Browsing by Subject "Lightning Detection"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Houston LDAR II network: design, operation, and performance analysis(Texas A&M University, 2008-10-10) Ely, Brandon LeeThe Houston LDAR II network is an array of twelve VHF time-of-arrival (TOA) sensors operated by Texas A&M University. The goals of the network are to conduct indepth studies of thunderstorm electrification and provide timely lightning threats to the Houston area. Before analyses are conducted using data from the Houston LDAR network, it is necessary to understand the LDAR network? s performance and limitations, such as the LDAR source detection efficiency, network range, and location accuracy. Initial results from the 31 October 2005 Mesoscale Convective System (MCS) timing error analysis revealed an RMS timing error for the Houston LDAR network of 90 ns for 6 sensor solutions. This gives a three-dimensional location accuracy of 1 km at a distance of 150 km and 100 m over the center of the network. Reanalysis with updated sensor positions decreased the RMS timing error to 75 ns. This decrease in RMS timing error increased the median three-dimensional location accuracy by ~100 m at a 100 km range. The network has been operated at both 70 MHz and 40 MHz. Model results of detection efficiency suggest that the change to 40 MHz yields an increase of 9 - 10 dB in network sensitivity. Analysis of VHF source power distributions shows a similar shift from that expected from the model. These results show that the 40 MHz LDAR network detects ~3.3 times more VHF sources than the 70 MHz network. The analysis of the usable network range for research purposes is currently set by rough guidelines of location accuracy and detection efficiency. For location accuracy, a 1 km limit allows storm analysis out to a range of more than 150 km. For the detection efficiency analysis, results based on source power distributions suggest a gradual fall off with range. Examining the change in VHF source density by range reveals different results. VHF source density remained fairly constant out to a range of 100 km at which point a significant fall off was observed. Based on these results the usable network range for the Houston network is 100 km.Item The Houston Lightning Mapping Array: Network Installation and Preliminary Analysis(2013-06-25) Cullen, Matthew RyanThe Houston Lightning Mapping Array (LMA) is a lightning detection network providing total lightning mapping for the Houston metropolitan area and southeast Texas. The network is comprised of twelve Very High Frequency (VHF) time-of-arrival total lightning mapping sensors built by New Mexico Institute of Mining and Technology and purchased by Texas A&M University. The sensors, installed in April 2012, are of the latest, modular design and built to be independent stations that utilize a solar panel for electricity and cellular data modems for communication. Each sensor detects the time of arrival of a VHF impulse emitted as part of the electrical breakdown and lightning propagation process. Data from each sensor are processed on a central LMA server to provide three-dimensional mapping of these impulses, also called LMA sources. This processing facilitates the analysis of variations in thunderstorm structure and the associated changes in both space and time. The primary objectives for the installation of the Houston LMA network are twofold: first, to provide a dataset enabling research into thunderstorm electrification in the context of a coastal, urban, polluted environment; and second, to enable improvements in operational forecasting and public safety by providing total lightning data to partners including the National Weather Service (NWS). A workflow was established to create and share real-time data to these partners, while simultaneously maintaining a full, research-quality dataset. Data are retrieved from the field sensors and backed up to a central LMA server for processing and storage. Archived network data are available from July 2012 through the present. The network measures 150 km from north to south, with stations in College Station and Galveston complementing the ten sites surrounding downtown Houston. This extends the region constrained by the network beyond the immediate metropolitan Houston area, resulting in increased accuracy in locating sources further from the network center. Based on initial analyses, the effective range of the Houston LMA is 75 km for three-dimensional mapping and approximately 250 km for two-dimension mapping.