Aerosol Impacts on Simulated Supercell Thunderstorms in VORTEX2 and VORTEX-SE
Environmental factors are found to strongly affect aerosol impacts on convective thunderstorms. In this study, the storm sensitivity to cloud condensation nuclei (CCN) concentration is explored in five aspects: general storm development, hydrometeor, updraft, precipitation and cold pool from a microphysics point of view. Idealized simulations of the 31 March 2016 and 30 April 2016 cases from the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX)-Southeast (SE) field campaign, and the 5 June 2009 and 9 June 2009 cases from VORTEX2 field campaign are conducted at 6 CCN concentrations (100-3000 cm-3 ) with the Advanced Regional Prediction System (ARPS) model. The triple-moment version of the National Severe Storms Laboratory (NSSL) microphysical scheme is used to predict explicitly hydrometeor mass mixing ratio, number concentration and radar reflectivity factor. A budget analysis is performed to understand the impact of each relevant microphysical process on large ice category production, updraft strength, and cold pool intensity. For the simulated supercells, an increase in CCN concentration leads to increasing mass mixing ratios and decreasing sizes of cloud droplets. The opposite is the case for raindrops, as expected, except for the 5 June 2009 case that exhibits a unique reverse trend of cloud mass mixing ratio below 4 km. The cold pool slightly intensifies or weakens with increasing CCN in the VORTEX-SE cases while largely weakens in the VORTEX2 cases. Generally, the influence is more significant in the VORTEX2 than in the VORTEX-SE cases. Other simulated quantities exhibit different responses to CCN enhancement as a function of the environment. For instance, the mean mass diameter of hailstones peaks at the lowest CCN level in the 30 April 2016 case, at the highest in the 9 June 2009 case and at an intermediate value in the 31 March 2016 case. Updraft strength is monotonically increasing with a reduction of CCN concentration in the Jun 5 2009 case but non-monotonically changing in other cases. The CCN impact on the precipitation rate is also non-monotonic except for the 5 June 2009 case. The 5 June 2009 case is found to exhibit several unique features compared with other cases and is further investigated by running sensitivity simulations using the relative humidity profile, the hodograph or both from the 9 June 2009 case.
Dawson, Purdue University.
Meteorology|Atmospheric sciences|Environmental science
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