Evaporation and Precipitation

	Figure 4

Modern Estimates

We have compiled modern estimates of evaporation and precipitation over the ocean to develop a more complete picture of water fluxes across the air-sea interface.Taking the difference between evaporation (E) and precipitation (P) tells us the net gain or loss of water by the ocean.A new map of E-P shows where water evaporates (red) and precipitates (blue) (Figure 4.) The mid-latitude regions of the oceans tend to be dominated by evaporation under the trade winds. These regions supply water to the atmosphere, which transports it to a low latitude rainfall region known as the “Inter-tropical Convergence Zone” (ITCZ).  This is where rising warm, moist air drops its moisture burden back on the sea. The high latitude oceans also tend to gain more water from rain than is lost to evaporation.