Correction of wind bias for the lidar on board Aeolus using telescope temperatures

<p>The European Space Agency (ESA) Earth Explorer satellite Aeolus provides continuous profiles of the horizontal line-of-sight wind component globally from space. It was successfully launched in August 2018 with the goal to improve numerical weather prediction (NWP). Aeolus data have already...

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Autores principales:	F. Weiler, M. Rennie, T. Kanitz, L. Isaksen, E. Checa, J. de Kloe, N. Okunde, O. Reitebuch
Formato:	article
Lenguaje:	EN
Publicado:	Copernicus Publications 2021
Materias:	Environmental engineering TA170-171 Earthwork. Foundations TA715-787
Acceso en línea:	https://doaj.org/article/e3054c6892474c109eb92fedae1a263a
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spelling	oai:doaj.org-article:e3054c6892474c109eb92fedae1a263a2021-11-17T05:22:14ZCorrection of wind bias for the lidar on board Aeolus using telescope temperatures10.5194/amt-14-7167-20211867-13811867-8548https://doaj.org/article/e3054c6892474c109eb92fedae1a263a2021-11-01T00:00:00Zhttps://amt.copernicus.org/articles/14/7167/2021/amt-14-7167-2021.pdfhttps://doaj.org/toc/1867-1381https://doaj.org/toc/1867-8548<p>The European Space Agency (ESA) Earth Explorer satellite Aeolus provides continuous profiles of the horizontal line-of-sight wind component globally from space. It was successfully launched in August 2018 with the goal to improve numerical weather prediction (NWP). Aeolus data have already been successfully assimilated into several NWP models and have already helped to significantly improve the quality of weather forecasts. To achieve this major milestone the identification and correction of several systematic error sources were necessary. One of them is related to small fluctuations of the temperatures across the 1.5 m diameter primary mirror of the telescope which cause varying wind biases along the orbit of up to 8 m s<span class="inline-formula"><sup>−1</sup></span>. This paper presents a detailed overview of the influence of the telescope temperature variations on the Aeolus wind products and describes the approach to correct for this systematic error source in the operational near-real-time (NRT) processing. It was shown that the telescope temperature variations along the orbit are due to changes in the top-of-atmosphere reflected shortwave and outgoing longwave radiation of the Earth and the related response of the telescope's thermal control system. To correct for this effect ECMWF model-equivalent winds are used as a reference to describe the wind bias in a multiple linear regression model as a function of various temperature sensors located on the primary telescope mirror. This correction scheme has been in operational use at ECMWF since April 2020 and is capable of reducing a large part of the telescope-induced wind bias. In cases where the influence of the temperature variations is particularly strong it was shown that the bias correction can improve the orbital bias variation by up to 53 %. Moreover, it was demonstrated that the approach of using ECMWF model-equivalent winds is justified by the fact that the global bias of model <span class="inline-formula"><i>u</i></span>-component winds with respect to radiosondes is smaller than 0.3 m s<span class="inline-formula"><sup>−1</sup></span>. Furthermore, this paper presents the alternative of using Aeolus ground return winds which serve as a zero-wind reference in the multiple linear regression model. The results show that the approach based on ground return winds only performs 10.8 % worse than the ECMWF model-based approach and thus has a good potential for future applications for upcoming reprocessing campaigns or even in the NRT processing of Aeolus wind products.</p>F. WeilerM. RennieT. KanitzL. IsaksenE. ChecaJ. de KloeN. OkundeO. ReitebuchCopernicus PublicationsarticleEnvironmental engineeringTA170-171Earthwork. FoundationsTA715-787ENAtmospheric Measurement Techniques, Vol 14, Pp 7167-7185 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Environmental engineering TA170-171 Earthwork. Foundations TA715-787
spellingShingle	Environmental engineering TA170-171 Earthwork. Foundations TA715-787 F. Weiler M. Rennie T. Kanitz L. Isaksen E. Checa J. de Kloe N. Okunde O. Reitebuch Correction of wind bias for the lidar on board Aeolus using telescope temperatures
