The Winds 129 
WORLD WIDE SCHEME OF THE WINDS 
North Pole—80°N Arctic easterlies, high pressure, cold 
70°N-60°N Frontal zone, variable winds 
50°N—40°N Prevailing westerlies . 
30°N Horse Latitudes, fair, calm, high pressure 
20°N Northeast Trades 
10°N-10°S Doldrums, light variable winds, frequent 
showers, low pressure, cloudiness 
2028 Southeast Trades 
80°S Horse Latitudes, fair, calm, high pressure 
40°S “Roaring Forties” 
50°S “Howling Fifties,” prevailing westerlies 
60°S “Screeching Sixties” 
70°S Frontal zone, variable winds 
80°S-—South Pole Antarctic easterlies, high pressure, cold 
the sun heats land surfaces much more rapidly than the water 
surface, so that there is a tendency for air to move toward the 
land giving rise to a “sea breeze.” With the coming of night 
the land cools more rapidly than does the water so that winds 
arise in the opposite direction, the “land breeze.” 
AIR MASSES 
A very important concept in weather analysis is the idea of 
an air mass. Certain continents, bodies of water, etc., act as 
source regions for quantities of air with particular character- 
istics. A land mass in the high north, for example Canada, 
produces cold, dry air masses; a body of water like the Gulf 
of Mexico produces warm, wet air. Weather forecasters 
keep careful track of the movements of these air masses from 
day to day and find the study of great aid in forecasting 
weather conditions. A warm air mass displacing a cold one 
