Determination of Mean Rainfall from the Special Sensor Microwave/Imager (SSM/I) Using a Mixed Lognormal Distribution

View More View Less
  • 1 Colorado Center for Astrodynamics Research, University of Colorado, Boulder, Colorado
  • | 2 The Analytic Sciences Corporation, Reading, Massachusetts
© Get Permissions
Full access

Abstract

Global estimates of monthly, seasonal, and annual oceanic rainfall are computed for a period of 1 year using data from the Special Sensor Microwave/Imager (SSM/I). Instantaneous rainfall estimates are derived from brightness temperature values obtained from the satellite data using the Hughes D-matrix algorithm, which was originally developed by Environmental Research and Technology, Inc. (ERT). The instantaneous rainfall estimates are stored in 1° square bins over the global oceans for each month. A mixed probability distribution combining a lognormal distribution describing the positive rainfall values and a spike at zero describing the observations indicating no rainfall is used to compute mean values. The resulting data for the period of interest are fitted to a lognormal distribution by using a maximum-likelihood method. Mean values are computed for the mixed distribution and qualitative comparisons with published historical results as well as quantitative comparisons with corresponding in situ raingage data are performed.

Abstract

Global estimates of monthly, seasonal, and annual oceanic rainfall are computed for a period of 1 year using data from the Special Sensor Microwave/Imager (SSM/I). Instantaneous rainfall estimates are derived from brightness temperature values obtained from the satellite data using the Hughes D-matrix algorithm, which was originally developed by Environmental Research and Technology, Inc. (ERT). The instantaneous rainfall estimates are stored in 1° square bins over the global oceans for each month. A mixed probability distribution combining a lognormal distribution describing the positive rainfall values and a spike at zero describing the observations indicating no rainfall is used to compute mean values. The resulting data for the period of interest are fitted to a lognormal distribution by using a maximum-likelihood method. Mean values are computed for the mixed distribution and qualitative comparisons with published historical results as well as quantitative comparisons with corresponding in situ raingage data are performed.

Save