[1] This paper presents a comparison of a regional lightning detection network based on SAFIR sensors (Surveillance et Alerte Foudre par Interférometrie Radioélectrique) with the operational German lightning detection system (BLIDS) that uses LPATS (Lightning Positioning and Tracking System) and IMPACT (Improved Performance from Combined Technology) sensors. The Institute for Meteorology and Climatology (IMUK) of the University of Hannover runs a regional lightning detection network in northern Germany (UHSN). It consists of three SAFIR receiving stations in a triangle of about 180 km side-length. As an a priori assumption that either BLIDS or UHSN represents the truth is not possible, the relative performance of each system in comparison with the other one is investigated. Probability of detection (POD) is used to investigate flash events simultaneously sensed by both networks. POD of UHSN was calculated assuming BLIDS measurements as true and, vice versa, POD of BLIDS was calculated assuming UHSN measurements as true. This comparison yielded that UHSN, as expected, is far more sensitive to intracloud lightning. In contrast, the sensitivity of UHSN for cloud-to-ground lightning was much lower than that of the BLIDS network. Hence the sensitivity of UHSN for both lightning types together (total lightning) is dominated by intracloud lightning and is consequently higher than that for BLIDS. The sensitivity of UHSN was found to exhibit strong horizontal variations. These are dominated by the network geometry and data processing procedures. The present study shows strengths and weaknesses of both systems and contributes to a better assessment of the potentials of each system.
Abstract. This paper investigates the role of lightning in the production of nitrogen oxides (NOx) and their subsequent distribution by thunderstorms. These questions were addressed by the field experiment LINOX (lightning produced NOx), which was performed in southern Germany in July 1996. The structure of thunderstorms was observed by radar and satellite, the lightning activity was recorded by a lightning detection network, and airborne chemical measurements were performed aboard a jet aircraft penetrating the storm anvils. NOx concentrations in the storm anvils were found to typically range from 1 to 4 parts per billion by volume. The NO contribution to the total NOx was found to be dominant in narrow peaks produced by flashes as well as near cloud boundaries, probably because of increased photolysis rates of NO2. Using CO2 as an air mass tracer, the lightning-produced NO x amount was discriminated from the contribution due to transport of air from the boundary layer. It was found from a case study of a large storm anvil that lightning-produced NOx was present in the same order of magnitude as the amount of NOx originating from lower levels; during later stages of cloud development, the content of the former even exceeded the latter one. A simple two-dimensional model of advection and dispersion of the lightning-produced NOx was able to reproduce the general structure of the anvil NO x plume. Some NOx peaks could directly be attributed to flash observations close to the aircraft track.
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