Abstract

Since its launch in 2018, the European Space Agency’s Earth Explorer satellite Aeolus has provided global height resolved measurements of horizontal wind in the troposphere and lower stratosphere for the first time. Novel datasets such as these provide an unprecedented opportunity for the research of atmospheric dynamics and provide new insights into the dynamics of the upper troposphere and lower stratosphere (UTLS) region. Aeolus measures the wind component along its horizontal line-of-sight, but for the analysis and interpretation of atmospheric dynamics, zonal and/or meridional wind components are most useful. In this paper, we introduce and compare three different methods to derive zonal and meridional wind components from the Aeolus wind measurements. We find that the most promising method involves combining Aeolus measurements during ascending and descending orbits. Using this method, we derive global estimates of the zonal wind in the latitude range 79.7° S to 84.5° N with errors of less than 5 ms−1 (at the 2-sigma level). Due to the orbit geometry of Aeolus, the estimation of meridional wind in the tropics and at midlatitudes is more challenging and the quality is less reliable. However, we find that it is possible to derive meridional winds poleward of 70° latitude with absolute errors typically below ±5 ms−1 (at the 2-sigma level). This further demonstrate the value of Aeolus wind measurements for applications in weather and climate research, in addition to their important role in numerical weather prediction.

Highlights

  • In August 2018, the European Space Agency (ESA) launched the Earth Explorer Satellite Aeolus (ESA, 2008; Reitebuch et al, 2020)

  • The aim of this paper is to provide scientists studying synoptic scale phenomena especially in the stratosphere (e.g. stratospheric warmings (SSWs), quasi-biennial oscillation (QBO)) with a toolbox to convert the Aeolus Level 2B (L2B) products into 55 zonal and meridional wind components keeping the limitations of such conversion methods in mind

  • 300 In general, the quality of the estimation strongly depends on the angle between Aeolus horizontal line-of-sight (HLOS) and the different cardinal axes

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Summary

Introduction

In August 2018, the European Space Agency (ESA) launched the Earth Explorer Satellite Aeolus (ESA, 2008; Reitebuch et al, 2020). It carries the first wind lidar in space – the Atmospheric LAser Doppler Instrument (ALADIN; e.g. Reitebuch, 2012a), which provides global profiles of line-of-sight (LOS) winds and optical properties of clouds and aerosols (Stoffelen et al, 2020; Flament et al, 2021). ALADIN is a high spectral resolution Doppler wind lidar which is operated at a wavelength. With its high-power laser, ALADIN can penetrate the atmosphere and acquire measurements from roughly 30 km altitude down to either the ground or to the highest optically thick cloud layer. Multiple NWP centres have already shown the positive impact of Aeolus data (e.g. Rennie et al, 2021) and started its operational assimilation.

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