The Importance of Humidity Effect in Determining Flux-Profile Parameters of a Marine Surface Layer

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  • 1 Modelling and Integration Research Division, Atmospheric Environment Service, Downsview, Ontario Canada
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Abstract

The role of humidity in estimating marine surface layer stratification in terms of the ratio, R, of the humidity contribution to the total static stability is evaluated. A recent study of Geernaert and Larsen employs a system of simultaneous equations for calculating R. The present study requires only simple algebraic relations to arrive at the approximate solution of R. In the approximate solution, the value of R is explicitly represented in a single equation as a function of potential temperatures and the corresponding virtual potential temperatures. The exact solution of R is obtained directly using the Monin-Obukhov stability parameters with and without humidity effect. Static stability and transfer coefficients, as well as deposition velocity of SO2 over an air-sea interface, are calculated using the direct bulk aerodynamic method similar to that of Lo. Detailed study on characteristics of humidity effect on atmospheric stratification, especially for cases of large sea-air temperature differences under stable conditions, are presented. Implication of humidity effect on stability pertaining to the theory of “countergradient” phenomenon is also presented.

Abstract

The role of humidity in estimating marine surface layer stratification in terms of the ratio, R, of the humidity contribution to the total static stability is evaluated. A recent study of Geernaert and Larsen employs a system of simultaneous equations for calculating R. The present study requires only simple algebraic relations to arrive at the approximate solution of R. In the approximate solution, the value of R is explicitly represented in a single equation as a function of potential temperatures and the corresponding virtual potential temperatures. The exact solution of R is obtained directly using the Monin-Obukhov stability parameters with and without humidity effect. Static stability and transfer coefficients, as well as deposition velocity of SO2 over an air-sea interface, are calculated using the direct bulk aerodynamic method similar to that of Lo. Detailed study on characteristics of humidity effect on atmospheric stratification, especially for cases of large sea-air temperature differences under stable conditions, are presented. Implication of humidity effect on stability pertaining to the theory of “countergradient” phenomenon is also presented.

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