Exploring the spatial and temporal distribution characteristics of heat resources utilization efficiency of summer maize in growth season could provide theoretical basis for the adjustment of summer maize variety layout and guarantee of a high and stable maize yield. Based on the daily meteorological data of 15 agricultural meteorological observation stations from 1981 to 2019, and the observation data of the growing period of summer maize and wheat in the later crop rotation in Hebei Province, the regression analysis and spatial interpolation methods are used to analyze the spatial and temporal variations of heat resources utilization efficiency of summer maize in growth season under climate change. The results show that the potential growing days of summer maize in Hebei Province had no significant change from 1981 to 2019, while the potential accumulated temperature increased significantly (P<0.05). The utilization efficiency of heat resources during growth season increased significantly (P<0.05), the utilization efficiency of growing days increased from 80.4% in 1981 to 94.5% in 2019, and the utilization efficiency of accumulated temperature increased from 84.5% in 1981 to 94.9% in 2019. The potential growing days and accumulated temperature of summer maize were more in the south and less in the north, and the utilization efficiency of growing days and accumulated temperature were lower in the south and higher in the north. There was higher utilization efficiency (more than 95%) of growing days and accumulated temperature in Langfang, while in Handan the utilization efficiency of growing days was lower (less than 85%). The accumulated temperature of summer maize increased at a rate of 19.6 ℃·d·(10 a)^-1 before anthesis and 58.7 ℃·d·(10 a)^-1 after anthesis. The increase rate of accumulated temperature after anthesis was obviously higher than that before anthesis, and the ratio of accumulated temperature showed an obvious downward trend, it fell 28.5% from 1.6 in 1981 to 1.1 in 2019. The results demonstrate that the utilization efficiency of climate resources of summer maize in the southern Hebei had some space for improvement. The medium and late maturing varieties with a longer growing season could be selected, and the varieties with a longer filling stage could be selected for breeding or cultivation, so as to make full use of the heat conditions in the growing season and improve maize yield.

As an ecologically fragile region, the mass concentration of atmospheric particulate is an important indicator of ecological security. It is of great significance to study its temporal variation and influencing factors for environmental and ecological protection in this region. Based on the surface meteorological data from Gonghe County Meteorological Bureau and PM₁₀ mass concentration data at monitoring site of Hainan Prefecture Ecology and Environment Bureau in Qinghai Province from 2015 to 2020, the variation characteristics of PM₁₀ mass concentration and its influencing factors in the Gonghe Basin are analyzed. The results show that downward trend of PM₁₀ average mass concentration at annual time scale, in spring and winter is significant, while in autumn and summer it is insignificant. The average monthly distribution of PM₁₀ mass concentration presents a bi-modal pattern. In spring, PM₁₀ mass concentration remains high due to the combined influence of southeasterly and northwesterly wind-dominated, by which pollutants is transported horizontally to the Gonghe Basin. In winter when westerly wind prevail, PM₁₀ mass concentration is second. With the arrival of the rainy season in summer and autumn, southeastly wind prevails in the Gonghe Basin, and pollutant horizontal transport weakens, and PM₁₀ mass concentration is low. The monthly average PM₁₀ mass concentration is positively correlated with monthly average wind speed, especially, the PM₁₀ mass concentration reaches the highest in spring when wind speed becomes greater. The cold air activity is the main reason to cause PM₁₀ heavy pollution in the Gonghe Basin, and there are two paths of air mass influencing heavy pollution in the Gonghe Basin, one is from southwest, and the other is from west.

