As the fourth major staple crop after rice, wheat and corn, potato is of great significance for ensuring the national food security. In order to explore the response characteristics of potato (Solanum tuberosum L.) yield, leaf photosynthetic physiology, dry matter accumulation characteristics to water stress in the semi-arid region of the Loess Plateau, the soil water stress experiment was conducted in 2021 by using the main potato variety “Xindaping” as the test material. The soil water was controlled during the critical period of tuber enlargement (August). Field water capacity was set at 40%±5% (moderate water stress, T1 treatment) and 55%±5% (mild water stress, T2 treatment), and 75%±5% (full water treatment, T3) was used as the control for analysis. The results show that under water stress, the maximum tuber weight per plant, tuber weight per plant and yield all decreased, the number of tubers decreased, the weight and the number of pellet potato increased significantly (P<0.05), and compared with T3 the yield of potato under T1 and T2 treatments decreased by 30% and 13%, respectively. The net photosynthetic rate (P_n), stomatal conductance (G_s) and intercellular CO₂ concentration (C_i) of potato leaves decreased significantly, among them the G_s decreased by 59%, and the water use efficiency (WUE) of T1 treatment was 31% higher than that of T3. In the weak light area, the effect of moderate and mild water stress on P_n is not obvious (P>0.05), when the light intensity was higher than 300 μmol·m^-2·s^-1, the differences between treatments increased, and P_n under T1 and T2 treatments decreased by 42% and 32% on average compared with T3. Under the influence of water stress, the maximum net photosynthetic rate (P_nmax), light compensation point (LCP) and dark respiration rate (R_d) decreased significantly (P<0.05), and light saturation point (LSP) under mild water stress was the highest (893.32 μmol·m^-2·s^-1). The range of available photosynthetically active radiation (PAR) of leaves decreased under moderate water stress, and the ability to use strong light decreased. The dry matter weight of roots, stems, leaves and petioles decreased under water stress, and under moderate water stress, the petiole decreased the most (63%), followed by leaves (57%) and roots (50%). This study can provide theoretical basis for potato drought damage assessment and soil water efficient utilization in semi-arid area of Loess Plateau.

Drought is a major meteorological disaster with the highest frequency, the longest duration and the widest scope of harm in the world today, which has a huge and extensive impact on agriculture, ecology, social development and national economy all over the world. The drought is an important factor affecting agricultural production which determines the stability of crop production, further relates to the national food security. China is a large agricultural country, and also is a country with frequent drought disaster. Therefore, to improve the monitoring, forecasting and warning level of agricultural drought disaster, it is necessary to deeply understand its formation, influence characteristics, drought intensity, severity and physiological process and mechanism of crop victimization. It is also an important scientific problem to reduce and prevent drought disaster losses and improve national food security production. This paper comprehensively reviews the recent internal and overseas research progress of agricultural drought with different degrees and its impact on crop production, and explores the influence characteristics and mechanism of drought from the aspects of crop morphology, physiology, cellular and molecular levels, etc. The main indicators, indexes, methods and early warning systems in current agricultural drought monitoring are reviewed around food production to cope effectively agriculture drought. According to the new characteristics of agricultural sustainable development and drought, the current situation of drought disaster prevention and mitigation and agricultural drought coping are discussed. A series of drought coping measures both adaptation and mitigation are emphasized. On this basis, combining with the needs of national, regional and industrial development, the paper puts forward the important scientific problems, research countermeasures and the prospect of discipline development which should be emphasized in the future.

