Seminário: Where are the lightning hotspots on Earth?

08/04/2016 - 14:00
Auditório IAG (Rua do Matão, 1226, Cidade Universitária)

O seminário do Departamento de Ciências Atmosféricas do IAG será apresentado pela Profa. Dra. Rachel I. Albrecht (IAG/USP).
Where are the lightning hotspots on Earth?
The earth’s total lightning hotspots are revealed with very high resolution lightning climatology derived from 16 years of space-based Lightning Imaging Sensor observations. The peak hotspot occurs in Venezuela over Lake Maracaibo.
Previous total lightning climatology studies using TRMM Lightning Imaging Sensor (LIS) observations were reported at coarse resolution (0.5°) and employed significant spatial and temporal smoothing to account for sampling limitations of TRMM’s tropical to sub-tropical low-earth orbit coverage. The analysis reported here uses a 16 year reprocessed data set to create a very high resolution (0.1°) climatology with no further spatial averaging. This analysis reveals that the Earth’s principal lightning hotspot occurs over Lake Maracaibo in Venezuela, while the highest flash rate density hotspot previously found at the lower 0.5° resolution sampling was found in the Congo Basin in Africa. Lake Maracaibo’s pattern of convergent windflow (mountain-valley, lake and sea breezes) occurs over the warm lake waters nearly year-round and contributes to nocturnal thunderstorm development 297 days per year in average. These thunderstorms are very localized and their persistent development anchored in one location accounts for the high flash rate density. Several other inland lakes with similar conditions, i.e., deep nocturnal convection driven by locally forced convergent flow over a warm lake surface, are also revealed.
Africa is the continent with the most lightning hotspots, followed by Asia, South America, North America, and Australia. A climatological map of the local hour of maximum flash rate density reveals that most oceanic total lightning maxima are related to nocturnal thunderstorms, while continental lightning tends to occur during the afternoon. Most of the principal continental maxima are located near major mountain ranges, revealing the importance of local topography in thunderstorm development.