Wojciech W. Grabowski - Invigoration of Deep Convection in Polluted Environments: Myth or Reality?

Event type: 
3 October 2018
2.00 - 3.00 pm

Climate Change Research Centre, Seminar Room, Mathews Building 4th floor, UNSW, Sydney

Dr. Wojciech W. Grabowski
National Center for Atmospheric Research (NCAR), Boulder, USA
Climate Change Research Centre, UNSW

Influence of atmospheric pollution on moist convection continues to be a controversial topic. The prime example is the hypothesized invigoration of deep convection in high CCN environments. Arguably, only appropriately designed numerical simulations can clearly separate impact of aerosols from effects of other factors, such as the atmospheric sounding, magnitude surface fluxes, or effects of larger-scale perturbations (e.g., waves) that all affect moist convection independently of aerosols. Moreover, separating the dynamical impact (i.e., convective invigoration) from purely microphysical effects (e.g., increased upper-tropospheric cloudiness due to higher ice crystal concentrations and thus smaller particle sizes and lower sedimentation rates) is difficult using traditional cloud-scale simulations and virtually impossible in observations. The piggybacking modeling methodology that Wojciech has developed and used in past studies allows clear separation of dynamical and microphysical impacts. This presentation will illustrate misconceptions concerning aerosol effects on deep convection, briefly explain the piggybacking method, and present results from piggybacking simulations of daytime convective development over land. The simulations show that microphysical effects dominate aerosol impacts on deep convection and that dynamical effects play a relatively minor role. In particular, model results question deep convection invigoration in polluted environments.


Brief Biography: Wojciech did a master and PhD at the Institute of Geophysics of the Polish Academy of Science in Warsaw, Poland in 1981 and 1987 respectively. He then moved to the National Center for Atmospheric Research in Boulder, Colorado, as a Postdoctoral Fellow in the Advanced Study Program. Currently, he is a Senior Scientist and section head of the Mesoscale and Microscale Meteorology Division at NCAR working in a range of topics related with geophysical fluid dynamics and cloud physics.