Hemisphere, upwelling is common where the wind
blows parallel to the coast and the surface water is
transported away from the coast. In the process of
upwelling, the exchange of water takes place only in the
Generally, the following statements are true
regarding the effects of ocean currents along the west
coasts of continents:
The west coasts of continents in middle and
higher latitudes are bordered by warm waters, which
cause a distinct maritime climate characterized by cool
summers and relatively mild winters with small annual
range of temperatures (upper west coasts of the United
States and Europe).
The 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 fogs, but generally the areas (southern
California, Morocco, etc.) are arid (dry).
Effects on the East Coasts
The effects of currents along the eastern coasts of
continents are less dramatic than those of the west
coasts because of the west-to-east flow of weather. The
effects, however, are just as significant.
In the tropical and subtropical regions, warm ocean
currents introduce warm, rainy climates, especially on
the windward sides of mountainous landmasses. As the
latitudes, warm, moist air produces a hot, humid
climate with frequent rain showers during the summer.
Winters are relatively moderate (but still cold) along the
coast due to the transport of warm water. The higher
latitudes along eastern shores normally have cold
waters flowing southward from the polar region; warm
ocean currents rarely extend very far north. The regions
where the two currents meet have cool summers and
cold winters with extensive fogs. This is especially true
along the Grand Banks of Newfoundland and the
Kamchatka Peninsula of eastern Asia.
regarding the effects of ocean currents along the eastern
coasts of continents:
The east coasts in the tropics and subtropical
latitudes are paralleled by warm currents and have
resultant warm and rainy climates. These areas lie in the
western margins of the subtropical anticyclone regions
(Florida, Philippines, and Southeast Asia).
The east coasts in the lower middle latitudes
(leeward sides of landmasses) have adjacent warm
waters with a modified continental-type climate. The
winters are fairly cold, and the summers are warm and
The east coasts in the higher middle latitudes
typically experience cool summers with cool ocean
currents paralleling the coasts.
Ocean currents also affect the location of 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 strong and where a large
amount of warm water is being transported into the
middle latitudes. The fact that these frontal zones are
located near large amounts of energy suggests that
cyclones developing in these regions along the primary
front may be of thermodynamic origin. The main
hurricane tracks in the Atlantic and Pacific also appear
to follow warm waters. Extratropical cyclones also tend
to occur in warm waters in fall and early winter.
Human activity and vegetation can have marked
effects on the climates of local areas. Eventually mans
activities could affect larger areas and ultimately whole
It has been known for years now that urban areas
and industrial complexes have an influence on climate.
Atmospheric pollution is increased, for example, and
the radiation balance is thereby altered. This change
affects the daily maximum and minimum temperatures
in cities, where they tend to be generally higher than in
nearby suburbs. A higher concentration of hygroscopic
condensation nuclei in cities results in an increased
number of fogs. Also, with the greater heat source
found in cities, increased convection gives rise to
greater amounts of cloudiness and precipitation. An
apparent benefit of this increased heat is a slight
decrease in severe weather occurring in large cities
(Chicago, for example) as compared to adjacent areas.