The Challenge of Surface Type Changes Over the Aral Sea for Satellite Remote Sensing of Precipitation

• Published in: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
• Main Authors: Quanhua Liu, Yong-Keun Lee, Christopher Grassotti, XingMing Liang, Stanley Q. Kidder, Sheldon Kusselson
• Format: Article in Journal/Newspaper
• Language: English
• Published: IEEE 2022
• Subjects: Aral sea; microwave integrated retrieval system (MiRS); surface type; Ocean engineering; TC1501-1800; Geophysics. Cosmic physics; QC801-809; Antarc*; Antarctica
• Online Access: https://doi.org/10.1109/JSTARS.2022.3212647; https://doaj.org/article/2a0a6318527543628c94eec9670d12db

Frequent false signals of precipitation in satellite passive microwave retrievals over the Aral Sea have been identified as being caused by an outdated surface database. The database includes the surface type, elevation, and the percentage of the primary surface type in each grid. It was also found that the grid resolution of 1/6 degree (∼18 km at the equator) of the outdated surface data was too coarse to process global precipitation measurement mission microwave imager data, which have a field of view resolution of 31.68 km 2 for channels at 89, 166.5, and 183.31 GHz). In this article, we generated a new surface database at a resolution of $0.05^\circ \times 0.05^\circ $ (∼5.6 km at the equator). Using the new surface data, the false precipitation problem above is addressed. At the same time, the retrieval accuracy for other parameters such as total precipitable water over the Aral sea is significantly improved as well. The resolution of the database is suitable for most microwave and infrared sounding measurements of atmospheric temperature and moisture profiles as well as precipitation. By comparing this new surface data against the outdated surface data, we also see the loss of permanent ice in Antarctica and a dramatic reduction of water surface over the Aral sea. Using a 40-year record of remote sensing data, we can observe the steady decrease in size of the Aral sea, as a result of regional water use policies and natural climate change.