Sensitivity of Aeolus HLOS winds to temperature and pressure specification in the L2B processor

Šavli, Matic; Pourret, Vivien; Payan, Christophe; Mahfouf, Jean‐François

doi:10.5194/amt-14-4721-2021

Cited by 7 publications

(10 citation statements)

References 22 publications

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“…However, only a few instruments measure this part of the atmosphere. Since 2018, the satellite Aeolus has been providing wind measurements up to 30 km that have demonstrated in the stratosphere their usefulness for model analyses [51]. Similar data should be added as infra-sound measurements deployed with the ARISE network [19] to complete the wind field representation at higher altitudes.…”

Section: Discussionmentioning

confidence: 99%

Assessment of ERA-5 Temperature Variability in the Middle Atmosphere Using Rayleigh LiDAR Measurements between 2005 and 2020

et al. 2022

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In this study, the temperature biases and the ability of the ERA-5 product to reproduce the LiDAR variability in the 30–80 km altitude range were evaluated for the period 2005–2020, both for the winter and the summer months. During winter, temperatures from the ERA-5 dataset were in good agreement with LiDAR observations up to 45 km, while in the mesosphere, almost 70% of the ERA-5 profiles were cooler than those from LiDAR, except around 65 km. During summer, negative biases of −3 K were observed up to the stratopause, while significant positive biases of more than +10 K were found in the mesosphere. For the winter months, the variability observed by LiDAR, even during sudden stratospheric warming (SSWs) events, was reproduced accurately by the model in the upper stratosphere, but not in the mesosphere. Surprisingly, the LiDAR variability mainly due to propagating gravity waves in the summertime was also not reproduced by ERA-5 in the whole middle atmosphere. The model uncertainty associated with this variability, evaluated afterward with a new method, grew as expected with altitude and was more significant in winter than summer. A principal component analysis of the fluctuations of the temperature differences between the LiDAR and ERA-5 was performed to investigate the vertical coupling between 30 km and 70 km. The three first vertical modes illustrated 76% and 78% of the fluctuations of the temperature difference profiles in summer and winter, respectively, confirming the connection between the studied layers. The leading modes of the summer (49%) and winter (42%) possessed an anti-correlation between the upper stratosphere and the mesosphere, where fluctuations increased (at least ±5 K at 65 km) for both seasons due to the coarse vertical resolution in the model. The other modes showed an agreement between the LiDAR and ERA-5 fluctuations in the upper stratosphere and had a wave-like structure mainly located in the mesosphere, confirming that the model either overlooked or simulated imprecisely the gravity waves, leading to mesospheric inversions. Finally, SSWs impacted the ERA-5 temperature (deviation of ±3K) some days before and after its trigger around the stratopause.

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Section: Discussionmentioning

confidence: 99%

Assessment of ERA-5 Temperature Variability in the Middle Atmosphere Using Rayleigh LiDAR Measurements between 2005 and 2020

et al. 2022

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“…To correct for temperature and pressure effects in the Rayleigh wind retrieval, profiles of temperature and pressure are used from the ECMWF model forecast (e.g., Dabas et al, 2008; Šavli et al, 2021). These data are included in the auxiliary meteorological data product (AUX_MET), which is described further in Section 2.3.…”

Section: Methodsmentioning

confidence: 99%

Validation of the Aeolus L2B Rayleigh winds and ECMWF short‐range forecasts in the upper troposphere and lower stratosphere using Loon super pressure balloon observations