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 one of the major agro-meteorological disasters to restrict the improvement of grain production and quality in China. The soil moisture and mineral elements affect alternately to the growth and development of winter wheat as well as the yield and quality. The response of leaves mineral elements accumulation, yield and grain quality of winter wheat to different grades drought stress was explored at the moisture critical period, which has a certain realistic significance to scientific fertilization and drought disaster prevention. At the moisture critical period (jointing to flowerings stage), the winter wheat ‘Qimai 2’ was used as material to set the water control experiments with five gradients (T1 treatment, soil moisture at 20 cm depth was suitable (60%-80%) in the whole period, and T2, T3 and T4 treatments were supplied once with water at 80%, 50% and 25% of 75.0 mm base recharge, respectively, while T5 treatment wasn’t supplied water)， the influences of drought stress on the accumulation of nitrogen, phosphorus and potassium mineral elements, photosynthetic pigments and photosynthetic parameters, yield and grain quality of winter wheat were simulated and analyzed. The results show that the total nitrogen, total phosphorus, photosynthetic pigment content and the maximum net photosynthetic rate (P_nmax), apparent quantum efficiency (AQE) and light saturation point (LSP) of winter wheat leaves were all the highest under T1 treatment during the water control to rewatering. Due to drought stress, the above-mentioned indicators reduced significantly under T2, T3, T4 and T5 treatments, and the heavier the drought stress, the greater the reduction was. Compared with T1 treatment, the total nitrogen, total phosphorus content, chlorophyll a, chlorophyll a+b, carotenoid content, P_nmax, AQE and LSP of leaves reduced by 1.68%, 0.15%, 0.90 mg·g^-1, 1.05 mg·g^-1, 0.21 mg·g^-1, 64.6%, 65.8% and 31.2% under T5 treatment, respectively. However, the total potassium content and light compensation point (LCP) of leaves increased with the aggravation of drought stress, and those under T5 treatment were 1.20% and 84.0% higher than under T1 treatment, respectively. In addition, the drought stress decreased significantly spike grains number, forming spike rate and thousand grains weight. Compared with T1 treatment, the theoretical yield and grain protein content decreased by 56.6% and 30.1%, respectively, while the grain starch content increased by 11.6% under T5 treatment.

To improve the forecast and early warning ability for the low visibility along the expressway, the hourly observation data of 10 traffic meteorological stations along Shaanxi section of the Lian-Huo expressway and the hourly reanalysis data of the European Center for Medium-Range Weather Forecasts are employed to analyze the distribution characteristics of low visibility and to explore the relationship of low visibility with other meteorological factors. The results show that along Shaanxi section of the Lian-Huo expressway, January has the most low visibility, while February has the least. During a day, the low visibility mostly happens from 00:00 to 10:00, and the low visibility of 0-50 m mainly occurs from 05:00 to 06:00. The low visibility duration is short with the majority of within 2 hours and the longest of 17 hours. The low visibility weathers occur frequently from Xingping to Changxing and Chencang section, where attention should be paid in daily traffic meteorological service. Accordingly to the analysis of the relationship between low visibility and other meteorological factors, the low visibility generally occurs under the conditions of air temperature from 0 to 5 ℃, relative humidity above 90%, wind speed less than 1.0 m·s^-1 and northeast to east winds. The low visibility weather in summer and winter is mostly associated with precipitation, which usually occurs during or after the precipitation and is accompanied by weather systems always. Compared with the low visibility caused by radiation cooling, the low visibility associated with precipitation exhibits longer duration and the wider range. The low visibility weathers occur at different relative humilities in different seasons, which in winter, summer and autumn are high, while in spring are relatively low.

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.

Based on the hail weather observation data of 84 surface meteorological observation stations in Guizhou Province from 1961 to 2020, the temporal and spatial distribution characteristics of hail are analyzed, the features of hail weather such as regularity of the occurrence dates of the first and last hail, hail diameter and duration of a hail are explored further. Finally, suggestions for artificial hail prevention are proposed. The results show that the spatial distribution of annual average hail days in Guizhou was uneven, there was a regional difference which is the annual average hail days is more in west than in east and the annual average hail days is more in central than in north and south. Hail days decreased significantly （P<0.01） in the past 60 years. The frequent months of hail in Guizhou is from February to May, accounting for 85.0% of the annual hail days, the frequent period of hail is from 14:00 BST to 02:00 BST of the next day. In past 60 years, the average time of the first hail in Guizhou starts from east to west from late February to mid May, and the last hail ends from east to west from late March to late July. The occurrence frequency of middle-diameter hail accounts for 68.9%, and the duration of a hail is mainly concentrated within 10 minutes. Due to the obvious regional differences in seasonal and diurnal variation, and the occurrence dates of the first and last hail, local hail regularity should be fully mastered when carrying out hail prevention, and various artificial hail prevention work should be arranged reasonably.

