In order to carry out the cloud-seeding operation scientifically and accurately, the King-air 350 aircraft (no.3523) equipped with airborne particle measurement systems (PMS) entered the cloud for vertical and horizontal detection, and combined with FY-2F satellite, weather radar and other data, the microphysical structure of a low trough cold front stratified cloud system in southern North China on February 28, 2021 and the rainfall enhancement operation conditions were comprehensively analyzed. The results show that the precipitation cloud system is a medium and low cloud. The cloud top height observed by the aircraft is 6 014 m, the cloud top temperature is -17.7 ℃, the cloud bottom height is less than 582 m, the 0 ℃ layer height in the cloud is 1 300 m, the cloud body thickness is more than 5 400 m, the warm cloud thickness is more than 700 m, and the cold cloud thickness is more than 4 700 m. The cloud top height retrieved by satellite ranged from 5 to 6 km, which is consistent with the aircraft measurement result. The cloud top temperature retrieved by satellite ranged from -40 to -25 ℃, which is lower than the aircraft measurement result. The microphysical structure of the cloud system during the whole detection period is nonuniform. In the cold cloud, the second layer of ice water mixing zone (height ranged from 3 427 to 4 985 m, temperature ranged from -12.4 to -6.3 ℃) and the third layer of ice water mixing zone (height ranged from 5 449 to 6 014 m, temperature ranged from -18.3 to -15.3 ℃) appear large particle number concentration areas detected by cloud drop probe (CDP), the maximum values are 146.80 cm^-3 and 170.75 cm^-3, and the supercooled water content reach 0.12 g·m^-3 and 0.20 g·m^-3, respectively. The microphysical distribution of warm clouds is relatively uniform. The particle number concentration fluctuates at a height of 557-575 m and 844-866 m. The particle number concentration detected by CDP varies relatively large, while the concentration of particles detected by cloud imaging probe (CIP) and by the high volumeprecipitation spectrometer (HVPS) vary relatively small.The microphysical distribution of clouds within cold clouds is not uniform. The number concentration fluctuations of cloud particle within the cold cloud region are significant at a height of 3 603-3 617 m, 5 445-5 542 m, and 5 705-5 847 m, with multiple jumps.The particle spectral widths detected by CIP and HVPS in warm cloud region are narrower than those in cold cloud region, and the cold cloud is mainly composed of solid ice particles. In the early spring, the mixed stratiform clouds are prone to appear in the early stages of precipitation systems of low trough cold front stratiform clouds, and there is a certain amount of supercooled water near the cloud top. It is suitable to identify the rain-increasing timing and the precipitation-increasing location for sowing cold cloud catalysts. Artificial seeding has great potential for catalysis.

Boundary layer parameterization scheme is one of the most important sources of numerical model predict error. Selecting the suitable planetary boundary layer parameter scheme for the simulation of the Bohai costal area typhoon rainstorm can provide reference for the subsequent business application and scientific research in this area. Eight planetary boundary layer (PBL) parameterization schemes (ACM2, BouLac, GBM, MYJ, MYNN, QNSE, UW, YSU) in the Weather Research and Forecast Model (WRFV4.3) are used to simulate the torrential rain caused by northward Typhoon In-Fa (2106). The discrepancies of the simulated torrential rain based on the different schemes are compared, and the simulated PBL thermo-dynamical structure are examined based on ERA5 data. The results are as follows: Firstly, the simulated typhoon rainfall (including 24 h accumulated rainfall, the maximum and position of the accumulated rainfall, equitable threat scores, the hourly maximum rain and the rainfall areas of 10.0 mm and 20.0 mm precipitation per hour) during the typhoon northward period present significant difference, and the simulated track difference mainly occurred in the middle-late simulation period. Secondly, the local closure scheme-BouLac test has the best equitable threat scores for the 24 h accumulated rainfall above 10.0 mm, while the non-local closure scheme-ACM2 simulated the accumulated rainfall above 25.0, 50.0 and 100.0 mm best, which has the highest equitable threat score compared to the other PBL parameterization schemes. In addition, simulation results of the ACM2 scheme show the maximum accumulated rainfall, 24 h accumulated rainfall averaged on a region and mean hourly maximum rainfall are closest to ERA5 data. Therefore, the ACM2 scheme is best suitable for the torrential rain simulation of Typhoon In-Fa (2106) under the background of the land-sea coexistence in the Bohai coastal region. Thirdly, compared to the other PBL parameterization schemes, the ACM2 scheme has the simulation results which are closest to real-time for the height of PBL, the profiles of potential temperature and water vapor mixing ratio. This is why the ACM2 scheme is more accurate in forecasting the heavy rainfall and the rain magnitude above it. Finally, the strength of the 700 hPa vertical movement simulated by the eight PBL schemes has an important effect on the northward typhoon precipitation, which basically determines the change trend of the hourly maximum precipitation and the relative magnitude of the regional average 24-hour cumulative precipitation.

