Abstract

Abstract. The launch and operation of the first spaceborne Doppler wind lidar (DWL), Aeolus, is of great significance for observing the global wind field. Aeolus operates on a sun-synchronous dawn–dusk orbit to minimize the negative impact of solar background radiation (SBR) on wind observation accuracy. Future spaceborne DWLs may not operate on sun-synchronous dawn–dusk orbits due to their observational purposes. The impact of the local time of ascending node (LTAN) crossing of sun-synchronous orbits on the wind observation accuracy was studied in this paper by proposing two given Aeolus-type spaceborne DWLs operating on the sun-synchronous orbits with LTANs of 15:00 and 12:00 LT. On these two new orbits, the increments of the averaged SBR received by the new spaceborne DWLs range from 39 to 56 mW m−2 sr−1 nm−1 under cloud-free skies near the summer and winter solstices, which will lead to uncertainties of 0.19 and 0.27 m s−1 in the increment of the averaged Rayleigh channel wind observations for 15:00 and 12:00 LT orbits using the instrument parameters of Aeolus with 30 measurements per observation and 20 laser pulses per measurement. This demonstrates that Aeolus operating on the sun-synchronous dawn–dusk orbit is the optimal observation scenario, and the random error caused by the SBR will be larger on other sun-synchronous orbits. Increasing the laser pulse energy of the new spaceborne DWLs is used to lower the wind observation uncertainties, and a method to quantitatively design the laser pulse energy according to the specific accuracy requirements is proposed in this study based on the relationship between the signal-to-noise ratio and the uncertainty of the response function of the Rayleigh channel. The laser pulse energies of the two new spaceborne DWLs should be set to 70 mJ based on the statistical results obtained using the method. The other instrument parameters should be the same as those of Aeolus. Based on the proposed parameters, the accuracies of about 77.19 % and 74.71 % of the bins of the two new spaceborne DWLs would meet the accuracy requirements of the European Space Agency (ESA) for Aeolus. These values are very close to the 76.46 % accuracy of an Aeolus-type spaceborne DWL when it is free of the impact of the SBR. Moreover, the averaged uncertainties of the two new spaceborne DWLs are 2.62 and 2.69 m s−1, which perform better than that of Aeolus (2.77 m s−1).

Highlights

  • The first spaceborne Doppler wind lidar (DWL) mission, the Atmospheric Dynamics Mission (ADM) ADM-Aeolus, designed by the European Space Agency (ESA) was launched successfully on 22 August 2018

  • Regarding multi-satellite joint observation scenarios, according to the World Meteorological Organization’s (WMO) Observing Systems Capability Analysis and Review Tool (OSCAR) (Eyre, 2018), an observation cycle of 12 h with Aeolus operating on a sun-synchronous dawn–dusk orbit would meet “the minimum” requirements that have to be met to ensure the observations are useful for global Numerical weather prediction (NWP)

  • For sun-synchronous orbits, a spaceborne DWL operating on a dawn–dusk orbit (LTAN of 18:00 LT) would receive the minimum amount of solar background radiation (SBR), and a spaceborne DWL operating on a noon–midnight orbit (LTAN of 12:00 LT) would receive the maximum amount of SBR

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Summary

Introduction

The first spaceborne Doppler wind lidar (DWL) mission, the Atmospheric Dynamics Mission (ADM) ADM-Aeolus, designed by the European Space Agency (ESA) was launched successfully on 22 August 2018 This mission has improved our knowledge of the global wind field. Regarding multi-satellite joint observation scenarios, according to the World Meteorological Organization’s (WMO) Observing Systems Capability Analysis and Review Tool (OSCAR) (Eyre, 2018), an observation cycle of 12 h with Aeolus operating on a sun-synchronous dawn–dusk orbit would meet “the minimum” requirements that have to be met to ensure the observations are useful for global NWP. When another Aeolus-type satellite operates on a sun-synchronous noon– midnight orbit combined with Aeolus, the observation cycle may become 6 h, which would meet breakthrough requirement that, if achieved, would result in a significant improvement in global NWP compared with those based on dawn– dusk Aeolus

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