From the afternoon to night on 5 July 2021, severe convective weather including short-time heavy precipitation, thunderstorm wind and small hail occurred in the central region of Beijing-Tianjin-Hebei. The atmospheric environmental conditions and mesoscale characteristics of the formation of this weather process were analyzed by using the data of egional automatic meteorological station, Doppler radar, FY-2G meteorological satellite and microwave radiometer, and the fifth generation atmospheric reanalysis ERA5 from European Centre for Medium-Range Weather Forecasts. The results show that favourable water vapor conditions appeared before the occurrence of the severe convective weather including heavy precipitation, thunderstorm winds and local hail. Strong convergence of water vapor fluxes in lower and middle layers occurred 1 to 2 hours earlier than precipitation. The whole layer atmospheric precipitable water had accumulated continuously under strong uplift. The heat and power unstable environment of severe convection breaking out was created by formation of vertical θ_se energy frontal zone, maintenance of "upper dry and lower wet" unstable stratification, establishment of strong vertical wind shear from 0 to 6 km and enhancement of CAPE, K and SI indexes. Unstable stratification formed by eastward movement of the upper though carrying dry and cold air southward and low warm tongue, which had provided synoptic-scale upward movement for the occurrence of severe convection. The strong convective happening released more energy in the afternoon than in the evening. Heavy rainfall caused the local temperature to drop significantly and cold pool effect was more significant, which corresponded to the heavy precipitation area during the southward movement process. The surface convergence line at the cold pool boundary was the mesoscale trigger system. The cloud base height dropped and infrared brightness temperature increased rapidly, which indicated the formation of strong convective cloud cluster. The clear shadow at the southeast boundary of cloud body indicated the strong development of cumulonimbus cloud. Under the background of large-scale weather system, the important characteristic indexes obtained from in-depth analysis of mesoscale system can be used for the short term forecast and warning of severe convective weather.

Based on daily precipitation data, upper-air observation data and ERA5 hourly reanalysis data with 0.25°×0.25° resolution from 2010 to 2020, the rainstorms caused by the northwest vortex in Shaanxi are counted, and the characteristics of rainstorms caused by the northwest vortex with and without influence of typhoon are comparatively analyzed. The results show that the rainstorms caused by the northwest vortex in Shaanxi mostly occurred in July and August, and it occurred more in northern Shaanxi. The night rain characteristics of the rainstorms are obvious. The rainstorm intensity was stronger under influence of typhoon, and the falling area was to the north of two latitudes than that without influence of typhoon. The northwest vortex, which caused rainstorms in Shaanxi, was located at about 7-8 latitudes to the north of the ridge line of the western Pacific subtropical high. The northwest vortex had the dynamic characteristics of convergence at low level and divergence at high level. The upward motion of the northwest vortex was strengthened by the topographic forcing uplift, and the low-level water vapor transport and convergence provided favorable conditions for the occurrence of rainstorms caused by the northwest vortex. Under the influence of typhoon, the subtropical high was westward and northward, the water vapor and energy in the periphery of the typhoon were transported to the northwest vortex with the southwesterly low-level jet, the atmosphere at lower layer of the northwest vortex was convective instability, and the positive vorticity advection in front of the high trough and strong divergence on the right side of the high-level jet promoted the development and enhancement of the vortex, the strong updrafts on the south and east sides of the vortex triggered the release of unstable energy and formed strong frontogenesis in northern Shaanxi, the frontogenesis further enhanced the vertical movement on the south and east sides of the vortex, which caused heavy rainstorms on the south and east sides of the vortex. When there was no influence of typhoon, the subtropical high was eastward and southward, the southwest wind speed was smaller and the water vapor transport was weaker, the southwest wind in front of the plateau trough transported water vapor from the Bay of Bengal and the South China Sea to Shaanxi, the atmosphere at lower layer of the northwest vortex was stable, the strong updraft was located in the south of the vortex, the cold and warm air converged in central and southern Shaanxi, which resulted in scattered weak frontogenesis and caused rainstorms in the south of the vortex center.

