بررسي رابطه بين بارش و توپوگرافي در دامنه هاي شرقي و غربي منطقه كوهستاني تالش

Study of the Relationship between Precipitation and Topography in Eastern and Western Slopes of Talesh Mountainous region

Topography and geography variables including altitude, latitude, distance from moist source and other topographical variables such as slope, direction of valleys and distance from obstructive barrier in eight geographical directions have been considered in order to study the relationship between precipitation and geography and topography characteristics of eastern and western slopes of Talesh Mountains. The 26-year (1981-2006) precipitation statistics in 41 climatology and rain-measuring station of the region have been used in this research. Topography-geography variables extracted through 1:50000, 1:100000 and 1:250000 topographical maps of the region. Correlation coefficients between topography-geography variables have been calculated with event type of annual and seasonal precipitation at Eastern and western slopes and forecast equations of region rains have been prepared by employing stepwise regression method. The results show that the amount of precipitation at Eastern slopes of Talesh are much higher than that of the western slopes and Talesh mountains act as a barrier against Khazar rains and prevent the penetration of humidity toward western slopes of Talesh. Elevation variable has a positive relationship with precipitation at western slopes and a negative one at eastern slopes. Also, effects of topographical variables vary with geographical directions. The findings of the research demonstrate that topographical variables were more effective at eastern slopes of Talesh than the western ones. We can observe the least effect of topographical and geographical factors on precipitations at both slopes in winter.