Validation of the Aeolus Level-2B wind product over Northern Canada and the Arctic
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Published:2022-08-02
Issue:15
Volume:15
Page:4443-4461
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ISSN:1867-8548
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Container-title:Atmospheric Measurement Techniques
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language:en
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Short-container-title:Atmos. Meas. Tech.
Author:
Chou Chih-ChunORCID, Kushner Paul J.ORCID, Laroche Stéphane, Mariani ZenORCID, Rodriguez Peter, Melo Stella, Fletcher Christopher G.ORCID
Abstract
Abstract. In August 2018, the European Space Agency (ESA) launched the Aeolus satellite, whose Atmospheric LAser Doppler INstrument (ALADIN) is the
first space-borne Doppler wind lidar to regularly measure vertical profiles of horizontal line-of-sight (HLOS) winds with global sampling. This mission
is intended to assess improvement to numerical weather prediction provided
by wind observations in regions poorly constrained by atmospheric mass, such
as the tropics, but also, potentially, in polar regions such as the Arctic
where direct wind observations are especially sparse. There remain gaps in
the evaluation of the Aeolus products over the Arctic region, which is the
focus of this contribution. Here, an assessment of the Aeolus Level-2B (L2B) wind product is carried out, progressing from specific locations in the Canadian North to the pan-Arctic. In particular, Aeolus data are compared to a limited sample of coincident ground-based Ka-band radar measurements at
Iqaluit, Nunavut, to a larger set of coincident radiosonde measurements over the Canadian North, to Environment and Climate Change Canada (ECCC)'s
short-range forecast, and to the reanalysis product, ERA5, from the European Centre for Medium-Range Weather Forecasts (ECMWF). Periods covered include
the early phase of the first laser flight model (flight model A – FM-A; September to October 2018),
the early phase of the second laser flight model (flight model B – FM-B; August to September 2019),
and the middle phase of FM-B (December 2019 to January 2020).
The adjusted r-squared
between Aeolus and other local datasets is around 0.9 except for
lower values for the comparison to the Ka-band radar, reflecting limited sampling opportunities with the radar data. This consistency is degraded by
about 10 % for the Rayleigh winds in the summer due to solar background
noise and other possible errors. Over the pan-Arctic, consistency, with
correlation greater than 0.8, is found in the Mie channel from the planetary
boundary layer to the lower stratosphere (near surface to 16 km a.g.l.) and
in the Rayleigh channel from the troposphere to the stratosphere (2 to 25 km a.g.l.). In all three periods, Aeolus standard deviations are found to be
5 % to 40 % greater than those from ECCC-B and ERA5. We found that the L2B
estimated error product for Aeolus is coherent with the differences between
Aeolus and the other datasets and can be used as a guide for expected consistency. Our work shows that the high quality of the Aeolus dataset that
has been demonstrated globally applies to the sparsely sampled Arctic
region. It also demonstrates the lack of available independent wind
measurements in the Canadian North, lending urgency to the need to augment
the observing capacity in this region to ensure suitable calibration and
validation of future space-borne Doppler wind lidar (DWL) missions.
Funder
Canadian Space Agency
Publisher
Copernicus GmbH
Subject
Atmospheric Science
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