scholarly journals Validation of Aeolus Level 2B wind products using wind profilers, ground-based Doppler wind lidars, and radiosondes in Japan

2021 ◽  
Vol 14 (11) ◽  
pp. 7255-7275
Author(s):  
Hironori Iwai ◽  
Makoto Aoki ◽  
Mitsuru Oshiro ◽  
Shoken Ishii
Keyword(s):  
Random Error ◽  
Laser Energy ◽  
European Space Agency ◽  
Horizontal Line ◽  
Positive Trend ◽  
Random Errors ◽  
Space Agency ◽  
Scattering Ratio ◽  
Wind Bias ◽  
Wind Profilers

Abstract. The first space-based Doppler wind lidar (DWL) on board the Aeolus satellite was launched by the European Space Agency (ESA) on 22 August 2018 to obtain global profiles of horizontal line-of-sight (HLOS) wind speed. In this study, the Raleigh-clear and Mie-cloudy winds for periods of baseline 2B02 (from 1 October to 18 December 2018) and 2B10 (from 28 June to 31 December 2019 and from 20 April to 8 October 2020) were validated using 33 wind profilers (WPRs) installed all over Japan, two ground-based coherent Doppler wind lidars (CDWLs), and 18 GPS radiosondes (GPS-RSs). In particular, vertical and seasonal analyses were performed and discussed using WPR data. During the baseline 2B02 period, a positive bias was found to be in the ranges of 0.5 to 1.7 m s−1 for Rayleigh-clear winds and 1.6 to 2.4 m s−1 for Mie-cloudy winds using the three independent reference instruments. The statistical comparisons for the baseline 2B10 period showed smaller biases, −0.8 to 0.5 m s−1 for the Rayleigh-clear and −0.7 to 0.2 m s−1 for the Mie-cloudy winds. The vertical analysis using WPR data showed that the systematic error was slightly positive in all altitude ranges up to 11 km during the baseline 2B02 period. During the baseline 2B10 period, the systematic errors of Rayleigh-clear and Mie-cloudy winds were improved in all altitude ranges up to 11 km as compared with the baseline 2B02. Immediately after the launch of Aeolus, both Rayleigh-clear and Mie-cloudy biases were small. Within the baseline 2B02, the Rayleigh-clear and Mie-cloudy biases showed a positive trend. For the baseline 2B10, the Rayleigh-clear wind bias was generally negative for all months except August 2020, and Mie-cloudy wind bias gradually fluctuated. Both Rayleigh-clear and Mie-cloudy biases did not show a marked seasonal trend and approached zero towards September 2020. The dependence of the Rayleigh-clear wind bias on the scattering ratio was investigated, showing that there was no significant bias dependence on the scattering ratio during the baseline 2B02 and 2B10 periods. Without the estimated representativeness error associated with the comparisons using WPR observations, the Aeolus random error was determined to be 6.7 (5.1) and 6.4 (4.8) m s−1 for Rayleigh-clear (Mie-cloudy) winds during the baseline 2B02 and 2B10 periods, respectively. The main reason for the large Aeolus random errors is the lower laser energy compared to the anticipated 80 mJ. Additionally, the large representativeness error of the WPRs is probably related to the larger Aeolus random error. Using the CDWLs, the Aeolus random error estimates were in the range of 4.5 to 5.3 (2.9 to 3.2) and 4.8 to 5.2 (3.3 to 3.4) m s−1 for Rayleigh-clear (Mie-cloudy) winds during the baseline 2B02 and 2B10 periods, respectively. By taking the GPS-RS representativeness error into account, the Aeolus random error was determined to be 4.0 (3.2) and 3.0 (2.9) m s−1 for Rayleigh-clear (Mie-cloudy) winds during the baseline 2B02 and 2B10 periods, respectively.

scholarly journals Validation of Aeolus Level 2B wind products using wind profilers, ground-based Doppler wind lidars, and radiosondes in Japan

2021 ◽  
Author(s):  
Hironori Iwai ◽  
Makoto Aoki ◽  
Mitsuru Oshiro ◽  
Shoken Ishii
Keyword(s):  
Systematic Error ◽  
Random Error ◽  
European Space Agency ◽  
Horizontal Line ◽  
Positive Trend ◽  
Random Errors ◽  
Space Agency ◽  
Scattering Ratio ◽  
Wind Bias ◽  
Wind Profilers

