Fog and haze are disaster weathers which endanger human health and affect social and economic development. Accurate and detailed monitoring data can play an important role in the prevention and control of fog and haze. The accuracy of China Meteorological Administration Land Data Assimilation System (CLDAS) visibility and relative humidity fusion products in identifying fog, light fog and haze is analyzed by using the observation data of national stations in Tianjin and its surrounding areas from December 1, 2017 to November 30, 2020, Himawari-8 L1 full-disk data and L3 aerosol optical depth product. The results show that compared with the station observation data, the average detection rates of CLDAS products in identifying light fog, fog and haze are 90.4%, 84.2% and 78.8%, respectively. The detection rates of light fog in different months are 81.1%-96.4%. In the months with more fog and haze, the detection rates are about 80.0%. The cases analysis shows that the fog, light fog and haze identified by CLDAS products are basically consistent with the results of Himawari-8 satellite and observations. The failure of CLDAS products to correctly identify fog, light fog and haze mainly shows that fog is misjudged as light fog (3.8%-21.4% at different stations) and haze is missed (8.6%-25.0% at different stations). When the horizontal visibility of the station is between 0 and 0.75 km, the error of CLDAS visibility mainly causes fog to be mistakenly identified as light fog. When the horizontal visibility of the station is between 0.75 and 7.5 km，the error of CLDAS visibility mainly leads to haze being missed. When the station visibility is between 7.5 and 15 km, the error of CLDAS visibility mainly leads to light fog and haze being reported empty. When the relative humidity of the station is greater than 40% and less than or equal to 60%, the error of CLDAS relative humidity mainly leads to haze being misjudged as light fog. In general, the accuracy of CLDAS products in identifying fog, light fog and haze in Tianjin area is good, which can provide reference for fine monitoring of fog, light fog and haze, and improve the status quo of scarce visibility observation stations and insufficient space coverage in fog and haze monitoring.

 Using conventional surface and upper meteorological observations, wind profile radar data and WRF model data, this paper analyzed physical field and trigger conditions of a rainstorm process with low-altitude jet enhancing in Jiangxi. The results are as follows: (1) The rainstorm happened under the weather situation of subtropical high jumping northward and southwest jet strengthening, and it was caused by joint action of multi-systems such as subtropical high, short-wave troughs in the westerlies, monsoon, mesoscale convergence system and low-altitude shear. (2) Increase of both temperature and humidity in the low-level layer, invasion of cold convection in middle troposphere and abnormal value of all kinds of thermal instability indexes took high energy, high humidity and high instability over north of Jiangxi Province, and formed mesoscale θse energy front and dew point front over northeast Jiangxi. Frontogenesis was one of causes of this rainstorm. (3) Low-altitude jet strengthening brought enough water vapor and mesoscale convergence system developing along the jet produced mesoscale energy and temperature front. And condensation latent heating released by convective precipitation promoted meso-scale convective system. That helped strong rainfall. The jet pulsation with the speed more than 16 m·s-1 from 1.5 to 3 km  would forecast strong rainfall in downstream zone of southwest wind 1-3 hours in advance. (4) The 500 hPa positive vorticity advection developing increased the cyclone vorticity in middle troposphere, which caused positive vorticity column to grow, and made a secondary circulation with descending motion in the north of vorticity column. Meanwhile, high potential vorticity center developed downwards, which was favorable to cyclonic vorticity and frontogenesis development in low layer, promoting rising motion, and rainstorm keeping.

Based on daily precipitation, mean air temperature, maximum and minimum air temperature, wind speed and direction (four times a day) data during 1961-2018, and hourly precipitation data during 1978-2018 from 6 national meteorological stations around the Poyang Lake as well as the reanalysis data of European Center during 1979-2018, the climate difference between the east and the west side of the Poyang Lake caused by the cold-heat source effect on different time scales was analyzed. The results are as follows: (1) There was an obvious cold-heat source effect in the Poyang Lake. The diurnal temperature range in the Poyang Lake area was 2-4 ℃ smaller than that in mountainous areas, and the high temperature days was half of that in other areas of the same latitude in Jiangxi Province. (2) The precipitation in the Poyang Lake was also less than other areas of Jiangxi. The precipitation in the east and the west side of the lake presented the cyclical fluctuation in a year, there were more precipitation from August to October in the west side of the lake, while there were more rainfall in other months in the east side of the lake, the difference was obvious especially in middle of winter and summer. (3) There were differences of precipitation between the east and the west of the lake at day and night. The precipitation in the east of the lake was more obvious at night in January, while in September it was more obvious in the west of the lake at day. (4) Lake-land wind existed in the Poyang Lake. The average wind speed at 02:00 BST in January at Yongxiu station in the west side of the lake was higher than that of Duchang station in the east side of the lake, and the west wind component occurred more. In August, the average wind speed at Duchang station was higher than that of Yongxiu station at 14:00 BST, and the south wind occurred more frequently. (5) Compared with 14:00 BST, the atmospheric ascending motion was more obvious at 02:00 BST in the main area of the Poyang Lake in January, the near-surface wind field converged. While compared with 02:00 BST in August, subsidence movement was more obvious at 14:00 BST, and near-surface wind field diverged.