A three-dimensional transport model for the middle atmosphere

Physics

Scientific paper

Rate now

  [ 0.00 ] – not rated yet Voters 0   Comments 0

Details

32

Atmospheric Composition And Structure: Middle Atmosphere-Composition And Chemistry, Meteorology And Atmospheric Dynamics: General Circulation

Scientific paper

In this paper we describe the fundamental properties of an ``off-line'' three-dimensional transport model, that is, a model which uses prescribed rather than predicted winds. The model is currently used primarily for studying problems of the middle atmosphere because we have not (yet) incorporated a formulation for the convective transport of trace species, a prerequisite for many tropospheric problems. The off-line model is simpler and less expensive than a model which predicts the wind and mass evolution (an ``on-line'' model), but it is more complex than the two-dimensional (2-D) zonally averaged transport models often used in the study of chemistry and transport in the middle atmosphere. It thus serves as a model of intermediate complexity and can fill a useful niche for the study of transport and chemistry. We compare simulations of four tracers, released in the lower stratosphere, in both the on- and off-line models to document the difference resulting from differences in modeling the same problem with this intermediate model. These differences identify the price to be paid in going to a cheaper and simpler calculation. The off-line model transports a tracer in three dimensions. For this reason, it requires fewer approximations than 2-D transport model, which must parameterize the effects of mixing by transient and zonally asymmetric wind features. We compare simulations of the off-line model with simulations of a 2-D model for two problems.
First, we compare 2-D and three-dimensional (3-D) models by simulating the emission of an NOx-like tracer by a fleet of high-speed aircraft. The off-line model is then used to simulate the transport of 14C and to contrast its simulation properties to that of the host of 2-D models which participated in an identical simulation in a recent NASA model intercomparison. The off-line model is shown to be somewhat sensitive to the sampling strategy for off-line winds. Simulations with daily averaged winds are in very good qualitative agreement but are less diffusive than when driven with instantaneous winds sampled at half-hour intervals.
Simulations with the off-line and 2-D models are quite similar in the middle and upper stratosphere but behave quite differently in the lower stratosphere, where the 3-D model has a substantially more vigorous circulation. The off-line model is quite realistic in its simulation of 14C. While there are still systematic differences between the 3-D calculation and the observations, the differences seem to be substantially reduced when compared with the body of 2-D simulations documented in the above mentioned NASA intercomparison, particularly at 31°N.

No associations

LandOfFree

Say what you really think

Search LandOfFree.com for scientists and scientific papers. Rate them and share your experience with other people.

Rating

A three-dimensional transport model for the middle atmosphere does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with A three-dimensional transport model for the middle atmosphere, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A three-dimensional transport model for the middle atmosphere will most certainly appreciate the feedback.

Rate now

     

Profile ID: LFWR-SCP-O-870127

  Search
All data on this website is collected from public sources. Our data reflects the most accurate information available at the time of publication.