Sandstorm is a serious natural disaster in north China. It is of great significance to carry out relevant research to improve the forecast level of this kind of catastrophic weather. Based on the RegCM-dust model, an extended period numerical prediction analysis of a typical severe sandstorm process in north China is conducted, and the results are compared with NCEP reanalysis data and other analysis results. The results show that the regions with high sediment discharge simulated by the model are mainly located in southern Xinjiang, Mongolia and western Inner Mongolia. The model has a certain forecasting ability for 10 m wind speed, but the simulated wind speed is smaller than the reanalysis data. The changes of dust column content and total sedimentation simulated by the model can reflect the characteristics of the dust storm weather process. The simulated sand-dust mixing ratio has a certain correspondence with the urban pollution index, which indicates that the model has certain forecasting ability for the pollution weather caused by sand-dust.

From January to June 2023, meteorological droughts of varying degrees occurred in southwestern China, eastern North China, northern East China, central southern China, southern South China, and central Northeast China, seriously affecting agricultural production and restricting local economic development. To improve the ability to respond to drought disasters, timely carry out disaster prevention and reduction work, and conduct real-time summaries of drought situations. This article uses K index, MCI index, T-N flux and CABLE land surface model, as well as meteorological observation data, reanalysis data, soil moisture data to comprehensively analyze the spatiotemporal distribution characteristics and causes of regional drought events. The results are as follows: (1) In the first half of 2023, severe regional drought occurred in southwestern China and eastern Inner Mongolia. The southwestern region experienced a transition from sustained to sudden drought, while Inner Mongolia continued to experience drought. (2) During the same period, the 500 hPa geopotential height field showed a two trough and two ridge pattern at mid to high latitudes. The western Pacific subtropical high pressure abnormally extended westward and uplifted northward, and the Rossby waves at mid latitudes in Eurasia were abnormally weak, resulting in a weakening of the influence of flat westerly winds and cold air in mid to high latitudes, resulting in less precipitation in the southwest and eastern Inner Mongolia, leading to regional drought. (3) In the first half of 2023, the winter La Niña event shifted to the spring El Niño event, resulting in weak convective activity in the southwest region and triggering sustained hot and dry weather; The distribution of sea surface temperature sensitive areas in Inner Mongolia has led to the stability of its upstream high-pressure ridge, resulting in drought and limited rainfall in the eastern region of Inner Mongolia.

Recently, the droughts attack frequently in the Yangtze River basin, resulting in more and more loss. To further improve regional drought risk management and drought resistance capabilities, it is of great significance to conduct research on the spatio-temporal evolution characteristics of drought in typical drought-prone areas. “Heng-Shao-Lou drought corridor” in Hunan Province is a region with most severe droughts, the standardized precipitation index (SPI) dataset based on monthly precipitation data from 33 meteorological stations in this area from 1971 to 2022 is constructed. Citing the case of Shaoyang County, run theory is applied to integrate drought events, and Gumbel-Copula is adopted to construct the joint distribution function of drought duration and severity, then the joint return periods of drought are calculated and the method is extended to the whole study area. On the basis of it, the classification standard of drought grades is established, and the spatial distribution characteristics of drought probability for each level in the whole study area are analyzed. The results show that the peaks of theoretical joint return period of drought duration and severity for the type Ⅰ and type Ⅱ in Shaoyang County are around 97 a and 27 a, respectively, which indicates that the probability of drought events with long duration and high severity is very small and far lower than that of drought events with long duration or high severity, it is a common feature of drought events in research area. Furthermore, the combination of drought duration and severity joint distribution can effectively avoid segmentation of the whole drought event when drought grades are identified by a single variable, and can evaluate the complexity and large-scale impact of drought more accurately. In the past 52 years, the slight drought occurs most frequently in western region of the “Heng-Shao-Lou drought corridor”, while the frequency of severe or extreme drought is low. Extreme drought mainly distributes in Shaoyang County, Shaodong County and Shuangfeng County.

The climate in the Yellow River Basin has undergone significant changes in recent years, which has a significant impact on surface hydrological and ecological processes in the basin. Studying the spatial and temporal variation of evapotranspiration in the Yellow River Basin is indicative for understanding deeply land-atmosphere interactions and regional water resources management. In this paper, the appliability of ERA5-Land evapotranspiration in the Yellow River Basin was evaluated using in-situ observations of Haibei, SACOL (Semi-Arid Climate and Environment Observatory) and Yucheng stations which are selected as representative stations from the source region, Hetao region and the lower reach of the Yellow River Basin, respectively. Then based on monthly latent heat flux from ERA5-Land data, the spatial and temporal variation of evapotranspiration in the Yellow River Basin in the past 42 years (1980-2021) are analyzed using EOF (Emipirical Orthogonal Function), power spectrum and regression analysis methods. The results show that ERA5-Land data can reflect the variation characteristics of evapotranspiration at Haibei, SACOL and Yucheng stations with good correlation and small error and root mean square deviation, which is applicable for the analysis on spatial and temporal variation of evapotranspiration in the Yellow River Basin. There are multi-timescale variations of evapotranspiration in different regions of the Yellow River Basin, with significant oscillation periods of main 5 a and 15 a, and obvious inter-annual and inter-decadal variations. The first mode in different regions of the Yellow River Basin characterizes the consistency in spatial distribution, which decreases around 2004. The second mode is dipole distribution, indicating the reverse change in space. The deceleration of evapotranspiration in the Yellow River Basin in the past 42 years is not same in different regions, with the fastest rate of -3.74 mm·a^-1 in the lower reaches and -2.82 mm·a^-1 in the Hetao area, while the deceleration in the source area is relatively gentle. The summer evapotranspiration variability is the largest, and the deceleration is faster in the Hetao area and the lower reaches. The winter evapotranspiration variability is smaller, but the source area has the largest winter evapotranspiration deceleration of -0.48 mm·a^-1.

