Analysis and distribution of annual and seasonal land surface temperature in Iran's elevation floors using MODIS data

Introduction Climate change is the term used to describe the significant and ongoing variations occurring in the Earth's climate, such as changes in temperature, precipitation, and wind patterns. These changes have been increasingly observed in recent decades, and they are mainly caused by human activities, particularly the emission of greenhouse gases that trap heat in the atmosphere, leading to global warming. An increase in the Earth's surface temperature is a crucial factor in climate change because it affects the exchange of energy between the Earth's surface and the atmosphere, and this, in turn, impacts weather patterns and systems. To monitor and study temperature changes, scientists often use thermal infrared remote sensing data, which enables the remote measurement of the Earth's surface temperature and provides valuable information for understanding interactions between the hydrosphere, biosphere, and atmosphere. The consequences of climate change are far-reaching and pose significant challenges to human security worldwide. Changes in temperature and rainfall patterns can lead to crop loss, threaten food security, exacerbate water scarcity, and contribute to the frequency and severity of natural disasters. To mitigate the harmful effects of climate change, it is necessary to take measures to reduce greenhouse gas emissions and adapt to climate change, such as adopting new agricultural technologies and practices, improving water management, and so on.

Materials and methods To begin with, the elevation floors that were studied were extracted from the digital model map of Iran. In the next step, the seasonal and annual time series of land surface temperature day were analyzed for the entire study area, as well as for each elevation floors individually. These analyses were conducted using MODIS images, and the statistical period of 2001-2022 was taken into account.In order to analyze temperature changes in each altitude class and to achieve more accurate and reliable results, the trends of parameters such as Min, Max, Mean, STD, Variety, Majority and Minority were calculated. The 8-day MODIS.MOD11A2.061 images are the main source of the present study and were obtained for free from the LP DAAC system (https://lpdaac.usgs.gov) and they include a total of 966 images, each year having 46 images. All calculations and preparation of maps have been done through Arc GIS, GIS Pro Arc and Excel software.

Results and Discussion Studies on the climate of Iran have revealed that the highest average temperature is during spring and summer. These studies, which were conducted based on statistical surveys of temperature on an annual and seasonal scale, have shown an increasing trend of temperature during these periods. Conversely, the temperature has been observed to decrease in the autumn season. Moreover, the minimum temperature has increased and the difference between the minimum and maximum temperature has decreased, leading to a reduction in spatial temperature variation in the area under study. The southwestern regions of Iran, including the Khuzestan province, and the central Lut desert, are the hottest parts of the country during the summer season. During other months of the year, the hottest areas are found on the Lut desert , coasts of the Oman Sea , the provinces of Sistan and Baluchistan and Hormozgan, which have the lowest altitude above sea level. On the other hand, higher altitudes such as Damavand and Zagros mountains have been observed to have the lowest average temperature. Elevation floor 2 has an annual average temperature of 38.4 degrees Celsius, while elevation floor 10 has the lowest annual average temperature of 9.8 degrees Celsius. In general, areas with higher altitudes have lower temperatures than those with lower altitudes in all seasons of the year.

Conclusion The highest annual average was recorded in 2021 with a temperature of 28 degrees Celsius. While the years 2007, 2009, 2011 and 2012 have the lowest average temperature with a temperature of 25 degrees Celsius. The 2nd floor with a height of 400-800 meters includes the highest temperature. This class is mostly focused on the catchment area of the Central Plateau, which, including the vast deserts of Dasht Kavir and Kavir Lut, has a hot and dry climate with the highest average temperature in spring and summer. In parts of the first floor of Koirlu and parts of the coastal areas of the Oman Sea and the Persian Gulf, due to the role of the specific heat of water, the highest average temperature has been allocated in the autumn and winter seasons. On the other hand, the 10th floor, which includes the heights of Alborz and Zagros, has the lowest average temperature.