Based on European Centre for Medium-Range Weather Forecasts （ECMWF） fifth-generation global atmospheric reanalysis （ERA5） every day from May to August during 1979-2020, three land-atmosphere indexes to investigate land-atmosphere coupling processes were calculated,characteristics of land-atmosphere coupling in climatology and their difference under different dry and wetsoil conditions were analyzed over eastern and southern Asia. The results show that Northeast and North China,the Tibetan plateau, India, Yunnan Province of China and Southeast Asia,the middle latitude arid zone were strong land-atmosphere coupling zones in climatology. In the middle latitude arid zone, land-atmosphere coupling had no significant difference under different soil conditions due to the low soil moisture and its little variability. In the other strong coupling zones, the coupling strength decreased with increasing soil moisture condition because of the bigger variability of soil moisture in these regions, and this law is applicable to the coupling processes between soil moisture（SM） and evapotranspiration （ET）, between ET and water vapor condition of boundary layer, between ET and instability condition of boundary layer. The land-atmosphere couplings over South China were weak in climatology, coupling between SM and ET was significant only under dry soil conditions, while the coupling between ET and atmospheric boundary layer were not significant under all soil moisture conditions.

According to “the Regulations on Monitoring and Evaluation of Regional Important Processes” issued by China Meteorological Administration in 2019, the basic situations of China’s climate and main meteorological disasters in summer 2021 are comprehensively analyzed based on the meteorological observation data of more than 2400 ground stations in China from 1961 to 2021. The results are as follows: (1) In the summer of 2021, both the average temperature and the average precipitation were higher than that in the same period of the previous years. The rainy season in the north started earlier with enhanced intensity, while it delayed in the south with weakened intensity. These two factors, together with the decreased number of landing typhoons, contributed to the fact that the summer precipitation zones dominated North China. (2) In the summer of 2021, China’s climate conditions were generally worse than normal, the situation of meteorological disasters was complicated and severe, accompanied with frequent occurrences of extreme weather and climate composite events, including flood, heat wave and drought, and moreover, the disasters exhibited periodic and regional features. The number of regional rainstorm processes was 4.9 times lower than that in previous summers, but the extremeness was much stronger. North China, Huanghuai, Jianghan and other places have suffered from severe rainstorms and floods consecutively. Regional high temperature occurred frequently and periodically. The number of regional high temperature processes was 3.4 times higher than that in previous summers, which mainly impacted Huanghai, Jiangnan, South China, the east of Northwest China, the west of Inner Mongolia and the south of Xinjiang. Meteorological droughts appeared in the south and the north simultaneously, with significant regional, periodic and compounding characteristics. And the number of regional drought processes was 1.1 times higher than that in previous summers. South China and Northwest China witnessed the compound development of high temperature and drought.

Based on the potato yield data in Hebei Province from 1983 to 2019, the average temperature, precipitation and sunshine hours every ten days from 21 meteorological stations during the same period, the meteorological key factors influencing potato yield were determined by means of factor puffing and correlation analysis. The forecast model of potato yield was established and this model was tested during 1983-2015 and was applied during 2016-2019. The results show that potato yield in Hebei Province was sensitive to temperature and sunshine from July to September, and the effect of temperature on potato yield was greater than sunshine hours. The average trend backtesting accuracy ranged from 75.7% to 91.7% for different initial forecast time, the average backtesting accuracy of forecast potato yield ranged from 83.6% to 91.4%, and the forecast accuracy of potato yield during 2016-2019 ranged from 83.5% to 95.3%, and with the backward of initial forecast time, the forecast accuracy improved gradually.

Based on daily meteorological observation data in main apple producing areas of China from 1971 to 2017, the crop coefficients at different growth stages of apple were corrected, firstly. And on this basis the precipitation suitability model at each growth stage of apple was constructed. Then, combined with the geographical distribution of apple in advantageous areas, the threshold of precipitation suitability of apple, and the spatial and temporal distribution characteristics of precipitation suitability at each growth stage of apple were analyzed. Furthermore, the temporal and spatial anomalies were discussed by using empirical orthogonal function (EOF) decomposition method. The results are as follows: (1) The thresholds of precipitation suitability at initial growth stage, vigorous growth stage and later growth stage of apple were 0.30-1.29, 0.63-1.78 and 0.62-2.84, respectively. The areas within the threshold range at each growth stage of apple accounted for 94.8%, 94.7% and 95.9% of main producing areas, respectively. The change trend of precipitation suitability in most regions at three growth stages of apple wasn’t significant from 1971 to 2017. (2) The variance contribution rates of the first eigenvector field of precipitation suitability at initial growth stage and vigorous growth stage of apple were 50.53% and 32.26%, respectively. The eigenvalues were almost positive in the whole region, which indicated that the spatial change of precipitation suitability had good consistency, and the oscillation intensity of precipitation suitability strengthened from northeast and southwest to the middle. The variance contribution rate of the first eigenvector field of precipitation suitability reached 49.51% at later growth period, and the distribution pattern in Liaoning Province and the local part of eastern Hebei Province was opposite to other areas. (3) The second eigenvector field of precipitation suitability appeared an opposite phase distribution pattern in the east and the west at initial growth period of apple, while that were anti-phase distribution pattern in northern and southern parts at vigorous growth period and later growth period of apple. 

