Lightning atmospherics count rates observed at Halley, Antarctica

Lightning is considered to be a sensitive indicator of global change in the troposphere. In this paper we report the first results from the lightningatmospherics (sferics) counter deployed as part of the VELOX II experiment at Halley Station, Antarctica (76°S,27°W). We present examples of high-resolution and survey data for the instrument from its deployment in April 1997 up to March 1998. We show that time resolution causes saturation effects in the data when the activity level is high. However, we show how a simple simulation algorithm is used both to calibrate the system and to model the observed response to a high level of accuracy. We show evidence of a departure of the distribution of VLF noise amplitudes in the high-resolution time series produced for the model from the lognormal form assumed by many authors and in the design of the present instrument. Comparison is also made with a Rayleigh distribution. We compare the corrected flash rate with lightning power measurements, indicating that previous estimates of long-term changes in sferic power made from Halley are consistent with less than 5% change in flash rate in 25 years.

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