Tracer transport in the tropical lower stratosphere. Ph.D. Thesis

Technical Report · Fri Jan 01 04:00:00 EST 1993

OSTI ID:404799

Trepte, C R

Distributions of aerosol extinction ratio (beta r) and ozone, derived from the Stratospheric Aerosol and Gas Experiment (SAGE 1/2) satellite experiments (1979-1981 and 1984-1992), are used in conjunction with conventional meteorological analyses to deduce patterns of stratospheric tracer transport. Following volcanic eruptions at low latitudes, the aerosol observations suggest that two transport regimes exist in the tropical lower stratosphere. Aerosols disperse rapidly poleward and downward within a layer several kilometers above the tropopause. More pronounced transport is biased toward the winter hemisphere. At higher altitudes, however, volcanic aerosols tend to remain over the equator in a reservoir bounded by strong meridional gradients near 20 deg N and S. Over the equator, enhanced lofting of aerosols occurs during QBO easterly shear, while subsidence relative to the mean meridional flow takes place during QBO westerly shear. While particle growth and evaporation effects are important, many interesting features of the aerosol distribution can only be explained by air motions. It is also shown that QBO induced ozone anomalies over the equator are also consistent with QBO aerosol variations. In the upper transport regime, the subtropical gradients of beta r coincide with the location of a meridional gradient in potential vorticity. Since isentropic transport is inhibited across potential vorticity gradients, the tropics are temporarily isolated from eddy mixing taking place in the winter extratropics. Zonal mean distributions of ozone; however, do not have similar meridional gradients in the subtropics. This difference probably reflects a different source/sink distribution for ozone in comparison to that for aerosol and potential vorticity. Detrainment of aerosol from the equatorial reservoir depends upon the phase of the QBO and the strength of winter eddy disturbances in the subtropics.

• Research Organization: Wisconsin Univ., Madison, WI (United States). Space Science and Engineering Center
• OSTI ID: 404799
• Report Number(s): N--96-27644; NIPS--96-06217
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
AEROSOLS
ATMOSPHERIC CIRCULATION
OZONE
STRATOSPHERE
TRACER TECHNIQUES
TROPICAL REGIONS