Abstract
Abstract. Hurricane Matthew (2016) was observed by the ground-based polarimetric Next Generation Weather Radar (NEXRAD) in Miami (KAMX) and the National Oceanic and Atmospheric Administration WP-3D (NOAA P-3) airborne tail Doppler radar near the coast of the southeastern United States for several hours, providing a novel opportunity to evaluate and compare single- and multiple-Doppler wind retrieval techniques for tropical cyclone flows. The generalized velocity track display (GVTD) technique can retrieve a subset of the wind field from a single ground-based Doppler radar under the assumption of nearly axisymmetric rotational wind, but it has been shown to have errors from the aliasing of unresolved wind components. An improved technique that mitigates errors due to storm motion is derived in this study, although some spatial aliasing remains due to limited information content from the single-Doppler measurements. A spline-based variational wind retrieval technique called SAMURAI can retrieve the full three-dimensional wind field from airborne radar fore–aft pseudo-dual-Doppler scanning, but it has been shown to have errors due to temporal aliasing from the nonsimultaneous Doppler measurements. A comparison between the two techniques shows that the axisymmetric tangential winds are generally comparable between the two techniques, and the improved GVTD technique improves the accuracy of the retrieval. Fourier decomposition of asymmetric kinematic and convective structure shows more discrepancies due to spatial and temporal aliasing in the retrievals. The strengths and weaknesses of each technique for studying tropical cyclone structure are discussed and suggest that complementary information can be retrieved from both single- and dual-Doppler retrievals. Future improvements to the asymmetric flow assumptions in single-Doppler analysis and steady-state assumptions in pseudo-dual-Doppler analysis are required to reconcile differences in retrieved tropical cyclone structure.
Highlights
Doppler radar can provide high-resolution wind measurements within tropical cyclones (TCs), but the measurement is limited to the projection of the wind along the radial direction of the radar beam
The dual-Doppler analyses from the four aircraft passes into Hurricane Matthew are optimal for evaluating the performance of the generalized velocity track display (GVTD) technique because we can obtain all coefficients (Eqs. 16 to 20) from the Fourier decomposition of VT and VR, known storm motion, and mean wind components, which ensures the comparability of the wind field
Jou et al (2008) has shown that the GVTD technique improves the capability of the ground-based velocity track display (GBVTD) and can retrieve a subset of the wind field from a single ground-based Doppler radar under the assumption of nearly axisymmetric rotational wind
Summary
Doppler radar can provide high-resolution wind measurements within tropical cyclones (TCs), but the measurement is limited to the projection of the wind along the radial direction of the radar beam. Doppler observations simultaneously sampling Hurricane Matthew (2016) are analyzed to provide the first comprehensive comparison between ground-based single-Doppler and airborne multi-Doppler wind retrieval techniques in a TC. In Lee et al (1994), the velocity track display (VTD) technique was proposed to retrieve the TC kinematic structure from a single airborne Doppler radar. The GVTD formulation can be applied to the extensions of the velocity track display (VTD) techniques (e.g., GBVTD-simplex, Lee and Marks, 2000) to improve their performance It expands the capability of using ground-based Doppler radar data in TC forecasts but provides researchers with an opportunity to examine TC kinematic and some derived dynamic variables in detail (such as vertical velocity, angular momentum, and vertical vorticity).
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