Abstract. The first space-based Doppler wind lidar (DWL) onboard the Aeolus satellite was launched by the European Space Agency (ESA) on 22 August 2018 to obtain global profiles of horizontal line-of-sight (HLOS) wind speed. In this study, the Raleigh-clear and Mie-cloudy winds for periods of baseline 2B02 (from 1 October to 18 December 2018) and 2B10 (from 28 June to 31 December 2019 and from 20 April to 8 October 2020) were validated using 33 wind profilers (WPRs) installed all over Japan, two ground-based coherent Doppler wind lidars (CDWLs), and 18 GPS-radiosondes (GPS-RSs). In particular, vertical and seasonal analyses were performed and discussed using WPR data. During the baseline 2B02 period, a positive bias was found to be in the ranges of 0.46–1.69 m s−1 for Rayleigh-clear winds and 1.63–2.42 m s−1 for Mie-cloudy winds using the three independent reference instruments. The biases of Rayleigh-clear and Mie-cloudy winds were in the ranges of −0.82−+0.45 m s−1 and −0.71−+0.16 m s−1 during the baseline 2B10 period, respectively. The systematic error for the baseline 2B10 was improved as compared with that for the baseline 2B02. The vertical analysis using WPR data showed that the systematic error was slightly positive in all altitude ranges up to 11 km during the baseline 2B02 period. During the baseline 2B10 period, the systematic errors of Rayleigh-clear and Mie-cloudy winds were improved in all altitude ranges up to 11 km as compared with the baseline 2B02. Immediately after the launch of Aeolus, both Rayleigh-clear and Mie-cloudy biases were small. Within the baseline 2B02, the Rayleigh-clear and Mie-cloudy biases showed a positive trend. For the baseline 2B10, the Rayleigh-clear wind bias was generally negative at all months except August 2020, and Mie-cloudy wind bias gradually fluctuated. The systematic error was close to zero with time in 2020 and did not show a marked seasonal trend. The dependence of the Rayleigh-clear wind bias on the scattering ratio was investigated, showing that the scattering ratio had a minimal effect on the systematic error of the Rayleigh-clear winds during the baseline 2B02 period. On the other hand, during the baseline 2B10 period, there was no significant bias dependence on the scattering ratio. Without the estimated representativeness error associated with the comparisons using WPR observations, the Aeolus random error was determined to be 6.71 (5.12) and 6.42 (4.80) m s−1 for Rayleigh-clear (Mie-cloudy) winds during the baseline 2B02 and 2B10 periods, respectively. The main reason for the large random errors is probably related to the large representativeness error due to the large sampling volume of the WPRs. Using the CDWLs, the Aeolus random error estimates were in the range of 4.49–5.31 (2.93–3.19) and 4.81–5.21 (3.30–3.37) m s−1 for Rayleigh-clear (Mie-cloudy) winds during the baseline 2B02 and 2B10 periods, respectively. By taking the GPS-RS representativeness error into account, the Aeolus random error was determined to be 4.01 (3.24) and 3.02 (2.89) m s−1 for Rayleigh-clear (Mie-cloudy) winds during the baseline 2B02 and 2B10 periods, respectively.

scholarly journals First validation of Aeolus wind observations by airborne Doppler wind lidar measurements

2020 ◽  
Vol 13 (5) ◽  
pp. 2381-2396 ◽  
Author(s):  
Benjamin Witschas ◽  
Christian Lemmerz ◽  
Alexander Geiß ◽  
Oliver Lux ◽  
Uwe Marksteiner ◽  
...  
Keyword(s):  
Early Stage ◽  
European Space Agency ◽  
Global Scale ◽  
Horizontal Resolution ◽  
Line Of Sight ◽  
Horizontal Line ◽  
Random Errors ◽  
Space Agency ◽  
Wind Lidar ◽  
German Aerospace