Based on the refined numerical prediction products of the European Center of Medium-range Weather Forecast (ECMWF), precipitation guidance products from China Meteorological Administration (TP_CMA) and precipitation observation data at 340 meteorological stations of Gansu Province, the objective divisions of precipitation at 340 meteorological stations of Gansu Province from April to September during 2017-2019 were done by using spatial cluster and Tyson polygon (SCTP) approach. On this basis, the physical quantity factors related to precipitation were selected and used to build prediction model by using random forest (RF) algorithm, and the correction experiment of short-term quantitative precipitation objective forecast in Gansu Province was carried out, the forecast effect was verified. The results are as follows: (1) There were 7, 6, 14, 13, 14 and 11 precipitation regions in sequence from April to September in Gansu Province. (2) In terms of rain probability forecast, the forecast ability of SCTP-RF products in flood season (from June to August) in Gansu Province was better than that of TP_CMA guidance products and ECMWF model products, and the prediction accuracy improved by 6.1% and 4.2%, respectively. In space, SCTP-RF products had a certain ability to correct rain probability forecast at all stations of Gansu Province, and the prediction accuracy at most stations improved by 5%, especially in the east of Yellow River in Gansu (Hedong area). (3) For graded precipitation forecast, the forecast ability of SCTP-RF products to moderate rain and heavy rain was superior to TP_CMA guidance products and ECMWF model products, and the correction effect at most stations was better, especially in the middle part of Hedong and southeastern Gansu. However, the correction ability to light rain and rainstorm forecast was unstable during the heavy rainfall processes, especially to light rain in southeastern Gansu.

Based on data such as first frost date in Ningxia, geopotential height, sea surface temperature (SST), snow cover area, and sea ice area from 1981 to 2019, the influence of external forcing factors including sea surface temperature, sea ice area, and snow cover area on the abnormally early and late first frost in Ningxia was studied. On the basis of above, a physical conceptual model and an objective prediction model for predicting first frost date were established. The results are as follows: (1) In the early years of first frost, the SST in the equatorial central and eastern Pacific continued to be significantly warmer in the early period, and the SST anomaly presented an obvious ENSO model. When the SST of the equatorial central and eastern Pacific was warmer in the early period, the east Asian trough was stronger and the subtropical high was weaker, which was conducive to cold air activity. So, first frost date was early, otherwise it was late. (2) The snow cover area in the northern hemisphere from May to August in the early period and the sea ice area of Greenland from January to July had a continuously and significantly negative correlation with the date of first frost. When the snow cover in the northern hemisphere decreased or the sea ice in Greenland decreased, the east Asian trough was weaker and the western Pacific subtropical high was relatively stronger, which was not conducive to active cold air, causing first frost to be late, and vice versa. (3) The main factors affecting the date of first frost in Ningxia were the intensity of the east Asian trough, the SST anomaly in the NINO3.4 area, the SST anomaly in the tropical south Atlantic, the snow area in the northern hemisphere, the intensity of the western Pacific subtropical high, and the area of Greenland sea ice. The objective prediction model established by using the multiple regression equation had a good prediction effect.

:Respiratory diseases greatly affected children’s health, and its occurrence was related to meteorological conditions closely. In order to analyze the effects of meteorological conditions on children’s lower respiratory diseases in Qinhuangdao, predict the number of patients and provide new method for medical meteorological service, the data of children with lower respiratory diseases from 2015 to 2016 and the meteorological data within the same time were used, prediction models were established by stepwise regression analysis and BP artificial neutral network separately, and the prediction effects were evaluated. The results show that the meteorological conditions, especially the staged weather changes and climate anomalies, had a significant effect on the patients’ number with these diseases. The number of patients was negatively correlated with air temperature and average relative humidity, and positively correlated with air pressure, wind speed and temperature fluctuation in 72 hours, and good correlation was showed between patient number and air temperature, followed by air pressure and average relative humidity. The prediction accuracy of the stepwise regression model and BP artificial neural network model was 72.75% and 76.30%, respectively. Between the two models established, the overall performance of BP artificial neural network model was better.

