Analysis of convective instability data derived from a ground-based microwave radiometer before triggering operations for artificial lightning

Abstract

Artificially triggered lightning is useful in scientific studies of the physical processes of lightning because it is predictable in both time and space. However, the triggering operations need to be carried out under suitable weather conditions. Ground-based microwave radiometers can be used to obtain thermodynamic information about the Earth's atmosphere and can show the evolution of atmospheric instability at a high temporal resolution. They could therefore be used to find a suitable time to trigger artificial lightning. Data were collected with an MWP967KV ground-based microwave radiometer installed at the Field Experiment Base on Lightning Science of the China Meteorological Administration from May 21 to July 31, 2018, and June 1 to July 10, 2019, and the convective available potential energy (CAPE) and convective inhibition (CIN) were calculated for use in the analysis of convective instability. Comparison of the datasets for 11 non-precipitation days and 11 triggering operation days showed that on non-precipitation days both the CAPE and CIN increase from about 6:00 am and then gradually decrease after reaching a maximum value. By contrast, both the CAPE and CIN experienced a cliff-like decrease on the triggering operation days just before the start of the operation to trigger the artificial discharge of lightning. The decreasing trends shown by the CAPE were similar to the trends for CIN. It was common for the CAPE to decrease from >1000 J/kg before triggering to <300 J/kg, while the CIN decreased from <300 J/kg to about 0 J/kg. The rates of decrease of the CAPE and CIN were 22.96 and 4.38 J/kg/min, respectively. The values of CIN before the triggering operations were usually lower than those on non-precipitation days.