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The paper presents a systematic description about the observation scheme analysis and practical observation of artificially triggered lightning with a ground-based microwave radiometer together with other discharging observation instruments at Guangzhou Field Experiment Site for Lightning research and testing in Conghua, Guangdong in the thunderstorm season of the 4 consecutive years from 2016 to 2019. The results from statistical analysis of the brightness temperature data observed from 2017 to 2019 show that: (1) The frequencies such as 28, 30, 51.25 and 51.76 GHz in atmospheric window are more likely to respond with outstanding brightness temperature pulses than other observation frequencies of the radiometer; (2) When the elevation angle is 30°, the observation distance is relatively short (99 m in this study), and the "lightning observation mode" is adopted, the efficiency for a ground-based microwave radiometer to capture the lightning heating effect caused by artificially triggered lightning can be improved; (3) The observation efficiency of the 3 years as a whole is 71.4% but gradually increases year by year; (4) The radiometer observation data can be used to reveal the characteristics of lightning heating effects such as duration and lightning current integral; (5) Combined with the lightning current data measured by a coaxial shunt during the experiment, it was found that the estimated lightning heating effect durations based on 25 artificially triggered lightning observations are well consistent with the lightning current durations, as shown by the correlation coefficient of 0.73. This also implies that the radiometer working on the lightning observation mode presented by this paper can observe the lightning heating effect and estimate its duration. • Triggered lightning is observed with a ground-based microwave radiometer in 2016–2019. • Observation scheme is formed based on the simulation calculations and data analysis. • Lightning heating duration averaged 0.5 s, variations are the same as current duration. • The observation efficiency is 71.4% and keeps increasing every year from 2017 to 2019. [ABSTRACT FROM AUTHOR]

The coastal area of Guangdong Province underwent an extreme rainstorm in Aug. 2018. In this paper, using the convection-permitting WRF simulation results, a comparative analysis was given to the cloud microphysical conversion processes simulated under four cloud microphysics schemes, i.e. WSM6, WDM6, WSM7 and WDM7, as well as the accompanying latent heat budget. The maintenance mechanism of the rainstorm is discussed. In all four schemes, water vapor condensing into cloud water and accretion of cloud water by rain water were the top two conversion processes. In WSM6/WDM6 scheme, the third largest conversion process was accretion of rain water by graupel; in WSM7/WDM7, however, the third largest was cloud water evaporating to water vapor. The most important source of rain water was accretion of cloud water by rain, but the differences in hydrometeors conversion between rain water and graupel, snow and hail were the leading cause of differences in simulated rainfall under different schemes. The top three releasing latent heat processes were water vapor condensing into cloud water, water vapor deposited to cloud ice, and snow sublimation. The top two absorbing latent heat processes were cloud water and rain water evaporating to water vapor. In WSM6/WDM6/WSM7 schemes, the third major process of absorption of latent heat was snow sublimating to water vapor, in WDM7, however, it was hail melting into rain water. Compared with ice-phase processes, liquid-phase processes provide more latent heat. Differences in the release and absorption of latent heat were found in the mid-high troposphere. Hydrometeors in the troposphere maintain efficient conversion and release large amounts of latent heat that formed positive feedback with convection, which was the critical reason for the development and maintenance of the extreme rainstorm. • The top two microphysical conversion and latent heat processes of four schemes were consistent. • Conversion between rain water and graupel, snow and hail led different rain intensity. • Liquid-phase processes provided more latent heat than ice-phase processes. • Differences in latent heat processes were mainly found in the mid-high troposphere. • Rapid conversion of particles and latent heat processes formed positive feedback with convection. [ABSTRACT FROM AUTHOR]

