梅雨锋面对流的动力和微物理特征雷达观测研究
发布时间：2018-09-07 11:01
【摘要】：梅雨锋中国东部江淮地区夏季主要的天气系统,其产生的强降水常常引发城市内涝等气象灾害,并造成巨大的生命和经济损失。以往对梅雨锋降水的对流特征等研究较多,但是对锋面雨带内部对流的动力和微物理特征的研究较少。2014年7月11日至12日,江淮地区发生一次典型的梅雨锋降水过程,持续时间长,降水强度大,24小时累计降水量最大超过100mm。在此锋面雨带南北两侧存在不同特征的对流降水。本文利用南京大学C波段双偏振多普勒天气雷达和合肥雷达、定远C波段双偏振雷达的观测资料,结合先进的双多普勒雷达风场反演技术,对此梅雨期锋面雨带中对流的动力和微物理特征进行分析。首先,通过环境假相当位温将梅雨锋面雨带分为南北两个部分,并利用雷达观测识别出梅雨锋面雨带中的对流单体。对锋面南北两侧对流进行分析表明,锋面南侧对流主要由较强的对流单体和线状对流组成的对流降水区域,对流降水强度较强,四小时最大累积降水量达到60 mm,而锋面北侧为镶嵌在层云降水区域内的对流降水,对流发生频数相对南侧较少,四小时累积降水量最大值仅达20 mm。锋面南侧对流中上升速度较北侧强,最大值达到5 ms-1,对流发展高度高,回波强度强,冰相过程强;而锋面北侧对流发展高度和对流强度都相对南侧较弱。由于锋面南北两侧环境湿度和动力结构差异,使得南北两侧对流的微物理特征有着较大的差异。锋面南侧对流中冰相过程较强,0℃层以上冰相降水粒子种类和数量较多,融化层以下降水粒子降落过程中增长效率较大,低层降水粒子的ZDR主要分布在0～2.0 dB范围内,最大值达到3 dB(粒径约为2.3 mm),有较大降水粒子存在,但数量较少,锋面南侧对流中有着高浓度的小粒子;而锋面北侧对流中弱上升运动使得冰相过程较弱,冰相粒子含量较少,融化层以下降水粒子较小,尺度集中在0.3～1.5dB之间,最大粒径约为1.8 mm。与日本梅雨锋面对流降水相比,江淮梅雨锋面对流降水的粒子粒径偏小,粒子数浓度更高。锋面南侧对流中的冰水和液态水含量远大于锋面北侧。锋面南侧对流的降水效率为65.9%,高于锋面北侧;尽管锋面南侧对流过程总降水和总水汽通量都比台湾季风中对流降水高,锋面南侧对流降水贡献与台湾地区接近。进一步分析锋面南侧一孤立对流生命周期中不同阶段动力和微物理特征变化显示,初生阶段对流尺度较小,15 dBZ回波顶高仅达到10 km高度,以少量大粒子为主。在成熟阶段,对流发展高度不断增加,回波强度增强,对流中小粒子数量不断增加;初生、分裂和成熟阶段对流中都有少量大粒子存在,ZDR都超过3 dB;成熟阶段上升运动最强,对流强度达到最强,最大回波达到58 dBZ,回波顶高达到12 km。同时成熟阶段的冰相过程也最强,产生大量冰雹和霰粒子,冰水(≥4.0 gm-3)和液态水(～8.0 gm-3)含量达到最大,产生的强降水中存在大量小粒子和中等粒径粒子;消散阶段,上升运动较弱,对流强度开始减弱,最大回波仅达46 dBZ,无大粒子存在,ZDR最大达到1.6 dB。同时由于环境较干,较小的雨滴被蒸发,消散阶段对流降水雨滴粒径集中为中等粒径的降水粒子。
[Abstract]:Meiyu front is the main synoptic system in the east of China in summer. The heavy precipitation produced by Meiyu front often leads to urban waterlogging and other meteorological disasters, and causes enormous life and economic losses. From July 11 to 12, 2000, a typical Meiyu front precipitation process occurred in the Yangtze-Huaihe region. It lasted a long time, the precipitation intensity was high, and the maximum cumulative precipitation was over 100 mm in 24 hours. The dynamic and microphysical characteristics of the convection in the front rain belt during the Meiyu period are analyzed by combining the observation data of the dual polarization radar and the advanced wind field inversion technique of the dual Doppler radar. Convective Monomer. The analysis of convection on the north and south sides of the front shows that the convection on the south side of the front is mainly composed of strong convective monomer and linear convection. The intensity of convective precipitation is strong, the maximum cumulative precipitation in four hours reaches 60 mm, while the convective precipitation on the north side of the front is embedded in the stratospheric precipitation area, and the frequency of convection occurs. Compared with the southern side, the maximum accumulated precipitation of four hours is only 20 mm. The southern side of the front is stronger than the northern side, and the maximum value is 5 ms-1. The convective development height is high, the echo intensity is strong, and the ice process is strong. The microphysical characteristics of convection on the south side of the front are different from those on the north side because of the difference of force structure. The value is 3 dB (particle size is about 2.3 mm), there are large precipitation particles, but the number is small, there are high concentration of small particles in the convection south of the front; and the weak upward motion in the convection north of the front makes the ice process weak, the content of ice particles is small, the precipitation particles below the melting layer is small, the scale concentrates between 0.3-1.5 dB, the maximum particle size is about 0.3-1.5 dB. Compared with the convective precipitation of the Meiyu front in Japan, the particle size of the convective precipitation of the Meiyu front in the Yangtze-Huaihe River is smaller and the concentration of the particles is higher. The total water vapor flux is higher than that of convective precipitation in the Taiwan monsoon, and the contribution of convective precipitation in the south of the front is close to that in the Taiwan area. In the mature stage, the height of convective development increases continuously, the echo intensity increases, and the number of small and medium particles in the convection increases continuously. In the primary, splitting and maturing stages, there are a small number of large particles in the convection, and ZDR exceeds 3 dB. In the mature stage, the ascending motion is the strongest, the convective intensity reaches the strongest, the maximum echo reaches 58 dBZ, and the echo top reaches 12 km. At the same time, the ice phase process in the mature stage is also the strongest, producing a large number of hail and graupel particles, ice water (> 4.0 gm-3) and liquid water (~ 8.0 gm-3) content reaches the maximum, resulting in a large number of small and medium-sized particles in heavy precipitation; at the dissipation stage, the ascending motion is weakened, the convective intensity begins to weaken, the maximum echo is only 46 dBZ, no large particles exist. The maximum of ZDR is 1.6 dB. At the same time, the smaller raindrops are evaporated because of the dry environment. In the dissipation stage, the convective raindrops are concentrated on the middle-sized particles.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P412.25