In order to explore the response mechanism of photosynthetic physiological process of spring maize to soil water and temperature changes in semi-arid region of the Loess Plateau under the background of climate change, taking spring maize as the research object, the pot water control experiment was carried out in the Dingxi Arid Meteorology and Ecological Environment Experimental Base of China Meteorological Administration in 2017. Control treatment (CK treatment, soil moisture at 80% of field water capacity) and water treatment (WS treatment, soil moisture at 45%-50% of field water capacity) were set at spring maize seven-leaf stage. Three leaf temperature gradients were set, which were optimum temperature 25 ℃, high temperature 35 ℃ and extreme high temperature 40 ℃ (CK treatment corresponds to CK-25, CK-35 and CK-40; WS treatment corresponds to WS-25, WS-35 and WS-40). The response characteristics of leaf gas exchange parameters and water use efficiency to soil moisture and temperature changes at seven-leaf stage of spring maize were analyzed. The results show that within a certain range of photosynthetically active radiation (PAR), the net photosynthetic rate (P_n) of leaves gradually increased with the increase of PAR. When water supply was insufficient, with the increasing of PAR, stomatal limiting factors of spring maize leaves under WS treatment transferred to non-stomatal limiting factors, and photosynthesis is inhibited obviously. The P_n of spring maize leaves under WS-35 treatment was the highest, and P_n of maize leaves under WS treatment was significantly lower than that under CK treatment in the PAR high value area. The PAR at light saturation point decreased under different temperature gradients. Compared with CK-40 treatment, the P_n of spring maize leaf under WS-40 treatment decreased significantly with the increase of PAR (P<0.05), and photoinhibition was obvious. When the water supply was sufficient, the transpiration rate (T_r) increased with temperature increasing. When the water supply was insufficient, compared with CK-40 treatment, the T_r and stomatal limitation (L_s) of spring maize leaf decreased significantly (P<0.05), while intercellular CO₂ concentration (C_i) increased significantly (P<0.05) under WS-40 treatment. With the increase of PAR, T_r decreased and water use efficiency (WUE) of spring maize treated by WS-40 was higher than that CK treatment. This study can provide reference for the physiological characteristics of spring maize in semi-arid region of the Loess Plateau under the background of climate change.

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.

As the impact of climate warming on agro-ecosystems intensifies, the arid and semi-arid crops in the northwest, where water resources are extremely scarce, will face major challenges. In this paper, the water control starts from the corn tasseling period to the end of the growth period (T1 treatment) and the natural drought at the whole growth period (T2 treatment) in arid and semi-arid regions, the similarities and differences of the formation of drought disasters to the same crop were revealed in arid and semi-arid regions, in order to provide a theoretical basis for grasping the crop drought inducing-disaster process in different climatic regions. The results showed that different drought stresses affected significantly the plant height, leaf area and chlorophyll content of maize in arid and semi-arid regions. During the whole growth period of drought treatment, the response of maize in arid area to drought stress was more sensitive than that in semi-arid area, while T1 treatment had more significant effects on the growth of maize plant height and leaf area per plant in semi-arid rain-fed area. The leaf area per plant of maize under different drought treatments in semi-arid area showed an increasing trend from the horse chestnut stage to grain filling stage as a whole. Although drought stress reduces the leaf area per plant of maize, in order to ensure the later growth and development of plants, the increase of leaf area make up for the lack of photosynthetic yield due to drought stress. Therefore, in order to ensure the yield of maize in arid and semi-arid regions, semi-arid areas are suitable for planting varieties with strong photosynthetic capacity, arid areas are suitable for planting varieties with suitable plant height and leaf area, and the tasseling period is a sensitive period for maize growth and development to drought in semi-arid regions.

