Controls and interrelationships between the convective components of simulated and observed mid-latitude deep convection

 

Category

Convective clouds, including aerosol interactions

Authors

Robert Jeff Trapp — University of Illinois at Urbana-Champaign Paloma Borque — Pacific Northwest National Laboratory
Sonia Lasher-Trapp — University of Illinois at Urbana-Champaign Holly Mallinson — University of Illinois at Urbana-Champaign
Steve Nesbitt — University of Illinois at Urbana-Champaign Bryan Engelsen — University of Illinois at Urbana-Champaign
Geoff Marion — UIUC

Description

A fundamental yet outstanding question about deep cumulus convection regards how convective-storm updrafts, downdrafts, and cold pools are interrelated, and how these three convective components are modulated by external and internal factors. The particular foci of this research are environmental and microphysical factors. Our primary research tool is CM1, a non-hydrostatic, fully compressible, 3D cloud-resolving model. Our use of CM1 is supplemented by observations collected during Mid-latitude Continental Convective Clouds Experiment (MC3E). A series of idealized simulations have been conducted using environments described by an analytic sounding as well as by a pre-convective sounding collected on 23 May, 2011 during MC3E. Both environments support supercellular convection, which is our convective mode of choice here because it possesses definitive convective components. We find that environmental vertical wind shear exerts significant control on updraft width, especially when the shear is characterized by a curved hodograph; our analyses of linear and nonlinear dynamic pressure forcing readily explain this control. The nearly linear and monotonic increase of updraft width with hodograph radius is accompanied by a corresponding increase in downdraft width, and, within the limitations of grid resolution, increases in cold-pool depth. We additionally find that cold-pool intensity is highly sensitive to the representation of microphysical processes, and are currently determining whether/how this sensitivity applies to the other convective components. Finally, our analysis of the MC3E radar kinematic and dual-polarization retrievals, profiler vertical velocity, and cold-pool depth information, and mesonet data, as well as coincident geostationary satellite-derived overshooting tops, is providing us the means to evaluate the veracity of the simulated interrelationships and further explore the controls. As we have noted previously, these results have important implications on convective parameterization schemes, which tend not to account for the effects of vertical wind shear on convective organization, intensity, and duration.