Based on the conventional observation data，Doppler radar products and observations of automatic meteorological station，the paper analyzed a heavy hailstorm weather occurred in the south edge of Zhunger Basin on May 2，2010 from weather situation，cloud images change，evolution of physical quantity field and radar echo．The results showed that the hail weather occurred under the weather condition of unstable convective stratification，dry and cold at the middle or upper layer，but humid at the low layer;abundant vapor condition，a  esoscale convergent shear on the ground，the suited height of the 0℃layer and－20℃layer，strong vertical wind shear were all favorable to this weather process．The Doppler radar can properly monitor the developing processe of the hailstone weather．The appearance of＞50 dBZ echo section and cove configuration，convergence region and adverse wind region，increase of VIL value(Vertical Integration of Liquid water)and STI(storm track information)，these all have indication to occurrence of hail weather．

The paper analyzed a hailstone weather occurred in the Zhunger south edge’s region on June 28，2010 based on the routine
data，automatic meteorological station data and CINRAD/CC Doppler radar data．The results showed that the heavy convection weather
occurred under the condition of high altitude trough cooperated with ground cold front and instable atmospheric stratification，dry and cold in middle－high layer and warm and wet in low layer，abundant water vapor，fitting height of 0℃layer and－2．0℃layer，meanwhile there was heavy vertical wind shear．Doppler radar reflectivity factor PPI appeared＞50 dBZ heavy echo section and＞60dBZ heavy echo center．The RHI appeared cove configuration，and the height of＞50 dBZ echo section was more higher than that of 0 ℃layer．The radial velocity map showed mesocyclone，against the wind section．It presented low layer convergence and high layer divergence in hailstone area．Updraft in PPI of different elevations showed circumrotating and rising．Strong echo section corresponded well to against the wind section and mesocyclone，meanwhile VIL，mesocyclone and storm track information products had good indication for hailstone drop．

Based on precipitation and temperature data of 21 stations in January in Ningxia region,  NCEP / NCAR monthly height and wind grid data of 2.5 × 2.5 °over Northern Hemisphere from 1961 to 2008, and NCEP Eurasian snow cover data from 1973 to 2007, the formation mechanism of the extremely cold and snowy weather event accurred in January 2008 in Ningxia region was analyzed. Results show that the anomalous atmospheric circulation was one of the most important causes. La Nina event and Eurasian snow cover anomalies resulted in atmospheric circulation anomaly, then anomalous precipitation occurred in January in Ningxia.

Using TERRA ／MODIS data in some typical vegetation regions during plant growth period in 2003 and vegetation type data，the sDatial and temporal characteristics of MODIS／NDVI and MODIS／EVI in Northwest China an d the influences of atmosphere con'ec-ti0n on the two vegetation indexes were an alyzed in this paper for comparing the diferences between NDVI and EVI．The results show that distributi0ns of NDVI an d EVI are consistent in space and nearly the same as that of precipitation．Th e diference between NDVI and EVI is larger as vegetation coverage increases．In addition．the infl uence of atmosphere on NDVI and EV1 was obvious，and atmos-DheIle c0n．ecti0n made NDVI values increase and EVI values reduce；the values of NDVI are smaller than those of EVI before atmos--DheIle c0rrecti0n：while after the correction，values of NDVI are larger than those of EVI in most regions． By comparing NDVI and EVI in th0se regi0ns containing more aerosols．we found that EVI had a good performance in removing the infl uence 0l aerosols．

Based on constant altitude p lane data of reflectivity factor from new generation weather radarwhich are interpolated with 3D - Barnes scheme, vertically integrated liquid water content (V IL) of hail cloud cell calculated with its theoreticalmodel, vertically integrated liquid water content density( V ILD) calculated by the ratio of V IL value to top height of hailcloud cell, the daily variation character, size distribution and the relations between the maximum diameter of hail on the ground (Rmax) and V ILmax, as well as V ILDmax of hailcloud cell during hail fall on the northeast of Tibetan Plateau are studied with statistic method. Results are as follows:(1)On the northeast part of Tibetan Plateau, hail fall was mainly in middle size hailstones ( diameter range: 5 - 20 mm) , and then smaller size hailstones ( diameter less than 5 mm) , larger hailstones ( diametermore than 20 mm) occurred less; (2) Local hail fall occurred mainly in the afternoon and evening, and there are two peak periodswhich are from 15: 00 to 16: 00 and from 20: 00 to 21: 00,and this result is accordant to the former research of Chen qian et al. on the whole but earlier in occurring period; ( 3) As a whole,there is a positive correlation between Rmax and V ILmax orV ILDmax, but the correlation between V ILDmax and Rmax is better; some difference exists in V ILDmax values of hail cloud cells corresponding to the same size hail but it is small and less than 0. 1 g. m - 3 ;( 4) The cone of silence for radar detecting, strong echo area leaning and echo overhanging of hail cloud cell are major factorswhich resulted in negative correlation between Rmax and V ILmax orV ILDmax.

