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Home The River Basin People and the River Governance Resource Management
The River Basin
 Introduction
Geography
Climate and Weather
 Principles of Climate and Weather
 Hydrologic Cycle
 Climate Variability
Climate Classification
 Water Scarcity
 Drought
 Climate of the Kunene Basin
 Climate Change
Hydrology
Water Quality
Ecology & Biodiversity
Watersheds
 References

 



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Climate Classification  

Classification serves to simplify a description of regional climates by grouping similar climates together.

One of the most widely used climate classification systems today is the Köppen-Geiger Climate Classification system. It is based on the assumption that native vegetation is the best expression of climate and combines annual and monthly averages of temperature and precipitation. It covers five major climatic types with each type being denoted by a capital letter, as described below:

  • A - Tropical moist climates: all months have average temperatures above
    18° C
  • B - Dry climates: 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

For details of each of these major climate types, see the box below the Köppen-Geiger climate map.

World map of Köppen-Geiger climate classification.
Source: Peel, M. C. and Finlayson, B. L. and McMahon, T. A. (2007)
( click to enlarge )

The Kunene River is split roughly in half with a category C climate in the upper reaches of the catchment and category B in the lower reaches and towards the coast. For more details of the distribution of climatic zones in the Kunene River basin, see Climate Classification in the Basin.

Detailed Description of the Köppen Climatic Types

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
1 500 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° C. 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° C, while night time temperatures average 22° C. 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 1 000 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 (plants able to survive in climates with little or no water). 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: Cw have dry winters, Cs dry summers and in Cf there is significant precipitation throughout the year. Each of these can in turn be subdivded into categories a, b or c (for example Cwa, Cwb, Cwc) depending on the temperature in summer months, with a being in general the warmest.

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° C, while the coldest month is less than -3° C. 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.

These in turn can be subdivided into categories a, b, c and d depending on the summer temperatures.

Polar Climates (E)

Polar climates have year-round cold temperatures with the warmest month less than 10° C. 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. 

Source: Pidwirny 2006

 

 



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