scholarly journals Lightning risk assessment at a high spatial resolution using the resident sub-district scale: A case study in Beijing metropolitan areas

2016 ◽  
Author(s):  
Hai Bo Hu ◽  
Jing Xiao Li
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Metropolitan Areas ◽  
Detection Efficiency ◽  
Lightning Flash ◽  
Lightning Stroke ◽  
Multiple Contacts ◽  
Lightning Location System ◽  
Cg Lightning

Abstract. Lightning risk indexes identifying the potential number of dangerous lightning events (NDLEs) and ground sensitivity to lightning in resident sub-districts of Beijing metropolitan areas have been unprecedentedly estimated on a 5 m resolution grid. The gridded cloud to ground (CG) lightning stroke density was used in the NDLE calculation, on account of multiple contacts formed by CG lightning flash multiplicity. Meanwhile, in the NDLE estimates, the critical CG stroke gridded densities derived from the lightning location system (LLS) data were corrected for network detection efficiency (DE). This case study on resident sub-district indicates that the site-specific sensitivity to lightning, which is determined by the terrain factors related to lightning attachment, as well as lightning rod effects induced by nearby structures, differs greatly across types of underlying ground areas. The discrepancy of the NDLE which is the numerical product of sensitivity and CG stroke density, is predominated by the sensitivity on account of the relatively stationary CG stroke density in a resident sub-district scale. Conclusively, the visualization of lightning risk sensitivity and NDLE discrepancy in parts of a resident sub-district at high spatial resolution makes it convenient in risk reduction and risk control for lightning risk management.

scholarly journals An algorithm for estimating the detection efficiency of a lightning location system

2017 ◽  
Author(s):  
Haibo Hu ◽  
Xiya Zhang
Keyword(s):  
Probability Distribution ◽  
Detection Efficiency ◽  
Lightning Flash ◽  
Mountainous Areas ◽  
High Attenuation ◽  
Density Correction ◽  
Location System ◽  
Single Station ◽  
Lightning Location System ◽  
Cg Lightning

Abstract. This paper puts forward an algorithm for estimating the detection efficiency (DE) of a lightning location system (LLS). The algorithm can be applied to lightning flash/stroke density correction (e.g., cloud-to-ground (CG) lightning flash/stroke density) and LLS performance evaluation. A lightning strike density correction for DE promotes the applicability of the LLS data. Fundamentally, the generalized extreme value (GEV) distribution was found to best fit the probability distribution of the signal strengths of the lightning observed by the ADTD detectors in Beijing, China. With respect to this probability distribution, we estimated the single-station acceptance damped by the uneven underlying land surface conductivity. Accounting for the multi-detector location modes supported by single-station acceptance, the iterative algorithm was applied for deducing the DE of a LLS. In this case study, the DE estimates of the ADTD network were lower in the mountainous areas than in the plains. These lower estimates can be due to the low underlying conductivity of the mountainous areas, which creates a high attenuation effect on the lightning electromagnetic signals, and the greater distances from the lightning detectors. Subsequently, the cloud-to-ground (CG) lightning flash/stroke density derived from the ADTD data was corrected for the DEs. The results indicated that the CG lightning flash/stroke densities in the northern and northwestern mountainous areas are lower than that in the highly urbanized plains. This anomaly is due to the effects of the increased roughness of the underlying land surfaces, enhanced aerosols, urban heat island (UHI), and intensifying thunderstorm activities in urban areas, but this anomaly is not likely related to the DE discrepancy.

scholarly journals Exploitation of Sentinel-2 Time Series to Map Burned Areas at the National Level: A Case Study on the 2017 Italy Wildfires

2019 ◽  
Vol 11 (6) ◽  
pp. 622 ◽  
Author(s):  
Federico Filipponi
Keyword(s):  
Time Series ◽  
Spatial Resolution ◽  
Satellite Data ◽  
High Spatial Resolution ◽  
National Level ◽  
Burned Area ◽  
Commission Error ◽  
Burned Areas ◽  
Sentinel 2

Satellite data play a major role in supporting knowledge about fire severity by delivering rapid information to map fire-damaged areas in a precise and prompt way. The high availability of free medium-high spatial resolution optical satellite data, offered by the Copernicus Programme, has enabled the development of more detailed post-fire mapping. This research study deals with the exploitation of Sentinel-2 time series to map burned areas, taking advantages from the high revisit frequency and improved spatial and spectral resolution of the MSI optical sensor. A novel procedure is here presented to produce medium-high spatial resolution burned area mapping using dense Sentinel-2 time series with no a priori knowledge about wildfire occurrence or burned areas spatial distribution. The proposed methodology is founded on a threshold-based classification based on empirical observations that discovers wildfire fingerprints on vegetation cover by means of an abrupt change detection procedure. Effectiveness of the procedure in mapping medium-high spatial resolution burned areas at the national level was demonstrated for a case study on the 2017 Italy wildfires. Thematic maps generated under the Copernicus Emergency Management Service were used as reference products to assess the accuracy of the results. Multitemporal series of three different spectral indices, describing wildfire disturbance, were used to identify burned areas and compared to identify their performances in terms of spectral separability. Result showed a total burned area for the Italian country in the year 2017 of around 1400 km2, with the proposed methodology generating a commission error of around 25% and an omission error of around 40%. Results demonstrate how the proposed procedure allows for the medium-high resolution mapping of burned areas, offering a benchmark for the development of new operational downstreaming services at the national level based on Copernicus data for the systematic monitoring of wildfires.

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