Characterizing Buoy Wind Speed Error in High Winds and Varying Sea State with ASCAT and ERA5

Buoys provide key observations of wind speed over the ocean and are routinely used as a source of validation data for satellite wind products. However, the movement of buoys in high seas and the airflow over waves might cause inaccurate readings, raising concern when buoys are used as a source of wi...

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Autores principales:	Ethan E. Wright, Mark A. Bourassa, Ad Stoffelen, Jean-Raymond Bidlot
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	buoys calibration scatterometers waves sea state Science Q
Acceso en línea:	https://doaj.org/article/1a77aebfcfe94fddaf288b5d36fac8c5
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spelling	oai:doaj.org-article:1a77aebfcfe94fddaf288b5d36fac8c52021-11-25T18:54:13ZCharacterizing Buoy Wind Speed Error in High Winds and Varying Sea State with ASCAT and ERA510.3390/rs132245582072-4292https://doaj.org/article/1a77aebfcfe94fddaf288b5d36fac8c52021-11-01T00:00:00Zhttps://www.mdpi.com/2072-4292/13/22/4558https://doaj.org/toc/2072-4292Buoys provide key observations of wind speed over the ocean and are routinely used as a source of validation data for satellite wind products. However, the movement of buoys in high seas and the airflow over waves might cause inaccurate readings, raising concern when buoys are used as a source of wind speed comparison data. The relative accuracy of buoy winds is quantified through a triple collocation (TC) exercise comparing buoy winds to winds from ASCAT and ERA5. Differences between calibrated buoy winds and ASCAT are analyzed through separating the residuals by anemometer height and testing under high wind-wave and swell conditions. First, we converted buoy winds measured near 3, 4, and 5 m to stress-equivalent winds at 10 m (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>U</mi><mrow><mn>10</mn><mi>S</mi></mrow></msub></mrow></semantics></math></inline-formula>). Buoy <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>U</mi><mrow><mn>10</mn><mi>S</mi></mrow></msub></mrow></semantics></math></inline-formula> from anemometers near 3 m compared notably lower than buoy <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>U</mi><mrow><mn>10</mn><mi>S</mi></mrow></msub></mrow></semantics></math></inline-formula> from anemometers near 4 and 5 m, illustrating the importance of buoy choice in comparisons with remote sensing data. Using TC calibration of buoy <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>U</mi><mrow><mn>10</mn><mi>S</mi></mrow></msub></mrow></semantics></math></inline-formula> to ASCAT in pure wind-wave conditions, we found that there was a small, but statistically significant difference between height adjusted buoy winds from buoys with 4 and 5 m anemometers compared to the same ASCAT wind speed ranges in high seas. However, this result does not follow conventional arguments for wave sheltering of buoy winds, whereby the lower anemometer height winds are distorted more than the higher anemometer height winds in high winds and high seas. We concluded that wave sheltering is not significantly affecting the winds from buoys between 4 and 5 m with high confidence for winds under 18 ms<sup>−1</sup>. Further differences between buoy <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>U</mi><mrow><mn>10</mn><mi>S</mi></mrow></msub></mrow></semantics></math></inline-formula> and ASCAT winds are observed in high swell conditions, motivating the need to consider the possible effects of sea state on ASCAT winds.Ethan E. WrightMark A. BourassaAd StoffelenJean-Raymond BidlotMDPI AGarticlebuoyscalibrationscatterometerswavesseastateScienceQENRemote Sensing, Vol 13, Iss 4558, p 4558 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	buoys calibration scatterometers waves sea state Science Q
spellingShingle	buoys calibration scatterometers waves sea state Science Q Ethan E. Wright Mark A. Bourassa Ad Stoffelen Jean-Raymond Bidlot Characterizing Buoy Wind Speed Error in High Winds and Varying Sea State with ASCAT and ERA5
description	Buoys provide key observations of wind speed over the ocean and are routinely used as a source of validation data for satellite wind products. However, the movement of buoys in high seas and the airflow over waves might cause inaccurate readings, raising concern when buoys are used as a source of wind speed comparison data. The relative accuracy of buoy winds is quantified through a triple collocation (TC) exercise comparing buoy winds to winds from ASCAT and ERA5. Differences between calibrated buoy winds and ASCAT are analyzed through separating the residuals by anemometer height and testing under high wind-wave and swell conditions. First, we converted buoy winds measured near 3, 4, and 5 m to stress-equivalent winds at 10 m (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>U</mi><mrow><mn>10</mn><mi>S</mi></mrow></msub></mrow></semantics></math></inline-formula>). Buoy <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>U</mi><mrow><mn>10</mn><mi>S</mi></mrow></msub></mrow></semantics></math></inline-formula> from anemometers near 3 m compared notably lower than buoy <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>U</mi><mrow><mn>10</mn><mi>S</mi></mrow></msub></mrow></semantics></math></inline-formula> from anemometers near 4 and 5 m, illustrating the importance of buoy choice in comparisons with remote sensing data. Using TC calibration of buoy <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>U</mi><mrow><mn>10</mn><mi>S</mi></mrow></msub></mrow></semantics></math></inline-formula> to ASCAT in pure wind-wave conditions, we found that there was a small, but statistically significant difference between height adjusted buoy winds from buoys with 4 and 5 m anemometers compared to the same ASCAT wind speed ranges in high seas. However, this result does not follow conventional arguments for wave sheltering of buoy winds, whereby the lower anemometer height winds are distorted more than the higher anemometer height winds in high winds and high seas. We concluded that wave sheltering is not significantly affecting the winds from buoys between 4 and 5 m with high confidence for winds under 18 ms<sup>−1</sup>. Further differences between buoy <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>U</mi><mrow><mn>10</mn><mi>S</mi></mrow></msub></mrow></semantics></math></inline-formula> and ASCAT winds are observed in high swell conditions, motivating the need to consider the possible effects of sea state on ASCAT winds.
format	article
author	Ethan E. Wright Mark A. Bourassa Ad Stoffelen Jean-Raymond Bidlot
author_facet	Ethan E. Wright Mark A. Bourassa Ad Stoffelen Jean-Raymond Bidlot
author_sort	Ethan E. Wright
title	Characterizing Buoy Wind Speed Error in High Winds and Varying Sea State with ASCAT and ERA5
title_short	Characterizing Buoy Wind Speed Error in High Winds and Varying Sea State with ASCAT and ERA5
title_full	Characterizing Buoy Wind Speed Error in High Winds and Varying Sea State with ASCAT and ERA5
title_fullStr	Characterizing Buoy Wind Speed Error in High Winds and Varying Sea State with ASCAT and ERA5
title_full_unstemmed	Characterizing Buoy Wind Speed Error in High Winds and Varying Sea State with ASCAT and ERA5
title_sort	characterizing buoy wind speed error in high winds and varying sea state with ascat and era5
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/1a77aebfcfe94fddaf288b5d36fac8c5
work_keys_str_mv	AT ethanewright characterizingbuoywindspeederrorinhighwindsandvaryingseastatewithascatandera5 AT markabourassa characterizingbuoywindspeederrorinhighwindsandvaryingseastatewithascatandera5 AT adstoffelen characterizingbuoywindspeederrorinhighwindsandvaryingseastatewithascatandera5 AT jeanraymondbidlot characterizingbuoywindspeederrorinhighwindsandvaryingseastatewithascatandera5
_version_	1718410573486489600

Characterizing Buoy Wind Speed Error in High Winds and Varying Sea State with ASCAT and ERA5

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