IX International Symposium on

Lightning Protection

26th

-30th

November 2007 – Foz do Iguaçu, Brazil

LIGHTNING CHARACTERISTICS ASSOCIATED TO SEVERE RAINFALL EVENTS, AROUND BELÉM–PA–BRAZIL

Arthur da Costa Almeida Brigida Ramati Pereira da Rocha UFPA UFPA

arthur@ufpa.br brigida@ufpa.br

José Humberto Araújo Monteiro José Ricardo Santos de Souza UFPA UFPA

humbertomont@gmail.com jricardo@ufpa.br

Gabriela Ribeiro Vieira Everaldo Barreiros de Souza UFPA UFPA

engenheira_04@yahoo.com.br everaldo@ufpa.br

Helder Tiago Sebastião da Cunha Williams Alan Pinheiro Souza UFPA UFPA

nuget_zero11@yahoo.com.br w.alan01@gmail.com

UFPA (Federal University of Pará) - Rua Augusto Corrêa, 01 CEP 66075-110 - Belém - Pará – Brazil

Abstract - Lightning variables monitored by a LDN which includes 12 LPATS IV VAISALA sensors distributed over eastern Amazonia were analyzed during five severe rainstorm occurrences in Belém-PA-Brazil. These case studies referred to rainfall events, which produced more than 40 mm of precipitation totals, registered by a tipping bucket automatic pluviometer located at 1°24’ S, 48°26’ W. This instrument is placed at approximately 2.5 km from one lightning sensor installed at 1°24’ S, 48°27’ W. Centered at this location, a 20 km radius circle was drawn by means of a geographic information system, and the data from lightning occurrences within this area were set apart for analysis. The severe storm events selected occurred during: 09, 11, 27/January, 14/February and 02/March of 2007. This period corresponds to the beginning of the local rainy season of that year. The results show that lightning frequency of occurrences and peak current intensities rise substantially from a few minutes to more than one hour before intense rainfall occurs. The associated CG lightning events do not show a recognizable displacement pattern over the neighboring area. These case studies constitute a basis for future warnings of severe rainfall in Belém, other locations and seasons, in the Region.

1 INTRODUCTION The city of Belém is located on the southern shore of the

mouth of the Amazon River, about 150 Km from the

Atlantic Ocean. The daily tidal variation there reaches

over 2.5 m in the period between January and April. This

period coincides with the maximum rainfall accumulation

in Belém, brought about by the passage of the Inter

Tropical Convergence Zone (ITCZ) center axis over its

latitude.

Several days every year the maximum tide and severe

rainfall events occur simultaneously and flood the former

marshlands, nowadays taken over by the drainage

channels of the city, impairing traffic and resulting in

economic losses to the local people.

The losses would be reduced if the civil defense were able

to warn people of the situation, through the local

communications media.

With this purpose a project involving several operational

and research local institutions (UFPA, SIPAM, SECTAM,

INMET), and the Civil Defense agents, is being carried

out. This paper is part of a joint effort to use

meteorological information, including lightning detection

capabilities, to develop an alert system of severe rainfall

events in Belém, especially during the critical months

mentioned above, seeking to lessen the disturbances

caused by flooding in the city.

The Amazonian Protection System (SIPAM), lightning

detection network, includes 12 LPATS IV VAISALA

sensors, four of which, installed in Belém, Breves,

Paragominas and Tucuruí, are less than 350 km from one

another, therefore reasonably covering the area of interest.

This system monitors continuously the lightning

occurrence rate, number of strokes per flash, flash type,

stroke polarity and peak currents, as well as their time of

occurrence in microseconds.

This information associated to severe rainfall events

registered by a tipping bucket automatic rainfall gauge

operated by the Brazilian National Meteorological

Institute (INMET) in the city, might give some parameters

related to lightning produced by the same clouds, early

enough to warn the local population.

The relationship between lightning parameters,

precipitation and the convective meteorological systems

producing them has been studied by several methods. [1]

and [2], used satellite images, [3], [4], [5] and [6], used

radar, air borne balloon rawinsondes plus LDN at the

surface, to study the relation between lightning parameters

and precipitation in Taiwan, U.S.A. and Spain. In the

Amazon region, particularly around Belém, the first

attempts to estimate rainfall, from the lightning frequency

of occurrence were made by [7] and [8]. The installation

of the SIPAM’s LDN represent an opportunity to advance

these applied studies, locally, with improved technology

of lightning location.

2 MATERIALS AND METHODS

Intense rainfall events which produced more than 40 mm

of accumulated precipitation measured by a tipping bucket

pluviometer (Campbell Instruments, Inc) of an automatic

meteorological surface station located at 1°24’S; 48°26’

W, were selected for analysis. This data collected by

INMET showed that events satisfying this condition

occurred during days 09, 11, 27 of January, 14 of

February and 02 of March, 2007. Lightning data obtained

through SIPAM’s LDN and processed by VAISALA’s

LTrax software in Belém, provided the input to a

geographic information system ArcGIS which separated a

sub set of data, of lightning occurrences within a 20 km

circle drawn around the sensor located at 1°24’S,

48°27’W in Belém.

This sub set of lightning data collected during the above

mentioned days of intense rainfall events was the object

analysis for this paper.

3 RESULTS AND DISCUSSION

Figure 1 shows the time behavior of the lightning

frequency of occurrence and the hourly average

precipitation in Belém, during five intense rainfall events

registered on the days indicated.

