Influence of Terrain Attributes on the Number of Snow-Covered Days Over Karoon River Basin, Iran

Abstract

Objectives: The purpose of this study is to find the relationships of snow-covered days (SCDs) with topographic variables such as elevation, slope and aspect by using MODIS data. Methods/Statistical Analysis: MODIS data were used from 1 January 2003 to 31 December 2015. Due to cloud contamination in the daily data of MODIS snow products, it is not reasonable to use the data without any processing aimed at reducing cloud blockage. To reduce cloud cover effect, the daily data of MOD10A1 and MYD10A1 were combined and a three day filtering technique was applied to further reduce cloud cover effect. Findings: 1) The relationship of SCDs with elevation is not necessarily a linear relation; 2) The slope value of 22° is the critical slope in the Basin above which the snow accumulation decreases; and 3) The most SCDs are on the N and NE facing slopes and the least SCDs are on the SW facing slopes. Application/Improvements: The study showed that the slopes steeper than 22 degree are not suitable for snow accumulation. So in a country like Iran that is 3 degree Celsius warmer than the globe and snowfall frequency is dramatically low and this may be considered as a new restriction to accumulation of snow in high altitudes of the country.