Abstract. Soon after the launch of Aeolus on 22 August 2018, the first ever wind lidar in space developed by the European Space Agency (ESA) has been providing profiles of the component of the wind vector along the instrument's line of sight (LOS) on a global scale. In order to validate the quality of Aeolus wind observations, the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt e.V., DLR) recently performed two airborne campaigns over central Europe deploying two different Doppler wind lidars (DWLs) on board the DLR Falcon aircraft. The first campaign – WindVal III – was conducted from 5 November 2018 until 5 December 2018 and thus still within the commissioning phase of the Aeolus mission. The second campaign – AVATARE (Aeolus Validation Through Airborne Lidars in Europe) – was performed from 6 May 2019 until 6 June 2019. Both campaigns were flown out of the DLR site in Oberpfaffenhofen, Germany, during the evening hours for probing the ascending orbits. All together, 10 satellite underflights with 19 flight legs covering more than 7500 km of Aeolus swaths were performed and used to validate the early-stage wind data product of Aeolus by means of collocated airborne wind lidar observations for the first time. For both campaign data sets, the statistical comparison of Aeolus horizontal line-of-sight (HLOS) observations and the corresponding wind observations of the reference lidar (2 µm DWL) on board the Falcon aircraft shows enhanced systematic and random errors compared with the bias and precision requirements defined for Aeolus. In particular, the systematic errors are determined to be 2.1 m s−1 (Rayleigh) and 2.3 m s−1 (Mie) for WindVal III and −4.6 m s−1 (Rayleigh) and −0.2 m s−1 (Mie) for AVATARE. The corresponding random errors are determined to be 3.9 m s−1 (Rayleigh) and 2.0 m s−1 (Mie) for WindVal III and 4.3 m s−1 (Rayleigh) and 2.0 m s−1 (Mie) for AVATARE. The Aeolus observations used here were acquired in an altitude range up to 10 km and have mainly a vertical resolution of 1 km (Rayleigh) and 0.5 to 1.0 km (Mie) and a horizontal resolution of 90 km (Rayleigh) and down to 10 km (Mie). Potential reasons for those errors are analyzed and discussed.

scholarly journals Validation of the Aeolus Level-2B wind product over Northern Canada and the Arctic

2021 ◽  
Author(s):  
Chih-Chun Chou ◽  
Paul J. Kushner ◽  
Stéphane Laroche ◽  
Zen Mariani ◽  
Peter Rodriguez ◽  
...  
Keyword(s):  
Early Phase ◽  
Weather Prediction ◽  
European Space Agency ◽  
Arctic Region ◽  
The Arctic ◽  
Horizontal Line ◽  
Polar Regions ◽  
Near Surface ◽  
Northern Canada ◽  
Space Agency

Abstract. In August 2018, the European Space Agency launched the Aeolus satellite, whose Atmospheric LAser Doppler INstrument (ALADIN) is the first spaceborne Doppler wind lidar to regularly measure vertical profiles of horizontal line-of-sight (HLOS) winds with global sampling. This mission is intended to assess improvement to numerical weather prediction provided by wind observations in regions poorly constrained by atmospheric mass, such as the tropics, but also, potentially, in polar regions such as the Arctic where direct wind observations are especially sparse. There remain gaps in the evaluation of the Aeolus products over the Arctic region, which is the focus of this contribution. Here, an assessment of the Aeolus Level-2B wind product is carried out from measurement stations in Canada’s north, to the pan-Arctic, with Aeolus data being compared to Ka-band radar measurements at Iqaluit, Nunavut; to radiosonde measurements over Northern Canada; to Environment and Climate Change Canada (ECCC)’s short-range forecast; and to the reanalysis product, ERA5, from the European Centre for Medium-Range Weather Forecasts (ECMWF). Periods covered include the early phase during the first laser nominal flight model (FM-A; 2018-09 to 2018-10), the early phase during the second flight laser (FM-B; 2019-08 to 2019-09), and the mid-FM-B periods (2019-12 to 2020-01). The adjusted r-square between Aeolus and other local datasets are around 0.9, except for somewhat lower values in comparison with the ground-based radar, presumably due to limited sampling. This consistency degraded by about 10 % for the Rayleigh winds in the summer, presumably due to scattering from the solar background. Over the pan-Arctic, consistency, with correlation greater than 0.8, is found in the Mie channel from the planetary boundary layer to the lower stratosphere (near surface to 16 km a.g.l.) and in the Rayleigh channel from the troposphere to the stratosphere (2 km to 25 km a.g.l.). Zonal and meridional projections of the HLOS winds are separated to account for the systematic changes in HLOS winds arising from sampling wind components from different viewing orientations in the ascending and descending phases. In all cases, Aeolus standard deviations are found to be 20 % greater than those from ECCC-B and ERA5. We found that L2B estimated error product for Aeolus is coherent with the differences between Aeolus and the other datasets, and can be used as a guide for expected consistency. Thus, our work confirms the quality of the Aeolus dataset over the Arctic and shows that the new Aeolus L2B wind product provides a valuable addition to current wind products in regions such as the Arctic Ocean region where few direct wind observations have been available to date.

