XIV International Conference on Atmospheric Electricity, August 08-12, 2011, Rio de Janeiro, Brazil
Lightning and Rainfall at the Southeast of Brazil: a comparison study
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Flávio de Carvalho Magina1, Osmar Pinto Jr.1, Javier Tomasella1, Eymar Silva Sampaio Lopes 2, Lúbia Vinhas 2 1. Earth System Science Centre - CCST, National Institute for Space Research - INPE, Cach. Paulista, São Paulo, 12630-000, Brazil, flavio.magina@inpe.br, javier.tomasella@inpe.br S.J. Campos, São Paulo, 12227-010, Brazil, osmar@dge.inpe.br 2. Image Processing Division - DPI, National Institute for Space Research - INPE, S.J. Campos, São Paulo, 12227-010, Brazil, eymar@dpi.inpe.br, lubia@dpi.inpe.br ABSTRACT: In this study it was conducted a comparison of lightning and rainfall data with the aim of studying the correlation between both phenomena in the Southeast of Brazil, since it is well know that it is strongly dependent on the geographic location. The rainfall data were obtained by surface automatic stations and lightning data - intra-cloud (IC) and cloud-to-ground (CG) were obtained by LS7000 sensors belong to the Brazilian Lightning Detection Network (BrasilDat). The comparison was done in the summer seasons of 2008-2009 and 2009-2010 at the Southeast of Brazil. Lightning data were selected in the region around the rainfall stations considering different distances to the station. Geoprocessing techniques and specific application software (TerraView and Sismaden) developed by the National Institute of Space Research (INPE) was utilized to extract and analyze relevant information from these data. 1.
INTRODUCTION Storms are usually associated with lightning and rain, suggesting that the two quantities must be related. In
recent years, studies and texts have been frequent in the attempt to associate quantitatively the occurrence of both natural events (e.g., Pessi and Businger, 2009; Rakov and Uman, 2003). These efforts have shown a new and promising field for scientific research with applications in the field of numerical weather prediction modeling and therefore in warning and monitoring systems for natural disasters. In addition the lightning detection systems have become an economically alternative for monitoring lightning storms. Since the relationship of lightning and rain events are well understood, such lightning detection systems can be used to trigger alarms against natural disasters in a given region. In this preliminary study it was compared lightning and rain data, with the aim to investigate the correlation between both phenomena in the southeast region of Brazil where landslides and floods events have been frequent in consequence of heavy storms. 2.
MATERIALS The region selected for this study was the Southeast of Brazil, Serra do Mar mountains and the Northern
Coast of São Paulo state as show in Figure 1. ∗ Correspondence to: Flávio de Carvalho Magina, Earth System Science Centre - CCST, National Institute of Space Research - INPE, Cach. Paulista, São Paulo, 12630-000, Brazil, flavio.magina@inpe.br
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XIV International Conference on Atmospheric Electricity, August 08-12, 2011, Rio de Janeiro, Brazil
Figure 1. Location of study area (Source: IBGE) The right part of Figure 1 shows a map of the municipalities in the study area and the location of the eight Data Collection Platforms (DCPs) used to obtain the rainfall data. Table 1 below presents information and location of eight DCPs used in this study. Around each DCP location, using the TerraView GIS (INPE-DPI, 2010) buffers of 1, 2, 5 and 10 Km of radius meters were drawn. The hourly accumulated rainfall was collected during 2008-2009 and 2009-2010 summer seasons with a resolution of 0.25 mm and typical accuracy of 5% quoted by the tipping bucket rain gauge model TB4 manufactured by Campbell Scientific Inc. for each one of the DCPs. Table 1 - Location of DCPs #
DCP ID
City
Latitude
Longitude
1 2
30885
Cunha
-23.079472
-44.946194
30887
Ubatuba
-23.358111
-44.850417
3
30888
Paraibuna
-23.407320
-45.587758
4
30892
São Luiz do Paraitinga
-23.324806
-45.094000
5
69030
São Sebastião
-23.790544
-45.552797
6
69031
Ubatuba
-23.390800
-45.118483
7
69032
Caraguatatuba (PESM)
-23.589500
-45.424333
8
69033
Caraguatatuba (Rio Claro)
-23.699853
