Kleber P. Naccarato

Monthly distribution of cloud‐to‐ground lightning flashes as observed by lightning location systems

Figure 1. RINDAT sensor configuration at the end of2004. Also indicated is the region considered in thisanalysis.Figure 2. Normalized mean monthly distribution of thenumber of CG flashes observed at different countries forlong time periods.Figure 3. Normalized mean monthly distribution of thepercentage of positive CG flashes observed at differentcountries for long time periods.Figure 4. Normalized mean monthly distribution of thepositive peak current of CG flashes observed at differentcountries for long time periods.

Methods to Overcome Lightning Location System Performance Limitations on Spatial and Temporal Analysis: Brazilian Case

AbstractOne of the most interesting attributes of Lightning Location Systems (LLSs) data is that they can be analyzed in several ways according to the objectives of the study. However, the quality of the data is governed by the system performance and has some limitations when analyzed at different temporal/spatial scales, and these limitations will depend on the analysis method. This work focuses on approaches to minimize the variations associated with LLS performance. In this way, specific network configurations for the Brazilian Lightning Detection Network (BLDN) were obtained through the reprocessing of selected sensor data, resulting in three distinct datasets. Each dataset was then evaluated using different procedures: trimmed flash (exclusion of low current discharges), thunderstorm days (TDs), and thunderstorm hours (THs). The comparison between TDs obtained from the LLS and TDs available from surface stations shows consistent results with a good correlation of those datasets. An 11-yr analysis of ...

Improvements on Lightning Density Estimation Based on Analysis of Lightning Location System Performance Parameters: Brazilian Case

Density maps are one of the most common and powerful lightning data applications, and they are more efficient the more detailed they are. When working with CG lightning data from lightning location systems, some aspects must be included in the analysis to overcome network performance variations. Two parameters are typically used to evaluate system performance: detection efficiency (DE) and location accuracy (LA).For the Brazilian National Integrated Lightning Detection Network, DE is typically evaluated by models, and LA is analyzed through confidence ellipses. This paper presents climatological analysis of lightning activity, including the most recent relative DE model developed in Brazil, as well as an adapted kernel smoothing method based on confidence ellipses [called Gaussian kernel based on confidence ellipses (GKBCE)] as approaches to minimize and/or include the spatial variation of the systems performance in the analysis. The maps are produced over the central-south portion of Brazil (mainly along ITAIPU power transmission lines), using 11 years of data available from the network (from January 1999 to December 2009). The model increased density by ~20% over the entire region, without making considerable changes to the spatial pattern. The GKBCE seems to work well in smoothing, obtaining better results than the standard cell count (quadrat) method, by working independently of the grid size (allowing the creation of high-resolution maps), and by including location errors in the analysis. The use of these procedures might result in more detailed maps and more suitable results when analyzing lightning data.

Lightning detection in Southeastern Brazil from the new Brazilian Total Lightning Network (BrasilDAT)

The Brazilian Total Lightning Network (BrasilDAT) combines advanced lightning detection technologies with modern electronics and already covers 11 States of Brazil. The network is composed of 48 EarthNetworks Lightning Sensors (ENLS), each of them with a GPS-based timing circuit, a digital signal processor (DSP) and onboard storage and internet communication equipment. The ENLS is a wideband system with detection frequency ranging from 1Hz to 12MHz. The wide frequency range enables the sensor to not only detect cloud-to-ground (CG) strokes, but also intra-cloud (IC) pulses. The sensor records whole waveforms of each event and sends them back, in compressed data packets, to the central processor. Instead of using only the peak values, the whole waveforms are used in locating the events and differentiating between IC and CG discharges. Sophisticated digital signal processing technologies are employed on the server side to ensure high-quality detections and to eliminate false locations. This paper presents some preliminary results of two severe storms in Southeastern Brazil that were tracked by BrasilDAT showing the spatial and temporal evolution of IC and CG discharges compared to radar, satellite images and numerical model products. Those results showed the potential of total lightning information for CG lightning warning purposes.

The new Brazilian lightning detection network: First results

A new lightning detection network using WeatherBug Total Lightning Sensors (WTLS) is being deployed in Brazil. The network can acquire detailed signals emitted from both IC and CG flashes and continuously sends information to a central server. A WTLS is composed of an antenna, a global positioning system (GPS) receiver, a high-accuracy GPS-based timing circuit, a digital signal processor (DSP), and onboard storage and internet communication equipment. The sensor is a wideband system with detection frequency ranging from 1Hz to 12MHz. The wide frequency range enables the sensor to not only detect strong CG strokes, but to also detect weak IC pulses. The sensor records whole waveforms of each flash and sends them back, in compressed data packets, to the central server. Instead of using some waveform parameters, the whole waveforms are used in locating the flashes and differentiating between IC and CG strokes. A 75-sensor network is being installed in the South, Southeast, Center and Northeast regions of the country and should operated simultaneously with the integrated lightning detection network (RINDAT), which is composed by 34 low-frequency (LF) sensors using Vaisala technology, covering the Southeast and parts of the South and Center regions of the country. Details of the new network configuration and its main applications will be described.

