A global lightning parameterization based on statistical relationships among environmental factors, aerosols, and convective clouds in the TRMM climatology

Abstract

The objective of this study is to determine the relative contributions of normalized convective available potential energy (NCAPE), cloud condensation nuclei (CCN) concentrations, warm cloud depth (WCD), vertical wind shear (SHEAR), and environmental relative humidity (RH) to the variability of lightning and radar reflectivity within convective features (CFs) observed by the Tropical Rainfall Measuring Mission (TRMM) satellite. Our approach incorporates multidimensional binned representations of observations of CFs and modeled thermodynamics, kinematics, and CCN as inputs to develop approximations for total lightning density (TLD) and the average height of 30 dBZ radar reflectivity (AVGHT30). The results suggest that TLD and AVGHT30 increase with increasing NCAPE, increasing CCN, decreasing WCD, increasing SHEAR, and decreasing RH. Multiple‐linear approximations for lightning and radar quantities using the aforementioned predictors account for significant portions of the variance in the binned data set (R2 ≈ 0.69–0.81). The standardized weights attributed to CCN, NCAPE, and WCD are largest, the standardized weight of RH varies relative to other predictors, while the standardized weight for SHEAR is comparatively small. We investigate these statistical relationships for collections of CFs within various geographic areas and compare the aerosol (CCN) and thermodynamic (NCAPE and WCD) contributions to variations in the CF population in a partial sensitivity analysis based on multiple‐linear regression approximations computed herein. A global lightning parameterization is developed; the average difference between predicted and observed TLD decreases from +21.6 to +11.6% when using a hybrid approach to combine separate approximations over continents and oceans, thus highlighting the need for regionally targeted investigations in the future.

Lightning and Associated Convection Features in the Presence of Absorbing Aerosols Over Northern Alabama

“…The difference between the means of log 10 (FR) in the intervals 0.2 ≤ AOD < 0.4 and 0.4 ≤ AOD < 0.6 are statistically significant (p = 0.002) in the presence of absorbing aerosols ( Figure S2). However, due to the smaller correlation coefficient (0.107) and the larger p value (0.009) for all the storm cases, we suggest that no significant linear relationship exists between AOD and FR in general, in contrast to Stolz et al (2015) and Stolz et al (2017). No significant correlation between AOD and FR shown in Figure 4 supports the previous modeling results (Grabowski, 2015;Grabowski & Morrison, 2016) that call the relevance of aerosols to convection invigoration into question, at least on a regional scale.…”

“…An adequately large volume of a strong updraft is necessary for cloud charge separation and lightning (Deierling et al, ; Deierling & Petersen, ; Schultz et al, ; Zipser, ). It has been suggested that aerosols may enhance lightning by modifying the cloud microphysics and local thermodynamics (Albrecht et al, ; Altaratz et al, ; Altaratz et al, ; Proestakis, Kazadzis, Lagouvardos, Kotroni, Amiridis, et al, ; Proestakis, Kazadzis, Lagouvardos, Kotroni, & Kazantzidis, ; Stolz et al, ; Stolz et al, ; Wang et al, ; Williams et al, ; Yuan et al, ). Increased aerosol particles lead to increased cloud condensation nuclei (CCN), resulting in a distribution of liquid cloud droplets with higher number concentrations and lower mean diameters, which lowers the efficiency of collision and coalescence (Albrecht, ; Feingold, ) during the warm precipitation phase of a storm.…”

CAPE Times P Explains Lightning Over Land But Not the Land‐Ocean Contrast

“…Over land, the varied topography and the large diurnal cycle contribute to the occasional buildup of large CAPE, which is subsequently released in explosive convection. One candidate is the higher aerosol concentration over land; higher concentrations of aerosols have been shown to invigorate convection (Koren et al, 2005) and lead to higher flash rates (Stolz et al, 2015(Stolz et al, , 2017Thornton et al, 2017). If precipitation were occurring primarily during high-CAPE events over land, then the CAPE × P proxy might naturally predict a large land-ocean contrast in lightning.…”

“…The failure of CAPE × P to explain the land-ocean lightning contrast means that some other factor is responsible. One candidate is the higher aerosol concentration over land; higher concentrations of aerosols have been shown to invigorate convection (Koren et al, 2005) and lead to higher flash rates (Stolz et al, 2015(Stolz et al, , 2017Thornton et al, 2017). Another candidate is the lower relative humidity over land, which is associated with a deeper subcloud mixed layer and, therefore, cloudy updrafts that are wider at birth and, therefore, more protected from the buoyancy-sapping effect of convective entrainment Williams & Stanfill, 2002).…”

Tropical Oceanic Thunderstorms Near Kwajalein and the Roles of Evolution, Organization, and Forcing in Their Electrification

“…The hypothesized sensitivity of oceanic lightning to the depth of the boundary layer has led some to use the thermodynamic parameter of cloud base height for predicting the probability of lightning (E. R. Williams et al, 2005;Zheng & Rosenfeld, 2015) or the surface Journal of Geophysical Research: Atmospheres 10.1029/2018JD029320 Bowen ratio (Hansen & Back, 2015; E. R. Williams & Stanfill, 2002). The predictive power of CAPE itself (or CAPE normalized by the depth of the unstable layer, as in Stolz et al, 2015), has a turbulent history throughout the literature (Hansen & Back, 2015;Seeley & Romps, 2015;Stolz et al, 2017). While on longer time scales global distributions of CAPE tend to match distributions of lightning, Riemann-Campe et al (2009) and many studies over land show strong relationships between CAPE and lightning (E. R. Williams, 1995; E. R. Williams & Renno, 1993); oceanic CAPE values are often comparable to those over land (Hansen & Back, 2015; E. R. Williams & Stanfill, 2002).…”