Use of polarimetric radar measurements to constrain simulated convective cell evolution: a pilot study with Lagrangian tracking
Authors: Fridlind Ann M. , van Lier-Walqui Marcus , Collis Scott , Giangrande Scott E. , Jackson Robert C. , Li Xiaowen , Matsui Toshihisa , Orville Richard , Picel Mark H. , Rosenfeld Daniel , Ryzhkov Alexander , Weitz Richard , Zhang Pengfei 
Published: June 2019

Abstract. To probe the potential value of a radar-driven field campaign
to constrain simulation of isolated convection subject to a strong aerosol
perturbation, convective cells observed by the operational KHGX weather radar
in the vicinity of Houston, Texas, are examined individually and
statistically. Cells observed in a single case study of onshore flow
conditions during July 2013 are first examined and compared with cells in a
regional model simulation. Observed and simulated cells are objectively
identified and tracked from observed or calculated positive specific
differential phase (KDP) above the melting level, which is
related to the presence of supercooled liquid water. Several observed and
simulated cells are subjectively selected for further examination. Below the
melting level, we compare sequential cross sections of retrieved and
simulated raindrop size distribution parameters. Above the melting level, we
examine time series of KDP and radar differential reflectivity
(ZDR) statistics from observations and calculated from simulated
supercooled rain properties, alongside simulated vertical wind and
supercooled rain mixing ratio statistics. Results indicate that the
operational weather radar measurements offer multiple constraints on the
properties of simulated convective cells, with substantial value added from
derived KDP and retrieved rain properties. The value of
collocated three-dimensional lightning mapping array measurements, which are
relatively rare in the continental US, supports the choice of Houston as a
suitable location for future field studies to improve the simulation and
understanding of convective updraft physics. However, rapid evolution of
cells between routine volume scans motivates consideration of adaptive scan
strategies or radar imaging technologies to amend operational weather radar
capabilities. A 3-year climatology of isolated cell tracks, prepared
using a more efficient algorithm, yields additional relevant information.
Isolated cells are found within the KHGX domain on roughly 40 % of days
year-round, with greatest concentration in the northwest quadrant, but
roughly 5-fold more cells occur during June through September. During this
enhanced occurrence period, the cells initiate following a strong diurnal
cycle that peaks in the early afternoon, typically follow a south-to-north
flow, and dissipate within 1 h, consistent with the case study examples.
Statistics indicate that ∼ 150 isolated cells initiate and dissipate
within 70 km of the KHGX radar during the enhanced occurrence period
annually, and roughly 10 times as many within 200 km, suitable for
multi-instrument Lagrangian observation strategies. In addition to ancillary
meteorological and aerosol measurements, robust vertical wind speed
retrievals would add substantial value to a radar-driven field campaign.