The tropical rain forest climate receives most of its rainfall as a result of

The rainforest biome remains warm all year and must stay frost-free. The average daily temperatures range from 20°C (68°F) to 25°C (77°F).

Rainforests receive the most rain of all of the biomes in a year! A typical year sees 2,000 to 10,000 millimeters (79 to 394 inches) of rain per year.

Vegetation

Vines, palm trees, orchids, ferns

Location

Between the Tropic of Cancer and the Tropic of Capricorn

Other

There are two types of rainforests, tropical and temperate. Tropical rainforests are found closer to the equator and temperate rainforests are found farther north near coastal areas. The majority of common houseplants come from the rainforest.

Example: Manaus, Brazil

Monthly Temperature and Precipitation from 1970 - 2000

Climograph

Location Map

Description

There are two types of rainforests, tropical and temperate. Tropical rainforests are found closer to the equator where it is warm. Temperate rainforests are found near the cooler coastal areas further north or south of the equator.

The tropical rainforest is a hot, moist biome where it rains all year long. It is known for its dense canopies of vegetation that form three different layers. The top layer or canopy contains giant trees that grow to heights of 75 m (about 250 ft) or more. This layer of vegetation prevents much of the sunlight from reaching the ground. Thick, woody vines are also found in the canopy. They climb trees in the canopy to reach for sunlight. The middle layer, or understory, is made up of vines, smaller trees, ferns, and palms. A large number of plants from this level are used as common houseplants. Because of the small amount of sunlight and rainfall these plants receive, they adapt easily to home environments. The bottom layer or floor of the rainforest is covered with wet leaves and leaf litter. This material decomposes rapidly in the wet, warm conditions (like a compost pile) sending nutrients back into the soil. Few plants are found on the floor of the forest due to the lack of sunlight. However, the hot, moist atmosphere and all the dead plant material create the perfect conditions in which bacteria and other microorganisms can thrive.

Climate Classification

The Köppen Climate Classification System is the most widely used system for classifying the world's climates. Its categories are based on the annual and monthly averages of temperature and precipitation. The Köppen system recognizes five major climatic types; each type is designated by a capital letter.

A - Tropical Moist Climates: all months have average temperatures above 18° Celsius.

B - Dry Climates: with deficient precipitation during most of the year.

C - Moist Mid-latitude Climates with Mild Winters.

D - Moist Mid-Latitude Climates with Cold Winters.

E - Polar Climates: with extremely cold winters and summers.

Tropical Moist Climates (A)

Tropical moist climates extend northward and southward from the equator to about 15 to 25° of latitude. In these climates all months have average temperatures greater than 18° Celsius. Annual precipitation is greater than 1500 mm. Three minor Köppen climate types exist in the A group, and their designation is based on seasonal distribution of rainfall. Af or tropical wet is a tropical climate where precipitation occurs all year long. Monthly temperature variations in this climate are less than 3° Celsius. Because of intense surface heating and high humidity, cumulus and cumulonimbus clouds form early in the afternoons almost every day. Daily highs are about 32° Celsius, while night time temperatures average 22° Celsius. Am is a tropical monsoon climate. Annual rainfall is equal to or greater than Af, but most of the precipitation falls in the 7 to 9 hottest months. During the dry season very little rainfall occurs. The tropical wet and dry or savanna (Aw) has an extended dry season during winter. Precipitation during the wet season is usually less than 1000 millimeters, and only during the summer season.

Dry Climates (B)

The most obvious climatic feature of this climate is that potential evaporation and transpiration exceed precipitation. These climates extend from 20 - 35° North and South of the equator and in large continental regions of the mid-latitudes often surrounded by mountains. Minor types of this climate include:

• BW - dry arid (desert) is a true desert climate. It covers 12% of the Earth's land surface and is dominated by xerophytic vegetation. The additional letters h and k are used generally to distinguish whether the dry arid climate is found in the subtropics or in the mid-latitudes, respectively.
• BS - dry semiarid (steppe). Is a grassland climate that covers 14% of the Earth's land surface. It receives more precipitation than the BW either from the intertropical convergence zone or from mid-latitude cyclones. Once again, the additional letters h and k are used generally to distinguish whether the dry semiarid climate is found in the subtropics or in the mid-latitudes, respectively.

