Seminarium fizyki atmosfery

Coupling between atmosphere and ocean on diurnal time scale: can we measure physical properties of atmosphere and ocean across an undisturbed air-sea interface.

dr Dariusz B. Baranowski

Instytut Geofizyki, Polska Akademia Nauk


6 października 2023 13:15, ul. Pasteura 5, B4.58 and online via ZOOM

Interactions across an air-sea interface are fundamental features of Earth’s climate system with substantial implications for ecosystems. The diurnal variations of local exchange between atmosphere and ocean impact both environments and rectifies into longer and larger scale through the interactions with mesoscale circulation. Therefore, such local processes can potentially influence the evolution of weather patterns as well as properties of an ocean’s circulation. At the same time, atmosphere and ocean models struggle with the realistic representation of diurnal variations across an air-sea interface.  The gaps in our understating of physical mechanisms behind these interactions stems from the fact that collocated, reliable measurements within coupled atmosphere and ocean environment, spanning across an air-sea interface are rare.

The exchange of physical properties, including but not limited to, energy and momentum across an air-sea interface depends on the environment within the air-sea transition zone, which can be defined as an area between the bottom of the oceanic mixed layer (~100m depth) and the top of the atmospheric boundary layer (~1000m). Thus, measurements of stratifications across are required to characterize coupled variability of the atmosphere and ocean, especially on a diurnal time scale. Although many observational techniques have been devised to observe stratification (e.g., vertical profiles of physical properties) within atmospheric and oceanic environments, they can rarely be applied at the same place or time in both environments without disturbing it. The emergence of the Uncrewed Aircraft Systems (UAS) enables a new opportunity for sampling across air-sea interface. A multirotor UAS equipped with atmosphere and/or ocean measurement capabilities can be launched from a vessel and perform measurements in its vicinity, in flow but not obstructed by the ship’s structure.

In my presentation I will discuss the opportunities provided by UAV-based measurement conducted in combination with other ship-borne observations to perform seamless observations across the air-sea transition zone. To that end, observations characterizing diurnal evolution of atmospheric and oceanic environments collected over tropical and subtropical Atlantic Ocean will be presented. Collected observations of atmospheric temperature, humidity, and winds profiles (surface to 500m) combined with observations of temperature in the top layer (top 10m) of the ocean can be used to identify the effect of air-sea fluxes on local variability in both environments. Results demonstrate the capability of ocean and atmosphere sensing UAS to measure coupled variability across an air-sea interface. Opportunities to expand such measurements in the future to other global basins and marginal seas (e.g., Baltic Sea) will be discussed as well.

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