Observational characteristics of thunderstorm gusts in Northeast China and their association with the Northeast China Cold Vortex

To improve the analysis and forecast ability of thunderstorm gusts (TGs) in Northeast China, climatic characteristics of TGs in Northeast China and their relation with Northeast China Cold Vortex (NCCV) are studied. TGs are identified based on comprehensive analysis of data collected at automatic weather stations and from lighting locators and Himiwari-8 satellite. In addition, the ERA5 reanalysis dataset is used to calculate the centers and radius of NCCV. The results show that TGs in Northeast China mainly occur in the regions from the Mongolian plateau to the west of the Greater Khingan mountains, Northeast China plain and the coastal area of Liaoning. About 50.6% of TGs are caused by NCCV and Liaohe plain is the area with the highest occurrence frequency of TGs caused by NCCV. The diurnal variation of TGs occurrence shows a high frequency in the afternoon, and the TGs caused by NCCV are more frequent in the late night and morning, accounting for 75%. The number of stations with TGs in one hour is generally less than 10, while the cases of regional TGs occurring at more than 10 stations are mostly related to NCCV and account for 56.5%. Compared with TGs not caused by NCCV, TGs caused by NCCV occur in a drier and colder environment with strong temperature lapse rate between 850 hPa and 500 hPa, strong vertical wind shear and storm bearing layer. The percentages of TGs occurring in different quadrants of NCCV in the NCCV TGs are 73.5% in the southeast quadrant, 17.5% in the southwest quadrant, 7.5% in the northeast quadrant and 1.5% in the northwest quadrant in descending order. The frequency of TGs occurring in the periphery of NCCV is more than that in the NCCV itself, and they are concentrated within 0.5—2 times of NCCV radius from the southeast quadrant of NCCV to the center of NCCV. In this area, there is a dry layer in the middle atmosphere, a large vertical temperature lapse rate in the lower atmosphere, a medium or higher vertical wind shear and a larger wind speed in the storm carrying layer, and they are more vulnerable to the impact of low-level shear line. This is the reason why NCCV TGs are concentrated in this area. The centers of NCCV that can cause TGs are concentrated over 45°—55°N and 111°—128°E, and the centers of NCCV that can cause regional TGs are concentrated at 116°E and 122°E with a meridional distribution. The geopotential height at the central and outermost areas of NCCV that can cause regional TGs is lower than that of NCCV responsible for local TGs, and the difference is more obvious in spring and autumn. Furthermore, the radius of NCCV that can cause local TGs in August slightly higher than that of NCCV that can cause regional TGs in spring and autumn, and vice versa. The results of this study have proved that NCCV is the most important system that causes TGs in Northeast China. The spatial distribution of TGs in different quadrants of NCCV and characteristics of NCCV that can generate regional TGs provide a reference for improving the forecast and early warning ability of TGs caused by NCCV.