Observed Characteristics of Ionospherically Propagated HF Atmospherics from Normal and Severe Thunderstorms.
Abstract
Using a directional HF antenna with a nominal beamwidth of 0.5 deg, atmospherics from midwestern thunderstorms classified as severe, and thus likely to produce tornadoes, were studied in California. The antenna was scanned across regions within a one-hop propagation distance likely to develop tornadoes at the time of the test. These regions were selected on the basis of National Weather Service severe weather forecasts. The existence of strong propagation from these regions at the radio frequencies used was verified by means of backscatter soundings. Analysis of the data recorded in those directions and periods for which severe storm events were reported led to the discovery of a class of radio atmospherics significantly different from those radiated during normal thunderstorm activity. Atmospherics of this new type take the form of randomly occurring impulses having certain distinctive characteristics. A technique was devised to extract this class of atmospherics from the remaining radio noise background. Based on 23 hours of data, taken on four separate days, a statistically significant correlation between the reception of these impulses and the presence of remote severe thunderstorms was found.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1977
- Accession Number
- ADA044737
Entities
People
- Walter B. Zavoli
Organizations
- SRI International