Analysis of a parallel stratiform mesoscale convective system during the Midlatitude Continental Convective Clouds Experiment

 
Poster PDF

Authors

Andrea J Skow — University of North Dakota
Michael R. Poellot — University of North Dakota
Zhaoxia Pu — University of Utah
David James Delene — University of North Dakota
Mark Askelson — University of North Dakota

Category

Cloud Properties

Description

The parallel stratiform (PS) mode of mesoscale convective systems (MCSs) has received little research attention compared to the trailing stratiform (TS) and leading stratiform modes. This case study examines the kinematic structure, cold pool effects, and microphysical characteristics of a PS MCS that was sampled during the Midlatitude Continental Convective Clouds Experiment (MC3E) on May 11, 2011.

This system is analyzed using in situ data obtained with the University of North Dakota Citation II Weather Research Aircraft, data obtained using a multitude of ground-based radars, data from a dense balloon sounding network specifically set up for MC3E, and data from the Oklahoma Mesonet. Gamma distributions are fit to 10-second averaged hydrometeor spectra that were collected during level Citation flight legs. Unimodal gamma-distribution parameters (N0, μ, and λ) for the MC3E PS case are compared to TS stratiform regions sampled during the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX). Further investigation of the cold pool is also made through comparing the observations with numerical simulations from mesoscale community Weather Research and Forecasting (WRF) model.

Storm-relative line-parallel and line-perpendicular wind vectors are calculated from radar Doppler velocities. The wind field in the leading portion of the MCS is similar to the wind field from an idealized, simulated PS MCS. In the trailing portion of the MCS, an area of westerly line-perpendicular inflow may signal the presence of a rear-inflow jet, a feature not seen in the simulated PS MCS. The surface cold pool expanded to the north and south beneath the MCS 30 minutes before the MCS transitioned from a PS to a TS mode, which suggests the cold pool was a factor in the transition. A number of similarities in the unimodal gamma-distribution parameters suggest that the microphysical processes experienced by particles sampled in the TS and PS systems were similar. However, there are some differences, such as the frequency of observed bimodal spectra, which are being investigated.