Even though the time of occurrences vary significantly,

one observes the lightning frequency of occurrence

exceeds 8 flashes per 10 min intervals and its peaks

preceded the rainfall maxima in all these cases.

A summary of the lightning and rainfall data analyzed is

presented on Table 1. One observes at Table 1 that,

considering only five events of intense rainfall it was not

possible to establish a statistical threshold for the

lightning frequency of occurrence associated to them.

Figura 1 - Lightning rate of occurrence versus average hourly

rainfall in Belém.

Table 1 – Lightning and Rainfall data – Belém-PA-Brazil – Case Studies

Overall 381 lightning flashes were detected during the

events analyzed. 197 occurrences were detected

simultaneously by more than four sensors of the system.

The stroke peak currents ranged from 11 to 186 kA and in

all cases studied, the number of negative CG lightning

exceed that of the corresponding positive strokes.

It appears that there was a positive, but yet undetermined,

relation between the ratio of CG to CC events number and

the accumulated rainfall in Belém.

Perhaps the most interesting fact displayed in Table 1 is

that, lightning occurrences within a 20 km radius around

Belém, preceded intense rainfall by 20 to 70 minutes. If

some lightning parameter threshold is established by

future studies, this time interval would become useful to

warn the local population when that situation would occur

simultaneously with high tide periods in Belém.

Fig 2 shows the lightning occurrences within the 20 km

circle drawn around the LPATS IV sensor position in

Belém.

The color coded dots represent each one of the five days

analyzed. One observes, as expected, a higher occurrence

of events over land surfaces, compared to the water

surfaces. Other than that, there was no clear pattern

observed for the time evolution of the lightning individual

events.

It seems that they occurred randomly and not as if some

cloud system were drifting over this area, during the

intense rainfall occurrences.

Fig 2 – Keraunic map showing the distribution of occurrences of

lightning during five events of intense rainfall in Belém–PA–

Brazil.

4 CONCLUSIONS

Lightning parameters observed around Belém-PA during

five events of intense rainfall in this city, were analyzed.

All events occurred between 16 and 22 hours UT or 13

and 19 hours, local time. It appears that the rainstorm

clouds originated themselves within or near a 20 km circle

around the city, since lightning flashes showed no clear

sequence of spatial displacement during all cases studied.

It was not possible yet to establish threshold values of the

lightning parameters indicative of the lightning

occurrences. This may be attributed to the relatively small

number of events analyzed so far.

A preliminary result indicates that a positive relationship

existed between the ratio of numbers of CG to CC

lightning occurrences and the precipitation totals observed

in each case. Further study is necessary however to

confirm this observation.

For all cases analyzed, lightning occurrence frequency

peaked from 20 to 70 minutes before intense rainfall

hourly events.

This delay seems a promising parameter to be considered,

for a future alert system of intense rainfall occurrences in

Belém.

5 ACKNOWLEDGEMENTS

The authors wish to thank the Brazilian Financier of

Studies and Projects (FINEP) for the support provided to

an applied research project in which they are involved.

They also thank Mr. José Raimundo de Sousa, Director of

INMET’s 2nd

District for facilitating access to rainfall

data.

6 REFERENCES

[1] P.B. Roohr And T.H. Vonder Haar. “A Comparative

Analysis of the Temporal Variability of Lightning

Observations and GOES Imagery”. Journal of Applied

Meteorology. Vol. 33, pp. 1271-1290, 1994.

[2] L. D. Carey, M. J. Murphy, T. L. Mccormick, N. W. S.

Demetriades. “Lightning location relative to storm structure

in a leading-line, trailing-stratiform mesoscale convective

system”, J. Geophys. Res., vol. 110, D03105,

doi:10.1029/2004JD004371, 2005.

[3] K. Y. Wang And S. A. Liao. “Lightning, radar reflectivity,

infrared brightness temperature, and surface rainfall during

the 2-4 July 2004 severe convective system over Taiwan

area”, J. Geophys. Res., Vol. 111, D05206,

doi:10.1029/2005JD006411,in press, 2006 (SCI)

[4] D. R. Macgorman, W. D. Rust, P. Krehbiel, W. Rison, E.

Bruning, K. Wiens. “The electrical structure of two

supercell storms during STEPS”. Mon. Wea. Rev., 133, pp.

2583–2607, 2005.

[5] B. Gungle, E. P. Krider. (2006). “Cloud-to-ground

lightning and surface rainfall in warm-season Florida

thunderstorms” J. Geophys. Res., 111, D19203,

doi:10.1029/2005JD006802, 2005.

[6] L. R. Soriano, F. de Pablo And E. G. Díez (2001).

“Relationship between convective precipitation and cloud-

to-ground lightning in the Iberian Peninsula”. Monthly

Weather Review 129: pp. 2998-3003. 2001

[7] B. R. P. Rocha, J. R. S. Souza, I. M. O. Silva, A. X. S.

Araújo. “Estimativas de Precipitação através da Frequência

de Raios Nuvem-Solo, em Belém”. Anais do V Congresso

Internacional da Sociedade Brasileira de Geofísica, Vol.

2, pp. 1163-1166, São Paulo - SP, 1997.

[8] B. R. P. Rocha, J. R. S. Souza, I. M. O. Silva, J. M. Costa.

“Precipitation Estimates from an Electromagnetic

Lightning Detector Data in Radiofrequencies”.

Proceedings of the Iinternational Microwave and

Optoelectronics Conference, Vol. 2, pp. 655-659, Natal -

RN, 1997.