Bley

Rennie

Žagar

et al. 2022

Quart J Royal Meteoro Soc

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The novel Aeolus satellite, which carries the first Doppler wind lidar providing profiles of horizontal line‐of‐sight (HLOS) winds, addresses a significant gap in direct wind observations in the global observing system. The gap is particularly critical in the tropical upper troposphere and lower stratosphere (UTLS). This article validates the Aeolus Rayleigh–clear wind product and short‐range forecasts of the European Centre for Medium‐Range Weather Forecasts (ECMWF) with highly accurate winds from the Loon super pressure balloon network at altitudes between 16 and 20 km. Data from 229 individual balloon flights are analysed, applying a collocation criterion of 2 hr and 200 km. The comparison of Aeolus and Loon data shows systematic and random errors of prefix−$$ - $$0.31 and 6.37 m·$$ \cdotp $$sprefix−1$$ {}^{-1} $$, respectively, for the Aeolus Rayleigh–clear winds. The horizontal representativeness error of Aeolus HLOS winds (nearly the zonal wind component) in the UTLS ranges from 0.6–1.1 m·$$ \cdotp $$sprefix−1$$ {}^{-1} $$ depending on the altitude. The comparison of Aeolus and Loon datasets against ECMWF model forecasts suggests that the model systematically underestimates the HLOS winds in the tropical UTLS by about 1 m·$$ \cdotp $$sprefix−1$$ {}^{-1} $$. While Aeolus winds are currently considered as point winds by the ECMWF data assimilation system, the results of the present study demonstrate the need for a more realistic HLOS wind observation operator for assimilating Aeolus winds.

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“…Despite the operational telescope M1‐mirror‐temperature dependent bias correction (Section 2.1), which leads to a large improvement in the HLOS wind data quality (Rennie et al ., 2021), a remaining bias with negative values in the troposphere and positive values around the tropopause and in the lower stratosphere is apparent for the Rayleigh wind observations (Figure 1a,b). The height dependency is assumed to be related to the atmospheric background temperature used for the Rayleigh–Brillouin correction (Šavli et al ., 2021). The investigation of this effect is, however, still ongoing.…”

Section: Data Quality and Consistency Of The Aeolus Hlos Windsmentioning

confidence: 99%

Impact of assimilating Aeolus observations in the global model ICON: A global statistical overview

Martin¹,

Weißmann

Cress

2023

Quart J Royal Meteoro Soc

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Global wind profiles provided by the satellite mission Aeolus are an important recent supplement to the Global Observing System (GOS). This study investigates the impact of Aeolus horizontal line‐of‐sight (HLOS) wind observations in the operational global assimilation and forecasting system of Deutscher Wetterdienst (DWD) that is based on the ICOsahedral Nonhydrostatic (ICON) model. For this purpose, an Observing System Experiment (OSE) was conducted and evaluated for a three months period from July 2020 to October 2020. The Aeolus Rayleigh clear and Mie cloudy data quality and consistency was derived from observation minus background statistics. To correct for an altitude‐dependent bias, a model‐based bias correction scheme has been implemented. Comparisons of the systematic changes in the analysis and the respective forecasts provide an overview of the overall impact of the Aeolus HLOS wind assimilation in ICON. Increased influence of Aeolus wind profiles is found in jet regimes (e.g. amplification of the zonal wind component), around large‐scale circulation systems and convectively active areas in the tropics. The reduction in forecast error is largest in the tropical upper troposphere and stratosphere as well as in the mid‐ and upper troposphere of the Southern Hemisphere. The Northern Hemisphere shows a somewhat smaller but still beneficial impact of Aeolus observations. The verification with other conventional observations shows a mean relative reduction in short‐range forecast error between 0.1 and 0.6% in the Northern Hemisphere and up to 1.6% in the tropics and the Southern Hemisphere. When verifying against the ERA5 reanalysis, forecast errors of zonal wind, temperature and geopotential up to five days lead time are reduced by 2 ‐ 4% on global average and up to 5 ‐ 8% around the tropical tropopause.This article is protected by copyright. All rights reserved.

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Sensitivity of Aeolus HLOS winds to temperature and pressure specification in the L2B processor

Cited by 7 publications

References 22 publications

Assessment of ERA-5 Temperature Variability in the Middle Atmosphere Using Rayleigh LiDAR Measurements between 2005 and 2020

Assessment of ERA-5 Temperature Variability in the Middle Atmosphere Using Rayleigh LiDAR Measurements between 2005 and 2020

Validation of the Aeolus L2B Rayleigh winds and ECMWF short‐range forecasts in the upper troposphere and lower stratosphere using Loon super pressure balloon observations

Impact of assimilating Aeolus observations in the global model ICON: A global statistical overview

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