The IASI Cloud Detection product (IASI CLD) is a cloud mask available at the IASI pixel level (L2) that was developed for climate applications purposes. The algorithm is detailed in Whitburn et al. (2022, Atmospheric Measurement Techniques). It combines (1) a high sensitivity to cloud detection, (2) a very good consistency over time and between the three IASI instruments and (3) simplicity in its parametrization. The method is based on the use of a supervised neural network using the version 6.5 of the operational IASI L2 cloud product as a reference dataset. As input parameters, it relies on IASI radiance information only. The consistency over time is ensured by careful selection of the IASI input channels, avoiding especially the spectral regions affected by long-lived absorbers and water vapor.
The version number is 1.0.
IASI/Metop CLD data are available daily from 2008 to 2020 for Metop-A, Metop-B and Metop-C in hdf format. For Metop-A before 2016, the algorithm was applied to reprocessed IASI L1C data for more homogeneity in the data set. Each file includes the latitude, the longitude, the neural network’s retrieval, and the IASI overpass time. Note that the retrieval of the neural network provides a value comprised between 0 and 1. This value is converted in a cloud mask using an appropriate threshold. We recommend using the thresholds provided in Whitburn et al. (2022) (i.e. 0.175 for land and 0.275 for oceans) but these can be adjusted depending on the application.
Data access : https://iasi-ft.eu/data-access/CLD/
Whitburn, S., Clarisse, L., Crapeau, M., August, T., Hultberg, T., Coheur, P. F., and Clerbaux, C.: A CO2-independent cloud mask from Infrared Atmospheric Sounding Interferometer (IASI) radiances for climate applications, Atmos. Meas. Tech., 15, 6653–6668, https://doi.org/10.5194/amt-15-6653-2022, 2022.
Simon Whitburn (email@example.com)
Whitburn, Simon. (2022). A CO2-free cloud mask from IASI radiances for climate applications (from IASI/Metop-A) [Data set]. ULB/LATMOS.