Abstract
Abstract. In August 2018, the first Doppler wind lidar in space called Atmospheric Laser Doppler Instrument (ALADIN) was launched on board the satellite Aeolus by the European Space Agency (ESA). Aeolus measures profiles of one horizontal wind component (i.e., mainly the west–east direction) in the troposphere and lower stratosphere on a global basis. Furthermore, profiles of aerosol and cloud properties can be retrieved via the high spectral resolution lidar (HSRL) technique. The Aeolus mission is supposed to improve the quality of weather forecasts and the understanding of atmospheric processes. We used the opportunity to perform a unique validation of the wind products of Aeolus by utilizing the RV Polarstern cruise PS116 from Bremerhaven to Cape Town in November/December 2018. Due to concerted course modifications, six direct intersections with the Aeolus ground track could be achieved in the Atlantic Ocean west of the African continent. For the validation of the Aeolus wind products, we launched additional radiosondes and used the EARLINET/ACTRIS lidar PollyXT for atmospheric scene analysis. The six analyzed cases prove that Aeolus is able to measure horizontal wind speeds in the nearly west–east direction. Good agreements with the radiosonde observations could be achieved for both Aeolus wind products – the winds observed in clean atmospheric regions called Rayleigh winds and the winds obtained in cloud layers called Mie winds (according to the responsible scattering regime). Systematic and statistical errors of the Rayleigh winds were less than 1.5 and 3.3 m s−1, respectively, when compared to radiosonde values averaged to the vertical resolution of Aeolus. For the Mie winds, a systematic and random error of about 1 m s−1 was obtained from the six comparisons in different climate zones. However, it is also shown that the coarse vertical resolution of 2 km in the upper troposphere, which was set in this early mission phase 2 months after launch, led to an underestimation of the maximum wind speed in the jet stream regions. In summary, promising first results of the first wind lidar space mission are shown and prove the concept of Aeolus for global wind observations.
Highlights
On 22 August 2018, the European Space Agency (ESA) launched the Earth Explorer Core mission Aeolus. This mission aims to demonstrate significant improvements in weather forecasting by measuring height-resolved wind profiles in the troposphere and lower stratosphere in order to advance the understanding of atmospheric dynamics and climate processes (ESA, 2019a; Straume et al, 2020)
The global wind observations that were assimilated at the European Centre for Medium-Range Weather Forecasts (ECMWF) in late 2016 (ECMWF, 2018) are mainly obtained by aircrafts and radiosondes and via atmospheric motion vectors (AMVs)
As no correction procedure was available at the early mission period we focused on, we skipped all height bins in which a hot pixel occurred as they significantly bias the Aeolus wind and aerosol products
Summary
On 22 August 2018, the European Space Agency (ESA) launched the Earth Explorer Core mission Aeolus This mission aims to demonstrate significant improvements in weather forecasting by measuring height-resolved wind profiles in the troposphere and lower stratosphere in order to advance the understanding of atmospheric dynamics and climate processes (ESA, 2019a; Straume et al, 2020). ALADIN is the first lidar (LIght Detection And Ranging) instrument on a European satellite It is the first space-borne instrument capable of measuring vertical profiles of one horizontal wind component on a global basis. The global wind observations that were assimilated at the European Centre for Medium-Range Weather Forecasts (ECMWF) in late 2016 (ECMWF, 2018) are mainly obtained by aircrafts and radiosondes and via atmospheric motion vectors (AMVs). We utilized the multiwavelength Raman polarization lidar PollyXT (Engelmann et al, 2016; Baars et al, 2016) in order to characterize the atmospheric state above RV Polarstern, which is part of the European Research Infrastructure EARLINET/ACTRIS (European Aerosol Research Lidar Network/European Research Infrastructure for the Observation of Aerosol, Clouds and Trace Gases)
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