Title

A Comparison Of Two- And Three-Dimensional Transport Within A Stratospheric Circulation Model

Date of Award

1984

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Meteorology and Physical Oceanography

Abstract

The use of the residual circulation for tracer transport in the stratosphere is compared to an exact three-dimensional transport calculation. To obtain the wind fields for this comparison, a mechanistic primitive equation model for the stratospheric circulation has been formulated. The model is semispectral, uses a split explicit time integration scheme and includes wave-wave interaction. Also, a numerical transport scheme, called the square root scheme, has been developed. This scheme avoids the problem of negative mixing ratios, has very little inherent diffusion and good shape preserving properties, and it is computationally simple, even in three spatial dimensions.Transport comparisons have been made for two cases: a modeled linear m = 1 warming and a perpetual January run without a major warming. A passive tracer has been transported for both cases, using once the three-dimensional velocity fields and again, using the residual circulation, diagnosed from the same runs. For the January case, the evolution of the mixing ratios of an ozone-like tracer has also been studied.It is confirmed that the residual circulation gives poor results during a major stratospheric warming. Even under the more quiet perpetual January condition, the error in the zonally averaged mixing ratios amounts to a factor of two. The residual circulation also does not properly treat the southward and upward mixing which occurs in subtropical latitudes and the fluctuations due to wave transience which occur on a time scale of approximately one month. Furthermore, the vertical transport is overestimated by the residual circulation.

Keywords

Physics, Atmospheric Science

Link to Full Text

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