Based on CLDAS grid temperature data from National Meteorological Information Center of China, SCMOC grid temperature forecast data from Central Meteorological Observatory of China and temperature observation data at weather stations of Shanxi Province, the applicability of CLDAS temperature in Shanxi Province was evaluated comprehensively by using non-independence test method. And on this basis, based on CLDAS grid temperature data, the objective correction of SCMOC temperature forecast field was studied by using the sliding training period scheme. The results are as follows: (1) The complex terrain in Shanxi Province had a certain influence on the accuracy of CLDAS temperature, and the maximum temperature of CLDAS exhibited a better accuracy than the minimum temperature of CLDAS, which indicated that the influence of terrain on deviation of the minimum temperature was more significant, and the deviation of the minimum temperature in high altitude areas was negative generally, while that in low altitude areas was positive. (2) The deviation of CLDAS grid temperature had a continuity of time in space. After the simple deviation correction, the accuracy of the maximum and minimum temperature of CLDAS promoted by 1.1% and 9.7%, respectively, the revised temperatures were more consistent with observation. (3) Based on improved CLDAS grid temperature, the accuracy rate of SCMOC temperature forecast improved significantly by using the sliding deviation correction scheme. Compared to SCMOC, the accuracy rate of the 24-hour maximum and minimum temperature forecast in Shanxi Province in 2019 respectively increased by 2.7% and 4.7% after the sliding deviation correction. The quality of short-term temperature forecast after the sliding deviation correction had greatly improved, and it was superior to the subjective forecast of forecasters.

Based on the model sounding analysis field and forecast field of North China RMAPS (rapid-refresh multi-scale analysis and prediction system), the environmental parameter characteristics of four types of severe convection weathers were contrastively analyzed in Shanxi Province, and the classification indexes and criterion of severe convection weathers were summarized. And on this basis, the category forecasting scheme of severe convection weathers was designed in Shanxi Province, then the occurrence probability of severe convection weathers with four types on grid points was calculated, and the feasibility of classification forecast of severe convection weathers was further explored. The results are as follows: (1) The environmental parameters including convective available potential energy (CAPE), K index, temperature difference between the middle and lower level, temperature dew point deficit on low level, 600 hPa temperature and low-level vertical wind shear had a certain indicative significance for distinguishing types of severe convection weathers in Shanxi. (2) The low-level vertical wind shear and 600 hPa temperature between hail or thunderstorm-gale and short-term heavy precipitation or thunderstorm had significant difference. Using the 20.0 ℃ temperature difference between 700 hPa and 500 hPa as a threshold, the thunderstorm-gale could be distinguished from short-term heavy precipitation, hail and thunderstorm weathers. Taking the 4.0 ℃ temperature-dew point deficit on 700 hPa as a threshold, the short-term heavy precipitation could be distinguished from hail, thunderstorm-gale and thunderstorm weathers. The above results could be used as the basic criteria of recognition of severe convection in Shanxi Province. (3) The classification forecasting scheme had a certain forecasting ability to severe convections in Shanxi Province, and it could capture the possible falling areas of hail, thunderstorm-gale and short-term heavy precipitation to some extent during a large-range severe convection process. The short-term forecasting ability of classification scheme was slightly higher than that of average level of forecasters’ subjective forecast, and the threat score was improved by about 0.01-0.06.

Based on daily precipitation data from 1960 to 2019 and hourly precipitation data in September 2019 from 109 meteorological stations in Shanxi Province and reanalysis data from European Centre of Medium-Range Weather Forecasts, the anomaly characteristics of the extremely regional rainstorm in central and southern Shanxi from 10 to 11 September 2019 and its causes were analyzed. The results are as follows: (1) The precipitation process affected a large area and lasted a long time, extreme daily precipitation events occurred at 46 stations, the daily precipitation of 11 stations exceeded the historical extreme value in September. (2) The water vapor, thermal and dynamic conditions in the middle and lower troposphere were better than the average state of regional rainstorm processes in the middle and south region of Shanxi since 1980, absolute values of normalized anomaly (|N|) of different physical quantities were higher than 2.5 and the upper quartile of historical data, especially for the water vapor and thermal conditions anomaly. (3) The subtropical high was anomalously strong and moved northward and westward, which led to abnormally strong water vapor and energy transport in mid-low troposphere, water vapor input in the western and southern boundaries of central and southern Shanxi Province played an important role in occurrence and development of extreme precipitation. (4) There was the potential instability in the inclined warm-moist southwesterly, warm shear line on 700 hPa and surface cold front initiated the convection, “train effect” produced due to echo moving continuously through heavy rain area. The stabilized shear line and abnormally cold wedge in lower troposphere provided sustained dynamic condition, abnormally plentiful vapor and its convergence maintained sustainably, which was the main causes of the extreme regional rainstorm, and the large range of physical quantities anomaly was the main influence factor of it.

Based on the hourly precipitation data from June to September of 7 national meteorological stations during 1996-2015 and 63 automatic weather stations during 2008-2015 in Taiyuan, and relative radiosonde and surface observation data, the synoptic patterns of circulation configuration on short-time heavy rainfall days in Taiyuan were classified and the characteristics of key environmental parameters under different patterns were studied. The results show that there were four circulation patterns on 500 hPa during short-time heavy rainfall processes in Taiyuan including cold vortex type, upper trough type, upper trough with subtropical high type and northwest flow type. Short-time heavy rainfalls in Taiyuan always happened under weak CAPE, and in most cases it was less than 1500 J·kg-1, and for all of cold vortex type it was less than 1000 J·kg-1. For northwest flow type, the ΔT850-500 was bigger and there always was stronger static instability and obviously dry layer on 500 hPa. For upper trough with subtropical high type, there always was a higher K index, and mean value of warm cloud thickness was 3576 m, which was significantly thicker than those of the other types. The entire cases of cold vortex type and 85% cases of upper trough type happened under weak vertical wind shear within 0-6 km, 35% cases of upper trough with subtropical high type and northwest flow type occurred under a moderate vertical wind shear condition. Cold vortex type and northwest flow type always had better vapor conditions on 700 hPa than that of 850 hPa. The extreme rainfall more than 70 mm·h-1 occurred under northwest flow type, which had moderate CAPE, strong unstable stratification, weak 0-6 km vertical wind shear, and plenty vapor from low to middle layer with warm cloud thickness more than 3550 m, the cooperation of these environmental parameters had denotative meaning for the strong precipitation efficiency.