Progress Towards the Assimilation of Cloud-Affected Radiances at the GMAO
Impact Experiments on GMAO Data Assimilation and Forecast Systems with MODIS Winds During MOWSAP
description
Transcript of Impact Experiments on GMAO Data Assimilation and Forecast Systems with MODIS Winds During MOWSAP
Lars Peter Riishojgaard
Yan-Qiu Zhu
Global Modeling and Assimilation Office
NASA Goddard Space Flight Center
Impact Experiments on GMAO Data Assimilation and Forecast Systems with MODIS Winds During MOWSAP
Presented by Ron Gelaro, NASA/GMAO
MODIS winds
Polar orbiting platform (NASA Terra, Aqua), primarily intended for aerosol/clouds/land surface measurements
Wind vectors calculated using geostationary feature tracking algorithms on high-latitude imagery from two MODIS channels
6.7µ water vapor channel for clear-sky moisture field 11µ window channel for clouds
Coverage in high latitudes (beyond 65o) where successive overpasses cover the same region
Useful complement to geostationary satellite winds that drop off sharply beyond 58o latitudes
Image repeat frequency tied to orbital period of ~100 min. Need for image triplets implies long acquisition time
(animation provided by Key et al., CIMSS)
Unlike geostationary satellites at lower latitudes, it is not be possible to obtain complete polar coverage at a snapshot in time with one or two polar-orbiters. Instead, winds must be derived for areas that are covered by two or three successive orbits, an example of which is shown here. The whitish area is the overlap between three orbits.
(slide provided by Key et al., CIMSS)
Example 6-hour data coverage; MODIS winds (left panel); all other satellite and conventional surface and upper air winds (right panel)
MODIS winds vertical distribution
Water Vapor Observations Infra-Red Observations
GMAO MODIS winds experiments
MOWSAP (MODIS Winds Special Acquisition Period): November 8, 2003-January 31, 2004
Winds generated by CIMSS and by NESDIS (pre-operational mode)
Same algorithm, different code bases Different backgrounds for QC and height assignment
Winds generated from MODIS Aqua and MODIS Terra imagery
Assimilation experiments by GMAO, ECMWF, Met Office, CMC
Experimental setup: 5-day forecast every other day; 42 members in the ensemble
GMAO GEOS4: fvGCM+PSAS analysis (1o x 55 levels)
Innovation statistics for raobs: Arctic
control
control+MODIS
height (m) u-wind (m/s)
RMS (obs – 6hr fcst)
control
MODIS
height (m) u-wind (m/s)
control
Innovation statistics for raobs: AntarcticRMS (obs – 6hr fcst)
control+MODIS
Forecast skill - ACC 500 hPa height NESDIS Winds
Forecast skill - ACC 500 hPa height at 120 hrsNorthern High-Latitudes: 60-90N
Forecast skill - ACC 500 hPa height at 120 hrsSouthern High-Latitudes: 60-90S
Forecast skill - ACC 500 hPa height at 120 hrsSouthern Mid-Latitudes: 60-90N
Forecast error evolution Jan 21, 2004; Control (left), MODIS (right)
Summary
MODIS winds complement other observations in the high latitudes; more so in the SH than in the NH due to the current data sparsity
Consistency of data delivery is acceptable Based on independent verification statistics, the quality of the
information is acceptable Positive overall contribution to forecast skill
Substantial impact in the SH Impact extends to entire hemisphere Improvements in average forecast skill results primarily from
improving the skill of the worst forecasts Timeliness remains an important issue; current delay is 4-6 hours;
some improvement possible via use of Direct Broadcast capability
Outlook
MODIS winds experiments with new GMAO assimilation system based on grid space analysis (GSI developed at NCEP)
Case study diagnostics; busts? Data density/QC studies WV vs. IR winds Two-satellite winds
End of Talk…Thank You.