"The rainfall maps show total monthly rainfall in millimeters [January 1998 to June 2016] as recorded by NASA’s Tropical Rainfall Measuring Mission (TRMM) satellite, which is a joint mission between NASA and the Japanese Space Agency. High rain totals are represented in dark blue, while small rainfall totals are shown in white. TRMM measures rainfall in the tropics. High-latitude regions, where TRMM does not record rainfall, are gray."
Animation source: "Total Rainfall" (EO-NASA).