-45.487347
Data from intra-cloud lightning (IC) and cloud-to-ground (CG) were obtained by using two sensors Vaisala LS7000 belonging to the Brazilian Network Lightning Detection Network (Pinto Jr., Osmar, 2005). The LS7000 lightning sensors are located in CTA - São José dos Campos and INPE - Cachoeira Paulista, these are only the two lightning sensors of this network capable to detect intra-cloud lightning. 2
XIV International Conference on Atmospheric Electricity, August 08-12, 2011, Rio de Janeiro, Brazil
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METHODS Using the TerraView GIS, we created a geographical database to hold the lightning data. The location and
the data from the lightning detection sensor were imported, with intra-cloud and cloud-to-ground lightning as attributes of the lightning sensor. Around each DCPs four influence areas (or buffers) were created at the distances 1, 2, 5 and 10 km of radius. An “intersection” topological operation was used to extract the lightning (intra-cloud and cloud-to-ground) data that occurred inside each buffer of each DCP. The selected intra-cloud and cloud-to-ground lightning data was exported from TerraView to a database created in MS Access. The rainfall data was inspected and corrected to remove values reported erroneously by the DCP´s satellite telecommunication system. The corrected rainfall data were imported to the same database created in MS Access to hold the selected lightning data. Then, through SQL commands the lightning flashes occurring within each time window of one hour were added resulting in accumulated flashes per hour registers. Also through SQL commands these lightning data were merged with hourly accumulated rainfall data resulting in an exported spreadsheet with the occurrence of both events simultaneously. Using the MS Excel the graphics of lightning versus rain were plotted for each DCP buffer circle area, as well the graphic with the sum of the lightning flashes and accumulated rain observed within all DCP´s buffers. 4.
RESULTS We made several comparisons between lightning and rain with different sizes of buffers: 1 km, 2 km, 5 km
and 10 km. The best results were obtained with buffers of 1km and intra-cloud lightning. Figure 2 shows the intra-cloud lightning and rainfall data plotted in a dispersion graphic. The few data points showed that a relationship probably exists between the lightning and rain rates. As the rain data represent only the point in which they were collected by the DCPs stations and the lightning occurred in an area in the vicinity of these stations, the results of comparison were affected by this limitation. It is suggested that in future studies, comparisons should be carried out in a large area using rain data from stations interpolated to yield values of accumulated rainfall associated with the cell area in a spatial grid. Rainfall data from other sources such as radar and satellites should also be considered in comparison with the lightning data.
Figure 2 – Intra-cloud lightning rate versus convective rainfall 3
XIV International Conference on Atmospheric Electricity, August 08-12, 2011, Rio de Janeiro, Brazil
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CONCLUSIONS We conclude that the results of this study, although quite preliminary, showed that it is worth investing in
this research area. Quantifying the relationship between lightning and rain can be used to estimate convective rainfall in numerical weather prediction models and in warning and monitoring system for natural disasters. ACKNOWLEDGMENTS The authors acknowledge the contribution of the INPE´s Research Group in Atmospheric Electricity (ELAT) in providing the lightning data used in this study. REFERENCES INPE-DPI. TerraView Tutorial. Available in http://www.dpi.inpe.br/terraview/php/docs.php?body=Tutorial_i Accessed in May 2011. Pessi, A., and S. Businger, 2009: Relationships Among Lightning, Precipitation, and Hydrometeor Characteristics over the North Pacific Ocean. Journal of Applied Meteorology and Climatology, 48, 833-848. Pinto Jr., Osmar. The Art of War against the Rays. São Paulo: Oficina de Textos, 2005 (In Portuguese). Rakov, V. A.; Uman, M. A. Lightning : Physics and Effects. Cambridge: Cambridge University Press, 850p., 2003.
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