Convection Invigoration by Aerosols: A Perspective from Updraft Core Statistics

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Tuesday, 4 February 2014: 4:30 PM
Room C207 (The Georgia World Congress Center )
Xiaowen Li, Morgan State University, Greenbelt, MD; and W. K. Tao

There have been many metrics used to measure convection invigoration by aerosols. For example, rainfall frequencies, rainfall amount, cloud top temperature/cloud top height, lightening rate, cloud ice content, updraft velocity, and convection percentages are some of the variables used to gauge convection invigorations. This presentation investigates impact of aerosol concentration on convective updraft core structures. In order to do this, we use a cloud-resolving model (Goddard Cumulus Ensemble Model) with a detailed spectral bin microphysical scheme (Hebrew University Cloud Microphysics Scheme) to simulate tropical convection during DOE's TWP-ICE field campaign. The large-scale forcing, thus the water and energy budget within the model domain, are fixed for all simulations. So is the total surface rainfall. The control simulation uses the observed mean aerosol concentration during the field campaign. In addition, a low aerosol scenario (half of the control run) and a high aerosol scenario (x10 of the control run) are carried out to study the sensitivity of updraft core statistics. With such highly constrained model setup, we ask the question: Is there signs of convection invigoration with the increasing aerosol number concentration? We found that the answer is yes. In this case, the convection invigoration manifests itself mainly in updraft core statistics. Although the mean updraft core statistics are similar, the strongest cores become more frequent as aerosol concentration increases. The locations of the maximum updraft move upward, too. These highly constrained simulations will also be compared with an open-boundary simulation (a TOGA COARE case) where the microphysics and storm dynamics interact freely, and convection invigoration manifest itself in all the metrics.