Eric C. Bruning

Secondary ice production (SIP) remains a major uncertainty in understanding deep convection because its rates and controlling conditions are poorly constrained. Using the Tracking Aerosol Convection Interactions Experiment (TRACER) C‐band and operational S‐band radar observations, Houston Lightning Mapping Array (HLMA) lightning data, and large‐eddy simulations (LESs), this study investigates negative observed above the melting layer as a potential signature of SIP and storm electrification. Among 413 observed deep convective cells, 238 cases (∼57.6%) exhibit negative above the melting layer, and 49 of 123 lightning‐active cases (∼39.8%) show negative near HLMA sources. These observations suggest that negative is associated with small, vertically oriented, electrically aligned ice particles. LESs with spectral bin microphysics reproduce negative with high likelihood only when SIP is included, especially fragmentation of freezing drops, which increases ice water path, decreases liquid water path, and reduces accumulated precipitation by ∼11.2% in the examined case.

An atypical thunderstorm with unusual lightning and charge structure characteristics propagated through Cordoba province, Argentina, during the austral warm season in late 2018. This storm exhibited echo tops near 10.5 km, with high lightning activity concentrated at low altitudes. Storm total flash rate surpassed 120 min ⁻¹ , with peak initiation altitude at 6 km, the inferred altitude interface between a lower positive charge region and an overlying negative region. An in‐depth analysis of kinematics, eddy dissipation rate (EDR), and microphysics was performed to understand what caused intense low‐altitude flash rates, bottom‐heavy charge structure, and few flashes in the upper‐level positive charge region. Environment and synoptic conditions led to the unusually cold troposphere and low freezing level, which influenced storm microphysics and charge structure characteristics. Positive buoyancy was limited to the −20°C isotherm level, and maximum updraft speed varied between 10 and 14 m s ⁻¹ during the period of highest flash rates. Larger volumes of graupel and hail were observed at altitudes associated with the lower positive charge layer. Larger volumes of high EDR fluctuated in altitude following surges in updraft volume, but no clear relation was found for flash initiation and propagation relative to EDR. Infrequent flashes in the upper positive charge layer suggest limited charging of ice crystals at that altitude. Small warm cloud depth and high cloud water content might have played a role in decreasing the charging reversal temperature and enhancing the development of a positive charge layer in the lower mixed‐phase layer.

Secondary ice production (SIP) remains a major uncertainty in understanding deep convection because its rates and controlling conditions are poorly constrained. Using the Tracking Aerosol Convection Interactions Experiment (TRACER) C-band and operational S-band radar observations, Houston Lightning Mapping Array (HLMA) lightning data, and large-eddy simulations (LESs), this study investigates negative K _DP observed above the melting layer as a potential signature of SIP and storm electrification. Among 413 observed deep convective cells, 238 cases (~57.6%) exhibit negative K _DP above the melting layer, and 49 of 123 lightning-active cases (~39.8%) show negative K _DP near HLMA sources. These observations suggest that negative K _DP is associated with small, vertically oriented, electrically aligned ice particles. LESs with spectral bin microphysics reproduce negative K _DP with high likelihood only when SIP is included, especially fragmentation of freezing drops, which increases ice water path, decreases liquid water path, and reduces accumulated precipitation by ~7.6% in the examined case.

Satellites in geostationary orbit provide continuous, hemisphere‐scale views of lightning, but each pixel covers a large area, and parallax and scattering can shift the apparent location of optical emissions. The Geostationary Lightning Mapper (GLM), aboard GOES, is an optical detector that continuously monitors lightning activity over the Western Hemisphere. Hazard mitigation benefits from real‐time lightning locations. Ground‐based networks have well‐characterized spatial characteristics, but space‐based imagers uniquely provide continuous, hemisphere‐scale monitoring. Improving confidence in space‐based lightning geolocation will broaden its use in hazard monitoring and risk assessment. We quantify the offset between GLM lightning locations and those from a ground‐based Lightning Mapping Array in Oklahoma and evaluate how sub‐flash processes are represented in GLM observations. GLM–LMA location differences reflect altitude‐dependent optical propagation, residual parallax, and the representation of moving optical sources by group centroids over finite integration periods. The largest and most variable offsets occur when luminous emitters move rapidly during a GLM integration, and therefore vary systematically with flash type and stage. Additionally, GLM group centroids provide more robust measurements of flash extent than pixel‐based methods, confirming prior work. These findings highlight the diagnostic value of cross‐platform analysis and demonstrate how space‐based lightning detection can improve climatologies, support hazard mitigation and broader atmospheric monitoring, and guide future multi‐wavelength observing systems.

