The impact of <scp>Aeolus</scp> wind retrievals on <scp>ECMWF</scp> global weather forecasts

Rennie, Michael; Isaksen, Lars; Weiler, Fabian; Kloe, Jos de; Kanitz, Thomas; Reitebuch, Oliver

doi:10.1002/qj.4142

Cited by 107 publications

(186 citation statements)

References 64 publications

Supporting

Mentioning

132

Contrasting

Order By: Relevance

“…As an alternative, active closed-loop vibration isolation systems based on sensing and counteracting the mechanical disturbances arising in the spacecraft show great promise in overcoming the limitations of passive systems. These can be implemented at the level of the source (Preda et al, 2018) and/or the payload (Sanfedino et al, 2021) and can significantly mitigate the micro-vibration environment in Aeolus follow-on and other future space lidar missions.…”

Section: Summary Conclusion and Outlookmentioning

confidence: 99%

ALADIN laser frequency stability and its impact on the Aeolus wind error

et al. 2021

Self Cite

View full text Add to dashboard Cite

Abstract. The acquisition of atmospheric wind profiles on a global scale was realized by the launch of the Aeolus satellite, carrying the unique Atmospheric LAser Doppler INstrument (ALADIN), the first Doppler wind lidar in space. One major component of ALADIN is its high-power, ultraviolet (UV) laser transmitter, which is based on an injection-seeded, frequency-tripled Nd:YAG laser and fulfills a set of demanding requirements in terms of pulse energy, pulse length, repetition rate, and spatial and spectral beam properties. In particular, the frequency stability of the laser emission is an essential parameter which determines the performance of the lidar instrument as the Doppler frequency shifts to be detected are on the order of 108 smaller than the frequency of the emitted UV light. This article reports the assessment of the ALADIN laser frequency stability and its influence on the quality of the Aeolus wind data. Excellent frequency stability with pulse-to-pulse variations of about 10 MHz (root mean square) is evident for over more than 2 years of operations in space despite the permanent occurrence of short periods with significantly enhanced frequency noise (> 30 MHz). The latter were found to coincide with specific rotation speeds of the satellite's reaction wheels, suggesting that the root cause are micro-vibrations that deteriorate the laser stability on timescales of a few tens of seconds. Analysis of the Aeolus wind error with respect to European Centre for Medium-Range Weather Forecasts (ECMWF) model winds shows that the temporally degraded frequency stability of the ALADIN laser transmitter has only a minor influence on the wind data quality on a global scale, which is primarily due to the small percentage of wind measurements for which the frequency fluctuations are considerably enhanced. Hence, although the Mie wind bias is increased by 0.3 m s−1 at times when the frequency stability is worse than 20 MHz, the small contribution of 4 % from all Mie wind results renders this effect insignificant (< 0.1 m s−1) when all winds are considered. The impact on the Rayleigh wind bias is negligible even at high frequency noise. Similar results are demonstrated for the apparent speed of the ground returns that are measured with the Mie and Rayleigh channel of the ALADIN receiver. Here, the application of a frequency stability threshold that filters out wind observations with variations larger than 20 or 10 MHz improves the accuracy of the Mie and Rayleigh ground velocities by only 0.05 and 0.10 m s−1, respectively, however at the expense of useful ground data.

show abstract

Section: Summary Conclusion and Outlookmentioning

confidence: 99%

ALADIN laser frequency stability and its impact on the Aeolus wind error

et al. 2021

Self Cite

View full text Add to dashboard Cite

show abstract

“…The quality of the Aeolus wind data contained in the L2B product was considerably improved by the correction for large systematic errors which had strongly degraded the wind data quality in the initial phase of the mission (Kanitz et al, 2020;. While dark current signal anomalies on single ("hot") pixels of the Aeolus detectors were successfully mitigated for by the implementation of dedicated calibration instrument modes (Weiler et al, 2020), wind biases that were introduced by variations in the temperature distribution across the primary telescope mirror were largely diminished by the socalled M1 correction based on ECMWF model winds Rennie et al, 2021).…”

Section: Statistical Parametermentioning

confidence: 99%

“…This goal was already achieved within the first half of the intended mission lifetime of three years with the successful assimilation of Aeolus winds into NWP models, after having identified and corrected for two large error sources that had diminished the wind data quality in the early phase of the mission (Kanitz et al, 2020;. Whereas the implementation of a dedicated calibration instrument mode allows to account for dark current signal fluctuations on the Aeolus detectors (Weiler et al, 2020), wind biases that were caused by variations in the temperature distribution across the primary telescope mirror were considerably reduced by a correction scheme based on ECMWF model-equivalent winds Rennie et al, 2021). Recent assessments of the significance of the Aeolus data have demonstrated statistically positive impact on the accuracy of NWP forecasts, especially in the tropics and at the poles, hence providing a useful contribution to the Global Observing System Rennie et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