The difference of land-atmosphere energy flux caused by the heterogeneity of underlying surface properties plays an important role in affecting the occurrence of local heavy precipitation. The transition of vegetation is fast in western part of the transition zone of China’s summer monsoon, the nature of vegetation is obviously different, and the surface heterogeneity is strong, so the extreme precipitation is prone to occurrence. In order to explore the influence of underlying surface heterogeneity on strong precipitation in this area, the characteristics of underlying surface were analyzed statistically. And on this basis the sensitivity tests with three or six kinds of landuse type and control test for a typical heavy rainfall process under the influence of the western Pacific subtropical high and cold air from 28 to 29 August 2017 were carried out by using the mesoscale model of WRF3.8 and NCAR-LSM land surface model. The influences of underlying surface change on rainstorm intensity, falling area and flux parameters were studied. The results show that the underlying surface with three to six kinds distributed in transition region of summer monsoon of China. The types of underlying surface were relatively few in eastern part of Qinghai to central Gansu, the heterogeneity was weak, while there were more than six kinds in southeastern part of Northwest China and northern Sichuan, the heterogeneity was strong. The proportion of representative vegetation in a single grid in the model was not high, and the contribution rate to land-atmosphere flux was less than 50%, which indicated that it was not suitable to consider the single underlying surface in calculating land-to-air flux during the heavy rain process. The area of precipitation with different magnitudes was closer to the actual situation with the increase of underlying surface types in the model, and the heterogeneity of land feature physical quantity strengthened in main rain zones. Compared with the control test, the simulated shallow surface temperature, surface heat flux, sensible heat flux and latent heat flux by two sensitivity tests reduced during the daytime, which shrank the bias to some extent, thus decreased convective available potential energy and restrained the occurrence of convective rainfall, further reduced the positive bias of precipitation.

The characteristics of the extreme drought event occurred from 1941 to 1943 in North China and its influence were analyzed in this paper． Results show that this drought event was the second extremely arid events during the Republic of China period，and He’ nan Province was the center of this event． It occurred on interdecadal relatively warm period and persisted long time． This drought event influenced so many provinces，and disaster was so serious with locust occurrence． It made population suffer severe losses and food prices soaring as well as ecological environment deterioration．
 

The characteristics and influence of the serious drought event lasting eleven years ( 1922 － 1932) in the Yellow River valley
was analyzed in this paper． The result shows that this serious drought event occurred at least once in two hundred years． It happened in
the relatively warmer period under the background of a century － scale drought，which was characterized by long time，wide area，and
heavy damage． During the period of 1922 － 1932，the natural disasters such as drought，locusts，earthquakes，pestilence intertwined
with the man － made disasters ( banditry and war) ，which led to a terrible calamity in the Yellow River valley，the entironment and agricultural
productivity suffered great devastation，and the people underwent all kinds of hardships．

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 .

Based on five - layer wind speed, air temperature, humidity and vapor p ressure of the gradient tower of Zhangye National Climate Observatory built in 2007 from Sep tember 2007 to August 2008, the percentage of missing value was calculated, and the climate characteristics of Zhangye in different seasons were also analyzed. The reliability of data from the gradient towerwas checked by comparing with some other observational stations.

The extreme drought eventoccurred in Sichuan and Chongqing region during the period of1935-1937 was analyzed. Itwas an extreme drought event thatmeet in one hundred years in warmer climate period, itpersisted long time and disserved severely, and people’s life and wealth suffered bigness harm. The low ability ofdefence droughtdisaster resulted in seriouse calamity. People in Sichuan and Chongqing regionmust strengthen defence drought and reduction disasterwork under the back ground ofglobal climatewarming.