Ms. Ting-Chen Chen

Ph.D. candidate, Atmospheric and Oceanic Sciences McGill University, Montreal, Canada

Slantwise convection, the process of releasing conditional symmetric instability, is often found to be associated with banded precipitation in strong baroclinic environments, especially in the frontal areas within cyclones. However, its potential impact on climate has received less attention.The first part of this talk presents our recent climatological study based on the ECMWF reanalysis data to assess the likelihood of occurrence of slantwise convection around the globe. A high association is also found between the slantwise convective available potential energy (slantwiseCAPE) release and the explosive development of cyclones.Since most commonly-employed cumulus parameterization schemes do not consider slantwise ascent, it is unclear whether mesoscale slantwise convection can be adequately resolved in global/climate models. As a first step toward addressing this issue, the second part of the talk investigates the sensitivities of simulated slantwise convection to the model grid-spacing under idealized framework. A two-dimensional, non-hydrostatic Weather Research and ForecastingModel is used at horizontal grid sizes ranging from 1 to 40 km. By applying an accurate inline budget retrieval method to the model analysis, we uncover new aspects of the slantwise convective dynamics and show that the non-hydrostatic pressure-perturbation field plays a significant role in the cloud evolution. Such perturbations can only be adequately resolved at grid lengths of 5 km or less. Thus, important characteristics of slantwise convection may be poorly resolved in most modern climate models.