Extraction of 3D Wind Profiles from Hyperspectral IASI Level 2 Products
Atmospheric Motion Vectors (AMV) commonly provide information of cloud motions at a single level in the troposphere. However, the vertical wind shear impacts the dynamic meteorology of the troposphere, and the assimilation of horizontal wind at different levels in NWP models is still a critical gap in user requirements. Apart from a direct measure using a wind profiler, such wind vertical profiles may theoretically be estimated from temperature and humidity profiles retrieved from hyperspectral sounding, for which the height information is already available together with the retrievals. Time sequences of extracted water vapour fields become in this approach the “imagery” for tracking winds.
Recent studies involving 3D optical flow Technics (Heas and Mémin, 2008) to extract AMV from humidity fields have been realised by EUMETSAT and have clearly shown the potential benefits of these methods. The latest version of the algorithm has been adapted to ingest both Metop/IASI level 2 humidity, temperature and ozone fields, and can extract dense wind fields from a pair of IASI data taken consecutively by Metop A and Metop B satellites over high latitudes areas (poleward 45 deg). The use of ozone field allows the extraction of wind fields in the lower stratosphere when the humidity fields are the main tracer used for the troposphere.
A one month demonstration period has been produced (June 2017). Comparison of 3D IASI winds against “classical” Atmospheric Motion Vectors extracted using AVHRR data, against forecast fields and winds retrieved by the algorithm from ECWMF forecast fields have been done to understand better the current performances and limitations of this technique.
The results are still in a preliminary stage but show the potential of these wind profile retrievals. We will also propose a way forward for future improvements.
