Climate-Scale Oceanic Rainfall Based on Passive Microwave Radiometry - Satellite-based Applications on Climate Change - page 217

Chapter 15
Climate-Scale Oceanic Rainfall Based on Passive
Microwave Radiometry

Long S. Chiu, Si Gao, and Dong-Bin Shin

Abstract In the microwave regime, the relatively low and stable emissivity of the
sea surface serves as an excellent background over which brightly emitting
hydrometeors can be distinguished. Space/time oceanic rainfall has been estimated
from microwave radiometry using a simple radiative transfer model of an atmo-
spheric rain column, a rain rate distribution to account for sampling deficiencies,
and an empirical correction of the nonuniformly filled field of view of the micro-
wave sensor. The microwave emission-based brightness temperature histogram
(METH) technique has been applied to the Defense Meteorological Satellite Pro-
gram (DMSP) Special Sensor Microwave Imager (SSM/I) to produce over 25 years
of monthly oceanic rainfall. The METH technique is described and the retrieved
parameters are assessed. The inter-satellite calibration of microwave and DMSP
SSM/I sensors provided a climate-scale oceanic rainfall time series capable of
examining climate trends and variabilities.

Keywords Microwave radiometry • SSM/I • Oceanic rainfall • Rain frequency •
Mixed lognormal distribution • Inter-satellite calibration • Climate trend

15.1 Introduction

Accurate measurements of global rainfall are crucial for advancing our understand-
ing of the climate system such as the water and energy cycles. The lack of global
gauge networks, especially over the ocean, in mountainous terrains, or in remote