AEROGRAPHER'S MATE 3 & 2 



Figure 14-24, — Satellite picture depicting ITCZ in the eastern Atlantic Ocean, 



209.375 



degree of convergence between the two air 

 currents. The zone of disturbed weather may 

 be as little as 20 to 30 miles in width or 

 as much as 300 miles. Under typical conditions, 

 frequent rainstorms, cumulus and cumulonimbus 

 type clouds and local thunderstorms occur. 

 Violent turbulence may be associated within these 

 storms. Cloud bases may lower to below 1,000 

 feet, or even be indistinguishable, in heavy 

 showers. Their tops frequently exceed 40,000 

 feet. An extensive layer of altocumulus and 

 altostratus usually occurs due to the spreading 

 out of the upper parts of the clouds. These 

 clouds vary in height and thickness with the 

 currents of the air masses. At higher levels 

 a broad deck of cirrostratus spreads out on 

 both sides of the zone. Visibility is generally 

 good except when reduced by heavy rain shower 

 activity. 



Surface wind in the vicinity of the ITCZ is 

 generally squally in the heavy shower areas. 



Ice formation in the heavy cloud masses 

 associated with the ITCZ is likely to reach 

 serious proportions when pilots are flying at 

 altitudes above 15,000 feet. (This is roughly 

 the average freezing level in equatorial 

 regions.) 



The intensity of the ITCZ varies inter- 

 diurnally, from day to day and to a lesser degree 

 annually. Over ocean areas, precipitation reaches 

 its maximum just before dawn with a minimum 

 occurring late in the morning or early after- 

 noon. Over land areas the reverse is true, except 

 on coastal areas when the wind has an onshore 

 component. In this case the diurnal maximum 

 of precipitation takes place in the early 

 morning. (See fig. 14-25.) 



338 