Climate change has caused highly uncertain precipitation regimes and associated hydrometeorological hazards over global drylands. Accurate precipitation measurements are vital for monitoring dryland ecohydrology. Satellite precipitation products (SPPs), including the Integrated Multi‐satellitE Retrievals for GPM (Global Precipitation Measurement) (IMERG‐V07) and the Global Satellite Mapping of Precipitation (GSMaP‐V08), provide quasi‐global coverage but require regional‐scale ground validation to assess errors and reliability, over drylands. We evaluated IMERG‐V07 and GSMaP‐V08 using measurements from 107 West Texas Mesonet (WTM) sites from 2018 to 2022. Precipitation over the semi‐arid WTM domain is concentrated during the May–October wet season. The observed southeast–to‐northwest precipitation gradient (i.e., higher to lower) exists primarily due to dryline‐induced convergence and orographic lifting. At monthly scale, IMERG (GSMaP) overestimates (underestimates), with GSMaP demonstrating greater overall accuracy. SPPs perform best during the peak precipitation months (May, September, and October) and reproduce interannual fluctuations well. The GSMaP performs better on monthly and annual timescales. The mean bootstrap 95% confidence interval for correlation coefficient were [0.759, 0.825] and [0.837, 0.892] for IMERG and GSMaP, respectively. Monthly accumulations of SPPs exhibit intensity dependent biases in high‐intensity precipitation regimes. For near‐real‐time (NRT) detection of extreme precipitation, IMERG‐Early shows higher sensitivity via higher detection but also more false alarms. The GSMaP‐NRT provides balanced event detection, with lower false alarms and higher critical success index in most cases. However, the GSMaP reliability‐flag and IMERG quality‐index were also found to be decisive factors. Results highlight the need for intensity‐ and timescale‐sensitive validation to improve SPP algorithms for advanced precipitation monitoring and forecasting over drylands.

In cumulus clouds, aerosol concentrations control cloud droplet concentrations, modifying cloud radiative properties, precipitation processes, and cloud electrification. However, mechanisms of aerosol-deep convection interactions are not well understood due to complex cloud dynamics and microphysics. We investigate the interaction of aerosols with isolated deep convection using Large Eddy Simulations of two cases during the TRacking Aerosol Convection interactions ExpeRiment (TRACER) near Houston, Texas, using a joint cell-thermal tracking algorithm. Cumulus thermals are droplet generators, since supersaturation and droplet nucleation coincide with thermal centers, where the strongest updrafts occur. Primary ice crystal formation does not take place inside thermals, but at layers where previous thermals detrained moisture. As subsequent thermals containing supercooled droplets penetrate these layers, hail and graupel form at or near these thermals. Higher aerosol concentrations result in higher droplet concentrations that suppress drizzle, delay warm rain processes, and transport more moisture aloft. This increases snow and ice amount, as well as graupel and hail, leading to more lightning. Polluted thermals initiate at slightly higher altitudes, and are slightly larger and faster, suggesting a weak invigoration. We also find more thermals per cell, but fewer isolated cells, since convection is more aggregated and intense, especially near the end of the 24 h simulation. Non-linear mesoscale feedback likely triggered by temperature and moisture responses to aerosol-thermal interactions causes the aggregation. Time-lagged aerosol-reinitialization experiments show that the mesoscale response is the predominant forcing for the invigoration. These changes happen within one day, on a smaller scale than previously suggested.

"Corrigendum" published on 30 Apr 2026 by American Meteorological Society.

