Dry Climate
These climates are characterized by the fact that precipitation is less than potential evapotranspiration. Desert areas, situated along the west coasts of continents at tropical or near-tropical locations, are characterized by cooler temperatures than encountered elsewhere at comparable latitudes (due to the nearby presence of cold ocean currents) and frequent fog and low clouds, despite the fact that these places rank among the driest on earth in terms of actual precipitation received. In this climate, summers are hot to very hot and it seldom rains. Winter days may be cool or warm, and winter nights can be very cold. The air is dry, there is little cloud; sunshine is intense and glare can be a problem.
Arid Climate
The Desert climate (in the Köppen climate classification), also known as an arid climate, is a climate in which precipitation is too low to sustain any vegetation at all, or at most a very scanty shrub,[citation needed] and does not meet the criteria to be classified as a polar climate.
An area that features this climate usually experiences from 25 to 200 mm (7.87 inches) per year of precipitation and in some years may experience no precipitation at all. Averages may be even less such as in Arica, Chile, where precipitation normals annually stand at around 1 mm per year.
Semi-arid Climate
A semi-arid climate or steppe climate is the climate of a region that receives precipitation below potential evapotranspiration, but not extremely. There are different kinds of semi-arid climates, depending on such variables as temperature, and they give rise to different classes of ecology.
A more precise definition is given by the Köppen climate classification, which treats steppe climates as intermediates between desert climates and humid climates in ecological characteristics and agricultural potential. Semi-arid climates tend to support short or scrubby vegetation and are usually dominated by either grasses or shrubs.
Other terms/definitions:
Precipitation- is any product of the condensation of atmospheric water vapor that falls under gravity.