Seasonal variation in precipitation patterns to the global ocean: An analysis of the GPCP version 2 data set

Abstract

Precipitation affects the thermohaline circulation, chemical mass balance, and primary productivity of surface ocean waters. An analysis of temporal and spatial variation of oceanic precipitation was conducted on the Global Precipitation Climatology Project (GPCP) version 2 data set, a monthly 2.5° × 2.5° latitude‐longitude gridded data set for the period 1979 to 1999. While the precipitation patterns observed are generally similar to those reported in previous climatologies, new features and greater detail of global precipitation were revealed from our analysis of the GPCP data set. High precipitation was observed in the intertropical convergence zone (ITCZ), the South Pacific convergence zone (SPCZ), and the storm tracks in the North Pacific and Atlantic Oceans. Low precipitation was observed in the Polar regions and in the subtropics of the East Pacific, East Atlantic, and the Southeast and Northwest Indian Ocean. The spatial coverage of these high and low precipitation regions changed through the year. A strong seasonal cycle of precipitation was observed for the Northern and the Southern Hemispheres. The area‐weighted mean precipitation increased from a minimum of ∼2 mm d−1 in February to a maximum of ∼5 mm d−1 in August in the Northern Hemisphere and from a minimum of ∼2.5 mm d−1 in September to a maximum of ∼3.5 mm d−1 in March in the Southern Hemisphere. Similar seasonal cycles of precipitation were observed for each ocean basin. Global precipitation also varied significantly with both latitude and longitude, with a latitudinal maximum at 56°S, 39°S, 4°S, 6°N, 39°N, and 56°N, and a longitudinal maximum over each ocean. The seasonal varying precipitation patterns are a foundation for evaluating the effect of wet deposition on ocean circulation, flux of chemical species, and its effect on marine ecosystems.