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Improving Quantitative Precipitation Estimation in Complex Terrain over the San Francisco Bay Area Using Profiler and Gap-filling Radar Observations

Presented by: Dr. Haonan Chen - Radar, Satellite, and Precipitation Research Scientist with CIRA and Physical Sciences Division of NOAA Earth System Research Laboratory
Date: September 19, 2019 9:30 am
Location: CIRA Director’s Conference Room

The San Francisco Bay Area is covered by two operational S-band WSR-88D: KMUX and KDAX. However, the KDAX radar beams are partially blocked at low elevation angles due to the mountainous terrain, whereas the KMUX radar is deployed at an elevation of over 1000 m, which can easily overshoot precipitation during the winter storm seasons in Northern California. As a result, these two radars are not sufficient to observe low-level atmospheric conditions and provide detailed precipitation information for quantitative hydrometeorological applications. This study aims to improve operational radar rainfall estimates using auxiliary remote sensing observations. In particular, a number of S-band profilers are deployed to investigate the vertical structure of precipitation at various locations in this complex terrain. The representative vertical profiles of reflectivity (VPR) measured by the profilers, which can better characterize the rainfall microphysical structure during its falling processes, are incorporated in WSR-88D radar data processing and the derivation of improved rainfall products. In addition, NOAA and CIRA are building an Advanced Quantitative Precipitation Information (AQPI) system to improve monitoring and forecasting of precipitation and coastal flooding in the San Francisco Bay Area. As part of the AQPI program, high-frequency (i.e., X-band) high-resolution gap-filling radars are being deployed to improve tracking of incoming storms and provide high-resolution coverage over populated and flood-prone urban areas throughout the Bay region. To date, two X-band radars have been deployed and collected a substantial set of precipitation measurements that contribute to the development of local radar rainfall algorithms. This talk will discuss the applications of vertical-pointing profilers and gap-filling scanning radars in enhancing monitoring and quantitative estimation of precipitation over the Bay Area. Results show that rainfall products derived with the aid of additional remote sensing observations have better performance compared to the operational radar products currently available in this particular domain.