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In the margin of the Dasht- e-Kawir there arc, unfortunately, not enough meteorological stations, and some of the stations do not have records for a long number of consecutive years. This make agro climatology planning difficult, especially when estimates of rainfall and evapotranspiration are concerned.
In order to estimate rainfall in the region multiple regression equations in valuing altitude, latitude and longitude have been calculated for mean, higher and lower annual rainfall by the author.
We must bear in mind that there are a few dominant factors influencing the rainfall value, in general, and in the region in particular, of which altitude, latitude and the source of moisture are the most important. The source of moisture is the air mass that comes from the Mediterranean Sea which lies some distance to the west of this area, and as the distance the air mass must travel increases, its effect decreases. Beaumont (1976) (1) believes <>. On the other hand, although the Caspian Sea is the source of moisture in the north of Iran, its moisture rarely passes to the central part of Iran from the Alborz mountains.
The statistical characteristics and regression equations have been calculated using the SPSS system by computer, and the data ha been used from 12 meteorological stations, records in the margins of the Dash - e -Kawir. The results of these calculations have been illustrated in the following tables.