In cumulus clouds, aerosol concentrations control cloud droplet concentrations, modifying cloud radiative properties, precipitation processes, and cloud electrification. However, mechanisms of aerosol-deep convection interactions are not well understood due to complex cloud dynamics and microphysics. We investigate the interaction of aerosols with isolated deep convection using Large Eddy Simulations during the TRacking Aerosol Convection interactions ExpeRiment (TRACER) in the Houston area, using a joint cell-thermal tracking algorithm. Cumulus thermals are droplet generators, since supersaturation and droplet nucleation coincide with thermal centers, where the strongest updrafts occur. Primary ice crystal formation does not take place inside thermals, but at layers where previous thermals detrained moisture. As subsequent thermals containing supercooled droplets penetrate these layers, hail and graupel form at or near these thermals. Higher aerosol concentrations result in higher droplet concentrations that suppress drizzle, delay warm rain processes, and transport more moisture aloft. This increases snow and ice amount, as well as graupel and hail, also associated with more lightning. Also, thermals initiate slightly higher, are slightly larger and faster, suggesting a weak invigoration. We also find more thermals per cell, albeit fewer isolated cells. Convection aggregates more, explaining the lower isolated cell count, and enhancing convection, especially near the end of the 24-hour integration. This non-linear mesoscale feedback is likely triggered by temperature and moisture responses due to aerosol-thermal interactions. Additional time-lagged aerosol-reinialization experiments show that the mesoscale response is the predominant forcing for the invigoration. These changes happen within one day, on a smaller scale than previously suggested.

In cumulus clouds, aerosol concentrations control cloud droplet concentrations, modifying cloud radiative properties, precipitation processes, and cloud electrification. However, mechanisms of aerosol-deep convection interactions are not well understood due to complex cloud dynamics and microphysics. We investigate the interaction of aerosols with isolated deep convection using Large Eddy Simulations during the TRacking Aerosol Convection interactions ExpeRiment (TRACER) in the Houston area, using a joint cell-thermal tracking algorithm. Cumulus thermals are droplet generators, since supersaturation and droplet nucleation coincide with thermal centers, where the strongest updrafts occur. Primary ice crystal formation does not take place inside thermals, but at layers where previous thermals detrained moisture. As subsequent thermals containing supercooled droplets penetrate these layers, hail and graupel form at or near these thermals. Higher aerosol concentrations result in higher droplet concentrations that suppress drizzle, delay warm rain processes, and transport more moisture aloft. This increases snow and ice amount, as well as graupel and hail, also associated with more lightning. Also, thermals initiate slightly higher, are slightly larger and faster, suggesting a weak invigoration. We also find more thermals per cell, albeit fewer isolated cells. Convection aggregates more, explaining the lower isolated cell count, and enhancing convection, especially near the end of the 24-hour integration. This non-linear mesoscale feedback is likely triggered by temperature and moisture responses due to aerosol-thermal interactions. Additional time-lagged aerosol-reinialization experiments show that the mesoscale response is the predominant forcing for the invigoration. These changes happen within one day, on a smaller scale than previously suggested.

This study investigates the effects of urbanization, specifically land use change and anthropogenic emissions (AE), on convection, lightning, and surface precipitation for a case of summertime sea‐breeze convection observed over the Houston metropolitan area. The unique capabilities of the NASA‐Unified Weather Research and Forecasting model allows us to conduct a series of sensitivity experiments with complex configurations, in particular including multi‐year land model spin‐up simulations, treatment of aerosols and their precursors, and explicit cloud charging and lightning. The simulation results show that urban land use primarily alters the temporal evolution of convection, lightning, and surface precipitation, leading to late afternoon thunderstorm development. The decrease in latent heat flux from the land surface caused by urbanization weakens convection in the early afternoon, while a condition suitable for convection development is maintained in the late afternoon due to less stabilization of the lower troposphere by the weaker convection development and high sensible heat flux from the surface. On the other hand, anthropogenic aerosols directly enhance convection, lightning, and surface precipitation by increasing convective updrafts due to the aerosol‐induced convective invigoration. The combined effects of urban land use and AE lead to even stronger thunderstorms in the late afternoon, mostly consistent with observations. These results indicate that urbanization increases the probability of late afternoon thunderstorms over the Houston area during the summer season. Advanced weather forecasting models that incorporate these urbanization effects might support sustainable urban planning to better mitigate the impacts of urbanization on local weather and public safety.