Moist Subtropical Mid-Latitude Climates (C)

This climate generally has warm and humid summers with mild winters. Its extent is from 30 to 50° of latitude mainly on the eastern and western borders of most continents. During the winter, the main weather feature is the mid-latitude cyclone. Convective thunderstorms dominate summer months. Three minor types exist: Cfa - humid subtropical; Cs - Mediterranean; and Cfb - marine. The humid subtropical climate (Cfa) has hot muggy summers and frequent thunderstorms. Winters are mild and precipitation during this season comes from mid-latitude cyclones. A good example of a Cfa climate is the southeastern USA. Cfb marine climates are found on the western coasts of continents. They have a humid climate with short dry summer. Heavy precipitation occurs during the mild winters because of the continuous presence of mid-latitude cyclones. Mediterranean climates (Cs) receive rain primarily during winter season from the mid-latitude cyclone. Extreme summer aridity is caused by the sinking air of the subtropical highs and may exist for up to 5 months. Locations in North America are from Portland, Oregon to all of California.

Moist Continental Mid-latitude Climates (D)

Moist continental mid-latitude climates have warm to cool summers and cold winters. The location of these climates is pole ward of the C climates. The average temperature of the warmest month is greater than 10° Celsius, while the coldest month is less than -3° Celsius. Winters are severe with snowstorms, strong winds, and bitter cold from Continental Polar or Arctic air masses. Like the C climates there are three minor types: Dw - dry winters; Ds - dry summers; and Df - wet all seasons.

Polar Climates (E)

Polar climates have year-round cold temperatures with the warmest month less than 10° Celsius. Polar climates are found on the northern coastal areas of North America, Europe, Asia, and on the landmasses of Greenland and Antarctica. Two minor climate types exist. ET or polar tundra is a climate where the soil is permanently frozen to depths of hundreds of meters, a condition known as permafrost. Vegetation is dominated by mosses, lichens, dwarf trees and scattered woody shrubs. EF or polar ice caps has a surface that is permanently covered with snow and ice.

Factors Influencing the World Climatic Regions

So far in this online textbook we have discovered that the climate of a particular place is the function of a number of factors. These factors include:

1) Latitude and its influence on solar radiation received.
2) Air mass influences.
3) Location of global high and low pressure zones. 4) Heat exchange from ocean currents. 5) Distribution of mountain barriers. 6) Pattern of prevailing winds. 7) Distribution of land and sea.

8) Altitude.

At a macro-level, the first three factors are most important in influencing a region's climate. The animated graphic below provides us with a generalized model of the Earth's annual climatic variations. It also describes the latitudinal effects of these top three factors through the following climatic features:

• Relative annual latitudinal location of the overhead Sun at solar noon.
• Intertropical convergence zone and its area of uplift, cloud development and precipitation.
• Subtropical high pressure zone and its associated descending air currents and clear skies.
• Polar front and its area of uplift, cloud development and precipitation.
• Polar vortex and its associated descending air currents and clear skies.
• Relative location of tropical/subtropical (red) and polar (light blue) air masses.
  

In the animation we can see that the intertropical convergence zone, the subtropical high pressure zone, polar front and the position of tropical/subtropical and polar air masses all move in response to the seasonal movements of the Sun. It is important to understand this concept because of its climatic ramifications for locations on the globe. The type of climate that a location experiences is to a large extent a function of seasonal migration of these weather features. For example, a location at 15° North latitude is influenced by the subtropical high pressure zone during winter solstice and by the intertropical convergence zone during the summer solstice. Another location, at 60° North latitude, would be influenced by polar air masses during the winter solstice, the polar front during the equinoxes, and by subtropical air masses and the subtropical high pressure zone during the summer solstice.

When studying about the Earth's Climatic Regions as described below, use this animation (Figure 7v-1) as a guide to understanding the large scale climatic processes that produce each location's particular climate.

Figure 7v-1: Solar influence on the movement of the Earth's global circulation patterns.

