Chapter 16 — FUNDAMENTALS OF OCEANOGRAPHY 



tongues of water with higher temperature flow 

 toward the north,, 



INDIAN OCEAN CURRENTS 



The oceanic circulation of the Indian Ocean 

 shows the influence of the Asiatic Monsoon 

 atmosphere circulation in the northern portion 

 of the ocean and the anticyclonic circulation 

 in the southern portion. 



The equatorial currents of the North Indian 

 Ocean are variable. During the northwest monsoon 

 (February and March) the wind aids the north 

 equatorial current, causing it to be well 

 developed in its circulation from east to west. 

 Immediately to the south of the North Equa- 

 torial Current during that season there is a 

 pronounced countercurrent. In August and 

 September during the southwest monsoon, the 

 North Equatorial Current flows from west to 

 east as the MONSOON CURRENT, and the 

 EQUATORIAL COUNTERCURRENT seems to 

 disappear. 



A large portion of the equatorial currents 

 reaching the east coast of Africa turns south- 

 ward. South of the Equator this branch is 

 known as the MOZAMBIQUE CURRENT to about 

 35°S lat, where it becomes known as the 

 AGULHAS STREAM. These waters are favor- 

 able to warm, moist air masses with moderate 

 rainfall along the southeast coast of Africa, 



Some of the equatorial waters make their 

 way to the West Wind Drift Current in the 

 South Indian Ocean and flow eastward toward 

 Australia. On reaching the vicinity of the west 

 coast of Australia, some of the waters of the 

 West Wind Drift flow northward bringing to that 

 area relatively cool sea surface temperatures 

 and the formation of fog and low stratus 

 clouds, 



SUMMARY 



In general, the following statements may be 

 made concerning the effects ocean currents 

 have on weather: 



fogs, but generally the areas are arid (southern 

 California, Morocco, etc.), 



2. West Coasts of Continents in Middle and 

 Higher Latitudes are bordered by warm waters 

 which cause a distinct marine climate. They 

 are characterized by cool summers and rela- 

 tively mild winters with small annual range of 

 temperatures (upper west coasts of the United 

 States and Europe). 



3. East Coasts in the Tropics and Subtropi- 

 cal Latitudes are paralleled by warm currents 

 and have resultant warm and rainy climates. 

 These areas lie in the western margins of the 

 subtropical anticyclones and are relatively 

 unstable (Florida, Philippines, Southeast Asia). 



4. East Coasts in the Lower Middle Lati- 

 tudes (leeward side) have adjacent warm waters 

 with a modified continental-type climate. The 

 winters are fairly cold, and the summers are 

 warm and hot, 



5. East Coasts in the Higher Middle Lati- 

 tudes. Cool ocean currents parallel the coasts 

 with subsequent cool summers. 



The indirect effects of ocean currents have 

 their influence upon the location of the primary 

 frontal zones and the tracks of cyclonic storms. 

 Off the eastern coast of the United States in 

 the winter two of the major frontal zones are 

 located in areas where the temperature gradient 

 is steep and where a large amount of tropical 

 water is being transported into the middle 

 latitudes. In contrast to the cold eastern side 

 of the continent, marked thermal temperature 

 contrasts occur. The fact that these frontal 

 zones are positioned in a location where large 

 amounts of energy are available suggests that 

 cyclones developing in these regions along the 

 primary front may be of thermodynamic origin. 

 Two of the main hurricane tracks in the 

 Atlantic also appear to follow warm waters, 

 one through the Caribbean and the other 

 following the warm waters off the northern and 

 eastern coasts of Florida and the Greater 

 Antilles, Extratropical cyclones, too, tend to be 

 attracted to warm waters in fall and early 

 winter. This is equally true in the United States 

 and in European waters. 



1. West Coasts of Continents in Tropical 

 and Subtropical Latitudes (except close to the 

 Equator) are bordered by cool waters, and their 

 average temperatures are relatively low with 

 small diurnal and annual ranges. There are 



WATER MASSES AND TYPES 



Chapter 14 of this training manual discussed 

 the concept of visualizing various bodies of air 



391 