description	<p>The European Space Agency (ESA) Earth Explorer satellite Aeolus provides continuous profiles of the horizontal line-of-sight wind component globally from space. It was successfully launched in August 2018 with the goal to improve numerical weather prediction (NWP). Aeolus data have already been successfully assimilated into several NWP models and have already helped to significantly improve the quality of weather forecasts. To achieve this major milestone the identification and correction of several systematic error sources were necessary. One of them is related to small fluctuations of the temperatures across the 1.5 m diameter primary mirror of the telescope which cause varying wind biases along the orbit of up to 8 m s<span class="inline-formula"><sup>−1</sup></span>. This paper presents a detailed overview of the influence of the telescope temperature variations on the Aeolus wind products and describes the approach to correct for this systematic error source in the operational near-real-time (NRT) processing. It was shown that the telescope temperature variations along the orbit are due to changes in the top-of-atmosphere reflected shortwave and outgoing longwave radiation of the Earth and the related response of the telescope's thermal control system. To correct for this effect ECMWF model-equivalent winds are used as a reference to describe the wind bias in a multiple linear regression model as a function of various temperature sensors located on the primary telescope mirror. This correction scheme has been in operational use at ECMWF since April 2020 and is capable of reducing a large part of the telescope-induced wind bias. In cases where the influence of the temperature variations is particularly strong it was shown that the bias correction can improve the orbital bias variation by up to 53 %. Moreover, it was demonstrated that the approach of using ECMWF model-equivalent winds is justified by the fact that the global bias of model <span class="inline-formula"><i>u</i></span>-component winds with respect to radiosondes is smaller than 0.3 m s<span class="inline-formula"><sup>−1</sup></span>. Furthermore, this paper presents the alternative of using Aeolus ground return winds which serve as a zero-wind reference in the multiple linear regression model. The results show that the approach based on ground return winds only performs 10.8 % worse than the ECMWF model-based approach and thus has a good potential for future applications for upcoming reprocessing campaigns or even in the NRT processing of Aeolus wind products.</p>
format	article
author	F. Weiler M. Rennie T. Kanitz L. Isaksen E. Checa J. de Kloe N. Okunde O. Reitebuch
author_facet	F. Weiler M. Rennie T. Kanitz L. Isaksen E. Checa J. de Kloe N. Okunde O. Reitebuch
author_sort	F. Weiler
title	Correction of wind bias for the lidar on board Aeolus using telescope temperatures
title_short	Correction of wind bias for the lidar on board Aeolus using telescope temperatures
title_full	Correction of wind bias for the lidar on board Aeolus using telescope temperatures
title_fullStr	Correction of wind bias for the lidar on board Aeolus using telescope temperatures
title_full_unstemmed	Correction of wind bias for the lidar on board Aeolus using telescope temperatures
title_sort	correction of wind bias for the lidar on board aeolus using telescope temperatures
publisher	Copernicus Publications
publishDate	2021
url	https://doaj.org/article/e3054c6892474c109eb92fedae1a263a
work_keys_str_mv	AT fweiler correctionofwindbiasforthelidaronboardaeolususingtelescopetemperatures AT mrennie correctionofwindbiasforthelidaronboardaeolususingtelescopetemperatures AT tkanitz correctionofwindbiasforthelidaronboardaeolususingtelescopetemperatures AT lisaksen correctionofwindbiasforthelidaronboardaeolususingtelescopetemperatures AT echeca correctionofwindbiasforthelidaronboardaeolususingtelescopetemperatures AT jdekloe correctionofwindbiasforthelidaronboardaeolususingtelescopetemperatures AT nokunde correctionofwindbiasforthelidaronboardaeolususingtelescopetemperatures AT oreitebuch correctionofwindbiasforthelidaronboardaeolususingtelescopetemperatures
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Correction of wind bias for the lidar on board Aeolus using telescope temperatures

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