Investigating Surface Changes in Snow Cover Concerning Land Surface Temperature, Evapotranspiration, and Vegetation Cover in the Aras Basin

Background: The climate change phenomenon and its effects and consequences have become a challenging issue for managers and planners, especially for water resources.Currently, climate change has attracted the attention of scientists due to its effects on human societies.Snow plays an important role in the protection of biodiversity, and changes in the amount of snow cover affect animal and plant life as well as the structure of ecosystems.Snow cover is very important in mountainous areas.Since snow is considered solid water, it is an important source for providing drinking water.Because snow cover contains a lot of air, it is a weak conductor of heat, thus the snow cover can protect agricultural products and trees from extreme cold.The current research aims to investigate changes in snow cover concerning land surface temperature, evapotranspiration, and vegetation cover components in the Aras Basin using MODIS sensor data products in annual, seasonal, and monthly periods.Methods: The studied area is the Aras Basin, which is considered a part of the western Caspian Lake sub-basin and forms the political border between Azerbaijan, Iran, Turkey, and Armenia countries.In this research, Terra satellite images were used to calculate snow cover, land surface temperature, vegetation cover, and evapotranspiration.In this way, the annual average, monthly average, and seasonal average were calculated for each of the mentioned variables based on the solar date.Daily products of snow, vegetation, surface temperature, and 8-day evapotranspiration product of the Terra satellite were used here.Finally, the images were transferred to the ArcMap 10.8 environment for calculation.To calculate the averages of the studied variables in the period of 2011-2018, 8644, 8642, 8325, and 1058 images were processed for snow cover, land surface temperature, vegetation cover, and evapotranspiration, respectively, using coding in Google Earth Engine.Results: The results showed that the hottest and highest temperatures were in 2000, 2001, and 2014, respectively, during 2000-2022, with the average maximum temperatures of 42, 40, and 40 C.The coldest year of the studied statistical period was 2017, with average maximum and minimum temperatures of 35 and 1 C, respectively.The highest average amount of greenness belonged to the years 2019 and 2021 with a value of 0.44, and the lowest average amount of greenness was recorded for the years 2007 and 2003 with a value of 0.34.In the studied years, 2019 and 2022 had the lowest and the highest annual averages of evapotranspiration, respectively.The evapotranspiration in 2018 was at the highest (20.96) and the lowest (3.57kg/m3), levels, respectively.In 2022, evapotranspiration was 37.42 in the highest state and 2.60 kg/m3 in the lowest state.In all the studied years, the southeastern and northern parts of the studied basin had the highest average evapotranspiration.In 2018, the maximum and the minimum average land surface temperatures were equal to 37.12 and 0.14 C, respectively.In 2022, the maximum temperature of the land surface temperature was 39.80 and its minimum was 5.66 C.As can be seen, there is a direct relationship between temperature and evapotranspiration in these years.During the years 2000-2022, the lowest and the highest averages of NDSI were observed in 2000 (17.31) and 2017 (26.23).In all the studied years, the most snow-bearing areas were the high-altitude areas located in the southern, southeastern, and southwestern parts of the Aras Basin.