一次西南涡过程的云-降水毫米波云雷达回波特征分析
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摘要
为了探究西南涡过程的云-降水垂直结构和回波特征,利用了垂直定向Ka波段毫米波云雷达资料结合地面、高空观测资料及FY-2E卫星资料,对四川稻城2016年7月20-22日一次西南涡过程的进行分析。结果表明:此次西南涡过程的云系变化呈现为:前期(20日)主要以积层混合云为主,云顶高达11 km,午后云系上层出现空洞,低层强回波区出现速度模糊,表明该处存在较大的雨滴。至中期(21日),稻城上空云系演变为对流云,回波顶升高,云系中下部回波强度增强,与水汽通量辐合区吻合。对流发展旺盛并且在午后达到最强,同时在雨强图上有持续时间小于1 h的、强度为65 mm/h阵性降水相配合,这表明此次降水对应一个或者少数几个对流单体。至后期(22日),稻城上空主要为层状云,云顶高度回降到9 km左右,回波较为平坦,云中气流以下沉气流为主,在距离地面2 km高度处有雷达回波亮带形成,它的形成是层状云降水的明显标志。毫米波云雷达在降雨的天气状况下相比其他雷达具有十分明显的优势,不仅能够穿透云层获得云系内部的微观结构特征,充分掌握云系的垂直结构,同时还可以清晰地获取云系内粒子回波强度的变化为研究云的宏观特性提供良好的支撑。
This paper uses Ka band millimeter-wave cloud radar data, conventional observation data and FY-2 E satellite data to observe the cloud precipitation echo during rain process of a southwest vortex generated in the southwest of Sichuan province from 20 Jul 2016 to 22 Jul. The changes of cloud system in the southwest vortex process are presented as follows:in the early stage(on 20 Jul), the clouds are mainly composed of cumulus embedded stratus, and clouds top height is 11 km. There is a hole in the upper part of the clouds on afternoon. Ambiguities of velocity exist in the strong echo region at the bottom. It indicates that there is a large raindrop.In the mid of this process(on 21 Jul), the nephsystem has changed into the convective cloud. The echo top increases, and the echo intensity enhances in the middle to lower part of the clouds. These conditions are inosculated with the change of the water vapor flux convergence region. For the strongest convection there is the showery precipitation. The precipitation intensity is 65 mm/h. The duration of rainfall is less than one hour. This rainfall is corresponding to one or a few convection cells.In the last period of the process(on 22 Jul), the radar bright band echo which is relatively flat exists in the stratiform cloud about 2 km off the ground marks there is the clear ice water conversion area. The MMW radar clearly obtains the change of echo intensity of the particles within clouds on the rainfall condition to provide good support for studying the macro characteristics of clouds. Moreover, it can cut through clouds to acquire the internal structure information of clouds. This can adequately master the vertical structure of clouds.
This paper uses Ka band millimeter-wave cloud radar data, conventional observation data and FY-2 E satellite data to observe the cloud precipitation echo during rain process of a southwest vortex generated in the southwest of Sichuan province from 20 Jul 2016 to 22 Jul. The changes of cloud system in the southwest vortex process are presented as follows:in the early stage(on 20 Jul), the clouds are mainly composed of cumulus embedded stratus, and clouds top height is 11 km. There is a hole in the upper part of the clouds on afternoon. Ambiguities of velocity exist in the strong echo region at the bottom. It indicates that there is a large raindrop.In the mid of this process(on 21 Jul), the nephsystem has changed into the convective cloud. The echo top increases, and the echo intensity enhances in the middle to lower part of the clouds. These conditions are inosculated with the change of the water vapor flux convergence region. For the strongest convection there is the showery precipitation. The precipitation intensity is 65 mm/h. The duration of rainfall is less than one hour. This rainfall is corresponding to one or a few convection cells.In the last period of the process(on 22 Jul), the radar bright band echo which is relatively flat exists in the stratiform cloud about 2 km off the ground marks there is the clear ice water conversion area. The MMW radar clearly obtains the change of echo intensity of the particles within clouds on the rainfall condition to provide good support for studying the macro characteristics of clouds. Moreover, it can cut through clouds to acquire the internal structure information of clouds. This can adequately master the vertical structure of clouds.