Aeolus: ESA’s wind mission. Status and future challenges

2021 ◽  
Author(s):  
Tommaso Parrinello ◽  
Anne Grete Straume ◽  
Jonas Von Bismark ◽  
Sebastian Bley ◽  
Viet Duc Tran ◽  
...  
Keyword(s):  
World Wide ◽  
Positive Impact ◽  
European Space Agency ◽  
Weather Forecast ◽  
Horizontal Line ◽  
Space Agency ◽  
Future Challenges ◽  
The Status ◽  
Other World ◽  
Atmospheric Backscatter

<p>The European Space Agency (ESA)’s wind mission, Aeolus, was launched on 22 August 2018. It is a member of the ESA Earth Explorer family and its main objective is to demonstrate the potential of Doppler wind Lidars in space for improving weather forecast and to understand the role of atmospheric dynamics in climate variability. Aeolus carries a single instrument called ALADIN: a high sophisticated spectral resolution Doppler wind Lidar which operates at 355 which is the first of its kind to be flown in space.</p><p>Aeolus provides profiles of single horizontal line-of-sight winds (primary product) in near-real-time (NRT), and profiles of atmospheric backscatter and extinction. The instrument samples the atmosphere from about 30 km down to the Earth’s surface, or down to optically thick clouds. The required precision of the wind observations is 1-2.5 m/s in the troposphere and 3-5 m/s in the stratosphere while the systematic error requirement be less than 0.7 m/s. The mission spin-off product includes information about aerosol and cloud layers. The satellite flies in a polar dusk/dawn orbit (6 am/pm local time), providing ~16 orbits per 24 hours with an orbit repeat cycle of 7 days. Global scientific payload data acquisition is guaranteed with the combined usage of Svalbard and Troll X-band receiving stations.</p><p>After almost three years in orbit and despite performance issues related to its instrument ALADIN, Aeolus has achieved most of its objectives. Positive impact on the weather forecast has been demonstrated by multiple NWP centres world-wide with four European meteorological centres now are assimilating Aeolus winds operationally. Other world-wide meteo centers wull start to assimilate data in 2021. The status of the Aeolus mission will be presented, including overall performance, planned operations and exploitation. Scope of the paper is also to inform about the programmatic highlights and future challenges.</p>

Assessment of Aeolus DWL data and impact of assimilation in the JMA’s global data assimilation system

2021 ◽  
Author(s):  
Izumi Okabe ◽  
Kozo Okamoto
Keyword(s):  
Data Assimilation ◽  
European Space Agency ◽  
Wind Data ◽  
Japan Meteorological Agency ◽  
Northwest Pacific ◽  
Horizontal Line ◽  
Northwest Pacific Ocean ◽  
Space Agency ◽  
The Northwest Pacific Ocean ◽  
Global Data

<p>The horizontal line of sight (HLOS) wind data from Aeolus Doppler Wind Lidar (DWL) is available from the European Space Agency (ESA) Earth Online Portal. The data quality after the mirror bias correction was investigated using data from July to September 2020. According to the first guess departure (observation minus background) statistics in Japan Meteorological Agency’s (JMA’s) global data assimilation (DA) system, the biases were very small for both  Rayleigh and Mie HLOS wind data after quality controlled. Significant positive impacts of Aeolus HLOS wind data assimilation in the global DA system on the analysis accuracy and forecasting scores were found in experiments with Rayleigh wind data under clear-sky condition and Mie wind data under cloudy condition. Improvement of tropical cyclone track forecasting was also found for the typhoons in the Northwest Pacific Ocean and for the hurricanes in the Atlantic Ocean. The details of results of data assessment and assimilation experiments will be shown in the presentation.</p>

Aeolus: ESA’s wind mission. Status and future challenges

2020 ◽  
Author(s):  
Tommaso Parrinello ◽  
Anne Grete Straume ◽  
Jonas Von Bismark ◽  
Sebastian Bley ◽  
Viet Duc Tran ◽  
...  
Keyword(s):  
European Space Agency ◽  
Weather Forecast ◽  
Horizontal Line ◽  
Space Agency ◽  
Future Challenges ◽  
The Status ◽  
Phase Calibration ◽  
Wind Lidar ◽  
Operation Phase ◽  
Atmospheric Backscatter

