Based on the merged data of CloudSat from June to August during 2007-2010, the occurrence probability, vertical structure, type, microphysical structure of single-layer and multi-layer clouds and their environmental temperature and humidity over Liaoning Province were investigated. The results are as follows: (1) The clouds were mainly composed of single-layer cloud over Liaoning Province in summer from 2007 to 2010, and then followed by double-layer cloud. The single-layer clouds were mainly consisted of cirrus and altostratus, and then followed by altocumulus and deep convection. The cirrus mainly distributed at upper layer of multi-layer clouds. The altocumulus, altostratus and stratocumulus mainly distributed at lower layer of double-layer clouds, while the altostratus and altocumulus mainly dominated at middle layer and the stratocumulus mainly dominated at lower layer of triple-layer clouds. (2) The echo intensity and cloud thickness for each layer of multi-layer clouds were less than those of single-layer cloud. (3) The vertical profiles of microphysical quantities (particle number density, effective radius and cloud water content) for each layer of multi-level clouds were similar to single-layer cloud, while their average values were relatively smaller, and they decreased gradually from top to bottom, which were related to cloud types, namely the values of deep convection were the largest and cirrus were the smallest. (4) Compared with clear sky, the specific humidity on cloudy weather was larger, which indicated that the water vapour of atmosphere on cloudy weather was more abundant. The average near-surface temperature was lower under the cloudy weather during the daytime, while it was opposite at night.

Based on conventional ground observation data of weather stations and pollutant mass concentration observation data from environment monitoring stations in Liaoning Province, ECMWF reanalysis data with 0.5°×0.5° spatial resolution, a heavy pollution process caused by straw burning from 7 to 10 November 2015 in Liaoning Province, the differences and its causes of pollution among different cities were analyzed. The results are as follows: (1) CO was main pollutant during the heavy pollution process. The mass concentration of PM2.5 appeared two peak stages, and it was well corresponded to CO and NO2 mass concentrations. The visibility was mainly affected by PM2.5 concentration and relative humidity. (2) The effect of previous weak precipitation more than 1.0 mm on wet deposition of pollutants was obvious in Yingkou and Panjin, while the precipitation in other cities was smaller, and the high humidity environment was conducive to moisture absorption and growth of pollutants. (3) The horizontal wind speed from ground to 700 hPa during the heavy pollution was close to 4 m·s-1, the atmospheric stratification was stable, and the temperature inversion was obvious, which was beneficial to inhibit the vertical diffusion of pollutants. (4) The warm layer around 0 ℃ between 850 hPa and 900 hPa over cities except for Jinzhou maintained for a long time, which might provide favorable environment for the melting, collision and growing of pollutant particles. (5) There were many fire points in Jilin and Heilongjiang Province during the pollution process. Therefore, the main sources of pollution in central Liaoning Province came from the wide straw burning upwind, so it was necessary to strengthen the control of local and external pollution sources under the favorable weather conditions to the pollutants accumulation.