Oceans evaporation zones

Solar beating of tropical oceans warms the surface water, promoting evaporation. Where the equatorial surface waters are warmest and the northeast and southeast trade winds meet, a band of cirrostratus and cirrus clouds spreads out from convective precipitation regions. This area is known as the Intertropical Convergence Zone. 

There is a zonal atmospheric circulation system associated with this normal ocean condition called the Walker Cell (Eig. 10-7). Evaporation rates are high over the warm pool and warm moist air ascends to great heights (deep convection) producing extensive cloud systems and rain. The Walker Cell is closed by westerly winds aloft and subsidence in the high-pressure zone of the eastern Pacific. 

Examples of environments where local high degrees of supersaturation are encountered include those associated with discharge of hydrothermal vent fluids into cold ocean water, regions where streams of highly acidic solutions mix with neutral pH water, zones of mixing between groundwater fluids, and sites of evaporation of soil water solutions. 

At the boundaries between thermal circulation at the equator, 30°, and 55° N and S latitude there are regions of calm. The observed net precipitation near the equator and the polar front is explained by rising moist air that cools. At 30° N and S latitude a strong subsidence of dry air occurs, since the air loses its moisture upon ascension in the equatorial zone. As a result, net evaporation of the oceans occurs from 10° to 40° N and S latitude. 

---