<p>The European Space Agency (ESA)’s wind mission, Aeolus, was launched on 22 August 2018. Aeolus is a member of the ESA Earth Explorer family and its main objective is to demonstrate the potential of Doppler wind Lidars in space for improving weather forecast and to understand the role of atmospheric dynamics in climate variability. Aeolus carries a single instrument called ALADIN: a high sophisticated spectral resolution Doppler wind Lidar which operates at 355 which is the first of its kind to be flown in space. It provides profiles of single horizontal line-of-sight winds (primary product) in near-real-time (NRT), and profiles of atmospheric backscatter and extinction. The instrument samples the atmosphere from about 30 km down to the Earth’s surface, or down to optically thick clouds. The required precision of the wind observations is 1-2.5 m/s in the troposphere and 3-5 m/s in the stratosphere while the systematic error requirement be less than 0.7 m/s. The mission spin-off product includes information about aerosol and cloud layers. The satellite flies in a polar dusk/dawn orbit (6 am/pm local time), providing ~16 orbits per 24 hours with an orbit repeat cycle of 7 days. Global scientific payload data acquisition is guaranteed with the combined usage of Svalbard and Troll X-band receiving stations.</p><p>The status of the Aeolus mission will be provided, including its performance assessment, planned operations and exploitation in the near future. This comprises the outcome of the instrument in its early operation phase, calibration and validation activities and a general review of the main scientific findings. Scope of the paper is also to inform about the programmatic highlights and future challenges.</p>

scholarly journals First validation of Aeolus wind observations by airborne Doppler Wind Lidar measurements

2020 ◽  
Author(s):  
Benjamin Witschas ◽  
Christian Lemmerz ◽  
Alexander Geiß ◽  
Oliver Lux ◽  
Uwe Marksteiner ◽  
...  
Keyword(s):  
Early Stage ◽  
European Space Agency ◽  
Global Scale ◽  
Data Sets ◽  
Random Errors ◽  
Space Agency ◽  
Lidar Measurements ◽  
Wind Lidar ◽  
German Aerospace ◽  
First Time

Abstract. Soon after the launch of Aeolus on 22 August 2018, the first ever wind lidar in space developed by the European Space Agency (ESA) has been providing profiles of the component of the wind vector along the instrument's line-of-sight (LOS) on a global scale. In order to validate the quality of Aeolus wind observations, the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt e.V., DLR) recently performed two airborne campaigns over Central Europe deploying two different Doppler wind lidars (DWL) on-board the DLR Falcon aircraft. The first campaign – WindVal III – was conducted from 5 November 2018 until 5 December 2018 and thus, still within the commissioning phase of the Aeolus mission. The second campaign – AVATARE (Aeolus Validation Through Airborne Lidars in Europe) – was performed from 6 May 2019 until 6 June 2019. Both campaigns were flown out of the DLR site in Oberpfaffenhofen, Germany. All together, 10 satellite underflights with 19 flight legs covering more than 7500 km of Aeolus swaths were performed and used to validate the early stage wind data product of Aeolus by means of collocated airborne wind lidar observations for the first time. For both campaign data sets, the statistical comparison of Aeolus data and the data of the reference lidar (2-µm DWL) on-board the Falcon aircraft shows enhanced systematic and random errors compared with the bias and precision requirements defined for Aeolus. In particular, the systematic errors are determined to be 2.1 m/s (Rayleigh) and 2.3 m/s (Mie) for WindVal III and −4.6 m/s (Rayleigh) and −0.2 m/s (Mie) for AVATARE. The corresponding random errors are determined to be 4.0 m/s (Rayleigh) and 2.2 m/s (Mie) for WindVal III, and 4.4 m/s (Rayleigh) and 2.2 m/s (Mie) for AVATARE. Potential reasons for those errors are analyzed and discussed.

scholarly journals HIPPARCOS Satellite and the Organization of the Project

1986 ◽  
Vol 109 ◽  
pp. 581-591 ◽  
Author(s):  
J. Kovalevsky
Keyword(s):  
Future Development ◽  
European Space Agency ◽  
Measurement Precision ◽  
Random Errors ◽  
The Past ◽  
Photon Count ◽  
Space Agency ◽  
Basic Measurement ◽  
Sensitivity Profile

