The Caspian Sea as a full-scale experimental facility supported by altimetry measurements of wind-driven waves

The Caspian Sea is the largest inland water body. Strong and stable winds regularly occur along its longest stretch of more than 1000 km from the Volga Lowland in Russia to the Iranian coast. During these events, wind speeds can exceed 20 m/s and significant wave heights 5 m. These wind directions often align with the tracks of satellite altimeters that have been monitoring the sea state since September 1992. This makes the Caspian Sea an ideal location replicating idealized conditions for the growth of wind-driven waves, and supported by a high-precision network of satellite altimeters.

The shape of the coastline and prevalent wind directions allowed us to view the sea as a full-scale wind-wave research facility. In situ measurements and observations of sea state in this area are scarce and inaccurate while the altimetry tracks provide a ready-to-use high-quality measurement network. We analyze data of satellite missions Jason-3 for years 2016-2022 and CFOSAT (Chinese-French Oceanography SATellite) for 2019-2023 to assess the potential of the full-scale experimental facility. These missions provide valuable data showcasing the Caspian Sea as a realistic model for the World Ocean with minimal contaminating effects of swell, tides and currents. This makes the “clean cases” of the Caspian Sea particularly valuable both as a reference for understanding general wave physics and for regional studies on sea wave dynamics.