A complete century series of temperature is the basis of climate change analysis. The local century temperature changes have general characteristics, also retain some differences. Based on temperature observation data at Wuhu station of Anhui Province during 1880-1937 and 1952-2020 and CRU (Climatic Research Unit) grid data of University of East Anglia during 1901-2020, the test and correction to observation data of temperature were conducted to obtain high quality data. And on this basis that the time series of temperature from 1880 to 2020 at Wuhu station was constructed by using the multiple stepwise regression method, its decadal characteristics were analyzed. The results show that the quality of monthly mean temperature at Wuhu station from 1880 to 1937 was improved after the difference and homogeneity corrections. Two temperature series were constructed by using the stepwise regression analysis based on CRU grid data during 1901-2020 and station observation data during 1901-1937 and 1953-2020, and the interpolated temperature by their average value could display perfectly the variation characteristic of monthly mean temperature at Wuhu station during 1938-1951. The spring, summer and winter temperature increased significantly at Wuhu station in past 140 years, and the increasing rate of spring temperature was the maximum, followed by summer and winter, while the warming in autumn wasn’t significant. The decadal characteristic of coldness and warmness alternation was obvious in each season from 1880 to 2020, but the warming stalled in recent 20 years. In addition, there were 40-50 a and 20-30 a periodic oscillations of mean temperature.

The phase state of precipitation in winter is relatively complex, and the consistency of transformation forecast between liquid and solid state is a difficulty in the forecast. In order to explore the application of muti-source data in rain-snow phase prediction, the precipitation phase characteristics of a rain-snow weather in Zhangjiakou area from 17 to 19 November 2020 were analyzed based on ERA5 reanalysis data, as well as cloud radar, microwave radiometer and SA dual polarization Doppler radar observation data. The results show that the rain-snow weather occurred under the coordination of upper trough, lower vortex and surface trough, the cold air from northwest behind the upper trough moved southward, which led to a rapid drop of air temperature and the change of precipitation phase. In the early stage of the process, the whole atmosphere was strong warm advection, and the ground temperature was high and the precipitation phase was rain. In the evening of November 18, the cold advection developed strongly, the temperature of each layer decreased rapidly, and the whole layer turned into cold layer, which led to the conversion of precipitation phase to snow. Through the dynamic diagnosis of divergence and vertical velocity, it was shown that the dynamic forcing during the rainfall period was mainly located in the upper layer, while during the snowfall period it was mainly located in the lower layer. The high-resolution data of cloud radar could reflect the change of 0 ℃ layer, and the change of mass center greater than 10 dBZ could indicate the change of precipitation intensity. The maximum basic velocity could reach 6-8 m·s^-1 during rainfall stage, while it was less than 2 m·s^-1 at snow stage. The high-resolution data of microwave radiometer could accurately judge the time of rain-snow conversion, and it was found that the integral water vapor appeared jump and peak value three to five hours before the precipitation. The combination of dual polarization radar and microwave radiometer could accurately judge the phase of precipitation particles, which could be used in prediction of precipitation phase.

