Relâmpagos no Nordeste do Brasil: ocorrência, variabilidade espaço-temporal e relação com microfísica das nuvens
It is estimated that about 60-75 million lightning occur annually, killing an average of 132 people every year in Brazil. The Northeast region of Brazil (NEB) accounts for 18% of the total deaths in the national territory. Considering the population of all Brazilian regions, the state of Piauí pr...
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| Formato: | Dissertação |
| Idioma: | por |
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Brasil
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/26328 |
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| Resumo: | It is estimated that about 60-75 million lightning occur annually, killing an average of 132
people every year in Brazil. The Northeast region of Brazil (NEB) accounts for 18% of the total
deaths in the national territory. Considering the population of all Brazilian regions, the state of
Piauí presented the highest mortality rate (1.8 deaths per million); which is higher than the
country’s total rate (0.8) and the NEB rate (0.5). Studies have shown that lightning formation
is associated with the collision between ice particles (crystal and graupel) in the presence of
supercooled water droplets in regions with strong updrafts. Therefore, the objective of this study
is to evaluate lightning spatial and temporal distribution in NEB, as well as to investigate the
relationship between lightning and cloud microphysics, during the period from 1998 to 2013.
Data from two orbital plataforms were used: i) Lightning Imaging Sensor (LIS), TRMM
Microwave Imager (TMI) and Precipitation Radar (PR) from the Tropical Rainfall Measuring
Mission (TRMM) satellite to provide information on the occurrence of total lightning
(intracloud and cloud-to-ground) and vertical content of the atmosphere (hydrometeors,
precipitation rate, rain type); ii) Advanced Spaceborne Thermal Emission and Reflection
Radiometer (ASTER), on board of Terra platform provide the ground elevation data, to verify
the influence of topography on lightning rates. The analysis was performed monthly, seasonaly
and general spatial distribution . The general spatial distribution was based on Cluster Analysis
and aided the identification of the greatest points of lightning occurrence (hotspots). Finally,
the lightning was analyzed according to the quantiles technique, finding the characterization
according to the microphysical characteristics of clouds. In the NEB territory, it was registered
great spatial and temporal variability in the lightning rates, with mean varying from 0 to 44.5
flashs.km-2
.year-1
. All the hotspots are located in Piauí, Maranhão states and west region of
Bahia. The topography of NEB seems to act as a facilitator of the convective process, by the
increases of intense updrafts formation, an essential factor for the generation of electric charges
inside the thunderclouds. The cluster analysis together with the investigation of the
characteristics of each of the hostspots allowed to infer that the Intertropical Convergence Zone
(ITCZ) and Mesoscale Convective Systems (MCS) are the systems most associated with
lightning in NEB territory, being the lightning hotspots characterized as occurrence sites of
these systems. Regarding the microphysical parameters of the cloud, it was observed that when
the lightning happens, the atmosphere has lower values of liquid water in the cloud, high
amounts of ice water, high convective precipitation rate, lift of height freezing level and high
probability of precipitation (or the occurrence of this); this information allowed the conceptual
model proposition of the microphysical characteristics present when lightning occurs in the
NEB. |
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