Monitoring the Earth surface temperature based on MODIS sensor products and remote sensing techniques (Case study: Kashan plain)

1. Introduction

Desertification manifests itself in its initial stages with less production in the ecosystem. In this situation, the balance of water and nutrients for the growth of plants becomes unfavorable compared to the past. In natural conditions, the ecosystem of dry areas is in a stable state in terms of water and energy conversion, but due to human intervention, this balance is subject to change. Obviously, when the vegetation is destroyed, the land becomes bare, its organic matter is destroyed and the structure of the soil is destroyed. In this situation, direct rain on the soil causes further destruction of the soil structure. The natural consequence of such conditions is the lack of rainwater storage and the drop in the level of underground water tables. Usually, severe reduction of vegetation, water and wind erosion, salinity, soil compaction, sedimentation and emptying of nutrients are considered as the main signs of desertification. According to the definition of the Convention to Combat Desertification (UNCED), desertification is the destruction of land in dry, semi-arid and dry and semi-humid areas due to human and climatic factors, which as a result reduces the productive power of the land. Water and soil are among the most valuable natural resources, and human societies, both farmers and ranchers, are active and dynamic agents of changing natural landscapes, and improper management, neglect, and excessive exploitation can lead to soil destruction, and as a result, human life is seriously threatened. be placed.

2. Methodology

To achieve the goals of the research; Modis sensor images were obtained from the NASA database during the years 2000-2020. In order to calculate the land surface temperature (LST) from the MOD11A1 product, to extract the Normalized Difference Vegetation Index (NDVI), from the MOD13Q1 product, to extract the Net Primary Production (NPP) index, from the MOD17A2H product with a spatial resolution of 500 meters in a time frame of 8 The MOD43A1 product of the Terra satellite was used to extract the albedo index. After preparing the MODIS sensor images, the indices of land surface temperature, normalized difference of vegetation cover, net primary production and albedo were estimated from the images and their correlation was checked.

3. Results and Discussion

Based on the results, LST is shown in three classes: low, medium and high. So, low to south moderate in the northwest and west and higher temperatures in the east of the study prevail. And based on the results, NDVI is classified into four areas with very poor, poor, moderate and dense coverage. Thus, the very weak layer is located in the north and northeast side, the weak layer is located in the northwest to south side, and the medium and dense layer is located in the northwest to southwest side. with increasing temperature; The normalized difference index of vegetation decreases and there is an inverse relationship between LST index and NDVI. with increasing temperature; Primary net production decreases and there is an inverse relationship between LST index and NPP. Based on the obtained results, it can be acknowledged that there is an inverse relationship between LST index and Albedo.

4. Conclusion

Based on the results obtained from the fourth chapter; The LST index during 2000-2020 was divided into three classes of low temperature, medium temperature and high temperature. So that; The largest area of the studied area had an average temperature, which was observed in the south and southwest. In the eastern and northeastern regions, the temperature was higher than in other regions, which corresponds to Namak Lake and Qom. Also, areas with low temperature were covered only in small parts from the northwest to the southwest of the region, which corresponds to the uneven heights of Karks. The NDVI index during 2000-2020 was divided into four classes: very weak, weak, medium and dense. So that; The largest area of the studied area had weak to weak silt cover, which was observed in the northwest to east range, which corresponds to Namak Lake and Qom. Also, it covered areas with medium to dense coverage only in small parts from the northwest to the southwest of the region, which corresponds to the uneven heights of Karks. Based on the results of NPP index changes during 2000-2020, the highest amount of primary net production was observed in the northwest to southeast of the studied area. This shows that the amount of primary net production is higher in this range. Also, the minimum amount of primary net production in the range from northwest to south corresponds to the heights of Vulture to Tanam, which indicates low production. Based on the results of changes in the Albedo index during the years 2000-2020, the highest amount of albedo was observed in the northeast to the east, so that these areas correspond to the salt lake and areas with weak vegetation, low net primary production and high temperature, because albedo and surface temperature The earth is affected by the amount of vegetation and relatively small changes in the characteristics of the vegetation cause changes in the albedo and temperature of the earth's surface. Between the normalized difference index data of vegetation and land surface temperature, net primary production and land surface temperature and albedo and land surface temperature, there was a significant relationship at the one percent level so that the correlation between vegetation and temperature, net primary production and temperature and albedo and the temperature was reversed and equal to 0.80, -0.84 and -0.85 respectively. The results of the study made it possible to create a desertification program by presenting a practical program for the Syr Regressive Road Dam and took an effective step towards sustainable development.