The sensitivity of tropical rainfall estimation from satellite to the configuration of the microwave imager constellation

The availability of rainfall-related measurements from space has greatly increased from the late 1980s with the Defense Meteorological Satellite Program and the launch of the Tropical Rainfall Measuring Mission in 1997 to the forthcoming Global Precipitation Measurement (GPM) program (GPM mission) whose core satellite is to be launched in 2014. The rainfall observing systems have become a constellation enhancing the frequency of measurements all over the globe. In this letter, the Megha-Tropiques TAPEER-BRAIN level-4 rainfall product is considered to explore what impacts the configuration of a microwave imager constellation has on accumulated rainfall and associated sampling error estimates at one-degree/one-day resolution in the tropics. One of the main findings of this letter is that sun-synchronous satellites providing observations separated of time intervals close to rainfall autocorrelation periods result only in small improvements of TAPEER-BRAIN quantitative precipitation estimations (i.e., rain and error estimations). By comparison, it is shown that the GPM constellation of satellites, particularly with satellites on low-inclination 'equatorial' orbits, has a high contribution to the improvements of rain and error estimates. The methodology developed in this letter could be also useful to explore the sensitivity of rainfall estimates at finer space and timescales.