Fixed echo rejection in sodar using non-coherent matched filter detection and Gaussian mixture model based post-processing

Kendrick, P; von Hünerbein, S

Abstract

Doppler sodar (SOund Detection and Ranging) is a technology used for acoustic based remote sensing of the lower planetary boundary layer. Sodars are often used to measure wind profiles however, they suffer from problems due to noise (both acoustic and electrical) and echoes from fixed objects, which can bias radial velocity estimates.


An experimental bi-static sodar was developed with 64 independent channels. The device enables flexible beam forming; beams can be tilted at the same angle irrelevant of frequency, a limitation in most commercial devices.


This paper presents an alternative sodar signal processing algorithm for wind profiling using a multi-frequency stepped-chirp pulse. A non-coherent matched filter was used to analyse returned signals. The non-coherent matched filter combines radial velocity estimates from multiple frequencies into a single optimisation.

To identify and separate sources of backscatter, noise and fixed echoes, a stochastic pattern recognition technique, Gaussian Mixture Modelling, was used to post-process the non-coherent matched filter data. This allowed the identification and separation of different stochastic processes. After identification, noise and fixed echo components were removed a clean wind profile produced. This technique was compared with traditional spectrum-based radial velocity estimation methods and demonstrated an improvement in the rejection of fixed echo components; this is one of the major limitations of sodar performance when located in complex terrain and urban environments.

• Journal Article Type: Article
• Acceptance Date: Oct 12, 2018
• Online Publication Date: Oct 26, 2018
• Publication Date: Jan 1, 2019
• Deposit Date: Nov 16, 2018
• Publicly Available Date: Oct 26, 2019
• Journal: Journal of Atmospheric and Oceanic Technology
• Print ISSN: 0739-0572
• Electronic ISSN: 1520-0426
• Publisher: American Meteorological Society
• Volume: 36
• Issue: 1
• Pages: 3-16
• DOI: https://doi.org/10.1175/jtech-d-18-0095.1
• Publisher URL: https://doi.org/10.1175/jtech-d-18-0095.1
• Related Public URLs: https://journals.ametsoc.org/toc/atot/current
• Additional Information: Access Information : © Copyright 2019 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. All AMS journals and monograph publications are registered with the Copyright Clearance Center (http://www.copyright.com). Questions about permission to use materials for which AMS holds the copyright can also be directed to [e-mail]. Additional details are provided in the AMS Copyright Policy statement, available on the AMS website (http://www.ametsoc.org/CopyrightInformation).