一种新型的光流多普勒展开技术

IF 1.9 4区 地球科学 Q2 ENGINEERING, OCEAN
A. Protat, V. Louf, M. Curtis
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引用次数: 0

摘要

多普勒雷达测量[-VN,VN]范围内的多普勒速度,其中VN是奈奎斯特速度。该范围之外的多普勒速度在该区间内“折叠”。所有多普勒“展开”技术都使用折叠速度本身。在这项工作中,我们研究了将光流技术导出的速度应用于雷达反射率场的潜力。使用六个月的多多普勒风反演对风速误差的分析表明,99.9%的所有点的特征是在5公里高度以下的误差小于26 ms-1,如果使用光流风来展开VN=26 ms-1的多普勒速度,则故障率小于0.01%。这些误差在5km高度以上大幅增加,表明应包括垂直连续性测试,以降低高海拔地区的故障率。根据这些结果,我们开发了两步光学流展开(TOFU)技术,其具体目标是准确展开VN=26ms-1的多普勒速度。TOFU性能通过具有挑战性的案例研究进行评估,与使用更高奈奎斯特速度的先进多普勒展开技术进行比较,6个月的高VN(47.2ms-1)数据被人工折叠到26ms-1。TOFU失败率非常低。造成这些错误的主要有三种情况:高水平风切变、与大风相关的云层升高以及雷达数据伪影。我们的建议是将这些展开的风作为先进多普勒展开技术的第一步。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
A Novel Doppler Unfolding Technique Using Optical Flow
Doppler radars measure Doppler velocity within the [-VN, VN] range, where VN is the Nyquist velocity. Doppler velocities outside of this range are “folded” within this interval. All Doppler “unfolding” techniques use the folded velocities themselves. In this work, we investigate the potential of using velocities derived from optical flow techniques applied to the radar reflectivity field for that purpose. The analysis of wind speed errors using six months of multi-Doppler wind retrievals showed that 99.9% of all points are characterized by errors smaller than 26 ms-1 below 5 km height, corresponding to a failure rate of less than 0.01% if optical flow winds were used to unfold Doppler velocities for VN = 26 ms-1. These errors largely increase above 5 km height, indicating that vertical continuity tests should be included to reduce failure rates at higher elevations. Following these results, we have developed the Two-step Optical Flow Unfolding (TOFU) technique, with the specific objective to accurately unfold Doppler velocities with VN = 26 ms-1. The TOFU performance was assessed using challenging case studies, comparisons with an advanced Doppler unfolding technique using higher Nyquist velocities, and six months of high VN (47.2 ms-1) data artificially folded to 26 ms-1. TOFU failure rates were found to be very low. Three main situations contributed to these errors: high low-level wind shear, elevated cloud layers associated with high winds, and radar data artefacts. Our recommendation is to use these unfolded winds as the first step of advanced Doppler unfolding techniques.
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来源期刊
CiteScore
4.50
自引率
9.10%
发文量
135
审稿时长
3 months
期刊介绍: The Journal of Atmospheric and Oceanic Technology (JTECH) publishes research describing instrumentation and methods used in atmospheric and oceanic research, including remote sensing instruments; measurements, validation, and data analysis techniques from satellites, aircraft, balloons, and surface-based platforms; in situ instruments, measurements, and methods for data acquisition, analysis, and interpretation and assimilation in numerical models; and information systems and algorithms.
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