LAUSR

Abstract The integrals of lightning current and its square over time, named as the electrical charge quantity and lightning current action integral, respectively, are indicative of the total charges and heat energy released by the lightning. The temperature of air molecules along the discharging path is thus increased and can be observed by a properly-configured ground-based microwave radiometer which is originally for atmospheric temperature remote sensing. Field experiments have been performed with a ground-based, MWP967KV type microwave radiometer, which is common for atmospheric temperature profile remote sensing but has been properly-configured in order to observe the artificially triggered lightning events in May–July in 2017 and 2018 at Guangzhou Field Experiment Site for Lightning research and test (GFESL). The brightness temperature (Tb) data from the radiometer and the lightning current data measured by a coaxial shunt have been processed. The results show that a relationship like Tbmax = a + b*exp.(c*It) may exist between the maximum pulse amplitude, Tbmax, in unit of K, observed in 30-50GHz band and the total current action integral, It, in unit of A2s, calculated from high temporal resolution lightning current records. The correlation coefficient is as high as 0.75 when taking the data of the two years as a whole (sample size = 16) while the coefficients a, b and c are equal to 21.53, 2.47 and 3.47, respectively. It is not evident that maximum pulse amplitude has a significant positive correlation with the total electrical charge quantity. In addition, it has been found that the variation trend of Tb pulse amplitude and lightning current integral values (i.e. current action integral and electrical charge quantity) in the lightning process are consistent.