Abstract
Abstract. The US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program's Southern Great Plains (SGP) site includes a heterogeneous distributed scanning Doppler radar network suitable for collecting coordinated Doppler velocity measurements in deep convective clouds. The surrounding National Weather Service (NWS) Next Generation Weather Surveillance Radar 1988 Doppler (NEXRAD WSR-88D) further supplements this network. Radar velocity measurements are assimilated in a three-dimensional variational (3DVAR) algorithm that retrieves horizontal and vertical air motions over a large analysis domain (100 km × 100 km) at storm-scale resolutions (250 m). For the first time, direct evaluation of retrieved vertical air velocities with those from collocated 915 MHz radar wind profilers is performed. Mean absolute and root-mean-square differences between the two sources are of the order of 1 and 2 m s−1, respectively, and time–height correlations are of the order of 0.5. An empirical sensitivity analysis is done to determine a range of 3DVAR constraint weights that adequately satisfy the velocity observations and anelastic mass continuity. It is shown that the vertical velocity spread over this range is of the order of 1 m s−1. The 3DVAR retrievals are also compared to those obtained from an iterative upwards integration technique. The results suggest that the 3DVAR technique provides a robust, stable solution for cases in which integration techniques have difficulty satisfying velocity observations and mass continuity simultaneously.
Highlights
The representation of deep convection at cloud-resolving and global climate model scales (CRMs and GCMs) remains a serious challenge (Lin et al, 2006; Jakob, 2010)
The environmental background wind fields are obtained from the Atmospheric Radiation Measurement (ARM) Merged Sounding value-added product that combines the observations from radiosonde soundings at the Southern Great Plains (SGP) Central Facility (CF), microwave radiometers, surface meteorological instruments, and European Centre for Medium Range Weather Forecasts (ECMWF) model output to produce a dataset at 1 min intervals and at 266 altitude levels (ARM, 1996)
This study addresses the utilization of the ARM SGP scanning radar network in retrieving robust air motion estimates in five deep convective cloud events observed during MC3E, with the inclusion of surrounding NEXRAD WSR-88D assets
Summary
The representation of deep convection at cloud-resolving and global climate model scales (CRMs and GCMs) remains a serious challenge (Lin et al, 2006; Jakob, 2010). During the Midlatitude Continental Convective Clouds Experiment (MC3E), a joint field campaign between the DOE ARM program and the National Aeronautics and Space Administration (NASA) Global Precipitation Measurement (GPM) mission Ground Validation (GV) program (Jensen et al, 2016), the SGP site collected unique datasets from a distributed scanning Doppler radar network and radar wind profilers (RWPs) for several deep convective systems. These 3-D wind fields are strongly desired to analyze structures and characteristics of convective events (e.g., Liu et al, 2015; Donner et al, 2016).
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