Under the background of climate warming, the global drought risk increases, especially in the arid and semi-arid region of northwestern China, which is highly sensitive to climate change, and the drought seriously restricts the sustainable development of regional economy. The scientific development of cloud water resources is an effective way to solve the shortage of water resources in this region. Based on the ground-based multi-channel microwave radiometer data and conventional meteorological observation data at Yongdeng national meteorological observation station in Gansu, the spatial and temporal distributions of atmospheric water vapor and liquid water in eastern section of the Qilian Mountains were analyzed, and their evolution characteristics before rainfalls with different properties were discussed. The results are as follows: (1) Under the influences of atmospheric circulation, topography, boundary layer and local and regional weather and climate conditions, etc., the atmospheric water vapor more than 98% in eastern section of the Qilian Mountains concentrated below 6.0 km, and the water vapor density decreased with height, while the liquid water content firstly increased and then decreased with height. The water vapor density and liquid water content increased significantly on rainy days, and the height with the maximum liquid water content decreased. (2) The seasonal variations of water vapor and liquid water were obvious. The atmospheric precipitable water in summer was much more than that in winter, and the vertical extension of liquid water and the height with maximum content in summer were higher than those in winter. (3) The diurnal variations of water vapor and liquid water were obvious, and they had seasonal differences. The diurnal peak value of water vapor appeared from afternoon to nightfall, and the trough value appeared from morning to noon. The occurring time of peak and trough values of water vapor in summer half year were later than those in winter half year, and the variation range was larger. The vertical extension of liquid water in the daytime was higher than that in the nighttime, and the distribution of liquid water in summer half year was deeper than that in winter half year. (4) There were main periodic changes with about 10-20 days and 8 days of precipitable water vapor in eastern section of the Qilian Mountains, and the periods with 4-7 days and 21-32 days were obvious in summer and autumn. (5) The water vapor and liquid water jumpily increased before precipitation with different properties, but there were differences about jumping increment, time and height. The time of jumping increase was the earliest before cumulus-stratus mixed cloud precipitation from July to August in eastern section of the Qilian Mountains, and the increment was the maximum and the jumping height was the highest before cumulus precipitation, while the jumping height was lower significantly before the precipitation of warm cloud.

The precipitation forecast performance of GRAPES_Meso model with 3 km spatial resolution and its cloud analysis system was investigated and compared through numerical experiments for 13 heavy rainfall cases in summer and batch forecast in July 2018 in Northwest China. The results are as follows: (1) GRAPES_Meso model with 3 km spatial resolution had a good forecasting skill and stable performance for precipitation forecast in Northwest China, it could provide favourable outputs for short-term forecasting and nowcasting business. The average threat score of light rain and above for 13 heavy rainfall cases was between 0.5 and 0.6, while the threat score of batch experiments in July was slightly worse than that of 13 heavy rainfall cases. (2) By introducing observed data of radar reflectivity, satellite TBB and CTA, the cloud analysis system could reasonably adjust cloud water, rain water and other hydrometeor content, consequently reduce spin-up time in the mesoscale model and improve the forecast ability of precipitation with different magnitudes. However, the forecast results of cyclic assimilations in cloud analysis system weren’t stable. (3) The predicted coverage of radar echo by GRAESP_Meso model and cloud analysis system was consistent with observations, while the intensity of composite reflectivity was higher than the observations.

Based on daily meteorological observation data at 227 weather stations of Northwest China during 1962-2017, the decadal change characteristics of drought frequency with different grades including light drought, moderate drought, heavy drought and extreme drought were analyzed by using SPEI index. The results are as follows: (1) The frequency of drought with different grades in Northwest China occurred inter-decadal transition from more to less in the 1980s. The drought mainly occurred in western part of Northwest China before the transition, while it mainly occurred in eastern part of Northwest China after the transition. (2) The frequency of light drought and moderate drought was significantly higher than that of heavy drought and extreme drought, and the frequency of light drought and moderate drought appeared opposite variation tendency after 1980. (3) The spatial difference of drought frequency with different grades was obvious. The light drought and moderate drought mainly occurred in eastern Xinjiang and southern Qinghai, while heavy drought and extreme drought mainly occurred in western part and eastern part of Northwest China, respectively.

As a major driving factor of environment change，characteristic analysis of climate change is very important for environment detection． In this paper，by taking the Ejin delta in the lower reaches of the Heihe River as the research area，on the basis of temperature and precipitation data during 1960 － 2012 from Ejin meteorological station，the characteristic of climate change over the past 53 years was analyzed firstly by using the methods of Mann － Kendall test，regression analysis and accumulative anomaly，and then Mann － Kendall test and R/S analysis were used to predict the future climate change trend． The results were as followed:The temperature in the Ejin delta increased and precipitation appeared non － remarkable trend over the past 53 years． There were remarkable differences in different decades， the temperature increased most from the 1980s to the 1990s，while precipitation appeared fluctuating change with less － more － less． A dryer and warmer climate trend would be obvious in the 21st century，and the warm winter phenomenon would be significant． Combining the data of GIMMS － NDVI，the East Juyan Lake area and runoff at the Zhengyi gauge station，through the Pearson correlation analysis， we concluded that warm and dry climate trend and the runoff reduction of the Heihe River led to shrink and salinization of the West and East Juyan Lakes，and the vegetation degradation． While the increase of the East Juyan Lake area from 2003 was the result of ecological conveyance water project in 2002，rather than the warming － wetting trend of climate．