Based on the tropical cyclone data in the North Indian Ocean released by the Joint Typhoon Warning Center (JTWC) and the synchronous reanalysis data with a resolution of 1°×1° from ERA-interim during 1979-2018, a study was conducted to investigate the monthly characteristics of different environmental factors affecting the tropical cyclone genesis over the North Indian Ocean. The results show that the sea surface temperature of the North Indian Ocean increased significantly, with moderate vertical wind shear (5- 10 m·s^-1) between 200 hPa and 850 hPa and sufficient water vapor supply in May, which led to the first peak of tropical cyclones of the whole year. From July to September, the relative humidity in the middle and lower troposphere was very plenty. However, due to the large vertical wind shear between 200 hPa and 850 hPa, it was difficult for disturbed convection to form a warm center structure, which was not conducive to the generation of tropical cyclones. From October to November, the average sea surface temperature of the North Indian Ocean was 27-29 ℃, accompanying with higher relative humidity of the middle atmosphere and more cyclonic circulation at 850 hPa. The vertical wind shear between 200 hPa and 850 hPa was reduced to 5-15 m·s^-1. Under these favorable environmental conditions, the generation of tropical cyclones over the North Indian Ocean reached the second peak of the whole year. Through quantitative study of different environmental factors affecting the monthly variability of tropical cyclones in two sea areas of the North Indian Ocean, it was found that although the number of tropical cyclones generated over the Arabian Sea and the Bay of Bengal assumed a bimodal monthly variation, the environmental factors presented different characteristics in the same month.

Based on the meteorological data of 8 sets of microclimate monitoring stations in the grape producing area in east foothills region of Helan Mountain and Yinchuan national reference station in 2019, the climate difference between Yinchuan station and the representative station was compared and analyzed, and the vertical changes of meteorological elements at Meiyu Winery were analyzed. The microclimate differences at four wineries in the same climate zone and five sub-regions in different climate zones were analyzed. The results are as follows: (1) Meteorological elements at Meiyu Winery and Yinchuan station in the same region were significantly different. (2) The 10 cm soil temperature fluctuated most and 40 cm soil temperature was most stable on a typical sunny day. The daily average soil temperature on a typical sunny day in autumn and winter increased in the order of 10 cm<20 cm<40 cm, and it decreased in the order of 10 cm>20 cm>40 cm in spring and summer. There was no significant difference of relative humidity in each month, growing seasons and the whole year between 50 cm and 150 cm height. (3) In the same climatic zone, the microclimate was greatly affected by topography, altitude and soil type. The higher the gravel content was, the higher the temperature was; the higher the altitude was, the lower the humidity and the greater the wind speed were. precipitation during the growing season was most at Liushi Winery with a lower altitude in front of the mountain, and it was least at Hennessy Winery. (4) The precipitation, air relative humidity and photosynthetic active radiation gradually decreased, and the temperature gradually increased from south to north in five small winery regions in east foothills region of Helan Mountain.

Based on the monthly maximum frozen soil depth at 68 meteorological stations in Shanxi Province during 1960-2018, the temporal and spatial distribution characteristics of the annual maximum frozen soil depth in Shanxi were studied by using EOF and wavelet analysis methods. The results are as follows: (1) The average annual maximum frozen soil depth at 68 stations in Shanxi during 1960-2018 was 71 cm, the extremely maximum value was 192 cm, and the extremely minimum value was 7 cm. In the past 59 years, the average annual maximum frozen soil depth at 68 stations in Shanxi showed a significantly decreasing trend with a climate tendency rate of -1.394 cm per decade, and it mutated in 1986. (2) The quasi-4-year period of average annual maximum frozen soil depth at 68 stations in Shanxi was detected. (3) The annual maximum frozen soil depth showed a spatial distribution characteristics with shallow in southern and deep in northern Shanxi, shallow in eastern and deep in western Shanxi. (4) The accumulated variance contribution rate of the first two modes of the annual maximum frozen soil depth in Shanxi reached 58.4%. The spatial pattern of the first mode was consistent in the whole province, while that of the second mode was reverse in southern and northern Shanxi.

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.

