Trade wind

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. 

The tropical regions of both of the hemispheres troposphere exhibit easterly flow called the trade winds. Finally the jet stream -sometimes described as a river of air - flows at mid-latitude of both hemispheres with velocities of 25 to 50 m/sec from west to east, often carrying material completely around the Earth at its altitude close to the tropopause. It is in this flow that balloonists attempt to circle the globe. 

The El-Niho southern oscillation (ENSO) phenomenon is an interannual perturbation of the climate system characterized by a periodic weakening of the trade winds and... 

South America to about the date line (180 ). These trade winds also drive near-equatorial surface flow westward as the South Equatorial Current (SEC). This piles up warm surface water in the western Pacific to create a deep warm pool and results in depression of the depth of the thermocline from east to west. The westward flow in the surface SEC is partly compensated by a return flow to the east in the thermocline ( 150m) called the Equatorial Undercurrent (EUC). 

During El Nino (Fig. 10-7) the trade winds weaken, and even reverse, in the central and... 

As shown in Figure 14.8, kaolinite concentrations are highest in tropical and equatorial latitudes, particiflarly off the western coasts of North Africa and Australia (>40%) and the northeastern coasts of Australia and South America (30%). The first two are the result of aeolian transport by the Trade Winds from the Saharan and Australian deserts, respectively. The other two are the result of river input from the eastern Australian continent and the Amazon River. 

Model 4-Tropics, Small Response of Production Rate to Trade Wind Forcing... 

I860 and the mid-1990s, areal deposition rates in the coastal waters increased by more than a fector of 10 and in open ocean regions by at least a factor of 2, particularly in the North Atlantic. The aeolian deposition pattern now reflects transport via the Westerlies from North America to Europe and via the Trade Winds from Africa to South America. 

Divergence Horizontal flow of water from a common center or zone that results in upweUing. This occurs in the open ocean at the equator and 60°S as result of surface currents driven by the Trade winds and Westerlies, respectively. 

Prospero, J. M., and R. T. Nees, Impact of the North African Drought and El Nino on Mineral Dust in the Barbados Trade Winds," Nature, 320, 735-738 (1986). 

Savoie, D. L., J. M. Prospero, and E. S. Saltzman, Non-Sea-Salt Sulfate and Nitrate in Trade Wind Aerosols at Barbados Evidence for Long-Range Transport, J. Geophys. Res., 94, 5069-5080 (1989). 

Li, X., H. Mating, D. Savoie, K. Voss, and J. M. Prospero, "Dominance of Mineral Dust in Aerosol Light-Scattering in the North Atlantic Trade Winds, Nature, 380, 416-419 (1996). 

Beatty, J. M., Trade Winds, Saturday Review, August 5,1961, p. 5. 

Figure 2. Global trade winds over North West Africa...

Zhu, X., Prospero, J.M. and Millero, F.J. (1997) Diel variability of soluble Fe11 and soluble total iron in North African dust in the trade winds at Barbados./. Geophys. Res., 102, 21297-21305. 

Saltzman and Cooper (6) measured the DMS concentration in the trade winds on two north-south transect across the Caribbean Sea. The mean of these data is 57 ppt. Averaging of the data into 4 hour intervals yielded a diurnal amplitude of 39 to 58 ppt, a factor of 1.49 variation in the maximum/minimum concentration. The data show an early morning maximum and a broad afternoon minimum, similar to that found in the Pacific by Andreae and Raemdonck (14). Interestingly, the diurnal variation found between the minimum and maximum concentration is similar for the two data sets. 

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