Distinct aerosol effects on cloud-to-ground lightning in the plateau and basin regions of Sichuan, Southwest China

Abstract

Abstract. The joint effects of aerosol, thermodynamic, and cloud-related factors on cloud-to-ground lightning in Sichuan were investigated by a comprehensive analysis of ground measurements made from 2005 to 2017 in combination with reanalysis data. Data include aerosol optical depth, cloud-to-ground (CG) lightning density, convective available potential energy (CAPE), mid-level relative humidity, lower- to mid-tropospheric vertical wind shear, cloud-base height, total column liquid water (TCLW), and total column ice water (TCIW). Results show that CG lightning density and aerosols are positively correlated in the plateau region and negatively correlated in the basin region. Sulfate aerosols are found to be more strongly associated with lightning than total aerosols, so this study focuses on the role of sulfate aerosols in lightning activity. In the plateau region, the lower aerosol concentration stimulates lightning activity through microphysical effects. Increasing the aerosol loading reduces the cloud droplet size, reducing the cloud droplet collision-coalescence efficiency and inhibiting the warm-rain process. More small cloud droplets are transported above the freezing level to participate in the freezing process, forming more ice particles and releasing more latent heat during the freezing process. Thus, an increase in aerosol loading increases CAPE, TCLW, and TCIW, stimulating CG lightning in the plateau region. In the basin region, by contrast, the higher concentration of aerosols inhibits lightning activity through the radiative effect. An increase in aerosol loading reduces the amount of solar radiation reaching the ground, thereby lowering CAPE. The intensity of convection decreases, resulting in less supercooled water transported to the freezing level and fewer ice particles forming, thus increasing the total liquid water content. Therefore, an increase in aerosol loading suppresses the intensity of convective activity and CG lightning in the basin region.

Evaluating a simple proxy for climatic cloud‐to‐ground lightning in Sichuan Province with complex terrain, Southwest China

“…The correlation between CBH and TCLW with lightning is reversed in plateau and basin regions. In the plateau region, the high TCLW and low CBH indicate that more liquid water is transported to the mixed‐phase region due to the compression effect of plateau topography on cloud, which is favourable for the noninductive electrification process, while, in the basin region, high TCLW and low CBH indicate strong warm‐phase process, which is unfavourable to ice‐phase process and lightning process (Zhao et al ., 2020). The strong convective intensity and ice‐phase process are favourable to the noninductive electrification of collision–separation between ice particles in the mixed‐phase region, which is favourable to the generation and development of lightning activity.…”

“…In North China, large CAPE is more favourable for mesoscale convective systems to produce high lightning frequency and precipitation rate (Liu et al ., 2011; Xia et al ., 2018). The lightning flash rate in western Sichuan Plateau is significantly lower than that in Sichuan Basin, while the ratio of positive lightning in the plateau region is higher than that in the basin, which may be related to spatial differences in CAPE, mid‐level relative humidity, and cloud properties (Zhao et al ., 2020, 2021).…”

Influence of convection on the upper-tropospheric O<sub>3</sub> and NO<sub><i>x</i></sub> budget in southeastern China

“…The WWLLN strokes and pulses are combined with ENTLN into one dataset (ENGLN) within 10 km and 0.7 s as mentioned in Virts and Goodman (2020). To increase the lightning data coverage in our study, the CG flashes of ENGLN and CNLDN datasets are combined using spatial and temporal clustering criteria of 10 km and 0.5 s (Zhao et al, 2020). Merging these three datasets should provide a sufficiently high CG flash detection efficiency for this analysis.…”

Potential Impacts of Aerosol on Diurnal Variation of Precipitation in Autumn Over the Sichuan Basin, China

“…Zhao et al. (2020) indicated that increased aerosols inhibit lightning activity in the basin through the radiative effect based on a ground‐based measurement in combination with reanalysis data. By means of numerical simulation, Fan et al.…”