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Exceptionally high‐energy lightning strokes >10⁶ J (X1000 stronger than average) in the very low‐frequency band between 5 and 18 kHz, also known as superbolts (SB), occur mostly during winter over the North‐East Atlantic, the Mediterranean Sea, and over the Altiplano in South America. Here we compare the World‐Wide Lightning Location Network database with meteorological and aerosol data to examine the causes of lightning stroke high energies. Our results show that the energy per stroke increases sharply as the distance between the cloud'scharging zone(where the cloud electrification occurs) and the surface decreases. Since thecharging zoneoccurs above the 0°C isotherm, this distance is shorter when the 0°C isotherm is closer to the surface. This occurs either due to cold air mass over the ocean during winter or high surface altitude in the Altiplano during summer thunderstorms. Stroke energy decreases with the warm phase of the cloud, as proxied by the cloud base temperature, and increases with a more developed cloud, as proxied by the cloud top temperature, but to a much lesser extent than the distance between the surface and 0°C isotherm. Aerosols play no significant role. It is hypothesized that a shorter distance between thecharging zoneand the ground represents less electrical resistance that allows stronger discharge currents.

 

The known effects of thermodynamics and aerosols can well explain the thunderstorm activity over land, but fail over oceans. Here, tracking the full lifecycle of tropical deep convective cloud clusters shows that adding fine aerosols significantly increases the lightning density for a given rainfall amount over both ocean and land. In contrast, adding coarse sea salt (dry radius > 1 μm), known as sea spray, weakens the cloud vigor and lightning by producing fewer but larger cloud drops, which accelerate warm rain at the expense of mixed-phase precipitation. Adding coarse sea spray can reduce the lightning by 90% regardless of fine aerosol loading. These findings reconcile long outstanding questions about the differences between continental and marine thunderstorms, and help to understand lightning and underlying aerosol-cloud-precipitation interaction mechanisms and their climatic effects.

 

Abstract. Aerosol–cloud interactions remain largely uncertain with respect to predicting theirimpacts on weather and climate. Cloud microphysics parameterization is oneof the factors leading to large uncertainty. Here, we investigate the impactsof anthropogenic aerosols on the convective intensity and precipitation of athunderstorm occurring on 19 June 2013 over Houston with the Chemistryversion of Weather Research and Forecast model (WRF-Chem) using the Morrisontwo-moment bulk scheme and spectral bin microphysics (SBM) scheme. We findthat the SBM predicts a deep convective cloud that shows better agreement withobservations in terms of reflectivity and precipitation compared with theMorrison bulk scheme that has been used in many weather and climate models.With the SBM scheme, we see a significant invigoration effect on convectiveintensity and precipitation by anthropogenic aerosols, mainly throughenhanced condensation latent heating. Such an effect is absent withthe Morrison two-moment bulk microphysics, mainly because the saturationadjustment approach for droplet condensation and evaporation calculationlimits the enhancement by aerosols in (1) condensation latent heat byremoving the dependence of condensation on droplets and aerosols and (2) ice-related processes because the approach leads to stronger warm rain andweaker ice processes than the explicit supersaturation approach. 

Abstract. Changes in land cover and aerosols resulting from urbanization may impactconvective clouds and precipitation. Here we investigate how Houstonurbanization can modify sea-breeze-induced convective cloud and precipitation through the urban land effect and anthropogenic aerosol effect. The simulations are carried out with the Chemistry version of the WeatherResearch and Forecasting model (WRF-Chem), which is coupled with spectral-bin microphysics (SBM) and the multilayer urban model with abuilding energy model (BEM-BEP). We find that Houston urbanization (thejoint effect of both urban land and anthropogenic aerosols) notably enhancesstorm intensity (by ∼ 75 % in maximum vertical velocity) andprecipitation intensity (up to 45 %), with the anthropogenic aerosoleffect more significant than the urban land effect. Urban land effectmodifies convective evolution: speed up the transition from the warm cloudto mixed-phase cloud, thus initiating surface rain earlier but slowing down the convective cell dissipation, all of which result from urban heating-induced stronger sea-breeze circulation. The anthropogenic aerosol effectbecomes evident after the cloud evolves into the mixed-phase cloud,accelerating the development of storm from the mixed-phase cloud to deepcloud by ∼ 40 min. Through aerosol–cloud interaction (ACI), aerosols boost convective intensity and precipitation mainly by activatingnumerous ultrafine particles at the mixed-phase and deep cloud stages. Thiswork shows the importance of considering both the urban land and anthropogenic aerosol effects for understanding urbanization effects on convective cloudsand precipitation. 

Cloud top radiative cooling rate (CTRC) is the leading term in the energy budget of a marine boundary layer capped by stratocumulus. It plays a significant role in the formation, evolution, and maintenance of the stratocumulus cloud system. This study demonstrates the feasibility of estimating the CTRC, with high accuracy, from passive satellite data only. The estimation relies on a radiative transfer model with inputs from satellite‐retrieved cloud parameters in combination with reanalysis sounding that is revised, in a physically coherent way, by satellite data. The satellite‐based estimates CTRC agree with ground‐based ones to within ~10%. The high accuracy largely benefits from the good capability of satellite data in constraining parameters of most influence to the CTRC such as free‐tropospheric sounding, cloud top temperature, and cloud optical depth. Applying this technique, we generate a climatology of CTRC during summer over the Southern Hemisphere tropical and subtropical oceans.

 

Aerosols have significant and complex impacts on regional climate in East Asia. Cloud‐aerosol‐precipitation interactions (CAPI) remain most challenging in climate studies. The quantitative understanding of CAPI requires good knowledge of aerosols, ranging from their formation, composition, transport, and their radiative, hygroscopic, and microphysical properties. A comprehensive review is presented here centered on the CAPI based chiefly, but not limited to, publications in the special section named EAST‐AIRcpc concerning (1) observations of aerosol loading and properties, (2) relationships between aerosols and meteorological variables affecting CAPI, (3) mechanisms behind CAPI, and (4) quantification of CAPI and their impact on climate. Heavy aerosol loading in East Asia has significant radiative effects by reducing surface radiation, increasing the air temperature, and lowering the boundary layer height. A key factor is aerosol absorption, which is particularly strong in central China. This absorption can have a wide range of impacts such as creating an imbalance of aerosol radiative forcing at the top and bottom of the atmosphere, leading to inconsistent retrievals of cloud variables from space‐borne and ground‐based instruments. Aerosol radiative forcing can delay or suppress the initiation and development of convective clouds whose microphysics can be further altered by the microphysical effect of aerosols. For the same cloud thickness, the likelihood of precipitation is influenced by aerosols: suppressing light rain and enhancing heavy rain, delaying but intensifying thunderstorms, and reducing the onset of isolated showers in most parts of China. Rainfall has become more inhomogeneous and more extreme in the heavily polluted urban regions.