本文编号：2228071
[Abstract]:Meiyu front is the main synoptic system in the east of China in summer. The heavy precipitation produced by Meiyu front often leads to urban waterlogging and other meteorological disasters, and causes enormous life and economic losses. From July 11 to 12, 2000, a typical Meiyu front precipitation process occurred in the Yangtze-Huaihe region. It lasted a long time, the precipitation intensity was high, and the maximum cumulative precipitation was over 100 mm in 24 hours. The dynamic and microphysical characteristics of the convection in the front rain belt during the Meiyu period are analyzed by combining the observation data of the dual polarization radar and the advanced wind field inversion technique of the dual Doppler radar. Convective Monomer. The analysis of convection on the north and south sides of the front shows that the convection on the south side of the front is mainly composed of strong convective monomer and linear convection. The intensity of convective precipitation is strong, the maximum cumulative precipitation in four hours reaches 60 mm, while the convective precipitation on the north side of the front is embedded in the stratospheric precipitation area, and the frequency of convection occurs. Compared with the southern side, the maximum accumulated precipitation of four hours is only 20 mm. The southern side of the front is stronger than the northern side, and the maximum value is 5 ms-1. The convective development height is high, the echo intensity is strong, and the ice process is strong. The microphysical characteristics of convection on the south side of the front are different from those on the north side because of the difference of force structure. The value is 3 dB (particle size is about 2.3 mm), there are large precipitation particles, but the number is small, there are high concentration of small particles in the convection south of the front; and the weak upward motion in the convection north of the front makes the ice process weak, the content of ice particles is small, the precipitation particles below the melting layer is small, the scale concentrates between 0.3-1.5 dB, the maximum particle size is about 0.3-1.5 dB. Compared with the convective precipitation of the Meiyu front in Japan, the particle size of the convective precipitation of the Meiyu front in the Yangtze-Huaihe River is smaller and the concentration of the particles is higher. The total water vapor flux is higher than that of convective precipitation in the Taiwan monsoon, and the contribution of convective precipitation in the south of the front is close to that in the Taiwan area. In the mature stage, the height of convective development increases continuously, the echo intensity increases, and the number of small and medium particles in the convection increases continuously. In the primary, splitting and maturing stages, there are a small number of large particles in the convection, and ZDR exceeds 3 dB. In the mature stage, the ascending motion is the strongest, the convective intensity reaches the strongest, the maximum echo reaches 58 dBZ, and the echo top reaches 12 km. At the same time, the ice phase process in the mature stage is also the strongest, producing a large number of hail and graupel particles, ice water (> 4.0 gm-3) and liquid water (~ 8.0 gm-3) content reaches the maximum, resulting in a large number of small and medium-sized particles in heavy precipitation; at the dissipation stage, the ascending motion is weakened, the convective intensity begins to weaken, the maximum echo is only 46 dBZ, no large particles exist. The maximum of ZDR is 1.6 dB. At the same time, the smaller raindrops are evaporated because of the dry environment. In the dissipation stage, the convective raindrops are concentrated on the middle-sized particles.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P412.25
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