Based on daily maximum and minimum temperature data of 99 national weather stations in Shaanxi, two methods of univariate linear regression and decaying average were used to correct the temperature forecasts of SCMOC (the data of the national meteorological center forecast), GRAPES_Meso (global/regional assimilation and prediction system) and ECMWF (European center for mediumrange weather forecasting). The result show that the prediction accuracy of daily minimum temperature was higher than that of daily maximum temperature for SCMOC, GRAPES_Meso and ECMWF. The accuracy of daily maximum and minimum temperature forecast of SCMOC was obviously highest among them, while that of GRAPES_Meso was lowest. The methods of univariate linear regression and decreasing average could significantly improve the accuracy of air temperature forecasts of GRAPES_Meso and ECMWF, but could not improve the accuracy of SCMOC. The accuracy of ECMWF’s daily maximum and minimum temperature forecast corrected from 2017 to 2019 was higher than that of SCMOC. The accuracy of GRAPES_Meso’s 24hour and 48hour daily maximum temperature prediction corrected in 2019 was higher than that of SCMOC, while the accuracy of daily minimum temperature prediction after correcting was still much lower than that of SCMOC. By comparison, the ability and stability of univariate linear regression method for rectifying air temperature forecast of numerical model were better than that of decreasing average method.

 Using FY-2G satellite data, ERA5 reanalysis data, and the integrated hourly resolution precipitation data from automatic weather stations, as well as CMORPH precipitation products, this paper focused on a comparative analysis of cloud-image characteristics, circulation features, and the parcel buoyancy instability of a pseudo adiabatic process and a reversible adiabatic process in two particularly strong precipitation periods from 03:00 BST to 15:00 BST 28 (the period 1) and from 20:00 BST 28 to 08:00 BST 29 (the period 2) during a heavy rain process occurring at the boundary between Sichuan and Shaanxi from June 26 to 29, 2015. The results show that the maintenance of strong divergence on 200 hPa, a steady shear on 500 hPa, and maintenance of 850 hPa wind convergence at this boundary provided favorable conditions for the occurrence and development of heavy rain during the period 1. The heavy precipitation in the period 1 forming at the boundary between Sichuan and Shaanxi was affected by a MαCS (meso-α convective system) moving northward steered by the southwest flow in middle to upper levels. The 500 and 700 hPa shear and the maintenance of a southerly airflow in the lower layers were important factors leading to heavy rain in the period 2. The development and merging of convective cloud clusters near the shear contributed to the formation of heavy rain in the period 2 at the boundary between Sichuan and Shaanxi. The low-level water vapor content over the rainstorm center in the period 1 was higher than that in the period 2. The updraft area over the rainstorm area extended higher, the updraft was stronger, and the cloud layer in the rainstorm area was deeper and denser in the period 1 than in the period 2. In both periods, the instability of the parcel’s vertical displacement according to a reversible adiabatic process was higher than that according to a pseudo-adiabatic process over the center of the heavy rain. The high-value areas of CAPE over the rainstorm centers of both periods all distributed between 800 and 700 hPa, which indicated that the parcel lifted between 800 and 700 hPa had large buoyancy during the adiabatic process. The favorable instability condition and the water vapor condition reinforced one another in the lower layer, which was conducive to development of heavy rain.

Based on the observation data of thunderstorm from 1998 to 2015 and the observation data from automatic weather stations at Changle Airport, daily reanalysis data from NCEP during 2010-2015, the temporal distribution characteristics of thunderstorm weather accompanying with wind shear at Changle Airport were analyzed, and the circulation types were summarized. Results show that the thunderstorm weathers occurred over Changle Airport all the year round, and it was most frequent in summer and its duration was longer. The daily change of thunderstorm weathers was obvious, it mainly occurred from the afternoon to the evening, and the duration was generally less than 2 hours, the majority of thunderstorms lasted less than an hour. The thunderstorm weathers occurred most easily in the westerly direction of Changle Airport. The probability of occurring wind shear from 3 hours before to 3 hours after the thunderstorm was 54%, and the probability of thunderstorms accompanying with wind shear in the westerly direction of Changle Airport was higher than that in other directions. The frequency of weak wind shear was much higher than that of moderate wind shear in Changle Airport, while the frequency of strong wind shear was the least. There were four main types of circulation situation for thunderstorm weathers accompanying with wind shear, they were the southern trough type, subtropical high control type, North China trough type and tropical cyclone type.