Combined Estimation of Nighttime Land Surface Temperature in Jazmourian Drainage Basin Using MODIS Sensor Data of Terra/Aqua Satellites

Land surface temperature (LST) estimation is widely used in many applied and environmental studies such as agriculture, climate change, water resources, energy management, urban microclimate and environment. LST, which is the result of atmospheric-earth interaction, due to the sensitivity and influence of land surface conditions such as soil cover, soil moisture, albedo, surface roughness and the interaction of these factors with the atmosphere, can well determine changes in land surface temperature conditions. In the present study, Modis nighttime sensor products of both Terra and Aqua satellites (MOD11C3 & MYD11C3) from http://reverb.echo.nasa.gov/reverb for LST estimation in the Jazmourian drainage basin (southeast of Iran), were used in the period 2013-2019. After providing the products with monthly and spatial time steps of 5 km, calculations on two matrices; One monthly with dimensions of 2784 x 204 (204 represents the number of observations in consecutive months of 17 years studied (17 x 12) and 2784 represents the number of gridded points (cells) in Jazmourian drainage basin area) and the other is a seasonal matrix with dimensions of 2784 x 68 (68 representing the number of observations in consecutive chapters (17 x 4) were performed. After performing the relevant statistical and spatial analyzes in Excel and GIS software environment, nighttime LST estimation was used. The results showed that the nighttime LST in the statistical period increased by about 1 degree Celsius and this increase was more in the minimum temperatures (cold period months of the year) than the maximum nighttime LST. According to the findings, the maximum nighttime LST has occurred in the low altitudes of the central and southern regions and the minimum LST has also occurred in the northern heights of the drainage basin. The seasonal spatial distribution of the Earth's nighttime LST indicates the distribution of nighttime LST in the range of -10 to +35°C in winter and summer, respectively. Extreme fluctuations in nighttime LST during the seasonal terrestrial surface well show the prominent role of altitudes and latitudes in the temperature distribution of the Jazmourian drainage basin. Also, the time analysis of the studied variable shows a positive trend of nighttime LST in all four seasons, among which the spring and winter seasons had a higher upward slope. In addition; spatial estimation of nighttime LST anomalies, while confirming its increasing trend, shows the maximum location of nighttime LST anomalies in the central and western parts and the minimum anomalies in the eastern parts and northern heights of the drainage basin. Also, the analysis of monthly anomalies of nighttime LST shows the maximum occurrence of positive anomalies with +0.07°C in September 2016 and the minimum anomalies with -0.01 °C. are in January 2008. In general, the values of the nighttime LST significantly increased from 2008 onwards, especially in the months related to the cold period of the year (with a greater increase in the minimum nighttime LST than the maximum nighttime LST). This indicates the nighttime LST trend of the cold period of the year towards a warmer pattern. These conditions can be considered as an indicator of climate change and lead to changes in some environmental parameters such as relative humidity, evapotranspiration, soil surface moisture, snow persistence, dew point temperature and nightly reflective energy. Considering the high capabilities of the Jazmourian drainage basin in agricultural products and also the capability of seasonal tourism in different areas of this drainage basin, the importance of investigating nighttime LST changes, in this regard, is undeniable. On the other hand, with the continuing increase of environmental sensitivities and the accelerating trend of continental climate in this drainage basin, it is suggested that in future research, while estimating other climatic variables, their correlations with LST are considered. This will provide more climate knowledge of the environmental changes that have occurred in this less studied drainage basin.