Estudo das características de relâmpagos nuvem-solo negativos através da análise comparativa de observações por múltiplas técnicas. / Study of negative cloud-to-ground lightning features from comparative analysis of observations by multiple techniques.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

For the first time in Brazil, an electric field antenna for lightning radiation, with 1.25 µs resolution was developed. From thunderstorms over Sao José dos Campos, between February and March of 2003, information of lightning synchronized to GPS time, were simultaneously obtained by this antenna, by a 1ms resolution high-speed camera and by the Brazilian Lightning Detection System (SDR or RINDAT). A comparative analysis of this information was done for the first time. Lightning features as multiplicity and return strokes time intervals were compared from electric field, high-speed fast camera and SDR data set, assuming the high-speed camera results as the most realistic reference. Electric field rise times and pulse widths were compared from electric field and SDR data set. The current peak versus electric field peak relation also was investigated. The main results obtained were: average multiplicity values were 4.00 from images of high-speed camera and 4.38 from electric field data; geometric mean values for the return stroke time intervals were 83 ms from images of high-speed camera and 76 ms from electric field data. These values are similar to those obtained in another places. It was verified that although high-speed camera observations are less likely to miss return strokes during recording, it may happen when close lightning with multiple channels have one or more channels out of view field of the high-speed camera, leading to errors in multiplicity. An electric field and high-speed camera data association is suggested to correct these errors. Rise times distributions are similar for both electric field and SDR observations. But, in many cases pulse widths from SDR observations were larger, perhaps due to lower noise level of SDR sensors. No dependence of rise time and pulse width on propagation distance was found for the considered region. It means that are not necessary to apply corrections models for propagation effects on rise times and pulse widths. The return stroke detection efficiency of SDR was 58% respect to electric field observations. However it is important to consider that at the period of this research, the sensors of SDR located at São José dos Campos and Cachoeira Paulista were not in operation. Current peaks of return strokes measured by the SDR and electric field peaks measured by the electric field antenna show a linear relation for distant lightning, indicating that the model used by the SDR to estimate current peaks is correct to the region of study.

ASSUNTO(S)

geophysics campos elétricos soils eletric discharges solos relâmpagos descarga de nuvem radiação eletromagnética geofÍsica lightning eletricidade atmosférica electromagnetic radiation tempestades eletric fields clound-to-groung discharges descargas elétricas thunderstorms atmospheric electricity

ACESSO AO ARTIGO

Documentos Relacionados