Updraft and Downdraft Core Size and Intensity as Revealed by Radar Wind Profilers: MCS Observations and Idealized Model Comparisons

Abstract

This study explores the updraft and downdraft properties of mature stage mesoscale convective systems (MCSs) in terms of draft core width, shape, intensity, and mass flux characteristics. The observations use extended radar wind profiler (RWP) and surveillance radar data sets from the U.S. Department of Energy Atmospheric Radiation Measurement program for midlatitude (Oklahoma, USA) and tropical (Amazon, Brazil) sites. MCS drafts behave qualitatively similar to previous aircraft and RWP cloud summaries. The Oklahoma MCSs indicate larger and more intense convective updraft and downdraft cores, and greater mass flux than Amazon MCS counterparts. However, similar size‐intensity relationships and draft vertical profile behaviors are observed for both regions. Additional similarities include weak positive correlations between core intensity and core width (correlation coefficient r ∼ 0.5) and increases in draft intensity with altitude. A model‐observational intercomparison for draft properties (core width, intensity, and mass flux) is also performed to illustrate the potential usefulness of statistical observed draft characterizations. Idealized simulations with the Weather Research and Forecasting model aligned with midlatitude MCS conditions are performed at model grid spacings (△x) that range from 4 km to 250 m. It is shown that the simulations performed at △x = 250 m at similar mature MCS lifecycle stages are those that exhibit draft intensity, width, mass flux, and shape parameter performances best matching with observed properties.

A Satellite‐Based Estimate of Convective Vertical Velocity and Convective Mass Flux: Global Survey and Comparison With Radar Wind Profiler Observations

“…Both RWP observations and satellite estimates show that w c generally increases with height, a feature that is commonly observed in DCCs (Giangrande et al, 2016;Heymsfield et al, 2010;Kumar et al, 2015;D. Wang et al, 2019D. Wang et al, , 2020.…”

“…Figure 2a shows the summary comparisons of w c profiles in terms of the updraft median and 95th percentile properties. Both RWP observations and satellite estimates show that w c generally increases with height, a feature that is commonly observed in DCCs (Giangrande et al., 2016; Heymsfield et al., 2010; Kumar et al., 2015; D. Wang et al., 2019, 2020). This is in line with the expectation that buoyancy acceleration within convective updraft is usually positive until air parcel overshoots which usually occurs at high altitudes near cloud top (Z. J. Luo et al., 2010; Takahashi & Luo, 2012; Takahashi et al., 2017).…”

“…Note, median w c values are slightly larger for satellite estimates than RWP values. This difference may be attributed to different sampling strategies as to defining “core” regions: the RWP vertical velocity profiles include contributions from intense convective updraft cores and the periphery DCC regions, provided that the measured vertical velocity exceeds 1.5 ms −1 (Giangrande et al., 2016; D. Wang et al., 2020). However, the ML16 method is designed to characterize the vertical velocity of only the well‐defined and active updrafts captured by CloudSat CPR.…”

“…In a similar fashion, ground-based (multi-) Doppler radars and wind profilers have been exploited using various methodologies to estimate convective vertical velocities remotely (Giangrande et al, 2013(Giangrande et al, , 2016Kumar et al, 2015;May & Rajopadhyaya, 1999;North et al, 2017;D. Wang et al, 2019D. Wang et al, , 2020Williams, 2012).…”

Challenges and outlook for convection-permitting climate modelling

“…Firstly, heavy rainfall tends to be too intense, which has been found consistently across studies using different CPMs and for different regions [2,32]. This deficiency is due to convection not being fully resolved at kilometre-scales, with updrafts being too deep and too wide with insufficient mixing [65][66][67][68]. Some groups have used a parametrization of shallow convection to try and improve the representation of small showers, only switching off the parametrization of deep convection.…”