Spatial-temporal distribution and environmental parameter characteristics for different types of thunderstorm gales in Hubei Province

Based on conventional observation data, NCEP reanalysis data, lightning locating data and radar data, we have conducted the analysis on weather types, spatial-temporal distribution and environment condition of thunderstorm gales in Hubei from 2007 to 2015. Moreover, according to the results in boxplots, we have discussed the environmental parameter characteristics for the different types of thunderstorm gales in different regions and seasons. The main results are as follow. (1) Thunderstorm gales in Hubei, which occur between March and August, can be divided into high-level cold advection forcing (HCAF), low-level warm advection forcing (LWAF), baroclinic frontogenesis (BCF), and quasi-barotropic (QBT) types, with 78% of them occurring in the summer (from June to August). Most of thunderstorm gales occur from 15∶00 BT to 19∶00 BT in a day, whose peak value is at 16:00 BT. The spatial distributions of thunderstorm gales are uneven, whose high frequency regions are located near Yichang of southwestern Hubei and Huangshi of east Hubei. (2) There are seasonal and regional differences in the spatial-temporal distribution of the different types of thunderstorm gales. Among those types, the BCF type occur mostly in spring, and most of HCAF, LWAF and QBT types occur in summer. The HCAF type occurs mostly in the northwest Hubei, and the LWAF type occurs more in Yichang area, Jianghan plain and eastern Hubei, while both the QBT type and the BCF type occur mostly in the eastern Hubei. (3) When the HCAF type thunderstorm gales occur, both the temperature difference (ΔT₈₅) between 850 hPa and 500 hPa and the wind vertical shear (S₉₅) in the mid- and low-level (925-500 hPa) are greater, while the dew-point at 850 hPa is lower. For the QBT type thunderstorm gales, both S₉₅ and K index are greater. For the QBT type, the convective available potential energy (CAPE) is greater, and both S₉₅ and the wind vertical shear (S₉₇) in the low-level (925-700 hPa) is less. For the BCF type, both S₉₅ and S₉₇ are greater. (4) When the thunderstorm gales in Hubei occur, the thresholds of convection parameters of K index, ΔT₈₅ and CAPE are 35 ℃, 25 ℃ and 925 J·kg^-1, respec tively. The dispersion of convection parameters is greater in the northwestern Hubei and eastern Hubei, therefore, summing up the thresholds of convection parameters in region has more indicative significance to the forecasting and warning of thunderstorm gales in Hubei.