Climatic Types

EQUATORIAL RAINFORESTS

Equatorial rainforests are mainly located in low latitudes around the equator, between 10°N and 10°S.

1. Amazon Basin (South America)
2. Congo Basin (Central Africa and Western Africa)
3. SE Asia – Indonesia, New Guinea

Climate: It is confined to the humid tropical zone, however rainfall contrasts may exist, e.g. Eastern and Western Amazonian receive 1800-2000 mm per year, with 1-3 dry moths (less than 60 mm) in the year.

• Temperatures are high and constant through out the year because the sun is always high in the sky.
• The annual temperature range is under 3℃ inland, e.g. Manus, and 1℃ on the coast, e.g. Belen.
• Mean monthly temperatures, ranging from 26℃ to 28℃, reflect the lack of seasonal change.
• Insolation is evenly distributed throughout the year with each day having approximately 12 hours of darkness.
• The diurnal rang is also small, about 10℃. Evening temperatures rarely fall below 22℃ and, due to the presence of afternoon cloud, daytime temperatures rarely rise above 32℃.
• Annual rainfall totals usually exceed 2000mm and most afternoon have a heavy shower.
• This result from the convergence of the trade winds at the ITCZ, and the subsequent enforced ascent of warm, moist, unstable air in strong convection currents.
• Evapotranspiration is rapid from the many rivers, swamps and trees.
• Some areas may have a drier season when the ITCZ moves a few degrees away from the Equator at the winter and summer solstice and a double maximum when the sun is directly overhead at the spring and autumn equinox.
• The winds at ground level at the ITCZ are light and sea breezes to develop in coastal areas.

POLAR REGION --- Greenland

Polar areas is located at high latitudes, above 66½º N & S.

Climate

• The average temperature is below 0ºC. The summers are cool and short, with average temperature above freezing and long-continued cold conditions.
• The solar rays are oblique. Solar energy is spread over a greater surface area. Radiation intensity decreases with the longer path through the atmosphere.
• The daytime varies between 0 and 24 hours from winter to summer, because the sun is below the horizon for approximately six months of the year.
• The snow cover reflects most insolation at day. The albedo is near 90%.
• The total rainfall is below 250mm. Most precipitation comes during summer; and under the anticyclonic conditions of the continental winter. The snow is usually dry and powdery in winter.
• The cold temperatures cause air to contract and sink. The pressure rises and the air becomes stable. It discourages the formation of precipitation.

By Lam Ka-yan and Suen Hoi-wing