Impacts of cloud microphysics parameterizations on simulated aerosol–cloud interactions for deep convective clouds over Houston

摘要

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.