Ozone Depletion, Greenhouse Gases, and Climate Change (1989) / Chapter Skim
Currently Skimming:
8 Theoretical Projections of Stratospheric Change Due to Increasing . . .
8 Theoretical Projections of Stratospheric Change Due to Increasing . . .
Pages 66-78
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 66... ...
However, the N2O anthropogenic source is about one-thircI of the natural source and thus is not negligible on long time scales. Nitrous oxide is a tropospheric greenhouse gas, but its small annual increases are contributing little to current increaser in infrared radiative forcing.
|
From page 67... ...
An increase would result in increased downward infrared radiative flux, complex chemical changes if stratospheric ice clouds form, and an increased ozone loss in the 30- to 50-km layer. I will next discuss what the NASA-WMO Ozone Trends Pane!
|
From page 68... ...
radiation penetrating to lower altitudes and creating more ozone in a kind of negative feedback process that tends to limit the depletion of total column ozone. Thus the change in the total column ozone is a comparatively small difference between two large numbers, given that the atmospheric mass drops off nearly exponentially with increased altitude.
|
From page 69... ...
This corresponds to the "fixed dynamical heating" limit; that is, the net heating of local air by dynamical processes does not change with changing absorbers, even though the temperature itself is free to change. However, when a real climate system such as the stratosphere is perturbed, the changed distribution of absorbers may or may not lead to a changed temperature
|
From page 70... ...
Such a two-dimensional model uses a latitudealtitude framework that has mean mass circulation directed upward in low latitudes, downward in high latitudes, and from equator to pole at stratospheric altitudes. Superunposed on the mean meridional motion is a meridional eddy diffusion of particles that is driven by upward-propagating tropospheric disturbances.
|
From page 71... ...
It appears that the tropospheric dynamical processes are strong enough to push the stratosphere some distance away from its radiative equilibrium condition. Thus dynamic modeling is essential for predicting changes correctly in the stratosphere.
|
From page 72... ...
On the left is a fixed dynamical heating upper stratosphere that will be partially compensated for in the lower stratosphere. But, the unpredicted antarctic ozone situation warns us to be wary of things that may be missing from current model calculations.
|
From page 73... ...
the troposphere should result in a weaker meridional temperature gradient, thus weakening tropospheric circulation and decreasing the flux of wave activity to the stratosphere. The stratospheric transport circulation would in turn be reduced.
|
From page 74... ...
We are beginning to understand the influence of the antarctic ozone seasonal depletion on the ozone climatology of the Southern Hemisphere. It appears that dilution is occurring, causing significant ozone decreases throughout the Southern Hemisphere, as pointed out in the presentations by Robert Watson and F
|
From page 75... ...
amount of chlorine species at any particular time in winter than does the southern region in winter, because the Northern Hemisphere region is dynamically more active. Stratospheric cooling due to the combined effects of greenhouse gases and reduced ozone will likely be accented in higher latitudes.
|
From page 76... ...
But as the stratosphere cools due to changed greenhouse gases, polar stratospheric clouds should become more common and widespread in the north. Also, reduced transport circulation in the Northern Hemisphere could lead to a further decrease of temperatures at high latitudes.
|
From page 77... ...
There was a tacit assumption that the stratosphere was in radiative equilibrium in the wintertime except during sudden warming events. However, we have learned that tropospheric forcing of the stratosphere does not permit radiative equilibrium to be established, a fact that was first theorized by Dickinson (1975~.
|
From page 78... ...
1980. Stratosphere sensitivity to perturbations in ozone and carbon dioxide: Radiative and dynamical response.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.