Thursday, 23 September 2004
Handout (413.2 kB)
A new method for instantaneous retrievals of near-surface specific humidity (Qa) and air temperature (Ta) over the oceans was developed by combining satellite microwave observations from AMSU-A, SSM/I and SSM/T2. A suite of retrieval methods are presented that include both single and multi-sensor approaches. The most accurate Qa retrieval method had an rms difference of 0.90 g/kg when using a combination of AMSU-A and SSM/I channels, while the most accurate Ta retrieval had a regression error of 1.53oC when using all three instruments. These differences were found to be significantly lower than those computed from previously published algorithms applied to daily values. A direct comparison with previous methods using an independent validation data set indicates the multi-sensor approach is more accurate. It was found that using multiple satellites to provide global coverage of Qa and Ta observations does have limitations. Global coverage every six hours can nearly be achieved using two NOAA satellites; however, such coverage would rely on many of the retrievals using a single AMSU-A instrument because the SSM/I satellites do not provide close time matches with the NOAA afternoon (2am/pm) satellite. As a result, a multi-sensor approach using AMSU-A, SSM/I and SSM/T2 on the NOAA and DMSP satellites at will at best provide daily mean global coverage.
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