Dew is an important part of vineyard water cycle, which plays a vital role in the regulation of vineyard microclimate, and it is also a necessary condition for the germination of microbial spores. Based on the hourly meteorological observation data during the growing period of wine grape from April to October at Yinchuan agro-meteorological station from 2003 to 2020 and microclimate station of Meiyu Chateau from 2019 to 2020 and the 10-minute leaf surface temperature data from a typical winery in the same area in June 2019, the leaf temperature and air temperature were compared, firstly. When the dewing temperature was less than leaf surface temperature, the dew occurred. Taking the vineyard of Meiyu Chateau as an example, the temporal variation characteristics of dewing temperature, dewing days, dewing duration and dewing time during the growing period of grape and its influencing factors in vineyards of eastern Helan Mountain area were analyzed. The results show that the monthly dewing temperature from April to October appeared single-peak pattern in vineyards of eastern Helan Mountain area, and it reached the peak in July and the minimum in October. In the past 18 years, the monthly dewing days and duration increased gradually during the growing period, and it was the most (longest) in September, while it was the least (shortest) in April, and their inter-annual changes were obvious. Dewing could occur in the whole day, but it mainly occurred from 17:00 to next 01:00, and the range of dewing time gradually increased from April to October, it was the widest in September and the narrowest in April. The dew point temperature was significantly positive correlated with the minimum temperature and precipitation, the dewing usually occurred before and after rainfall processes and under the low minimum temperature weathers. The pests and diseases had a closely relation with dewing, so when temperature was higher in the evening in September and October, the drying and ventilating was very important for preventing pests and diseases in the vineyard.

Based on the meteorological observation data at seven national stations in Chuzhou of Anhui Province from 1961 to 2019 and the observation data in growth periods and yield per unit area of wheat from 1980 to 2019, the characteristics of meteorological drought and flood in Chuzhou and its impact on wheat yield were discussed and analyzed by using the multi-time-scale SPEI. The results show that the monthly and seasonal variation characteristics of SPEI were obvious in Chuzhou, and the astringency of SPEI in each month of winter was the strongest, while the dispersion of SPEI in each month of summer was the biggest. The climate characteristic of drought in spring and flood in summer was obvious in Chuzhou. The continuous drought from spring to summer was the most serious seasonal continuous drought in Chuzhou, and the continuous flood from spring to summer was the most serious seasonal continuous flood in the whole year. There was a trend of drought in spring since 2000 in Chuzhou, and the climate in summer and winter became wet after the 1990s, especially in winter, while the trend of dry and wet in autumn wasn’t significant, but there was a slight humidifying trend after 2009. The correlation between SPEI3 in March and wheat climate yield was the most significant, and there was parabola relationship with negative quadratic coefficient between them. When the value of SPEI3 in March was greater than 0.81 or less than -1.93, the yield of wheat was likely to reduce highly.

Based on the mass concentrations of fine particulate matter (PM2.5) in Rongchang District in winter from 2016 to 2018, surface meteorological observation data, L-band radar sounding data, ERA-Interim reanalysis data and GDAS (global data assimilation system) data, combined with the HYSPILT model, the meteorological influencing factors and regional transmission of PM2.5 in winter were analyzed. The results are as follows: (1) The frequency of PM2.5 mass concentration exceeding 75 μg·m-3 was as high as 56.3% in winter in Rongchang District from 2016 to 2018, but the air quality became better year by year. The diurnal variation of the PM2.5 mass concentration in winter had two peak values, appearing at 12:00 and 23:00. (2) PM2.5 pollution was mainly influenced by precipitation, temperature inversion and low-level wind speed. The obvious temperature inversion stratification near 925 hPa and 700-600 hPa in the surface layer, northwesterly or flat westerly airflow on 500 hPa, and weak northeast wind below 850 hPa, were unfavorable to PM2.5 pollutant diffusion and prone to occur severe pollution weather. The precipitation more than 2.0 mm had a clear clearance effect on PM2.5, the scavenging ability increased with the increase of precipitation level. The precipitation less than 1.0 mm had negative effect in the removal of PM2.5. Unfavourable diffusion condition  and hygroscopic growth of particulate matter led PM2.5 mass concentration to increase during micro precipitation period. (3) The PM2.5 pollution situation was mainly affected by the regional transportion between Chengdu and Chongqing urban agglomerations within about 300 km from the northwest and northeast of Rongchang District. The transmission of particulate pollutants in the outer domain was an important cause of PM2.5 pollution in winter in Rongchang District.

