AE013-03
GPM-DPR observations on TGFs producing storms
GPM-DPR observations on TGFs producing storms
Friday, 11 December 2020: 05:38
Virtual
Abstract:
Unique spaceborne measurements of the 3-D structure of convective clouds producing terrestrial gamma ray flashes (TGFs) were performed using both active and passive microwave sensors on board the GPM-CO satellite, finding coherent features for 9 TGF-producing storms.The delineation of cloud structure using the radar reflectivity factor shows convective cells with significant vertical development and thick layers with high ice content.Compared to cumulonimbus clouds in the tropics, the TGFs counterparts have higher reflectivity values above 3 and 8 km altitude showing in all cases a cumulonimbus tower (CbT) and the TGFs locations are very close, or coincident, to these high Z columns, where reflectivity exceeds 50 dBz.
Using the dual polarization feature of the GMI radiometer, the presence and the orientation of non-spherical ice crystals in the area around the TGFs emission were estimated.Most thunderstorms show a very strong depression of polarized corrected temperature (PCT) at channel 89 GHz, indicating a strong scattering signal by ice in the upper cloud layers. At channel 166 GHZ the difference between vertical and horizontal brightness temperature signal always returns positive values, from 0.2 K up to 13.7 K indicating a complex structure with randomly/vertically oriented ice particles. The PCT was used to characterize the analysed storms in terms of hydrometeor types, confirming in 7/9 cases a high likelihood of hail/graupel presence.To perform analysis on the TGFs parent flashes, radio atmospherics data from the ENTLN lightning network were used. It is observed that all cases, are classified as high amplitude IC flashes and TGFs typically take place during the peak of flash rate production. Finally, the analysis of the most intense event, in terms of number of counts is shown.
The results shown in this paper potentially leads to important conclusions about the thunderstorm charging state conducive to TGFs.
Using the dual polarization feature of the GMI radiometer, the presence and the orientation of non-spherical ice crystals in the area around the TGFs emission were estimated.Most thunderstorms show a very strong depression of polarized corrected temperature (PCT) at channel 89 GHz, indicating a strong scattering signal by ice in the upper cloud layers. At channel 166 GHZ the difference between vertical and horizontal brightness temperature signal always returns positive values, from 0.2 K up to 13.7 K indicating a complex structure with randomly/vertically oriented ice particles. The PCT was used to characterize the analysed storms in terms of hydrometeor types, confirming in 7/9 cases a high likelihood of hail/graupel presence.To perform analysis on the TGFs parent flashes, radio atmospherics data from the ENTLN lightning network were used. It is observed that all cases, are classified as high amplitude IC flashes and TGFs typically take place during the peak of flash rate production. Finally, the analysis of the most intense event, in terms of number of counts is shown.
The results shown in this paper potentially leads to important conclusions about the thunderstorm charging state conducive to TGFs.