引文
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[15] 朱禾,邓北胜,吴洪.湿位涡守恒条件下西南涡的发展[J].Acta Meteorologica Sinica,2002,60(3):343-351.
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[17] 丁治英,吕君宁.积云对流与西南低涡的活动[J].南京气象学院学报,1992,15(3):428-435.
[18] 潘旸,李建,宇如聪.东移西南低涡空间结构的气候学特征[J].气候与环境研究,2011,16(1):60-70.
[19] 陈忠明,闵文彬.第二次青藏高原大气科学试验理论研究进展[M].北京:气象出版社,2000:268-378.
[20] 解明恩,琚建华,卜玉康.西南涡Ekman层流场特征分析[J].高原气象,1992,11(1):31-38.
[21] 陈忠明,闵文彬,缪强,等.高原涡与西南涡耦合作用的个例诊断[J].高原气象,2004,23(1):76-80.
[2] 何光碧.西南涡研究综述[J].气象,2012,38(2):155-163.
[3] 乔全明,张雅高.青藏高原天气学[M].北京:气象出版社,1994:156.
[4] 陶诗言.中国之暴雨[M].北京:科学出版社,1980:225.
[5] 刘国忠,丁治英,贾显锋,等.影响华南地区西南涡及致洪低涡活动的统计研究[J].气象,2007,33(1):45-50.
[6] 李强,王中,白莹莹,等.一次区域性大暴雨过程中尺度诊断分析[J].气象科技,2011,39(4):453-461.
[7] 张洪英,王英,赵敏芬,等.低空冷式切变线引发区域性大暴雨成因分析[J].气象科技,2010,38(增刊):29-34.
[8] 陈忠明,廖强,闵文彬.一次强烈发展西南涡的中尺度结构分析[J].应用气象学报,1998,9(3):273-282.
[9] 周春花,顾清源,何光碧.高原涡与西南涡相互作用暴雨天气过程的诊断分析[J].气象科技,2009,37(5):538-544.
[10] 顾清源,周春花,青泉,等.一次西南涡特大暴雨过程的中尺度特征分析[J].气象,2008,34(4):39-47.
[11] 黄福均.西南涡的合成分析[J].大气科学,1986,10(4):402-408.
[12] 高守亭.流场配置及地形对西南涡形成的动力作用[J].大气科学,1987,11(3):263-271.
[13] 罗四维.青藏高原及其邻近地区几类天气系统的研究[M].北京:气象出版社,1992:56-96.
[14] 赵平,孙淑清.一次西南低涡形成过程的数值试验和诊断(一)——地形动力作用和潜热作用对西南涡影响的数值试验对比分析[J].大气科学,1991,15(6):46-52.
[15] 朱禾,邓北胜,吴洪.湿位涡守恒条件下西南涡的发展[J].Acta Meteorologica Sinica,2002,60(3):343-351.
[16] 陈忠明,徐裕华.非对称结构影响西南低涡移动的初步研究[J].四川气象,1991,11(3):1-6.
[17] 丁治英,吕君宁.积云对流与西南低涡的活动[J].南京气象学院学报,1992,15(3):428-435.
[18] 潘旸,李建,宇如聪.东移西南低涡空间结构的气候学特征[J].气候与环境研究,2011,16(1):60-70.
[19] 陈忠明,闵文彬.第二次青藏高原大气科学试验理论研究进展[M].北京:气象出版社,2000:268-378.
[20] 解明恩,琚建华,卜玉康.西南涡Ekman层流场特征分析[J].高原气象,1992,11(1):31-38.
[21] 陈忠明,闵文彬,缪强,等.高原涡与西南涡耦合作用的个例诊断[J].高原气象,2004,23(1):76-80.
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