RANDOM ERRORS OF OCEANIC MONTHLY RAINFALL DERIVED FROM SSM-I USING PROBABILITY-DISTRIBUTION FUNCTIONS

Global averages and random errors associated with the monthly oceanic rain rates derived from the Special Sensor Microwave/Imager (SSM/I) da ta using the technique developed by Wilheit et al. are computed. Accou nting for the beam-filling bias, a global annual average rain rate of 1.26 m is computed. The error estimation scheme is based on the existe nce of independent (morning and afternoon) estimates of the monthly me an. Calculations show overall random errors of about 50%-60% for each 5-degrees X 5-degrees box. The results are insensitive to different sa mpling strategy (odd and even days of the month). Comparison of the SS M/I estimates with raingage data collected at the Pacific atoll statio ns showed a low bias of about 8%, a correlation of 0.7. and an rms dif ference of 55%.