“…Whereas the implementation of a dedicated calibration instrument mode allows to account for dark current signal fluctuations on the Aeolus detectors (Weiler et al, 2020), wind biases that were caused by variations in the temperature distribution across the primary telescope mirror were considerably reduced by a correction scheme based on ECMWF model-equivalent winds Rennie et al, 2021). Recent assessments of the significance of the Aeolus data have demonstrated statistically positive impact on the accuracy of NWP forecasts, especially in the tropics and at the poles, hence providing a useful contribution to the Global Observing System Rennie et al, 2021). Consequently, the operational assimilation of Aeolus observations was started at several weather services worldwide in 2020.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Retrieval improvements for the ALADIN Airborne Demonstrator in support of the Aeolus wind product validation

Lux

Lemmerz

Weiler

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

Abstract. The realization of the European Space Agency’s Aeolus mission was supported by the long-standing development and field deployment of the ALADIN Airborne Demonstrator (A2D) which, since the launch of the Aeolus satellite in 2018, has been serving as a key instrument for the validation of the Atmospheric LAser Doppler INstrument (ALADIN), the first-ever Doppler wind lidar (DWL) in space. However, the validation capabilities of the A2D are compromised by deficiencies of the dual-channel receiver which, like its spaceborne counterpart, consists of a Rayleigh and a complementary Mie spectrometer for sensing the wind speed from both molecular and particulate backscatter signals, respectively. Whereas the accuracy and precision of the Rayleigh channel is limited by the spectrometer’s high alignment sensitivity, especially in the near field of the instrument, large systematic Mie wind errors are caused by aberrations of the interferometer in combination with the temporal overlap of adjacent range gates during signal readout. The two error sources are mitigated by modifications of the A2D wind retrieval algorithm. A novel quality control scheme was implemented which ensures that only backscatter return signals within a small angular range are further processed. Moreover, Mie wind results with large bias of opposing sign in adjacent range bins are vertically averaged. The resulting improvement of the A2D performance was evaluated in the context of two Aeolus airborne validation campaigns that were conducted between May and September 2019. Comparison of the A2D wind data against a high-accuracy, coherent Doppler wind lidar that was deployed in parallel on-board the same aircraft shows that the retrieval refinements considerably decrease the random errors of the A2D line-of-sight (LOS) Rayleigh and Mie winds from about 2.0 m∙s−1 to about 1.5 m∙s−1, demonstrating the capability of such a direct detection DWL. Moreover, the measurement range of the Rayleigh channel could be largely extended by up to 2 km in the instrument’s near field close to the aircraft. The Rayleigh and Mie systematic errors are below 0.5 m∙s−1 (LOS), hence allowing for an accurate assessment of the Aeolus wind errors during the September campaign. The latter revealed different biases of the L2B Rayleigh-clear and Mie-cloudy horizontal LOS (HLOS) for ascending and descending orbits as well as random errors of about 3 m∙s−1 (HLOS) for the Mie and close to 6 m∙s−1 (HLOS) for the Rayleigh winds, respectively. In addition to the Aeolus error evaluation, the present study discusses the applicability of the developed A2D algorithm modifications to the Aeolus processor, thereby offering prospects for improving the Aeolus wind data quality.

show abstract

“…Together with floods they are the costliest natural hazards in Europe: they account for more than 30% (60%) of total (insured) losses (https://ec.europa.eu/jrc/sites/jrcsh/files/pesetaiv_task_13_windstorms_final_report.pdf). The Aeolus wind lidar have demonstrated a large impact in reducing forecast errors when assimilated by European Weather Forecasting Centers (Rennie et al, 2021). In addition to winds, cloud and precipitation measurements remain key for both Numerical Weather Prediction (NWP) applications and for advancing understanding of cloud processes and their role in climate simulations.…”

Section: Introductionmentioning

confidence: 99%

End to end simulator for the WIVERN W-band Doppler conically scanning spaceborne radar

Battaglia

Martire

Caubet

et al. 2021

Preprint

View full text Add to dashboard Cite

Abstract. The WIVERN (WInd VElocity Radar Nephoscope) mission, soon entering in Phase-0 of the ESA Earth Explorer program, promises to complement Doppler wind lidar by globally observing, for the first time, vertical profiles of winds in cloudy areas. This work describes an end to end simulator of the WIVERN conically scanning 94 GHz Doppler radar, the only payload of the mission. Specific features of the simulator are: the conically scanning geometry; the inclusion of cross-polarization effects and of the simulation of a radiometric mode; the applicability to global cloud model outputs via an orbital model; the incorporation of a mispointing model accounting for thermo-elastic distortions, microvibrations, star-trackers uncertainties, etc.; the inclusion of the surface clutter. Some of the simulator capabilities are showcased for a case study involving a full rotational scan of the instrument. The simulator represents a very useful tool for studying the performances of the WIVERN concept and possible trade-offs for the different configurations (e.g. different antenna sizes, pulse lengths, antenna patterns, .....). Thanks to its modular structure the simulator can be easily adapted to different orbits, different scanning geometries and different frequencies.

show abstract

The impact of Aeolus wind retrievals on ECMWF global weather forecasts

Cited by 107 publications

References 64 publications

ALADIN laser frequency stability and its impact on the Aeolus wind error

ALADIN laser frequency stability and its impact on the Aeolus wind error

Retrieval improvements for the ALADIN Airborne Demonstrator in support of the Aeolus wind product validation

End to end simulator for the WIVERN W-band Doppler conically scanning spaceborne radar

Contact Info

Product

Resources

About