Use of polarimetric radar measurements to constrain simulated convective cell evolution: a pilot study with Lagrangian tracking

Ann M. Fridlind, Marcus van Lier-Walqui, Scott Collis, Scott E. Giangrande, Robert C. Jackson, Xiaowen Li, Toshihisa Matsui, Richard Orville, Mark H. Picel, Daniel Rosenfeld, Alexander Ryzhkov, Richard Weitz (+1 others)
2019 Atmospheric Measurement Techniques  
<p><strong>Abstract.</strong> 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
more » ... ated cells are objectively identified and tracked from observed or calculated positive specific differential phase (<span class="inline-formula"><i>K</i><sub>DP</sub></span>) 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 <span class="inline-formula"><i>K</i><sub>DP</sub></span> and radar differential reflectivity (<span class="inline-formula"><i>Z</i><sub>DR</sub></span>) 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 <span class="inline-formula"><i>K</i><sub>DP</sub></span> 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&amp;thinsp;% 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&amp;thinsp;h, consistent with the case study examples. Statistics indicate that <span class="inline-formula">∼</span>&amp;thinsp;150 isolated cells initiate and dissipate within 70&amp;thinsp;km of the KHGX<span id="page2980"/> radar during the enhanced occurrence period annually, and roughly 10 times as many within 200&amp;thinsp;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.</p>
doi:10.5194/amt-12-2979-2019 fatcat:mv4kr5kt7feethdh66yx2i5voe