东亚和西太平洋闪电时空尺度及光辐射能

Spatio-temporal Scale and Optical Radiance of Flashes over East Asia and Western Pacific Areas

  • 摘要: 利用2002—2014年的TRMM/LIS(Tropical Rainfall Measuring Mission/lightning imaging sensor,热带测雨卫星/闪电成像仪)闪电观测数据分析了18°~36°N和70°~160°E范围内闪电尺度和光辐射能空间分布特征,并选取6个区域(区域1~6),探讨09:00—14:00(地方时,下同)和18:00—次日06:00两个时段闪电上述属性的逐月变化和参数分布特征。研究指出:闪电空间尺度和光辐射能在深海最大,次之为近海和陆地,持续时间在中国东部近海最大,次之为深海和陆地。不同闪电属性大值分布区域差异明显,小值则分布在区域1和区域2。多数区域分析时段内闪电空间尺度和光辐射能的逐月变化趋势较一致,陆地上它们与闪电活动逐月变化的反向对应关系较明显。分析时段内闪电时空尺度和光辐射能均呈对数正态分布,陆地闪电各属性值比海洋闪电更向小值方向集中。在LIS观测性能较高的18:00—次日06:00,各区域内闪电持续时间中值为0.18~0.29 s,通道延展距离中值为12~21 km,光辐射能中值为0.11~0.52 J·m-2·sr-1·μm-1。分析时段内闪电空间尺度与光辐射能的相关性明显优于它们与持续时间的相关性。

     

    Abstract: Distributions and correlations of flash properties including duration, length, footprint and radiance are investigated in the east Asia and western Pacific areas of 18°-36°N, 70°-160°E and six specially chosen regions (Region 1-6) within it, by analyzing data of lightning imaging sensor (LIS) aboard Tropical Rainfall Measuring Mission (TRMM) satellite from 2002 to 2014. While the flash density over land is generally greatest, followed by offshore waters and deep ocean, the spatial scale and radiance of flash over the deep ocean is the greatest, followed by offshore waters and land, and the duration of flash over offshore waters is the longest, followed by the deep ocean and land. Regions with the largest flash density, duration, spatial extent and radiance are the southern Himalayan front, offshore waters near the east coast of China, deep Pacific Ocean in the southern part of study area and ocean to the east of Japan, respectively. Meanwhile, the flash duration, spatial extent and radiance always have the smallest values over the Tibet Plateau and the southern Himalayan front. In most regions, based on samples during periods of 0900-1400 LT and 1800-0600 LT, the monthly variation of the flash spatial size and radiance is roughly unanimous, except for the ocean to the east of Japan. Inverse correlations of flash activity with flash spatial scale and radiance in the monthly variation is relatively obvious over land. In addition, it is found that some flash properties over some regions in monthly variation are different between periods of 0900-1400 LT and 1800-0600 LT. The flash spatial-temporal scale and the radiance follow lognormal distributions. Relative to the flash over ocean, properties of flash over land tend to concentrate toward smaller values. During 1800-0600 LT when the LIS is of relatively better performance, the median range of flash properties in 6 chosen regions are:Flash duration from 0.18 to 0.29 s, length from 12 to 21 km, and radiance from 0.11 to 0.52 J·m-2·sr-1·μm-1. Correlation analysis between different properties of flash show that relationships between flash properties during 1800-0600 LT are better than those during 0900-1400 LT, and the best correlation is between length and footprint, because they both represent the spatial scale of flash. Relationships between flash spatial scale and radiance are also strong, but the flash duration has weak correlations with flash spatial scale or radiance.

     

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