Analysis of daytime land surface temperatures in Iran based on MODIS sensor output

The air temperature parameter is one of the most important measures for identifying the climatic and environmental conditions of each region. Today, LST maps can be prepared without physical contact with objects or surfaces by using thermal infrared data. Awareness of the spatial and temporal distribution of LST is essential to determine the land energy balance, and evapotranspiration and meteorology studies are essential. LST is a function of pure energy on the land’s surface which depends on the amount of energy reaching it, surface emissivity, humidity, and air flow. The present study intends to investigate the state of daytime LST in Iran in different months of the year based on the output of MODIS Terra images. In this study, the fifth MODIS Terra product called (Mod11C3 v005) was used with a spatial resolution of 5×5 kilometres and a daytime time period which became monthly data after the necessary processing. In this study, considering the significant precision of the day-night-based physics algorithm of Wan et al. (2002), this method was used to study Daytimte LST in Iran. After the data were decoded, an array was obtained with the dimensions of 4855×62258. Land surface temperature zoning was conducted by using the kriging geo-statistical method with the lowest error rate and the highest precision in mountainous areas. The statistical characteristics of LST in Iran during different months showed that the highest average of LST in Iran with 46.1 °C was in July. In the warmest period of the year, and in particular in the hot zones of Iran (the southern coasts), there is less variation in the temperature which consequently leads to less variation in LST in the country. Hence, less spatial autocorrelation should be observed in the warm half of the year, which indicates a more stable temperature during the warm period. The study of LST during the 15-year period from 2001 to 2015 and based on the output of the MODIS sensor for different months of the year showed that the distribution of LST in Iran was severely affected by geographical conditions, especially its latitude and topographic condition. From West to East and from North to South, there was an increase in LST in all months of the year. The Lut Desert is the warmest area in the country with temperatures rising to 59° C on hot days. The spatial processing of daytime LST in Iran showed that LST was strongly affected by latitude and altitude, and topographic conditions played an important role in the spatiotemporal distribution of LST, which is completely consistent with the studies conducted by those who asserted that each temperature range has a high degree of consistency with its environmental and geographical properties, in particular with its elevation, latitude and slope characteristics. Although the temperature zones provided for the various months of the year have the considerable spatial continuity, some parts of a temperature cluster have appeared in the form of islands in other zones, indicating the effect of complex topographic and local conditions on the occurrence of these temperature islands compared to its surroundings, which causes a spatial variation in temperature and an increase in the desire to LST clustering in Iran, or in other words, to climatic implantation.