Abstract
The Fengyun-4A (FY-4A) Lightning Mapping Imager (LMI) is the first satellite-borne lightning imager developed in China, which can detect lightning over China and its neighboring regions based on a geostationary satellite platform. In this study, the spatial distribution and temporal variation characteristics of lightning activity over China and its neighboring regions were analyzed in detail based on 2018 LMI observations. The observation characteristics of the LMI were revealed through a comparison with the Tropical Rainfall Measuring Mission (TRMM)-Lightning Imaging Sensor (LIS) and World Wide Lightning Location Network (WWLLN) observations. Moreover, the optical radiation characteristics of lightning signals detected by the LMI were examined. Factors that may affect LMI detection were discussed by analyzing the differences in optical radiation characteristics between LMI and LIS flashes. The results are as follows. Spatially, the flash density distribution pattern detected by the LMI was similar to those detected by the LIS and WWLLN. High-flash density regions were mainly concentrated over Southeastern China and Northeastern India. Temporally, LMI flashes exhibited notable seasonal and diurnal variation characteristics. The LMI detected a concentrated lightning outbreak over Northeastern India in the premonsoon season and over Southeastern China in the monsoon season, which was consistent with LIS and WWLLN observations. LMI-observed diurnal peak flash rates occurred in the afternoon over most of the regions. There was a “stepwise” decrease in the LMI-observed optical radiance, footprint size, duration, and number of groups per flash, from the ocean to the coastal regions to the inland regions. LMI flashes exhibited higher optical radiance but lasted for shorter durations than LIS flashes. LMI observations are not only related to instrument performance but are also closely linked to onboard and ground data processing. In future, targeted improvements can be made to the data processing algorithm for the LMI to further enhance its detection capability.
Highlights
Lightning is an ultra-long-distance electric discharge phenomenon in the atmosphere and is a product of a convective weather system at a certain development stage [1,2]
The World Wide Lightning Location Network (WWLLN) dataset used in this study mainly provides the occurrence time, latitude, and longitude of the lightning strokes
Lightning Mapping Imager (LMI) flashes were more concentrated than WWLLN flashes over India, Bangladesh, Myanmar, Thailand, and Laos, whereas LMI flashes were less concentrated than WWLLN flashes over Southern East China, Southern South China, and the coastal waters of the East and South China Seas
Summary
Lightning is an ultra-long-distance electric discharge phenomenon in the atmosphere and is a product of a convective weather system at a certain development stage [1,2]. Very low frequency (VLF)/low frequency- and very high frequency (VHF)-based lightning detection methods were developed [11,12,13,14,15]. Several countries have established regional or global ground-based lightning location networks. The following networks are representative VHF lightning location networks: the Lightning Detection And Ranging (LDAR) network [23], the Lightning Mapping Array (LMA) [24], the Earth Networks Total Lightning Network (ENTLN) [25], and the Surveillance et Alerte Foudre par Interférometrie Radioélectrique (SAFIR) [26]
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