Characteristics and Conceptual Models of Convective Rainstorm Clouds in Henan Province
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摘要: 利用2005—2010年FY-2C/E和MODIS卫星资料、A0报文、自动气象站降水资料及常规观测资料,修订了河南省对流性暴雨中尺度对流系统标准,统计分析了暴雨中尺度对流系统的活动规律和降水特征,初步建立了河南省典型对流性暴雨概念模型。河南省对流性暴雨中尺度对流系统主要包括新生对流云团、β中尺度对流系统、α中尺度对流系统及带状中尺度对流系统。对流性暴雨易产生于中尺度对流系统的发生、发展期,多发于中尺度对流系统云顶亮温低中心附近及后侧梯度大值区, 云系上云光学厚度高值区为中尺度对流系统发展潜势区。低槽 (涡) 切变型和低槽型过程中干冷气团对中尺度对流系统的发生、发展起触发作用;高压后部型与午后边界层辐射增温关系密切,能量锋、边界层辐合线是中尺度对流系统的触发系统;切变型过程中干线的作用较重要。河南省对流性暴雨中尺度对流系统多发展于山区附近,移动路径有东移、东北移和东南移型,高层云导风可为中尺度对流系统的移动发展提供预报信息。Abstract: Study on severe weather's conceptual models is important for improving forecasting and early warning capabilities of severe weather. Using FY-2C/E and MODIS satellite data, A0 data, precipitation data of automatic weather stations and conventional observations, meso-scale convective systems criteria of convective rainstorm is revised, and their activity rhythm, as well as rainfall characteristics, are analyzed during convective rainstorm processes. In addition, convective rain storm conceptual models in Henan Province are studied based on analysis of cloud systems and synoptic situations. MCSs of convective rainstorm in Henan Province include newborn convective cloud clusters, MαCS, MβCS and banded MCSs. MCSs with different shape and scale have different characteristics of precipitation. Newborn convective clusters are easy to produce 20—29.9 mm·h-1 rain intensity. The probability of exceeding 30.0—49.9 mm·h-1 rain intensity brought by MβCS is obviously greater. The rain intensity exceeding 30.0 mm·h-1 is most likely caused by MαCS, but banded convective systems have higher probability of exceeding 50.0 mm·h-1 rain intensity than MαCS. However, each type of MCS can form strong intensity of rainfall over 80 mm·h-1 and the strongest intensity of rainfall is made by MβCS. The spatial and temporal variations and morphological characteristics of MCSs can give important information for forecasting thunder-rainstorm, and thunder-rainstorm is easy to occur during the formation and development of MCSs, and in the regions with big gradient of TBB in the back and the center of MCSs. Regions with high cloud optical thickness are potential areas of thunder-rainstorm. Dry and cold air masses in the processes of trough (vortex)-shear and trough's style play an important triggering role of MCSs. In the processes of high pressure's rear, MCSs are closely related to increasing temperature by radiation in boundary layer. Furthermore, energy front and convergence lines in boundary are the trigging systems. Dry lines in the shear line's processes are very important. Formation and development information of MCSs may be dependent on optical thickness. What's more, in the processes of high pressure's rear, the north of dark area on vapor images is easy to bring about MCSs. There are five potential regions of convective rainstorm in Henan Province, and four regions of them are near mountains. The routes of MCSs include eastward, northeastward and southeastward paths. Cloud track wind on high level can provide forecasting information of MCSs.
