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- Title
Tropical TGF Paradox: A Perspective From TRMM Precipitation Radar.
- Authors
Morales Rodriguez, Carlos A.; Montanyà, Joan; Velde, Oscar A.; Fabró, Ferran; Lopez, Jesus A.
- Abstract
The Terrestrial Gamma‐ray Flash (TGF) to lightning ratio, computed over the three tropical chimneys, presents a paradox: African thunderstorms produce the most lightning but yield the lowest fraction of TGFs when compared to American and Southeast Asian thunderstorms. To understand the physical insights into this asymmetry, Tropical Rainfall Measuring Mission Precipitation Radar measurements are used to depict the vertical precipitation structure and infer the vertical electrical charge fraction distribution of the observed thunderstorms in the three regions and the thunderstorms during TGF occurrences detected by the AGILE, Fermi‐GBM, and RHESSI sensors. Regional differences show that African thunderstorms are taller, smaller, and have a higher concentration of denser ice particles (graupel and or hail) above the freezing level in addition to having more lightning flashes per thunderstorm. The overall TGF‐related thunderstorms are taller, more intense (0.5–1.5 dBZ) and present similar radar reflectivity decay with height independent of the region. The two dimensional precipitation vertical distribution diagrams indicate that TGF thunderstorms develop to a mature stage. Independent of the region, thunderstorms show a midlevel negative charge center varying from 4.6 to 8.1 km in height and an upper level positive charge center ranging from 7.4 to 14.6 km. TGF thunderstorms have thicker positive inferred charge layer and present larger vertical distances between the opposite charging layers in comparison with the overall thunderstorm population, here defined as Climatology. African TGF thunderstorms have higher fraction of positive charges near the negative layer, helping to produce more and shorter lightning discharges. Plain Language Summary: Terrestrial Gamma ray Flashes (TGFs) have been detected in space above thunderstorms worldwide, but their main triggering mechanism has not yet been fully understood. In the last two decades, several measurements from ground and satellite instruments have provided information to help our understanding. For instance, TGF emissions are concentrated in the tropics and one of the possible theories suggests to be related to intense intracloud lightning processes produced by thunderstorms that have considerable vertical charge center separations. Although African thunderstorms have the highest lightning activity in the world, they produce fewer TGFs per number of lightning flashes than thunderstorms in America and the Southeast Asia tropical regions, posing a paradox. To explore this asymmetry, this study employed 3D measurements from the Precipitation Radar on board the Tropical Rainfall Measuring Mission (TRMM) satellite to describe the main precipitation vertical structure observed in the three most important tropical thunderstorm regions in the world (Climatology) and in the thunderstorms that produced TGFs. African thunderstorms are taller, smaller, having more ice aloft and lightning discharges. TGF thunderstorms show similar precipitation variation decay with height, are taller and more intense, in addition to showing different vertical cloud charge structure and larger distance between the opposite charge layers. Key Points: Terrestrial Gamma‐ray Flash (TGF) thunderstorms have greater distance between the inferred electrical opposite charging layers in relation to the ClimatologyAfrican TGF thunderstorms have more positive charges close to the negative charging layerVertical profiles of TGF‐related thunderstorms are associated with developing to mature stage
- Subjects
THUNDERSTORMS; GAMMA-ray scattering; GAMMA ray polarization; LIGHTNING; ATMOSPHERIC electricity
- Publication
Journal of Geophysical Research. Atmospheres, 2021, Vol 126, Issue 14, p1
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2021JD034698