Cloud-to-Ground Lightning Observations in Brazil

A comprehensive review of cloud-to-ground (CG) lightning observations in Brazil is presented. Brazil is the largest country in the tropical region and it is believed to have the largest cloud-to-ground (CG) lightning activity in the world, estimated from thunderstorm days and satellite data in about 50 millions CG lightning flashes every year. Emphasis is given to recent observations made by lightning location systems and high-speed cameras in the Southeast region of the country. At the present time, they correspond to the largest CG lightning data set available for the tropics. Some specific parameters emerging from these observations are quantified. The observations are compared with similar ones made in other tropical and temperate countries, as well as with past observations obtained by other techniques in Brazil.

Evaluation of BrasilDAT relative detection efficiency based on LIS observations and a numeric model

The BrasilDAT total lightning detection network provides the capability of detecting total lightning on a continental scale. An understanding of the detection efficiency of BrasilDAT is necessary for use of total lightning data in applications such as severe weather detection and derivation of rainfall rates. BrasilDAT relative detection efficiency is studied by comparing lightning flashes seen by the network and by the Lightning Imaging Sensor (LIS) on board of the low earth orbit satellite TRMM. Also projections of BrasilDAT relative detection efficiencies will be computed based on calculations of ELATs 4th generation relative detection efficiency model.

Detection of upward lightning by lightning location systems

We report upward lightning observations in São Paulo city, SP, Brazil and compare them to data from Lightning Location System (LLS). These data are provided by 4 different networks from different technologies: BrasilDAT, RINDAT, Worldwide Lightning Location Network (WWLLN), and Earth Networks Global Lightning Network (ENGLN). Several upward flashes were observed from 2012-2014 using GPS time-stamped optical sensors and electric field measurements. These upward flashes were initiated from tall towers located at Jaragua Peak (70 and 130 m) and along Paulista Avenue (23 towers with heights between 50 and 220m). Time-correlated analyzes allowed to evaluate the network detection efficiency, intracloud (IC) / cloud-to-ground (CG) misclassification percentage, and location accuracy of the 4 different LLS. We will also show how different upward flash physical processes (leader initiation, recoil leaders, return strokes) are detected and classified by the distinct LLS technologies. Preliminary results show that in general, recoil leaders were not detected; on the other hand, several cases of return strokes and some cases of M-component were detected by one or more LLS networks.

High resolution lightning density maps to study elevation effects at microscale

Lightning location systems have evolved over the years in both location accuracy and detection efficiency. For the Brazilian integrated lightning detection network (RINDAT), the mean location accuracy has increased along the years as the network was expanded and the performance and sensibility were being improved. With the improved location accuracy, accurate and reliable high-resolution lightning distribution maps may be obtained. These maps might then be used to give a better understanding of the lightning distribution and its physical basis. In this paper we analyze the terrain effects in a microscale perspective, using eleven years (1999 to 2009) of data from the RINDAT network to produce the high-resolution maps. These maps are accomplished by a thunderstorm initiation analysis based on the lightning data. The results indicate some interesting elevation effects on the lightning distribution, especially over (isolated) mountains near Sao Paulo and Belo Horizonte and along the coastline of Sao Paulo, which might be related to local storms thermodynamic and/or channel attachment processes.

Preliminary comparison of direct electric current measurements in lightning rods and peak current estimates from lightning location systems

This work presents preliminary observations of the first lightning flash striking an instrumented lightning rod on the top of a common building in Brazil. The measurements include direct electric current in the lightning rod, high-speed recordings using different types of cameras and data from two lightning location systems (LLS) that operate in Brazil: RINDAT and BrasilDAT. The striking flash contained seven strokes. The current measurement of the first stroke had saturated and was not detected by both networks. We believe that the longer rise-time of the electric current prevented its detection by the LLS, since the lightning pulses are supposed to have a shorter rise time as shown in this work. The peak current of the detected strokes estimated by BrasilDAT and RINDAT networks were very close to the direct measurements. The average location error for BrasilDAT was 0.8 km (6 strokes detected, 86%) and for RINDAT was 0.4 km (2 strokes detected, 29%).