Orographic changes in precipitation using gradient-based IMERG data assessment in the Alborz Mountains, Iran

Abstract

This research investigates the effects of topographic factors on precipitation in the northern and southern slopes of the Alborz Mountains in Iran, because the complex relationship between precipitation and topography is particular dependent on a specific geographical location. Remote sensing data was used to investigate how topographic features, such as elevation, longitude, and latitude, affect precipitation from 2001 to 2010, 2011 to 2020, and 2001 to 2020. The precipitation gradient was calculated using IMERG V06 Final data and a digital elevation model (DEM) with an accuracy of 0.1 degrees. Furthermore, ground station data was utilized to confirm these findings. Precipitation in the study area was influenced by latitude by 10.52 % during the period 2001–2010, 9.34 % during the period 2011–2020, and 18.85 % during the long-term average (2001–2020) according to the results. The impact of longitude and elevation was less significant than that of latitude, with an effect size of 8.85 % and 0.25 % respectively. In the studied area, the observed precipitation gradient was only 18.29 % influenced by the combination of three topographic factors (longitude, latitude and elevation). On the other hand, the findings showed that latitude, elevation and longitude were each influential by 82.27 %, 57.42 %, and 52.50 % in precipitation gradients, respectively. These results indicate that orographic precipitation cannot be the only parameter affecting precipitation, because it is affected by temporal and climatic factors. These findings indicate that IMERG precipitation products are very useful in studying precipitation patterns in relation to time and space in water resources management operations.