Current Status of the IASI 3D Winds Product at EUMETSAT
The assimilation of horizontal wind at different levels in numerical weather prediction (NWP) models is still a critical gap in the user requirements. Apart from direct measurements using a wind profiler, such vertical wind profiles can be estimated from temperature and humidity profiles retrieved from hyperspectral sounders like the IASI (Infrared Atmospheric Sounding Interferometer) instrument on board the Metop satellites.
The IASI 3D Winds algorithm developed at EUMETSAT uses optical flow techniques in order to extract atmospheric motion information in multiple layers simultaneously from sequences of IASI level 2 temperature, humidity, and ozone products. The current version of the algorithm allows to derive the horizontal components of the atmospheric motion, as well as the vertical component of the motion in isobaric coordinates, over a configurable number of pressure levels (currently set to 25).
The production of dense horizontal wind fields covers high-latitudes areas (poleward of 45 deg) from the ground level to around 10 hPa in the stratosphere. Following the preliminary feedback received from the user community, a binning process has been implemented to reduce the amount of profiles and the correlation errors. After several years of development, the current version of the IASI 3D winds product is mature enough for scientific validation and testing in NWP.
In this paper, the latest version of the algorithm will be presented, together with a preliminary assessment of the product quality by means of comparing the retrieved winds with radiosonde observations and the corresponding forecast profiles.
