Convective Meteorology (Mesoscale Dynamics)

Investigation of Early Echoes: Pieces of the Spin-up Problem Puzzle

Jacob Carlin

School of Meteorology

29 January 2016, 3:00 PM

National Weather Center, Room 5600
120 David L. Boren Blvd.
University of Oklahoma
Norman, OK

The beginning stages of convection are of interest not only for understanding storm dynamics and microphysics, but also because of its potential help in alleviating the spin-up problem in modeled convection. Given that radar is a primary tool for addressing this issue, it is worthwhile to investigate characteristics of these early echoes to better understand the information they contain and how to best make use of it.

The first part of this presentation investigates the impact of cloud condensation nuclei (CCN) concentration and low-level moisture on the polarimetric characteristics of early echoes in developing storms. The Hebrew University Cloud Model (HUCM), coupled to a polarimetric radar operator, is used to simulate clean (CCNsfc = 100 cm-3) and polluted (CCNsfc = 3000 cm-3) convection for relatively moist and dry boundary layers. Consistent with past studies, the preliminary results found that higher CCN results in generally stronger storms with higher first echo heights and more rapid development. Low-level moisture also impacts the early echo characteristics more for low CCN concentrations. Additionally, an early signature of anomalously high ZDR was able to be reproduced for higher CCN concentrations and warrants further investigation.

The second part of this presentation addresses the potential for dual-polarization radar data to aid in reducing storm spin-up. HUCM simulations show good correlation between ZDR-columns and areas of saturation in modeled storms. A simple method of indirectly assimilating ZDR to enhance the qv field is explored using the Advanced Regional Prediction System for the 19 May 2013 Central Oklahoma tornadoes. Preliminary results of simple cycling trials will be presented.

Convective Meteorology (Mesoscale Dynamics) Seminar Series website