Orographic precipitation modeling with multiple linear regression

A multiple linear regression (MLR) model, in conjunction with Geographic Information Systems technology, was used to derive the relationship between annual precipitation and elevation, longitude, and latitude. The island of Crete, in Greece, was used as the case study. A multiscale precipitation analysis was performed on areas ranging from large areas (the whole island and the northern, southern, and eastern parts of the island), to medium areas (watersheds), to small areas (sub-basins). While the MLR annual precipitation estimates (which used elevation, latitude, and longitude information) were found to be more reasonable than estimates obtained using elevation only when applied to the whole island, the difference between the MLR estimates and the elevation-only estimates was smaller when applied to individual watersheds. The MLR provides realistic estimates for mean areal precipitation for the island of Crete: 700+/-100, 950+/-150, and 1,300+/-200 mm for dry, average, and wet years, respectively. Elevation-rainfall gradients are: 0.45-0.6, 0.6-0.9, and 0.9-1.3 mm/m for dry, average, and wet years, respectively. Of this, 44% falls on the northern, 33% on the southern, and 23% on the eastern parts of the island for a typical average year.