| Precipitation Structures of a Thermal Convective System Happened in the Central Western Subtropical Pacific Anticyclone |
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| 作者姓名： | Fu Yunfei Feng Jingyi Zhu Hongfang Li Rui Liu Dong |
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| 作者单位： | Institute of Heavy Rain CMA Wuhan 430074 School of Earth and Space Sciences University of Science and Technology of China，Hefei 230026，Office of Weather Modification in Anhui Hefei 230026，Weather Observatory Station in Anhui Hefei 230026，School of Earth and Space Sciences University of Science and Technology of China Hefei 230026，School of Earth and Space Sciences University of Science and Technology of China Hefei 230026 |
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| 基金项目： | 国家高技术研究发展计划(863计划);国家自然科学基金 |
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| 摘 要： | In this paper, characteristics of precipitating clouds in a thermal convective system (TCS) occurred in the southeastern mainland of China at 15:00 BT (Beijing time) on August 2, 2003 in the central western subtropical Pacific anticyclone (WSPA) is studied by using TRMM tropical rainfallmeasuring mission PR (precipitution radar) and IR Infrared radiation measurements. The precipitating cloud structures in both horizontal and vertical, relationship among storm top, cloud top, and surface rain rate are particularly analyzed. Results show that a strong ascending air at 500 hPa and a strong convergence of moisture flux at 850 hPa in the central WSPA supply necessary conditions both in dynamics and moisture for the happening of the TCS precipitation. The TRMM PR observation shows that the horizontal scale of the most TCS precipitating clouds is about 30-40 km, their averaged vertical scale is above 10 km, and the maximum reaches 17.5 km. The maximum rain rate near surface of those TCS clouds is beyond 50 mm h-1. The mean rain profile of the TCS clouds shows that its maximum rain rate at 5 km altitude is 1 km lower than the estimated freezing level of the environment. Compared with the mesoscale convective system (MCS) of "98.7.20", both systems have the same altitude of the maximum rain rate displayed from both mean rain profiles, but the TCS is much deeper than the MCS. From the altitude of the maximum rain rate to near surface, profiles show that rain rate reducing in the TCS is faster than that in the MCS, which implies a strong droplet evaporation process occurring in the TCS. Relationship among cloud top, storm top, and surface rain rate analysis indicates a large variation of cloud top when storm top is lower. On the contrary, the higher the storm top, the more consistent both cloud top and storm top. And, the larger the surface rain rate, the higher and more consistent for both cloud top and storm top. At the end, results expose that area fractions of non-precipitating clouds and clear sky are 86% and 2%, respectively. The area fraction of precipitating clouds is only about 1/8 that of non-precipitating clouds.
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| 关 键 词： | 热对流系统 太平洋 反气旋 高气压 |
| 收稿时间： | 2006/3/21 0:00:00 |
Precipitation Structures of a Thermal Convective System Happened in the Central Western Subtropical Pacific Anticyclone |
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| Fu Yunfei,Feng Jingyi,Zhu Hongfang,Li Rui,Liu Dong.Precipitation Structures of a Thermal Convective System Happened in the Central Western Subtropical Pacific Anticyclone[J].Acta Meteorologica Sinica,2006,20(2):232-243. |
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| Authors: | Fu Yunfei Feng Jingyi Zhu Hongfang Li Rui Liu Dong |
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| Institution: | [1]Institute of Heavy Rain, CMA, Wuhan 430074 [2]School of Earth and Space Sciences University of Science and Technology of China, Hefei 230026 [3]Office of Weather Modification in Anhui, Hefei 230026 [4]Weather Observatory Station in Anhui, Hefei 230026 |
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| Abstract: | In this paper, characteristics of precipitating clouds in a thermal convective system (TCS) occurred in the southeastern mainland of China at 15:00 BT (Beijing time) on August 2, 2003 in the central western subtropical Pacific anticyclone (WSPA) is studied by using TRMM tropical rainfallmeasuring mission PR (precipitution radar) and IR Infrared radiation measurements. The precipitating cloud structures in both horizontal and vertical, relationship among storm top, cloud top, and surface rain rate are particularly analyzed. Results show that a strong ascending air at 500 hPa and a strong convergence of moisture flux at 850 hPa in the central WSPA supply necessary conditions both in dynamics and moisture for the happening of the TCS precipitation. The TRMM PR observation shows that the horizontal scale of the most TCS precipitating clouds is about 30-40 km, their averaged vertical scale is above 10 km, and the maximum reaches 17.5 km. The maximum rain rate near surface of those TCS clouds is beyond 50 mm h-1. The mean rain profile of the TCS clouds shows that its maximum rain rate at 5 km altitude is 1 km lower than the estimated freezing level of the environment. Compared with the mesoscale convective system (MCS) of "98.7.20", both systems have the same altitude of the maximum rain rate displayed from both mean rain profiles, but the TCS is much deeper than the MCS. From the altitude of the maximum rain rate to near surface, profiles show that rain rate reducing in the TCS is faster than that in the MCS, which implies a strong droplet evaporation process occurring in the TCS. Relationship among cloud top, storm top, and surface rain rate analysis indicates a large variation of cloud top when storm top is lower. On the contrary, the higher the storm top, the more consistent both cloud top and storm top. And, the larger the surface rain rate, the higher and more consistent for both cloud top and storm top. At the end, results expose that area fractions of non-precipitating clouds and clear sky are 86% and 2%, respectively. The area fraction of precipitating clouds is only about 1/8 that of non-precipitating clouds. |
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| Keywords: | thermal convective system (TCS) subtropical anticyclone TRMM PR and IR |
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