中国东部及邻近海域暖季降水系统的闪电、雷达反射率和微波特征

Characteristics of the lightning activity,radar reflectivity and microwave brightness temperature of warm season precipitation systems over the eastern China and adjacent seas as observed by TRMM satellite

利用热带测雨卫星的测雨雷达、闪电成像仪和微波辐射计8个暖季的轨道观测资料,研究了中国东部及邻近海域不同类型降水系统的地理分布规律和日变化特征及其闪电活动、雷达回波顶高和微波亮温的特征,并进一步分析了闪电与雷达回波顶高、微波亮温和冰相降水含量之间的关系。结果表明,两个地区的降水系统绝大部分都是无冰散射系统(占85%以上),非中尺度冰散射系统占10%左右,中尺度冰散射系统仅占约1.5%。中国大陆东部降水系统的日变化特征明显,而东海地区日变化幅度很小。中国大陆东部和东海地区分别约有93%和97%的降水系统没有闪电记录,并且前者闪电发生概率高于后者。中尺度冰散射雷暴不但闪电频数最高,而且贡献了总闪电的一半以上。随着降水类型强度的增强,20 dBz最大高度明显增高,最小85 GHz和37 GHz极化修正亮温则逐渐降低。对于同样的20 dBz最大高度和最小85 GHz极化修正亮温,中国大陆东部降水系统发生闪电的概率均高于东海地区。降水系统尺度上的闪电频数与最小85 GHz极化修正亮温的关系在稳定性和相关性方面要好于其与20 dBz最大高度的关系,而闪电频数与7—11 km的总冰相降水含量之间的相关性又比其与最小85 GHz极化修正亮温有了较大的提高。进一步研究表明,单体尺度上的闪电频数和7—11 km总冰相降水含量之间也表现出了非常密切的关系,在两个研究地区的相关系数都超过了0.7。

The spacial distribution and diurnal variation as well as the characteristics of the lightning activity,radar echo height and microwave brightness temperature of precipitation systems over the eastern China and adjacent seas have been investigated by using the data from the precipitation radar（PR）,lightning imaging sensor（LIS）,and passive microwave imaging（TMI） onboard the Tropical Rainfall Measuring Mission（TRMM） satellite for the eight warm seasons of 1998-2005,and the relationship between the lightning activity and radar echo height,and between the microwave brightness temperature and ice precipitation content are analyzed quantitatively.The precipitation systems are classified as systems without ice scattering（Nolces）. systems with ice scattering（IcePSs） and systems with an MCS（McsPSs）.The results show that NoIces account for more than 85%of the population,IcePSs for about 10%,and McsPSs for about 1.5%over both of the regions.There is an obvious diurnal variation of precipitation systems over the eastern Chinese mainland,and the diurnal change amplitude over the East China Sea is small.93%and 97%of the precipitation systems over the eastern Chinese mainland and the East China Sea,respectively, have no lighting record and the probability of lightning occurrence over the former is higher than that over the latter. McsPSs not only have the highest flash rate,but also contribute more than half of the total lighting.With the enhancement of precipitation system intensity,the maximum height of 20 dBz significantly increases and the minimum polarization corrected temperatures（PCTs） at 85 GHz and 37 GHz gradually decrease.For the same value of maximum height of 20 dBz or minimum PCTs at 85 GHz.the probability of lightning occurrence of precipitation systems over the eastern Chinese mainland is higher than that over the East China Sea.The relationship between the flash rate and the minimum PCTs at 85 GHz is better than that between the flash rate and the maximum height of 20 dBz.and compared with relation between the two former,the correlation between the flash rate and the ice precipitation content within the layer of 7 - 11 km has a greater improvement.Further study indicates that there is a good dependence between the flash rate and the ice precipitation content within the 7-11 km on cell scales with the correlation coefficient higher than 0.7 over both of the regions.