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Developing Mobile VHF Lightning Mapping Technology

Description:

Lightning observations have many meteorological applications, which are continuously expanding as lightning detection technology improves.  Lightning detection networks monitor the low (LF), very-low (VLF), and very-high (VHF) frequency radiation emitted by lightning flashes.  Since cloud-to-ground (CG) flashes emit most strongly in the LF and VLF range, LF/VLF networks can detect a fraction of CG flashes globally with as few as 50 sensors.  However, intra-cloud (IC) lightning is more closely related to updraft intensity than CG lightning, making it more beneficial for diagnosing severe convection.  IC flashes emit most strongly in the VHF range, which propagates along a line of site and attenuates quickly, requiring a dense network of sensors to provide 3-D lightning observations within relatively small geographical regions.  Although Lightning Mapping Array (LMA; Rison et al. 1999) networks currently provide valuable information, their fixed locations limit the number and variety of storm environments that can be sampled.  Therefore, this proposal seeks to develop VHF lightning mapping technology that can be transported to remote regions (e.g., deep oceans and field campaign locations), deployed quickly, and operated remotely.  This new tool must leverage existing lightning detection technologies and recent field campaigns that have proven the value of unmanned aircraft systems (UASs) for observing thunderstorms. 

 

Project Goals:  It is expected that this technology will be used to better diagnose and predict extreme weather during future field campaigns and significant weather events, and also for validation of future space-borne lightning detection technologies (e.g., GOES-R Geostationary Lightning Mapper; GLM).  Several LMA networks are currently being deployed, which demonstrates the value of these 3-D lightning observations.  Recent field campaigns also have expended considerable effort to deploy LMA networks to Sao Paulo, Brazil and Northern Colorado.   The proposed tool would reduce the amount of effort required to deploy LMA networks for future field campaigns, and will lessen the need to deploy static LMA networks when they are only needed for significant events (e.g., rocket launches from government or private facilities).  VHF lightning observations from an aerial platform will reduce contamination from RF sources on the ground, and provide IC detection capabilities over a larger geographical area than present ground-based LMA networks.  The new technology also should include video observations to help understand how the amount of light leaving the cloud is related to both the intensity of lightning and amount/type of precipitation inside a cloud.  Outside of the present LMA domains (e.g., over the oceans), no technology currently exists to evaluate the quality of space-borne IC lightning observations relative to ground-based measurements.  Thus, this new technology will provide a valuable tool for validating the lightning observations provided by the GLM outside of the present LMA domains.  Once proven, the overall approach could be expanded upon to include different sensors and scientific objectives.

 

Phase I Activities and Expected Deliverables:

  • Identify VHF lightning detection technologies that are suitable for use aboard a small UAS
  • Examine potential aerial platforms that can house this sensor suite (e.g., VHF, GPS, video)
  • Determine the best option for flying multiple UASs in tandem
  • Identify methods for communication between individual sensors and a central hub

 

Phase II Activities and Expected Deliverables:

  • Incorporate lightning detection equipment into an UAS
  • Develop navigation and communication systems
  • Deploy a prototype network
  • Validate the new technology relative to an existing LMA network
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