Selection of variables for the purpose of regionalization of Iranʹs precipitation climate using multivariate methods

The study of precipitation climate in any region is important from the view of agricultural production, drainage of urban and agricultural lands, erosion, flood, drought, water resources and civilization. In the present study the regionalization of Iranʹs precipitation climate was considered. Since the use of various type and number of variables may lead to different boundaries in the resulting precipitation climates, it is helpful to select those precipitation related variables, which represent most of the information from all candidate variables. The selected variables were then used to regionalize Iranʹs precipitation climate using factor analysis and clustering techniques. Data from 77 weather stations in Iran were used from 1956 to 1998. Twelve variables were selected from the 57 candidate variables, using Procrustes Analysis. The H and Z-statistics, which are based on the L-moment technique, were used to test the homogeneity of each region and select the distribution which best-fitted annual precipitation records- in that region. The countrywide area was divided into six regions with homogeneous and one with heterogeneous precipitation climates. Growth curves, for dimensionless annual precipitation, are illustrated for each region.