In a region with semi-arid climate (from latin semi = half and aridus = dry, arid) exceeds six to nine months per year, the evaporation to precipitation . Semi-arid is a term for rooms and climates that are characterized by the occurrence of a distinctive dry season, but also have about three to five humid months over the course of the year . During this shorter period of time, when precipitation exceeds evaporation, rivers are periodically or episodically water-bearing.
In contrast to the arid climate , in which evaporation is greater than the amount of precipitation almost all year round, this imbalance, which is dangerous for animals and plants, alternates seasonally with a more precipitation-rich climate in which the humidity is higher. Semi-deserts are forming. Many living things are adapted to the seasonal change and can survive long dry periods. The climate diagrams based on the effective climate classification by Wladimir Peter Köppen and Rudolf Geiger clearly illustrate each climate area.
Using the example of the city of Mopti in the southern center of Mali , the zone of the semi-arid climate can be shown in a climate diagram. The most important characteristic is the relationship between temperature and precipitation. According to Köppen and Geiger, the climate of the city of Mopti is classified as type BSh . The amount of precipitation in Mopti in three months, between July and September, is above the evaporation. In nine months, the potential evaporation will therefore exceed the precipitation.
BSh climate according to Köppen and Geiger
- B = dry climate
- S = semi-arid
- h = hot
- k = cold
A BSh / BSk climate can be found in Central Africa, Southeast Africa, Pakistan, in the deforested part of Central India and in northern Australia. The climate, which is often promoted by desertification, does not allow for arable farming because of the short vegetation period.
- Nadja Podbregar, Karsten Schwanke , Harald Frater: Weather, Climate, Climate Change: Knowledge for a World in Transition , Springer, 2008, ISBN 3540792910 , page 246.