The summer monsoon transition zone in China is one of the regions with strong land-atmosphere interaction in the world, and it is also an area where extreme weather disasters are frequent and easy to cause serious economic losses. Further understanding of land-atmosphere interaction in the transition area will help to improve the disaster prevention and mitigation ability of this region. Based on the research results of the summer monsoon transition area related projects carried out by the Key Laboratory of Drought Climate Change and Disaster Reduction of China Meteorological Administration in recent years, this paper systematically summarizes the new progresses of land-atmosphere interaction in the summer monsoon transition zone, including the spatio-temporal distribution law of land-atmosphere interaction in the transition region, the new characteristics of the response of land surface water budget to summer monsoon, the spatio-temporal variation characteristics and development mechanism of the boundary layer, the influence of monsoon and land-atmosphere interaction on regional climate in the transition zone, the new progress of land-atmosphere interaction on crop yield in the transition zone and new schemes for parameterization of multi-factor and multi-scale kinetic roughness. According to the development trend of land-atmosphere interaction research in the summer monsoon transition zone, it is proposed that the multi-scale dynamic response of land-atmosphere interaction to summer monsoon should be explored in the future, and the climatic dynamic relationship between surface processes and key physical quantities in the atmospheric boundary layer should be established on the basis of the research on the response rule of land-atmosphere exchange multi-cycle process to the annual cycle of summer monsoon in order to improve and enhance the simulation of regional climate models in the future. This work is of great significance to promote the research of land-atmosphere coupling process in China, which can provide scientific and technological support for disaster prevention and mitigation in the summer monsoon transition zone in China.

The northwest region of China is located in the hinterland of Eurasia, in which the source of water vapor is scarce, and drought is its main climatic feature. In recent years, with the continuous increase of regional precipitation, the warming and wetting in Northwest China has attracted great attention from all walks of life. In order to scientifically respond to social concerns, the team used multi-source data to conduct in-depth research on the phenomenon of warming and wetting in Northwest China from multi-scale and multi-dimensional perspectives, and found that the trend of wetting in Northwest China had significant and nonlinear enhancement characteristics. It is recognized that the wetting in Northwest China is expanding eastward, and the land surface evapotranspiration there has a special negative feedback mechanism on climate warming. It is estimated that the warming and wetting trend will still maintain in Northwest China in this century, and the wetting trend is driven by multi-factor comprehensive driving mechanism. The multi-aspect impacts of the warming and wetting in Northwest China are evaluated, and the technical countermeasures to deal with the warming and wetting there are put forward, and the research results of “the enhancement and eastward expansion of climate warming and humidification, formation mechanism and important environmental impacts in Northwest China” are formed. The major consultation report based on the research results has played an important decision-making support for the national strategies such as the development of the western region in the new era and the ecological protection and high-quality development of the Yellow River Basin. The research results were selected as “China's Top Ten Scientific and Technological Progress in Ecological Environment” in 2022, and have also received extensive attention from the international academic communities.

As a land-atmosphere coupling “hot spot”, the northern China climate transition zone has a sharp spatial gradient of hydrothermal conditions, which plays an essential role in shaping the spatial and temporal pattern of evapotranspiration-precipitation coupling, but which mechanisms still remain unclear. Based on multi-source fusion of evapotranspiration, precipitation, temperature and satellite remote sensing soil moisture data, this study analyzes the spatial and temporal variation in evapotranspiration-precipitation coupling strength in the climate transitional zone of northern China and its relationship with soil moisture and air temperature. Results show that evapotranspiration-precipitation coupling strength gradually transitions from strong positive in the northwest to negative in the southeast and northeast corners. The evapotranspiration-precipitation coupling gradually increases with the decrease of spatial soil moisture and enhances with the increase of evapotranspiration variability. When considering the synergistic effect of water and heat, the synergistic effect of soil moisture and mean temperature is more influential than the synergistic effect of soil moisture and temperature variability on the spatial distribution of evapotranspiration-precipitation coupling strength, and plays a dominant role. Temporally, the coupling strength showed a intra-annual variation in the order of weakening in spring, summer, autumn and winter, and was characterized by obvious inter-annual fluctuations. Soil moisture variability and mean temperature are the main factors dominating the intra-annual variation of evapotranspiration-precipitation coupling in northern regions, and the mean soil moisture and soil moisture variability have significant effects on the inter-annual variation of evapotranspiration-precipitation coupling. When considering the synergistic effect, the intra-annual cycle of mean moisture and temperature jointly determines the intra-annual variation of evapotranspiration-precipitation coupling; and their effects on the inter-annual variation of evapotranspiration-precipitation coupling are significant only in the semi-arid region where the coupling is the largest. The results of the study can improve the understanding of the response of land-atmosphere coupling strength to the spatial and temporal changes of land surface state and provide a reference for improving the numerical simulation of land-atmosphere coupling.