Abstract
Abstract. After the successful launch of Aeolus, which is the first spaceborne wind lidar developed by the European Space Agency (ESA), on 22 August 2018, we deployed several ground-based coherent Doppler wind lidars (CDLs) to verify the wind observations from Aeolus. By the simultaneous wind measurements with CDLs at 17 stations over China, the Rayleigh-clear and Mie-cloudy horizontal-line-of-sight (HLOS) wind velocities from Aeolus in the atmospheric boundary layer and the lower troposphere are compared with those from CDLs. To ensure the quality of the measurement data from CDLs and Aeolus, strict quality controls are applied in this study. Overall, 52 simultaneous Mie-cloudy comparison pairs and 387 Rayleigh-clear comparison pairs from this campaign are acquired. All of the Aeolus-produced Level 2B (L2B) Mie-cloudy HLOS wind and Rayleigh-clear HLOS wind and CDL-produced HLOS wind are compared individually. For the inter-comparison result of Mie-cloudy HLOS wind and CDL-produced HLOS wind, the correlation coefficient, the standard deviation, the scaled mean absolute deviation (MAD) and the bias are 0.83, 3.15 m s−1, 2.64 m s−1 and −0.25 m s−1, respectively, while the y=ax slope, the y=ax+b slope and the y=ax+b intercept are 0.93, 0.92 and −0.33 m s−1. For the Rayleigh-clear HLOS wind, the correlation coefficient, the standard deviation, the scaled MAD and the bias are 0.62, 7.07 m s−1, 5.77 m s−1 and −1.15 m s−1, respectively, while the y=ax slope, the y=ax+b slope and the y=ax+b intercept are 1.00, 0.96 and −1.2 m s−1. It is found that the standard deviation, the scaled MAD and the bias on ascending tracks are lower than those on descending tracks. Moreover, to evaluate the accuracy of Aeolus HLOS wind measurements under different product baselines, the Aeolus L2B Mie-cloudy HLOS wind data and L2B Rayleigh-clear HLOS wind data under Baselines 07 and 08, Baselines 09 and 10, and Baseline 11 are compared against the CDL-retrieved HLOS wind data separately. From the comparison results, marked misfits between the wind data from Aeolus Baselines 07 and 08 and wind data from CDLs in the atmospheric boundary layer and the lower troposphere are found. With the continuous calibration and validation and product processor updates, the performances of Aeolus wind measurements under Baselines 09 and 10 and Baseline 11 are improved significantly. Considering the influence of turbulence and convection in the atmospheric boundary layers and the lower troposphere, higher values for the vertical velocity are common in this region. Hence, as a special note, the vertical velocity could impact the HLOS wind velocity retrieval from Aeolus.
Highlights
Reliable instantaneous vertical profiling of the global wind field, especially over the tropics and oceans, is crucial to many aspects of climate change, oceanography research, large-scale weather systems and weather prediction
The CDLretrieved HLOS wind velocities with and without vertical velocity correction are compared against the Aeolus molecular (Rayleigh) and particle (Mie) Level 2B (L2B) products and Rayleigh L2B products
It is found that the Aeolus L2B Rayleigh-clear HLOS wind profile in the atmospheric boundary layer and the lower troposphere is almost trustable, except for the lowest height bin of the Aeolus Rayleigh-clear HLOS wind profile, which has a large bias compared with the coherent Doppler wind lidars (CDLs)-retrieved HLOS wind
Summary
Reliable instantaneous vertical profiling of the global wind field, especially over the tropics and oceans, is crucial to many aspects of climate change, oceanography research, large-scale weather systems and weather prediction. Due to the lack of wind profiles over ocean areas from the radiosonde network and wind observations only at a specific flight altitude (around 10–12 km about ground level) in aircraft measurements, a first-ever spaceborne direct-detection wind lidar, Aeolus, which is capable of providing the globally high spatial and temporal vertical wind profiles, was developed by the European Space Agency (ESA) under the framework of the Atmospheric Dynamics Mission (Stoffelen et al, 2005; ESA, 1999; Reitebuch, 2012). In the Rayleigh channel, two coupled Fabry–Pérot interferometers are used to analyse the frequency shift in the broadband molecular return signal by the double-edge technique (Chanin et al, 1989; Flesia and Korb, 1999)
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