Based on daily gas load and meteorological observation data during heating period in Xi’an of Shaanxi Province from 15 November 2009 to 14 March 2019, the variation characteristics of gas load in heating period, holidays and weekends were analyzed. The significant influence factors on gas load were selected by using correlation analysis. And on this basis the daily forecast model of gas load in heating period was established by using multiple linear regression method, then the forecast model was tested. The results show that the natural gas consumption during heating period gradually increased in Xi’an in past 10 years, the daily gas load presented a single-peak pattern change, and the peak appeared in January. The weekend and holidays effects of gas load were obvious during heating period, the gas consumption on weekend and holiday was less than that on working days, and the longer holiday was, the less gas load was. The gas load was significantly and positively correlated with gas load on previous day, while that was significantly and negatively correlated with meteorological factors of the maximum and minimum temperature, mean temperature and human body comfortable degree, and the correlation between heating gas load separated from actual gas load and meteorological factors obviously improved. Based on the above five influence factors, the dynamic forecast model of daily heating gas load was established by using multiple linear regression method. Upon inspection, the average relative error of the model was 3.4%, and the model was more stable in rush hours of using gas, the average relative error was 2.77%, which could meet gas dispatch needs of natural gas companies.

The land-atmosphere coupling (LAC) strength can be used to characterize how the land surface influences precipitation, temperature or other atmospheric physical processes, and can be used to identify the hotspot of land-atmosphere interactions, which can deepen the understanding of landatmosphere interaction and climate system. In order to quantify the LAC strength in China, the spatial-temporal distribution characteristics of the LAC index of soil moisturelatent heat flux and latent heat flux-lifting condensation level, the Pearson and Kendall’s Tau correlation of soil moisturetemperature and soil moistureprecipitation were analyzed by using ERA5 reanalysis data. The results are as follows: (1) The latent heat flux increased with soil moisture increasing, providing water vapor for precipitation. The increase in latent heat flux led to the decrease of sensible heat flux, then temperature decreased, which weakened the drive of boundary layer and was not conducive to the uplift and condensation of air mass over arid and semiarid areas of northern China. This region was a hotspot of landatmosphere interaction in China. (2) There were obvious seasonal differences in LAC strength in China. The LAC strength over arid and semiarid regions was stronger in spring and summer, but weaker in autumn and winter. The soil was relatively dry in dry season over southwest China where LAC was significant. For landatmosphere coupling, we should not only consider the division of traditional climate zones, but also ponder the influence of rain belt dynamic changes.

Based on the meteorological conventional observation data, observational precipitation from automatic  weather stations and NCEP reanalysis data, the causes and mesoscale characteristics of the heavy rain occurring on July 16, 2019 in Heilongjiang Province under the background of northeast cold vortex were analyzed. The results show that there were two rainstorm areas in the western and eastern Heilongjiang Province affected by MCS and MCC activities, respectively. Both MCS and MCC clouds generated in Inner Mongolia and moved to Heilongjiang Province. Due to the enhanced convective instability and frontal generation, the MCC and MCS clouds developed, strengthened and moved from west to east along the convergence line. In the upper troposphere over the bottom of the cold vortex during the precipitation, there existed a dry intruding airflow with high momentum from the high latitude area. During the process of heavy rain caused by MCC, it presented strong convection instability in the lower atmosphere and moisture symmetry instability in the middle layer. The uplift of ground convergence line and frontal formation promoted the release of unstable energy. MCC was shown as a wide range of mixed cloud precipitation echo on the radar reflectivity products images. One of them was a supercell with hook echo structure, deep cyclone convergence and mesocyclone in middle and lower layers. Compared with MCS, the environmental field of MCC developing had greater vorticity in the middle and lower layers and stronger divergence in the upper layers. The upper levels had stronger pumping action, leading to a stronger upward movement. During the development of MCC, the environmental wind in the middle and lower levels increased significantly. There was greater vertical shear of horizontal wind resulting in stronger organization of mesoscale convective clouds.

Based on ERA reanalysis data during 1979-2017, the spatial-temporal variation characteristics of surface sensible and latent heat flux in Southwest China were analyzed by using empirical orthogonal function (EOF) and power spectrum methods. The results are as follows: (1) In Southwest China, the sensible heat flux in spring was larger than that in summer, while latent heat flux was larger in summer than in spring. The sensible heat flux in spring and summer began to weaken after 2000, while the latent heat flux in spring and summer had increased significantly since 2000. (2) There were three spatial patterns of sensible heat flux in spring, which were mainly characterized by east-west reverse, region-wide uniform and negative and positive dipole spatial distribution. There were mainly two spatial patterns in summer, which showed the consistency of spatial distribution. The corresponding time coefficients characterized the significant inter-decadal and inter-annual periodic variations of sensible heat fluxes in summer. There were three spatial patterns of latent heat flux in spring, which were mainly characterized by uniform region-wide, reverse east-west and decreasing outward in all directions from the center. There were mainly two spatial patterns of latent heat flux in summer. The first mode characterized the consistency in spatial distribution. The second mode indicated that the flux increased gradually from northwest to southeast in a trapezoidal manner. The change of corresponding time coefficients characterized that latent heat flux in spring and summer had significant inter-annual and inter-decadal variation characteristics. The sensible heat fluxes in spring and summer were characterized by inter-annual variations about 3 years and inter-decadal variations more than 10 years, and inter-decadal variations were stronger than inter-annual variations. The latent heat flux in spring and summer mainly had inter-decadal variations over 10 years in Southwest China.