Modeling Aerosol Impacts on Convective Storms in Different Environments

Abstract

Aerosols are known to have both direct and indirect effects on clouds through their role as cloud condensation nuclei. This study examines the effects of differing aerosol concentrations on convective storms developing under different environments. The Regional Atmospheric Modeling System (RAMS), a cloud-resolving model with sophisticated microphysical and aerosol parameterization schemes, was used to achieve the goals of this study. A sounding that would produce deep convection was chosen and consistently modified to obtain a variety of CAPE values. Additionally, the model was initiated with varying concentrations of aerosols that were available to act as cloud condensation nuclei. Each model run produced long-lived convective storms with similar storm development, but they differed slightly based on the initial conditions. Runs with higher initial CAPE values produced the strongest storms overall, with stronger updrafts and larger amounts of accumulated surface precipitation. Simulations initiated with larger concentrations of aerosols developed similar storm structures but showed some distinctive dynamical and microphysical changes because of aerosol indirect effects. Many of the changes seen because of varying aerosol concentrations were of either the same order or larger magnitude than those brought about by changing the convective environment.

Observations of aerosol‐induced convective invigoration in the tropical east Atlantic

“…The differences in COG, cloud top, and rain top are all positive; that is, the average is larger for polluted samples. Many of these differences are larger than 500 m. Also quite clear in both Tables 1 and 2 is the fact that the trends and differences are larger when the CAPE is lower, again consistent with previous studies such as Storer et al [2010]. Ice water path is less consistent than the other parameters, in that both positive and negative trends show significance.…”

“…Aerosol-induced increasing trends in COG, cloud top, rain top, and ice water path generally hold for all the CAPE environments. Similar to the results seen in Storer et al [2010], CAPE is the dominating factor when determining these properties, yet the aerosol loading has a notable effect. The trends are generally clearer for low and medium CAPE, which is also in keeping with Storer et al [2010], who noted decreased impacts of aerosols for storms in the most unstable environments.…”

“…Similar to the results seen in Storer et al [2010], CAPE is the dominating factor when determining these properties, yet the aerosol loading has a notable effect. The trends are generally clearer for low and medium CAPE, which is also in keeping with Storer et al [2010], who noted decreased impacts of aerosols for storms in the most unstable environments. While the effects of convective invigoration are still evident for the most favorable storm environments (i.e., those with the highest CAPE), aerosols generally have a more pronounced impact in low CAPE environments that only support weaker storms.…”

“…As previous work has found that aerosol indirect effects can differ depending on environmental parameters such as convective available potential energy (CAPE) [e.g., Storer et al, 2010] and lower tropospheric static stability (LTSS) [e.g., Matsui et al, 2004], it was useful to separate the aerosol trends found here by environmental regimes. Environmental variables were calculated using information from the ECMWF-AUX product, STORER ET AL.…”

“…Based on previous modeling studies [Lynn et al, 2005;Khain et al, 2005;van den Heever et al, 2006van den Heever et al, , 2011Rosenfeld et al, 2008;Storer et al, 2010;Storer and van den Heever, 2013;Fan et al, 2013], we would expect an increase in cloud ice with increased aerosol amounts. However, there is some uncertainty associated with the values of ice water path due to the fact that radar-based retrievals of ice water content are sensitive to the choice of the size and density parameters used [Protat et al, 2009].…”