Date of Award
Doctor of Philosophy (PhD)
Walter A. Petersen
Lawrence D. Carey
John R. Mecikalski
Radar meteorology., Precipitation (Meteorology)--Measurement., Rain and rainfall--Measurement., Polarimetry.
The accurate measurement of precipitation is vital to efficiently manage our water resources. Although dual-polarimetric radar technology has greatly improved radar rainfall estimation, there exist inherent sampling factors and uncertainties that must be addressed. One key factor is the height of the radar beam as it samples precipitation. Typically radar beam heights and associated pulse measurement volumes used to estimate rainfall at the ground, increase with distance from the radar and thus may not be representative of the amount of rainfall impacting the ground. The main goal of this study was to determine the effect of the vertical profile of polarimetric parameters (VP3), a radar manifestation of the evolving size and shape of hydrometeors as they fall to the ground, on dual-polarimetric rainfall estimation. Using dual-polarimetric radar and disdrometers, the physical characteristics of the VP3 were extracted and examined. We found that the characteristic size of raindrops (Dm) reaching the ground in stratiform precipitation often varies linearly with the depth of the melting layer. As a result, a radar rainfall estimator was formulated using Dm that can be used by dual-polarimetric as well as dual-frequency radars (e.g., space-based radars such as the GPM Dual-Frequency Precipitation Radar), to lower the bias and uncertainty of conventional single radar parameter rainfall estimates by as much as 20%. We also characterized the VP3 using high-resolution radar scans to reveal that the profile of ZDR in stratiform rainfall can bias dual-polarimetric rainfall estimators by as much as 50%, even after correction for the vertical profile of reflectivity (VPR). The VP3 correction technique that we developed can improve operational dual-polarimetric rainfall estimates by 13% beyond that offered by a VPR correction alone.
Gatlin, Patrick N., "Vertical variability of the raindrop size distribution and its effects on decal-polarimetric radar quantitative precipitation estimation" (2015). Dissertations. 62.