Developing proxy radar data with the aid of cloud-to-ground lightning for a nowcasting system

Abstract

Air traffic managers need up to date nowcast information over the entire CONUS for efficient operations in the National Airspace System. In areas of degraded or no radar coverage, cloud-to-ground lightning (provided by the National Lightning Detection Network) can provide valuable information through the creation of proxy vertically integrated liquid (VIL) and echo tops (ET). To develop these lightning-VIL and lightning-ET relationships, analysis of the lightning and radar data was done in "climate zones" throughout the CONUS, due to the potential for different lightning behavior in different areas of the country. After a quantile analysis revealed differences in the data between zones, lightning-VIL. and lightning-ET relationships were developed using a probability matching method for a baseline relationship (all climate zones) and for each individual climate zone. The potential benefits of the inclusion of each zone were analyzed through a bootstrap testing of the proxy VIL and proxy ET models, and performance was assessed using a system of binary scoring. For a given lightning flash rate, VIL values in the Mid-Latitude Land West zone were considerably lower than in other zones. The Mid-Latitude Land West zone also showed a noticeable improvement in the performance of the proxy VIL model. For a given lightning flash rate, ET values in the Mid-Latitude Water zone were considerably lower than in other zones. The Mid-Latitude Water zone appeared to provide a statistical improvement in the proxy ET model, but because of a lack of data in this zone on the days chosen for model testing, this improvement was not noticeable in the overall performance of the proxy ET model and needs to be investigated further.