Detecting land cover transitions and the impacts on temperature in the East Asian monsoon region

Abstract

Recently, human-induced land cover and land use (LCLU) changes have increased as enhancing our social and economic activities. The unprecedented LCLU change has been perturbing the physical state of the land surface and the chemical composition of the atmosphere. It is therefore important to quantify the LCLU changes and the impacts on the climates in the East Asian monsoon (EAM) region, where the extensive LCLU changes have been occurred. This study examined changes and transitions of land cover using the AVHRR Global Inventory Modeling and Mapping Studies Normalized Difference Vegetation Index dataset (AVHRR GIMMS NDVI3g) and the recently developed long-term LCLU maps spanning 1982 to 2015. In the regions identified as having undergone significant land cover transitions, we investigated the relationships of the transitions with 2m temperature from ERA5-Land reanalysis data. The results of a fractional analysis indicated that croplands were the major land cover in central and northeastern China and the western Korean Peninsula. Forests were dominant in southern China, the eastern Korean Peninsula, and entire Japan. Grasslands were distributed in marginal areas of Inner Mongolia. The results of a transition analysis revealed that in northeastern China, the dominant trend was forests and grasslands changing into croplands. In Sichuan, croplands were mainly converted to forests. The croplands to forests transition in Sichuan could affect the regional warming caused by warming effect of reforestation in alpine regions with reduced cooling of irrigation agriculture. The biogeophysical processes between the detected LCLU changes and the regional climates will be further explored.