Effects of cropland and woodland conversion on land surface temperature based on Google Earth and MODIS land data: A case study of the middle and lower reaches of the Yangtze River Basin and its adjacent areas
1. Heilongjiang Province Key Laboratory of Geographical Environment Monitoring and Spatial Information Service in Cold Regions, Harbin Normal University, Harbin 150025, China 2. Key Laboratory of Meteorological Disaster, Ministry of Education, Nanjing University of Information Science & Technology, Nanjing 210044, China; 3. Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
Revealing the impact of land conversion on land surface temperature is of great significance for understanding the climatic and environmental effects of human activities. Statistical analysis based on satellite remote sensing data is an important method to reveal the impact of land use/cover change on land surface temperature. However, in areas with high landscape fragmentation, the mixed pixel problem has become the main limiting factor for the use of this technology, especially in the Yangtze River Basin in southern China. In order to break through this limitation, 200 pairs of pure pixels of cropland and woodland were identified on the 1 km scale based on Google Earth high-definition images. Then, the differences of land surface temperature (LST), leaf area index (LAI), and albedo between cropland and woodland were compared and analyzed by MODIS land data products. The results show that the LST of cropland was higher than that of woodland, and the temperature differences between daytime and nighttime were about 2.75 ℃ and 1.15 ℃, respectively. Daytime temperature difference between cropland and woodland showed double peaks (May and October, with temperature differences about 3.18 ℃ and 3.33 ℃), and nighttime temperature difference showed a single peak (July, about 2.46 ℃). Temperature difference varied from place to place. The highest temperature difference was in the west—in the area bordering Shaanxi and Gansu Provinces, annual average temperature difference was about 3.83 ℃; and temperature difference was the smallest between central and southern Anhui Province (about 1.1 ℃). The difference of LST between cropland and woodland is mainly caused by the difference of evapotranspiration. The LAI of woodland is larger, the evapotranspiration is stronger, the latent heat flux from the surface to the atmosphere is higher, and the sensible heat used to directly heat the surface is relatively less, so the LST is relatively low. The above results show that the conversion of cropland to woodland in the Yangtze River Basin and adjacent areas has a cooling effect by increasing evaporation in recent years.
. 基于Google Earth和MODIS陆地数据的农林地转换对地表温度的影响——以长江中下游及毗邻地区为例[J]. 地理科学进展,
2019, 38(5): 698-708.
ZHANG Lijuan et al
. Effects of cropland and woodland conversion on land surface temperature based on Google Earth and MODIS land data: A case study of the middle and lower reaches of the Yangtze River Basin and its adjacent areas[J]. PROGRESS IN GEOGRAPHY,
2019, 38(5): 698-708.
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