A Summary of Convective Cloud Updrafts Observed during the MC3E by the ARM SGP Precipitation Radar Network

English Abstract:

Our understanding of convective clouds and their associated updrafts is vital to the progress and improvement of numerical weather and climate models. To this date, cloud resolving models (CRMs), which have recently been used as a benchmark for global circulation models (GCMs), are known to have nontrivial issues with their treatment of convection, including the significant overestimation of updraft strength in the upper 7-15 km of the atmosphere. However, there is a noticeable measurement gap in convective cloud observations, in particular the vertical air motion of these systems. Historically, in situ aircraft and profiling radars have been regarded as the most robust observational data sets for convective clouds, but these data sets offer only a limited footprint of the convective system being sampled. The U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) Program’s network of scanning Doppler precipitation radars at its Southern Great Plains (SGP) site can help bridge this measurement gap by providing coordinated, high resolution radial velocity observations of convective clouds over a large area (e.g., 10,000 km²). A 3D variational (3D-VAR) algorithm is then used to estimate the 3D wind field through the minimization of a cost function defined by these radial velocity observations, mass continuity, and other a priori constraints. Using a data set covering roughly 15 hours worth of observations from the Midlatitude Continental Convective Clouds Experiment (MC3E), we map individual convective updraft cores in three dimensions and document important properties such as their depth, projected area, volume, aspect ratio, and mass flux. This type of analysis can be reproduced on numerical model output, the results of which can be compared with their observational targets as a means to provide further constraints on convective parameterization schemes.