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图 2 2005年6月25日对流性暴雨过程中的天气系统和云系特征
(a)25日20:00天气系统和FY-2C红外云图,(b)25日14:00 FY-2C红外云图和雨强 (单位:mm·h-1),(c)25日18:00 FY-2C红外云图和雨强 (单位:mm·h-1),(d)26日02:00 FY-2C红外云图和雨强 (单位:mm·h-1),(e)25日13:20 MODIS水汽产品图像,(f)25日11:45 MODIS云光学厚度产品
Fig. 2 Weather system and cloud features during the thunder-rainstorm process on 25 June 2005
(a) weather system and FY-2C IR image at 2000 BT 25 June 2005, (b) FY-2C IR image and rain intensity (unit:mm·h-1) at 1400 BT 25 June 2005, (c) FY-2C IR images and rain intensity (unit: mm·h-1), (d) FY-2C IR image and rain intensity (unit: mm·h-1) at 0200 BT 26 June 2005, (e) water vapor product of MODIS at 1320 BT 25 June 2005, (f) cloud optical thickness product of MODIS at 1145 BT 25 June 2005
图 3 2006年7月31日对流性暴雨过程中的天气系统、FY-2C红外云图及MODIS云光学厚度
(a) 天气系统和红外云图, (b) 红外云图与雨强 (单位:mm·h-1),(c) MODIS云光学厚度产品 (白实线包围区为MCS发展潜势区)
Fig. 3 Weather system, IR image of FY-2C and cloud optical thickness product of MODIS during the convective-rainstorm process on 31 July 2006
(a) weather system and IR image, (b) IR image and rain intensity (unit:mm·h-1), (c) cloud optical thickness product of MODIS (area surrounded by white circle represents potential region of developing MCS)
图 4 2007年8月25日对流性暴雨过程中的天气系统、FY-2C红外云图和MODIS水汽产品图像
(a) 天气系统和红外云图 (云图为15:00;红实线为对流有效位能,单位:J/kg),(b) MODIS水汽产品图像 (白实线包围区为MCS发展潜势区)
Fig. 4 Weather systems, FY-2C IR image and water vapor product of MODIS during the convective rainstorm process on 25 August 2007
(a) weather system and IR image (IR image at 1500 BT; red contours are CAPE, unit: J/kg), (b) water vapor product of MODIS (area surrounded by white circle represents potential region of developing MCS)
图 5 2006年7月4日对流性暴雨过程中天气系统、红外云图及云光学厚度
(a) 天气系统和红外云图 (云图为14:00;虚线包围区K指数不低于32℃),(b) MODIS云光学厚度产品
Fig. 5 Weather system, IR image and cloud optical thickness during the convective-rainstorm process on 4 July 2006 (a) weather system and IR image (IR image at 1400 BT; area surrounded by dotted line: K≥32℃), (b) cloud optical thickness of MODIS
图 7 对流性暴雨MCS发生发展的典型FY-2C高层云导风环境场和红外云图
(黑线: TBB不大于220 K;蓝、紫色箭矢分别示意MCS移动方向和高层云导风显著气流方向) (a) 气流分流区,(b) 西南风辐散区,(c) 反气旋环流顶部
Fig. 7 Typical high-level cloud track wind field and IR image of FY-2C for developing MCS during convective rainstorm process
(black contours represent TBB no more than 220 K; blue and purple arrows indicate moving direction of MCSs and significant airflow direction of high-level cloud track wind, respectively) (a) airflow diversion area, (b) southwest wind divergence area, (c) anticyclonic circulation at the top
图 8 河南省对流性暴雨MCS发展区域及移动路径示意图
(底图为地形图;暖色调代表山区;灰色阴影区为MCS形成区域;粗箭矢路径频率不小于30%;细箭矢:路径频率小于10%)
Fig. 8 Development regions and movement paths of MCS during convective rainstorms in Henan Province
(bottom picture shows the topography and warm colors on behalf of the mountains; development regions of MCS are gray shaded; path frequency no less than 30% and less than 10% are represented by thick and thin arrows)
表 1 河南省对流性暴雨MCS的分类标准
Table 1 Criteria for MCS of thunder-rainstorm in Henan Province
名称 尺度特征 冷云罩强度中心 发展趋势 新生对流云团 最大冷云罩长轴小于100 km 只有1个TBB低值中心,中心值
大小不一,一般不超过-32℃满足尺度特征的时间低于3 h,消亡
或继续发展,或与其他MCS合并MβCS 最大冷云罩短轴为100~200 km
之间,偏心率不小于0.51~2个TBB低值中心,中心值较
低,不超过-52℃满足尺度特征的时间1~3 h, 减弱、
移出河南或继续发展、合并为MαCSMαCS 最大冷云罩短轴大于200 km,偏
心率不小于0.51个或1个以上TBB低值中心,
中心值不超过-52℃满足尺度特征的时间不低于
3 h,减弱或东移出河南省带状MCS 不低于-40℃冷云罩呈带状分布,
长轴不小于300 km,长短轴比不小于5:1多个TBB低值中心,中心值
一般不超过-52℃满足尺度特征的时间约2~6 h,
东或南移出河南省表 2 典型中尺度对流系统降水强度特征
Table 2 Characteristics of typical MCS rainfall intensity
种类 短时强降水
累计次数不同雨强出现概率/% 极大雨强
/(mm·h-1)20.0~29.9 mm·h-1 30.0~49.9 mm·h-1 ≥50.0 mm·h-1 新生对流云团 105 60 30 10 83.0 MβCS 127 52 37 11 92.0 MαCS 175 35 50 15 82.0 带状MCS 68 41 43 16 76.0 -
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