Climatic Region Descriptions

The following discussion organizes the climatic regions of the world into eight different groups. Categorization of these climates is based on their Köppen classification and seasonal dominance of air masses.

Tropical Wet

• Köppen Classification - Af.
• Dominated by Maritime Tropical air masses all year long.

The tropical wet climate is characterized by somewhat consistent daily high temperatures ranging between 20 to 30° Celsius. The monthly temperature averages vary from 24 to 30° Celsius. Annual range of monthly temperatures is about 3° Celsius. It has reasonably uniform precipitation all year round, and total rainfall over 2000 millimeters or greater.

The region experiencing this climate lies within the effects of the intertropical convergence zone all year long. Convergence and high maritime humidity creates cumulus clouds and thunderstorms almost daily.

Af - Andagoya, Columbia 5° N , Elevation: 65 m

Figure 7v-2: Mean monthly temperature and precipitation values for Andagoya, Columbia.

Af - Iquitos, Peru 4° S , Elevation: 104 m

Figure 7v-3: Mean monthly temperature and precipitation values for Iquitos, Peru.

Tropical Wet and Dry

• Köppen Classification - Aw and Am.
• Maritime Tropical air masses high Sun season and Continental Tropical air masses low Sun season.

This climate has distinct wet/dry periods. The seasonal pattern of moisture is due to the migration of the intertropical convergence zone. The wet season is synchronous with the high Sun and the presence of the convergence zone. The dry season is a result of the more stable air developing from the subsidence associated with the presence of the subtropical high zone during the low Sun season.

During the rainy season, the climate of this location is similar to the tropical wet climate: warm, humid, and has frequent thunderstorms. During the dry season more or less semi-desert conditions prevail. Some regions may experience intensification of rainfall because of monsoon development and orographic uplift.

Aw - Calcutta, India 22.5° N , Elevation: 6 m

Figure 7v-4: Mean monthly temperature and precipitation values for Calcutta, India.

Aw - Cuiaba, Brazil 13.5° S , Elevation: 165 m

Figure 7v-5: Mean monthly temperature and precipitation values for Cuiaba, Brazil.

Aw - Darwin, Australia 12.5° S , Elevation: 27 m

Figure 7v-6: Mean monthly temperature and precipitation values for Darwin, Australia.

Am - Mangalore, India 13° N , Elevation: 22 m

Figure 7v-7: Mean monthly temperature and precipitation values for Mangalore, India.

Subtropical Desert and Steppe

• Köppen Classification - BWh and BSh.
• Dominated by Continental Tropical air masses all year.

This climate type covers 12 percent of all land area on the continents. The heart of the tropical desert climate is found near the tropics of Cancer and Capricorn, usually toward the western side of the continents. Regions with this climate have the following common climatic characteristics:

• low relative humidity and cloud cover.
• low frequency and amount of precipitation.
• high mean annual temperature.
• high monthly temperatures.
• high diurnal temperature ranges.
• high wind velocities.

The tropical desert climate is influenced by upper air stability and subsidence which is the result of the presence of the subtropical high pressure zone. Relative humidity is normally low, averaging 10 to 30 percent in interior locations. Precipitation is very low in quantity and very infrequent in distribution, both temporally and spatially.

Temperature varies greatly both diurnally and annually. The highest average monthly temperatures on the Earth are found in the tropical desert. They range between 29 to 35° Celsius. Winter monthly temperatures can be 15 to 25° cooler than summer temperatures. This climate also has extreme diurnal ranges of temperature. The average diurnal range is from 14 to 25° Celsius.

BWh - Berbera, Somalia 10.5° N , Elevation: 8 m

Figure 7v-8: Mean monthly temperature and precipitation values for Berbera, Somalia.

BWh - Alice Springs, Australia 23.5° S , Elevation: 579 m

Figure 7v-9: Mean monthly temperature and precipitation values for Alice Springs, Australia.

BSh - Monterrey, Mexico 26° N , Elevation: 512 m

Figure 7v-10: Mean monthly temperature and precipitation values for Monterrey, Mexico.

Mid-Latitude Desert and Steppe

• Köppen Classification - BWk and BSk.
• Dominated by Continental Tropical air masses during summer and Continental Polar in winter.