The phenomenon of drought disaster chain caused by drought disaster and its secondary disasters has a great impact on natural environment, society, economy and so on. In order to review the current research of drought disaster chain, different definitions of drought disaster chain and its two development stages have been retrospected. Then the main contents of drought disaster chain has been summarized, including the classification of drought disaster chain, evolution mechanism and control measures. Moreover, the main research methods involved in the current research have also been reviewed, including qualitative analysis, correlation analysis, probability model based method, complex network based method, and so on. From the goal of building systematic disaster prevention and mitigation, the problems existing in the current research were finally identified. The top-level research design and quantitative results are still needed. In the future, with the support of multidisciplinary knowledge, we should establish the chain catastrophe theory and put forward a series of quantitative methods. The research of this paper will be helpful to systematically understand the current progress, key points and difficulties in drought disaster chain studies, and also provide some references for future research.

SCA-LEC 模型；人工影响天气；安全；风险评估

Research on highway traffic disaster risk is a new direction for the development of professional meteorological services, and it is an important content of traffic weather forecasting services in future. Based on the ground observation data at 94 weather stations in Shaanxi from 1980 to 2017, the temporal-spatial change characteristics of road icing under different weather conditions were analyzed by using EOF method, etc., firstly. And the risk warning model of road icing in Shaanxi was discussed and established. The results show that there were two centers of road icing in the northwest of Guanzhong to the west of northern Shaanxi and Shenmu of northern Shaanxi, and the ratio of sleet or snowfall road icing was the maximum. The road icing mainly occurred from November to next March in Shaanxi, and the beginning date of road icing generally occurred in mid-to-late October in northern Shaanxi and Guanzhong, while that occurred later in November in southern Shaanxi, but the ending date of road icing mainly occurred in March and April in three regions, and the road icing days in January was the most. After the 1990s, the days of road icing decreased. The risk warning model of road icing was established and applied to business system in Shaanxi, and it could complete automatic production, the prediction effect was better.

 Based on the precipitable water vapor calculated by radiosonde data (PWV_RS) at 00:00 UTC and 12:00 UTC in 2014 at Golmud station of Qaidam Basin, the accuracy of precipitable water vapor retrieved by GPS data (PWV_GPS) was tested. Meanwhile, the variation characteristics of PWV_GPS was analyzed at Golmud and Delingha stations in Qaidam Basin. The results show that daily variations of PWV_GPS and PWV_RS were consistent and the correlation coefficient between them was more than 0.9. The correlation was better in summer and autumn than in winter and spring, the correlation coefficient at 00:00 UTC was slightly higher than that at 12:00 UTC. At 00:00 UTC and 12:00 UTC, the RMSE of PWV_GPS was 1.8 and 2.4 mm, and the MRE was 0.2 and 0.4, and the BIAS was 4.2 and 4.3 mm, respectively. Monthly variation of PWV_GPS presented a single peak distribution, the maximum appeared in July and the minimum appeared in December. PWV_GPS was rich in summer and shortage in winter, and it was more in south and less in north. The diurnal variation of PWV_GPS ranged from 0.4 to 28 mm and the hourly PWV_GPS ranged from 6.9 to 7.3 mm.

Based on the observation data from Shaanxi expressway automatic meteorological stations including the road surface temperature, air temperature, relative humidity, wind speed and cloud cover of reanalysis data of ECMWF from August 2013 to December 2017, the distribution characteristics of the road surface temperature in different seasons and sky conditions were analyzed, and relations between the road surface temperature and meteorological factors were studied, and relevant multivariate regression equations were established. The results show that the road surface temperature had obvious diurnal variation in different seasons. It was easier to freeze on the road surface from 00:00 BST to 08:00 BST after snow. The air temperature was one of the most important factors affecting the road surface temperature. By fitting the measured and caculated values of the road surface temperature, the results show that the model fitted the minimum road surface temperature well in winter with the correlation coefficient above 0.94, and the standard deviation was less than 1 ℃, and the frequency of difference between the observed and mesured temperature ranging from -2 to 2 ℃ was 98%. In addition, the model fitted better when the road surface temperature was 0 ℃.

