Unit:
Department of PhysicsLibrary of the School of Science
Author:
Stathopoulos Christos-Marios
Dissertation committee:
Γεώργιος Κάλλος, Ομότιμος Καθηγητής, Τμήμα Φυσικής, ΕΚΠΑ
Γεώργιος Γαλάνης, Καθηγητής, Σχολή Ναυτικών Δοκίμων
Σαράντης Σοφιανός, Επίκουρος Καθηγητής,Τμήμα Φυσικής, ΕΚΠΑ
Μαρία Τόμπρου-Τζέλλα,Καθηγήτρια, Τμήμα Φυσικής, ΕΚΠΑ
Έλενα Φλόκα, Καθηγήτρια, Τμήμα Φυσικής, ΕΚΠΑ
Εμμανουήλ Αναγνώστου, Καθηγητής, University of Connecticut, USA
Ιωάννης Πυθαρούλης, Αναπληρωτής Καθηγητής, Τμήμα Γεωλογίας, ΑΠΘ
Original Title:
Study the air-sea interaction processes with the development of a coupled modeling system
Translated title:
Study the air-sea interaction processes with the development of a coupled modeling system
Summary:
Dynamics of atmosphere and oceans enclose a myriad of complex interactive processes regulating the weather and climatic events. The impact of air-sea interaction extends to all spatiotemporal scales. Processes such as the exchange of momentum, heat and moisture influence plenty of meteorological phenomena. The complexity of air-ocean interactive mechanisms and the plethora of parameters involved, suggest that many aspects require further analysis. Additionally, in wave/ocean and atmospheric models, a more accurate representation of the atmospheric and oceanic surface conditions and interactions is essential for better weather forecasting.
The main objective of this thesis is to better understand the role of certain atmospheric-ocean feedback mechanisms participating in the air-sea interface. More precisely, this work intends to examine (a) the mechanical processes expressed as momentum transfer between the lower atmosphere and the ocean and (b) the thermodynamical processes related to the effects in heat fluxes from the sea surface temperature (SST) forcing and the sea spray generated from wave breaking.
The wind-wave momentum exchange is assessed with the introduction of wave effects in the lower atmospheric layers. The impact of wave state conditions is considered on the sea surface roughness calculation influencing also the atmospheric and wave fields. Moreover, air-ocean heat exchanges are approached based on the thermodynamic disequilibrium between the ocean surface and the upper air. This is pursued by analyzing the impact and uncertainty of different SST forcing on Mediterranean Cyclones. The role of sea spray in the boundary layer is also investigated along with its relation to micro-physical processes such as condensation/evaporation of water droplets. To study the aforementioned atmospheric-ocean processes, a coupled modeling tool has been developed including the atmospheric modeling system RAMS/ICLAMS, the wave model WAM and the coupler OASIS. Within this system, a numerical description of sea spray thermodynamics is implemented. To test and analyze the impact of these air-ocean feedback mechanisms, several cyclonic events were simulated in two regions with different geomorphological and climatic characteristics, the North Sea and the Mediterranean Basin.
Wind-wave momentum exchange revealed that information stemming from wave properties employed in the expression of the ocean drag, has a detectable impact on the atmospheric model. Smaller errors appear close to the surface and vertically both for wind speed and temperature. Likewise, the ongoing wind-wave effect was also evident in the derived wave heights. Spatiotemporal deviations in the SST forcing seem to mainly contribute in the differences between the model results, mostly in the resulting heat fluxes and in precipitation. Implementation of sea spray fluxes in model physics, induced alterations both in horizontal and vertical scale. Effects were evident in the stability conditions with height in the atmospheric layers close to the ocean surface. Near-surface temperature and water vapor profiles were modified, leading to a non-linear feedback that also influenced wind patterns. Most noticeably, the impact on the marine layer structure found in a layer ranging from a few tens up to a few hundreds of meters depending on the storm characteristics.
The present work intends to contribute to the multi-parametric issue of air-sea interaction processes that affect marine forecasts and plenty of offshore activities and applications.
Main subject category:
Science
Keywords:
atmospheric – wave coupling; air-sea interaction; ocean roughness; sea spray; RAMS; WAM;
Number of references:
150
File:
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CStathop_phd.pdf
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