Using TERRA ／MODIS data in some typical vegetation regions during plant growth period in 2003 and vegetation type data，the sDatial and temporal characteristics of MODIS／NDVI and MODIS／EVI in Northwest China an d the influences of atmosphere con'ecti0n on the two vegetation indexes were an alyzed in this paper for comparing the diferences between NDVI and EVI．The results show that distributi0ns of NDVI an d EVI are consistent in space and nearly the same as that of precipitation．Th e diference between NDVI and EVI is larger as vegetation coverage increases．In addition．the infl uence of atmosphere on NDVI and EV1 was obvious，and atmos DheIle c0n．ecti0n made NDVI values increase and EVI values reduce；the values of NDVI are smaller than those of EVI before atmos-DheIle c0rrecti0n：while after the correction，values of NDVI are larger than those of EVI in most regions． By comparing NDVI and EVI in th0se regi0ns containing more aerosols．we found that EVI had a good performance in removing the infl uence 0l aerosols．

The large range rare fog process which occurred in East China from November 30 to December 4 in 2004 was analyzed, including the circulation background, its adjustment and evolvement, the climatic background, the atmospheric stratification condition and the vapor condition near surface, etc. Results show that the warm advection at the low level, the stable atmospheric stratification and the abundant vapor condition resulted in this rare fog process, and fog dissipation needs the cold air invasion with the cold front.

The effect of a hail suppression by anti-hail gun which occurred on June 25, 2005 in the east part of the Qilian Mountain was analyzed by using the CINRAD/CC products, including the layer composite reflectivity factors, the maximum values of the vertical reflectivity, echo tops, the horizontal wind field in the hail cell, the vertical structure and the maximum values of VIL, their changes before and after the hail suppression, as well as ground precipitation. Results show: (1) There are two aspects of hail suppression effect by anti-hail gun: The first is that silver iodide crystals sprinkle fleetly around the explosive point, and collide with the surrounding frozen droplets, reducing the average quality and diameter of frozen droplets; the second is that the power from shells exploding suppresses the developing of the updrafts under the explosive point. (2) The hail suppression by anti-hail gun is available for rainfall increase on ground. As for this hail suppression process, assuming that liquid water in the hail cloud falls completely as raindrops to the ground, the precipitation on the ground will increase 4.69%.

Through monitoring and analysis on atmospheric aerosol at surface boundary layer over Lanzhou city in March and April in 2002，some results are given out as follows：（1）The quality concentration of TSP over Lanzhou city is increasing evidently while the dust weather is occurring，and the more strong the sand dust is，the more high the quality concentration of TSP is，and the air pollution is more severe；（2）The quality concentration of TSP corresponds to that of PM10 well over Lanzhou city under different weather conditions，and the more strong the dust is，the more high the quality concentration of TSP and PM10 is，but the increase or decrease proportion of TSP and PM10 quality concentration is different；（3）The quality concentration of the same level particles is different under different weather conditions，but the quality concentration distribution of the diversified level particles is same under the same weather condition；（4）The sample chroma of TSP corresponds to the air quality in some degree ，if the value of L*，a*and b* is larger，then the sand dust in air is more and the air pollution is more severe，and the air pollution primarily comes from local black organic substance because the value of L*，a*and b* is much less under normal weather condition.

In this paper，the climate and weather characteristics in Suˊnan station which is located at the foot of the mid - section of Qilian mountain are analyzed in order to find the available weather patterns and days for weather modification. Results show that the annual precipitation in mid - section of Qilian mountain is much larger than that in Hexi basin，and the precipitation increases with the height above sea level，the annual average days available for weather modification are 146. 4 d，the monthly rainy（ snowy）days are more than 10 d from March to October in a year，it is convective rainfall mainly in May to August.

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