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.

Drought is one of the natural disasters with the widest global impact. The anomalous drought and heatwave event that occurred in the Yangtze River Basin in summer of 2022 is not only of high intensity but also of long duration, it is a rare and significant drought event leading to very serious socioeconomic impacts in China. In view of the extreme nature of this event, this paper reveals the possible influence of atmospheric circulation and external forcing anomalies on this drought event based on an objective analysis of the evolutionary characteristics of this event. It is found that the meteorological drought index and soil moisture monitoring results consistently indicate that this drought event started to appear in June, developed rapidly in July, and further expanded and intensified in both extent and intensity in August. At the same time, the overall temperature in the basin was high, with the number of high temperature days exceeding 40 days in some areas. In addition, anomaly of evapotranspiration over the basin in summer was the second highest on record since 1960, second only to the high temperature drought event in 2013, which further exacerbated the degree of water deficit in the Yangtze River Basin. From the perspective of circulation characteristics, the abnormal intensifying and westward extension of the western Pacific subtropical high pressure, the small area and weak strength of the polar vortex and the intensifying and eastward shift of the South Asian high pressure in summer jointly led to weak water vapor transport conditions and prevailing sinking air currents in the Yangtze River Basin, making the overall conditions unfavorable for the occurrence of precipitation. The persistence of the La Niña event, the appearance of negative Indian Ocean Dipole (IOD) and the persistence of the negative snow cover anomaly in the northwestern Tibet Plateau in spring may be the main external forcing factors leading to the circulation anomaly in this summer.

Drought is one of the natural disasters with the widest impact and the most serious economic losses in China, which directly threatens the country’s food security and socio-economic development. The understanding and research on drought will help to improve the national capacity of drought prevention and mitigation. Since 1949, China’s research on drought meteorology has achieved fruitful results. Based on the research results of the scientific research project group related to drought meteorology carried out by the Key Open Laboratory of Arid Climate Change and Disaster Reduction of China Meteorological Administration since the 21st century, through the achievement retrieval, this paper summarizes the new progress in drought monitoring technology, drought temporal and spatial distribution, drought disaster-causing characteristics, drought disaster risk and its response to climate warming, as well as drought disaster risk management and defense technology. At the same time, based on the frontier development trend of drought meteorology research, on the basis of strengthening the comprehensive drought observation test in drought prone areas under the background of climate change, this paper puts forward that China’s drought meteorology research in future should study quantitatively the formation mechanism of drought from different dimensions and scales, build a new comprehensive drought monitoring method of multi-source data fusion and multi-method combination, reveal the mechanism of drought disaster-causing and evaluate scientifically the drought disaster risk, putting forward the executable risk management strategies. This work is of positive significance to promoting drought meteorological research in China.

Soil heat flux plays an important role in energy flux exchange between land and atmosphere, especially in arid and semi-arid region. Based on soil heat flux at Zhangye National Climate Observatory, the diurnal variation of soil heat flux and the relationship between that and radiation flux are analyzed under different weather conditions for clear, cloudy and rainy day.The results show that the soil accepted heat from the air on clear day, on the contrary, the output heat of soil exceeded the input on cloudy and rainy day. In addition, most values of soil heat flux are negative in autumn and winter season, and positive in spring and summer .

The cloud—water resources of the Qilian Mountain were analyzed by using the observed data of eight meteorological stations from 1960 to 2002 and the NCEP／NCAR data(2．5。×2．5。)for the period of 1970—1997．Results show that the water vapor amount gradually increased from spring to summer，and then decreased；the precipitation there was concentrated in May to Septembe r which was in the proportion of 86．8％ to annual precipitation．Comparing the preceding period (1970—1986)with the succeeding period (1988—1997)of climatic change in Northwest China，the annual mean precipitation there increased more than 8．1％ in the succee—ding period (mainly in spring and summer)，which was beneficial to the ecological improvement there．The precipitation in the middle part of the Qilian Mountain was much more than that in eastern and western part．The annual water vapor input was 885．4×10 m ．which mostly cflme from the levels under 6O0 hPa，an d it divergenced over 600 hPa at most time of a year．The water vapor mainly canle from longitudinal input．

The cloud—water resources of the Qilian Mountain were analyzed by using the observed data of eight meteorological stations from 1960 to 2002 and the NCEP／NCAR data(2．5。×2．5。)for the period of 1970—1997．Results show that the water vapor amount gradually increased from spring to summer，and then decreased；the precipitation there was concentrated in May to Septembe r which was in the proportion of 86．8％ to annual precipitation．Comparing the preceding period (1970—1986)with the succeeding period (1988—1997)of climatic change in Northwest China，the annual mean precipitation there increased more than 8．1％ in the succeeding period (mainly in spring and summer)，which was beneficial to the ecological improvement there．The precipitation in the middle part of the Qilian Mountain was much more than that in eastern and western part．The annual water vapor input was 885．4×10 m ．which mostly cflme from the levels under 6O0 hPa，an d it divergenced over 600 hPa at most time of a year．Th e water vapor mainly canle from longitudinal input．