Zhu Shichao, Yuan Ye, Wu Yue, et al. Statistical characteristics of isolated convection in the Jianghuai Region. J Appl Meteor Sci, 2019, 30(6): 690-699. DOI:  10.11898/1001-7313.20190605.
Citation: Zhu Shichao, Yuan Ye, Wu Yue, et al. Statistical characteristics of isolated convection in the Jianghuai Region. J Appl Meteor Sci, 2019, 30(6): 690-699. DOI:  10.11898/1001-7313.20190605.

Statistical Characteristics of Isolated Convection in the Jianghuai Region

DOI: 10.11898/1001-7313.20190605
  • Received Date: 2019-07-15
  • Rev Recd Date: 2019-10-28
  • Publish Date: 2019-11-30
  • Isolated convective clouds are important precipitation cloud systems in the Jianghuai Region. Based on the analysis of radar data from June to September during 2013-2016, a total of 664 convective clouds are identified, in which 196 are isolated convective clouds. It is found that isolated convective clouds account for 29.5% of the total convective clouds in the Jianghuai Region. July and August are the high incidence periods of isolated convective clouds, while isolated convective clouds occur less in June and the frequency of occurrence is the least in September. At the same time, the high incidence time of isolated convective clouds is from 1200 BT to 1800 BT, and the lowest incidence time is from 0500 BT to 0700 BT. It is found that the circulation background has a great influence on the isolated convective clouds in this area. July-August is the high incidence of isolated convective clouds in the Jianghuai Region, which is mainly related to the circulation background during this period. The Jianghuai Region is often in the periphery of the subtropical anticyclone in July-August due to the high temperature and the increase of local unstable energy, and it often leads to the occurrence of local scattered convective clouds. In addition, in view of the isolated convective clouds at Dingyuan, Anhui Province on 20 July 2013, the Doppler radar and the C-band Frequency Modulation Continuous Wave radar detection data are comprehensively analyzed. It is found that there is a strong echo center alternately generated in the isolated convective clouds in the warm area, resulting in the wave structure of the internal echo reflectivity with the intensity distribution from weak to strong along the moving direction. In the vertical direction, the radar reflectivity factor increases at first and then decreases from top to bottom. The falling velocity intensity of precipitation particles correspond to it. The maximum falling velocity of precipitation particles appears in the strong echo region in the middle and lower parts of isolated convective clouds, and the velocity is over 10 m·s-1.
  • Fig. 1  The location of radars and the target area

    (× is the location of Doppler radar, Δ is the location of C-FMCW)

    Fig. 2  The frequency of isolated convective clouds in the Jianghuai Region from Jun to Sep during 2013-2016

    Fig. 3  500 hPa height (the contour, unit:gpm) and 850 hPa wind (the barb) at 0800 BT 31 Jul 2013

    Fig. 4  500 hPa height (the contour, unit:gpm) and 850 hPa wind (the barb) at 0800 BT 20 Jul 2013

    Fig. 5  Rainfall amount at Dingyun Station from 1000 BT to 1300 BT on 20 Jul 2013

    Fig. 6  Reflectivity of Hefei Doppler radar at 1042 BT 20 Jul 2013 (a)superimposition reflectivity, (b)enlarged view at the circle in Fig. 6a, (c)reflectivity cross sections at the black line in Fig. 6b

    Fig. 7  Superimposition of radar reflectivity at Dingyuan Station on 20 Jul 2013

    Fig. 8  Vertical structure of an isolated convection at Dingyuan Station on 20 Jul 2013 (a)reflectivity, (b)particle fall velocity

    Table  1  Main parameters of C-FMCW radar and Doppler radar

    雷达参数 多谱勒天气雷达 C波段连续波雷达
    探测方式 体扫描方式 固定式垂直指向
    探测量程 水平460 km,垂直20 km 150 m~24 km
    时间分辨率 6 min 3 s
    空间分辨率 1 km 30 m
    探测精度 ≤1 dBZ ≤1 dBZ
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    Table  2  The number of different convections from Jun to Sep during 2013-2016

    月份 孤立对流云数量 对流云数量 孤立对流云所占比例
    6 30 157 19.1%
    7 53 196 27%
    8 89 228 39%
    9 24 83 28.9%
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