Contribution of Tropical Cyclones to the North Atlantic Climatological Rainfall as Observed from Satellites

Abstract

The tropical cyclone rainfall climatological study performed for the North Pacific was extended to the North Atlantic. Similar to the North Pacific tropical cyclone study, mean monthly rainfall within 444 km of the center of the North Atlantic tropical cyclones (i.e., that reached storm stage and greater) was estimated from passive microwave satellite observations during an 11-yr period. These satellite-observed rainfall estimates were used to assess the impact of tropical cyclone rainfall in altering the geographical, seasonal, and interannual distribution of the North Atlantic total rainfall during June?November when tropical cyclones were most abundant. The main results from this study indicate 1) that tropical cyclones contribute, respectively, 4%, 3%, and 4% to the western, eastern, and entire North Atlantic; 2) similar to that observed in the North Pacific, the maximum in North Atlantic tropical cyclone rainfall is approximately 5°?10° poleward (depending on longitude) of the maximum nontropical cyclone rainfall; 3) tropical cyclones contribute regionally a maximum of 30% of the total rainfall northeast of Puerto Rico, within a region near 15°N, 55°W, and off the west coast of Africa; 4) there is no lag between the months with maximum tropical cyclone rainfall and nontropical cyclone rainfall in the western North Atlantic, whereas in the eastern North Atlantic, maximum tropical cyclone rainfall precedes maximum nontropical cyclone rainfall; 5) like the North Pacific, North Atlantic tropical cyclones of hurricane intensity generate the greatest amount of rainfall in the higher latitudes; and 6) warm El Niño?Southern Oscillation events inhibit tropical cyclone rainfall.