Return-stroke current and electric field play important roles in atmospheric electricity research. Aim of this paper is to examine the empirical formulas for calculating return-stroke peak-current in lightning location system according to sensored peak-electric-field, and to evaluate the detection efficiencies and the peak-current estimation of the Foshan Total Lightning Location System (FTLLS). Lightning was initiated artificially by rocket triggering procedure and the current waveform was recorded at the lightning channel-base. A total of 43 return-strokes in 8 flashes were triggered succesfully in 2014. Nine different regression formulas providing the best fit to the measured current-and-field data were derived. The empirical formulas were based on the directly measured return-stroke current and electric fields of 38 return-strokes within 4 flashes. The empirical formulas analyzed in the present study demonstrate the regional difference of the empirical formulas for various geographical-distributed stations of the FTLLS in Foshan, China. On the other hand, the return-stroke speeds were theoretically derived though the transmission line model considering the already known parameters of the corresponding measured-peak-current at triggering lightning site. The nine empirical formulas from the nine stations of the FTLLS were analyzed by the fact that the values of the inferred return-stroke speeds for each return-stroke and for each station are reasonable compared to those in the previous literatures. In addition, the detection efficiencies and peak-current estimation of the FTLLS and the LLS of Guangdong power grid in Guangdong Province were examined and were compared based on the directly measured current data at the triggering lightning site. It is shown that the detection efficiencies of the FTLLS for flashes and for return-strokes were 87.5% (7/8) and 93.0% (40/43), respectively. The peak-current estimation error reported by the FTLLS was 8% on average. The absolute value of the maximum error for the individual return-strokes were around 28%. Performance comparison to other global/regional lightning location systems are also presented. • We investigated the relationships between the peak-value of the distant electric fields the measured return-stroke current. • Nine different regression formulas providing the best fit to the measured current-and-field data are derived. • The detection efficiencies of the FTLLS for flashes and for return-strokes were 87.5% and 93.0%, respectively. Performance comparison to other global/regional lightning location systems are also presented. [ABSTRACT FROM AUTHOR]

The recent intensification of extreme rainfall events has the potential to aggravate the frequency and intensity of floods in urban areas and signals the urgent need for accurate and high spatiotemporal resolution precipitation data for flood monitoring and warning to alleviate the associated damages. In this context, this paper aims to statistically assess the latest Integrated Multisatellite Retrievals from Global Precipitation Measurement (IMERG) multisatellite constellation and radar quantitative precipitation estimation (QPE) products against dense rain gauge network observations under multiple temporal scales (hourly and 3-hourly) and three spatial scales (grid cumulative, regional, and grid) over the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) in China. The results indicate that (1) at the grid cumulative scale, QPE significantly outperforms IMERG products. The correlation coefficients of QPE (0.83 ≤ CORR ≤ 0.85) are much higher than those of IMERG products (0.35 ≤ CORR ≤ 0.56), the estimation of QPE is generally significantly underestimated (−0.23 ≤ BIAS ≤ -0.16), and the BIAS of IMERG products is larger than that of QPE (−0.24 ≤ BIAS ≤ 0.23). (2) At the regional scale, the accuracy of IMERG products has been significantly improved, with relatively high correlation coefficients (CORR≥0.8) and decreased root mean squared error (RMSE) values (1.18 mm ≤ RMSE ≤ 0.22 mm), and Taylor diagrams visually show that QPE is closer to the gauge observations than are IMERG products. (3) The evaluation results at the grid scale show that both IMERG products and QPE can accurately reflect the spatial distribution of precipitation. Among these results, the spatial distribution of QPE is the most consistent with the actual rainfall, although an obvious underestimation of rainfall occurs in areas with strong rainfall. (4) In terms of detection indicators, the three IMERG products are superior to QPE at capturing rainfall events and have more advantages over QPE in the estimation of instantaneous precipitation, especially for light rain events. However, QPE has better detection effects for rainfall events under rainstorm and heavy rainstorm events, indicating the hydrologic utility of this product. Among the three IMERG products, the IMERG Early Run (ER) product has the advantages of a short lag time and high accuracy, and it has the potential to be applied in flood forecasting. Future studies should improve IMERG algorithms and promote the application of QPE in urban rainstorm and flood research. • The quality of the IMERG products and radar quantitative precipitation estimation (QPE) is compared over the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) in China. • The dense rain gauge network observations are used for evaluation in the GBA. • The evaluation of multisource precipitation products under different temporal and spatial scales has different results and effects. [ABSTRACT FROM AUTHOR]