Based on the conventional meteorological observation data, regional automatic weather station observation data, and NCEP reanalysis data, the environmental field characteristics and triggering mechanism of a rainstorm in Shandong from 15 to 16 May 2018 were analyzed. The results are as follows: (1) This rainstorm process was consisted of both warm sector rainstorm and frontal rainstorm. The main influencing systems of warm sector rainstorm included the high trough, the warm shear line and the ground convergence line. (2) Before the beginning of the warm sector rainstorm, the atmosphere had unstable environmental conditions of convection. (3) The warm sector rainstorm near the warm shear on 850 hPa had obvious energy front, while the energy front of the rainstorm in the local geothermal area in the southward airflow on the south side of the warm shear was not obvious. (4) During the warm sector rainstorm, the vertical wind shear over the rainstorm area reached the shear magnitude of medium or higher intensity. Vertical environmental conditions were favorable for the occurrence and development of convective weather in warm sector. (5) The mesoscale convergence line on the ground was the trigger mechanism of rainstorm in warm area. The position and moving direction of convergence line were consistent with the falling area and moving direction of the rainbelt. (6) The enhancement and down propagation of low-level jet stream and ultra-low-level jet stream would also trigger the release of unstable energy.

Based on the sea surface temperature from NOAA, reanalysis data from NCEP/NCAR and monthly precipitation in Shandong from 1961 to 2016, the anomalous characteristics of monthly precipitation in Shandong Province and circulation in the following summer of El Niño events with different patterns were compared. The results show that the effects of El Niño events with different patterns on monthly precipitation in the following summer in Shandong were obviously different, but the intensity of rainfall anomaly in the following June of El Niño events with three types was weaker than that in the following July and August, and the distribution of extreme values was intensive. The precipitation in the following summer of Niño3 pattern in Shandong was less than that in normal years, and the precipitation was less in June and August, while that was more in July. When El Niño events occurred in the central Pacific (Niño4 area), the precipitation in the following summer was more in most areas of Shandong, and the precipitation was significantly more in June, while it was more in the middle and less in the east and the west in July, and it was more in the southeast and less in the northwest in August. When the distribution of El Nio events appeared Niño 3.4 pattern, the precipitation in the following summer was more in the north and less in the south of Shandong. The precipitation was less in June and more in July in most areas of Shandong, and it was less in the southeast and more in the northwest in August. The anomalous distribution of 500 hPa circulation, water vapor transport and convergence directly determined the characteristics of precipitation anomaly in Shandong in the following summer of El Niño events with different patterns, and the influence of sea surface temperature on circulation anomalies was significant.

Based on the multiple remote sensing data from satellite and rice yield, the temporal and spatial distribution of drought was monitored in five provinces of the middle and lower reaches of the Yangtze River (MLRYR) in 2012 and 2013 by using the multiple drought indexes including precipitation condition index (PCI), vegetation condition index (VCI), soil moisture condition index (SMCI), temperature condition index (TCI) and optimized vegetation drought index (OVDI). And on this basis the applicability of five drought indexes in this area was contrasted by taking standardized precipitation index (SPI) and reduction rate of crop as reference. The results show that PCI and SMCI were more suitable to monitor the drought, while TCI and VCI weren’t suitable to monitor the drought alone in five provinces of the MLRYR. The drought with different levels occurred in five provinces of the MLRYR in 2012 and 2013, and the drought in 2013 was more serious (the range of drought was wide and the frequency was high) than that in 2012. The drought mainly occurred from January to February and June to August of 2012, and the drought region with NE-SW strip distribution concentrated in the north of five provinces of the MLRYR. However, the drought was mainly occurred from January to February and June to October of 2013, and the drought covered the whole area, but the drought situation in each province wasn’t synchronous.