Using Radar Observations to Understand Detrainment and Entrainment Processes in Deep Convection

Gretchen L Mullendore, University of North Dakota, Grand Forks, United States, Nicholas Carletta, Science Systems and Applications, Inc., Lanham, MD, United States and Mariusz Starzec, University of North Dakota, Grand Forks, ND, United States

Contact First Author: Gretchen L Mullendore; gretchen@atmos.und.edu

Previously Published Material: A portion of these findings were published in Atmospheric Chemistry and Physics (ACP; Mullendore et al. 2013) in and presented at AGU (Carletta et al., 2013).  However, the findings have been updated with additional observations and analysis.

Abstract ID#: 34400

 

English Abstract:
Deep convective transport can alter the chemical makeup and water vapor balance of the upper troposphere and lower stratosphere (UTLS), which can affect cloud formation and the radiative properties of the atmosphere. It is therefore important to understand the exact altitudes at which mass is detrained from convection. Additionally, the relationship between the level of neutral buoyancy (LNB), as calculated from an environmental profile, and the observed level of maximum detrainment (LMD) gives insight into the amount entrainment that occurs in a particular storm.

Dual-Doppler derived vertical velocities are used to calculate LMD from cases from several field campaigns, including Deep Convective Clouds and Chemistry (DC3). The observed cases were a mix of storm morphologies, including both supercell and multicell storms. As expected, the LMD was generally below the LNB, the mean offset for all cases being over 2 km. However, there was a marked difference between the supercell and non-supercell cases. The supercell cases had LMDs within 0.3 km of the LNB. The variability in the LMD due to storm type has important implications for convective transport, and particularly the amount of mass that is transported directly into the lower stratosphere. This variability is lacking from models with parameterized convection.

Because radar-derived velocities are readily available in most cases, a method for using radar reflectivity alone is also presented. Since hydrometeors are advected by the storm motions, the level of maximum detrainment should be co-located with the level of maximum ice mass. To test this hypothesis, three methods were used to identify convective cores and anvil reflectivity locations. An empirical relationship relating ice mass to reflectivity was used to calculate total anvil mass, and vertical mass distribution plots were validated against dual-Doppler derived vertical mass divergence fields to identify the best method. Based upon this comparison, the best method for locating the LMD was determined to be the method that uses a horizontal reflectivity texture-based technique to determine convective cores and a multi-layer echo identification to determine anvil locations.

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