact• Winds from Terra now used operationally by

GMAO, ECMWF and others• Routine production of winds from MODIS

started at NESDIS on Nov. 8, 2003, using EMC analysis for background

• Initial tests with winds from Aqua gave decreased or even reversed impact in ECMWF and UKMO systems

MODIS winds data vs. other satellite and conventional winds data coverage

MOWSAP: MODIS winds Special Acquisition Period

• November 8, 2003-January 31 2004• Winds generated by CIMSS (Navy

background) and NESDIS (EMC background) from both Terra and Aqua

• Assimilation experiments done by GMAO, ECMWF, UKMO, CMC, using common diagnostics and measures of skill

Assessment of MODIS winds against GMAO model forecast (OmF)

• The statistics of Terra MODIS winds are similar to that of their corresponding Aqua MODIS winds

• NESDIS MODIS winds generally have larger average wind speeds than their corresponding CIMSS MODIS winds

• In the northern hemisphere, NESDIS MODIS winds tend to have smaller NRMSVD than their corresponding CIMSS MODIS winds

Forecast skills verified against their own analyses – CIMSS MODIS winds

Forecast skills verified against their own analyses – CIMSS/NESDIS MODIS winds

Forecast skills verified against NCEP analysis – CIMSS MODIS winds

Forecast skills verified against NCEP analysis – CIMSS/NESDIS MODIS winds

Forecast skills verified against NCEP analysis – CIMSS/NESDIS MODIS winds

Time series of H500 anomaly correlations

Time series of H500 anomaly correlations

Timeliness of MODIS winds• MODIS radiances currently acquired via the same path as

AIRS radiances: on-board storage and low-latitude downlinks• Winds algorithm based on image triplets; this introduces a

delay of one full orbital period in addition to the downlink delay– MODIS winds do not meet cut-off of EMC and most

regional/limited area data assimilation systems• Possible solution: Direct broadcast to high-latitude X-band

station(s); this eliminates the downlink delay– Northern Hemisphere: Fairbanks (NOAA), Kiruna (ESA);

Svalbard (EUMETSAT)– Southern Hemisphere: McMurdo; workshop at Ohio State in

March 2004 (http://amrc.ssec.wisc.edu/MGS/ )