| There is a high frequency of severe convective weather occurring in Jianghuai and Huanghuai region of China.Based on three-yr(2010-2012,April-October)conventional observation data and NCEP reanalysis data,the spatial distributions and the temporal variability?the typical synoptic weather environments and the statistical characteristics of key parameters of 418 convective events over Jianghuai and Huanghuai area(30-37°N,110-122°E)are investigated.Results show that severe convective events gradually decrease from 2010 to 2012 and mainly occur from June to September with a single-peak in August.With the seasonal change,severe convective events gradually increase from south to north over the study area till August,then from August to October they gradually decrease from north to south.Three areas were identified as high frequency of occurrence of severe convective events.The most favorable area of the severe convective events is the plain of east China with an occurrence frequency of 35.3%.The other two areas are around Dabie mountain and Huangshan mountain and near the southern boundary of Tai mountain,respectively.Their diurnal variation show a single peak in the late afternoon(15-21,LST)for the all cases and short-duration(with duration equal 1 hour)cases,while the long-duration cases(with duration greater than or equal 3 hours)have double peaks,the major peak as the short-duration cases and the minor peak in the early morning(06-09,LST).The largest frequency region of severe convections occurred shifts gradually from the northwest to the southeast of Jianghuai and Huanghuai area from morning to evening.In totally the strength of long-duration convection cases are more greater than those of short-duration cases.The related environmental conditions were classified into four major groups based on their 500 hPa synoptic weather maps based on NCEP reanalysis data:trough(TR,716 cases),subtropical high(STH,226 cases),cold vortex(CV,30 cases),tropical cyclone(TC,37 cases).With the composite analysis the mean locations of synoptic weather system and their associated convections are revealed.The mean environmental fields show that the precipitable water in STH and TC are the largest at the time of severe convective events occurring,The TR has moderate moisture whereas the CV is the driest with the lowest PW comparatively.The convective available potential energy(CAPE)in the STH and TC has the largest value,the TR is moderate and the CV has the lowest unstable condition comparatively.The composite of rawinsonde analyses before the time of severe convective events occurring show that the TC pattern features the largest moisture in the troposphere while the STH is associated with rich moisture in the lower layer.The TR has moderate moisture whereas the CV is the driest with the lowest lifting condensation level pressure(LCLP)comparatively.From the condition of instability point of view,the STH has the largest unstable condition,the TR is moderate and the CV has the lower unstable condition comparatively,the TC is the lowest unstable condition though it is the largest during the time of occuring.Study of dynamic characteristics show that all the pattens have the environment condition to the benefit of vertical movement.Compared with the convection-related parameters of different durations,the long-duration cases have the most favorable conditions in moisture,instability and dynamic lifting,and the Convective inhibition(CIN)is similar to the short-duration cases,which are consistent with the intensity characteristic of different durations.Compared to previous studies,the severe convective weather processes in the area investigated in the current study tend to form in a moister environment and with a background of comparable weaker unstability. |
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