Analysis of the relationship albedo with Elevation, slope, and Aspect in Iran

Surface albedo is a climatic parameter that is a function of surface type. In this study, to investigate the relationship between albedo and Elevation components in Iran from the combined data (Terra / Aqua) of Modis sensor in the period 3/20/2000 to 3/20/2019 (6940 days) on a daily basis and in a spatial resolution of 500 Meters were utilized. Also, Iran's Digital Elevation Model (DEM) data in spatial resolution of 500 meters and with a sinusoidal projection system coordinated with the spatial resolution and projection system of albedo data were downloaded from the NASA website. In the DEM data used, In data used, in addition to the elevation of the points, the slope and aspect information for each pixel is also in decis. Prior to data usage, some preprocessing was performed on digital data. Based on nearly 60 billion pixels, the albedo and DEM showed a linear fragmentary pattern. The results showed that the amount of albedo has 5 different patterns with increasing elevation. The first pattern shows the whiteness behavior at elevation below sea level. In these zones, albedo increases sharply with increasing elevation due to rising land surface temperature(LST). So that the albedo goes from 4% to about 16%. The second pattern shows the uniform behavior of the albedo at an elevation of 0-800 m. The third pattern of albedo decreasing behavior with elevation is revealed in the 1300-800 m belt. One of the reasons for the decrease in albedo in these elevation belts can be the expansion of cities and consequently the decrease in albedo due to the smooth surface of the asphalt of the streets and the paving of the streets. In the fourth pattern, a direct connection of albedo with elevation is observed in the belt of 3500-1300 meters. One of the main reasons for the increase in albedo in this elevation belt is the increase in snow cover in this elevation belt. The fifth pattern also shows a direct link between albedo and elevation above 3500 meters and is a continuation of the fourth pattern, with the difference that this pattern loses some of its order and shows a scattered pattern. The correlation of albedo and slope also showed that due to more sun exposure, the southern aspect of Iran has about 3% more albedo than the northern aspect. The correlation between the albedo and the slope is a straight line. As the albedo decreases to a slope of 30 °, the albedo will increase on slopes above 30 °.