Abstract
Global monthly rainfall maps derived from microwave sensors are now routinely produced from data collected by the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imager (SSM/I) and Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI). Since the DMSP (F-13 and F-14) and TMI satellites have different orbits and swath structure, they have different sampling errors. In this paper the non-systematic errors, which are dominated by sampling errors, of monthly oceanic rainfall over 5/spl deg/ latitude by 5/spl deg/ longitude boxes are calculated separately for SSM/Is and TMI for three years (1998 to 2000). The non-systematic errors are 21.4%, 21.9% and 19.1% for SSM/I of F-13 and F-14, and TMI, respectively. The nonsystematic error for TMI is less than 1 mm day/sup -1/ for rain rates up to 6 mm day/sup -1/, and is about 15-20% at higher rain rates. This is smaller than that for either F-13 or F-14 SSM/I alone at the low rain rates, but is comparable at the high rain rates (>6 mm day/sup -1/). A combination of F-13 and F-14 SSM/I rain rates reduces the nonsystematic error to slightly lower (15.2%) than that of the TMI alone. It is argued that a refined space-borne sampling strategy, such as that proposed by the Global Precipitation Mission (GPM), is needed to reduce the sampling errors to better than 10% at high rain rates.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have