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Study On The Physical Process Of Marine Atmospheric Boundary Layer Model And Numerical Simulation

Posted on:2009-11-06Degree:DoctorType:Dissertation
Country:ChinaCandidate:X LiFull Text:PDF
GTID:1100360245487837Subject:Physical oceanography
Abstract/Summary:PDF Full Text Request
The globe of the earth is surrounded by a gaseous atmosphere which is always in motion. When in contact with the land or the water surface of the earth the flow is reduced to zero, relative to the underlying surface, and it is this boundary flow that interests us here. As well as the planetary boundary layer in the air, also known as the Ekman layer, there is an oceanic boundary layer which interacts with the air above. An adequate description of physical processes and mechanisms that determine the structure of the interacting atmospheric and oceanic boundary layers as well as a theoretical background is needed for developing parameterization schemes. Exchange of the momentum and energy is important process of sea-air surface. In general, the energy of solar shortwave radiation absorbed by ocean is two times more than atmosphere. The warm sea surface transport energy to the atmosphere through the long-wave radiation and the latent and sensible heat, so the bottom of atmosphere is heated by ocean. Because the nonuniformity of heats in different latitude and rotation of the Earth, large-scale atmospheric circulation is produced, therefore the air has provided the momentum and energy to the sea with effect of wind. There are also exchange of material (for example greenhouse gas) between air and sea. One of the most important problems is the parameterization of the turbulent fluxes of momentum, latent and sensible heat at the sea surface. The oceans are the major source of atmospheric water and a major contributor to the heat content of the atmosphere. Most of the solar energy is absorbed by the oceans, and this energy becomes available to maintain the atmospheric circulation only through turbulent fluxes of latent and sensible heat. Radiative, sensible and latent fluxes determine the ocean surface energy flux and, consequently, the vertical structure of the upper ocean. The turbulent exchange processes at the air-sea interface are strongly influenced by the state of the sea surface which is varying in time. However, the sea surface temperature changes little over a diurnal cycle because water has a large heat capacity. The roughness of the sea surface depends on the atmospheric surface layer parameters and consequently, on the processes in the whole atmospheric boundary layer. It is believed that the sea surface roughness governs the degree of wind drag time variability. It is very important that the atmospheric motions generate surface waves which also contribute to a turbulent mixing of the atmosphere and ocean.This article briefly reviewed the development of atmospheric boundary layer model and research of the sea-air surface and the marine atmospheric boundary layer. Marine atmospheric boundary layer height, the surface radiation and energy balance and vertical structure are the major problem of the boundary layer process. Atmospheric boundary layer height is a important parameters for the boundary layer process of weather forecast model and climate system model. Sea-air interface processes connect the atmospheric boundary layer and ocean mixed layer, both the atmosphere force on the oceans and feedback are completed by the sea-air interface. As a coupled system of the Lower Atmosphere and Upper Ocean, we must study its interaction and the exchange process overall and comprehensive, including the atmospheric boundary layer, sea-air interface, the flux and the transmission of ocean mixed layer. Not only elements of the Upper Ocean and atmosphere decide the distribution of sea-air fluxes, but the change of sea-air fluxes also has a major impact on the elements of atmosphere and Upper Ocean. The previously work don't analyze the experiment data with the feedback mechanism, which about change of structure of Upper Ocean and atmosphere, and not analyze the change mechanism of sea-air flux exchange deeply. And this work discusses the physical characteristics of the marine atmospheric boundary layer and air-sea interface based on the analysis of the measured data and reanalyzed data.Recently the research of marine atmospheric boundary layer model has already acquired significant progress, but still has some insufficiencies. Little research has been discussed in our country; this mainly because there are some difficulties in the observation of the marine atmosphere boundary layer, the observed data are few and erroneous. In addition, marine atmospheric boundary layer contains a lot of very complex physical processes, which also make our research extremely difficult.This article also developed a high-resolution marine atmospheric boundary layer model, and discussed the effect of marine atmospheric boundary layer height, sea-air interface processes and the interaction between them by the numerical simulation. Thus can more in-depth understand the marine atmospheric boundary layer process for the climate system model and provide a basis for improvement of boundary layer parameterization schemes. Under the idealized conditions the effect of the sea surface on atmospheric boundary layer simulation have been studied, and several different sea surface roughness parameterizations were discussed, including the Smith (1988) scheme, Yelland and Tayor (1996) scheme, Tayor and Yelland (2001) scheme and Oost (2002) scheme. The results show that the simulation ability of these schemes is similar, but there is also a big error in some of the physical elements, such as the latent heat and sensible heat fluxes. To test the simulation capability of boundary layer model established by this paper, the mode has been applied in the Pratas of the South China Sea and the Arctic region, then analyzed and compared with the observation data. The results prove that the model is able to simulate well on the main physical process of marine atmospheric boundary layer and air-sea interface. Another column model has also been used to discuss cloud physical processes and radiation parameterizations (the CCM2 and RRTM scheme) on the Arctic region about the effects of numerical simulation of marine atmospheric boundary layer.
Keywords/Search Tags:atmospheric boundary layer, numerical simulation, parameterization of sea surface, radiation and energy budget
PDF Full Text Request
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