The HIPPARCOS satellite is an approved project of the European Space Agency since 1980. A sketch of the past and future development of the project is given. The resulting astrometric parameters and magnitudes of 100 000 stars should be available circa 1993. Many astronomical groups are involved in the preparation of the mission together with ESA bodies and industry. Their functions and mutual interfaces are described.The main features of the satellite are presented. While observing out of the atmosphere removes most of the effects that limit the accuracy of ground based astrometry, new causes of systematic or random errors appear in an instrument designed for a millisecond of arc level of precision. The main limitations that have been identified are discussed: basic angle unstability, mechanical jitter, grid irregularity, diffraction chromatism, shape of the image dissector sensitivity profile. The consequence is that the presently expected basic measurement precision is limited not only by the photon count errors. However, all these effects are taken into account when assessing a final accuracy of 0″.002 for the astrometric parameters of a 9-th magnitude star.

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

2021 ◽  
Vol 14 (6) ◽  
pp. 4721-4736
Author(s):  
Matic Šavli ◽  
Vivien Pourret ◽  
Christophe Payan ◽  
Jean-François Mahfouf
Keyword(s):  
Error Estimate ◽  
Weather Prediction ◽  
European Space Agency ◽  
Atmospheric Temperature ◽  
Horizontal Line ◽  
Model Errors ◽  
Space Agency ◽  
Temperature And Pressure ◽  
Nwp Model ◽  
The Impact

Abstract. The retrieval of wind from the first Doppler wind lidar of European Space Agency (ESA) launched in space in August 2018 is based on a series of corrections necessary to provide observations of a quality useful for numerical weather prediction (NWP). In this paper we examine the properties of the Rayleigh–Brillouin correction necessary for the retrieval of horizontal line-of-sight wind (HLOS) from a Fabry–Pérot interferometer. This correction is taking into account the atmospheric stratification, namely temperature and pressure information that are provided by a NWP model as suggested prior to launch. The main goal of the study is to evaluate the impact of errors in simulated atmospheric temperature and pressure information on the HLOS sensitivity by comparing the Integrated Forecast System (IFS) and Action de Recherche Petite Echelle Grande Echelle (ARPEGE) global model temperature and pressure short-term forecasts collocated with the Aeolus orbit. These errors are currently not taken into account in the computation of the HLOS error estimate since its contribution is believed to be small. This study largely confirms this statement to be a valid assumption, although it also shows that model errors could locally (i.e. jet-stream regions, below 700 hPa over both earth poles and in stratosphere) be significant. For future Aeolus follow-on missions this study suggests considering realistic estimations of errors in the HLOS retrieval algorithms, since this will lead to an improved estimation of the Rayleigh–Brillouin sensitivity uncertainty contributing to the HLOS error estimate and better exploitation of space lidar winds in NWP systems.

Experimental Validation and Assimilation of Aeolus Wind Observations

2020 ◽  
Author(s):  
Anne Martin ◽  
Alexander Geiss ◽  
Alexander Cress ◽  
Martin Weissmann
Keyword(s):  
Experimental Validation ◽  
European Space Agency ◽  
Doppler Frequency ◽  
Random Errors ◽  
Space Agency ◽  
Vertical Range ◽  
Explorer Mission ◽  
Global Coverage ◽  
Wind Lidar ◽  
Wind Profiles

<p><span>The earth explorer mission </span><span>Aeolus from the European Space Agency for the first time worldwide opens up the possibility to directly observe Earths’ wind profiles from space. Aeolus carries a Doppler wind lidar operating at 335 nm which measures the Doppler frequency shift of backscattered laser light from air molecules and particles up to 30 km accumulated in 0.25 - 2 km vertical range bins. It’s expected that such global coverage of wind profiles helps to fill a gap in the global observing system.</span></p><p><span>As part of the German initiative EVAA (Experimental Validation and Assimilation of Aeolus observations) validation and monitoring activities for Aeolus are performed to determine and understand observation systematic and random errors. Independent ground-based measurements from radiosondes and tropospheric radar wind profilers are used as reference for the evaluation of Aeolus winds. In addition monitoring results from the global model ICON from the German Weather Service (DWD) are used to examine</span> <span>the results and investigate bias dependencies. An accurate understanding of the systematic errors of Aeolus wind observations is necessary for data assimilation processes. First impact experiments with an established bias correction for Aeolus wind data were run at DWD showing encouraging results for forecast improvements in upper tropospheric and lower stratospheric tropics and southern hemisphere.</span></p>

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