STRATOSPHERIC MIXING FROM RADIOACTIVE FALLOUT
The radioactive fall-out during 1959 shows that the Russian October 1958 debris dominated the northern hemisphere and came down with a residence time corresponding to about 8 months. The rest of the world had a steady fall-out rate of about 0.06 mc/mi/sup 2//in. of rain throughout the year, whereas values for the northern hemisphere came down to this value in the months of September, October, and November when the Russian debris was apparently exhausted. Thus. it appears that there is a world-wide fall-out rate of about 0.06 mc/mi/sup 2//in. of rain which is nearly independent of the Russian polar debris and which is probably from the equatorial tests. Using the estimate of ihe amount of material injected into the stratosphere, this world-wide rate of fall-out corresponds to a residence time of about 5 years for equatorial injections. Goldie suggested that the meridional circulation at levels well within the stratosphere consists of an up-welling of air at the equator. followed by a polar fiow, a down-welling in the polar region, and an equatorward movement above the troposphere at approximately 24 km. In addition, a seasonal perturbation of this circulation occurs in the long winter night near the pole. It results in an accumulation of material at high levels near the pole, until the sun returns in the spring, when a sudden break-up occurs and the material is rapidly carried toward the troposphere. This model explains quite well most of the present observations on radioactive fall- out. The polar debris would Naturally have a shorter residence time because it would be introduced in the last steps of the cycle, the equatorial would have a longer residence time, having been introduced at the beginning of the cycle, and the spring breakup of the polar vortex would account for the well-known spring maximum in the rate of radioactive fall-out. The residence times of material injected near the equator and the pole, respectively, permit a quantitative estimate of the intensity and depth of the circulation to be made. The meridiomal velocity deduced for the equatorially directed low stratospheric current is about l to 3 miles per hour, whereas that for the poleward high stratospheric current is about one-tenth as large. This requires, of course, that 90% of the stratospheric air be concentrated in the high brand. (auth)
- Research Organization:
- Univ. of California, Los Angeles
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-15-001601
- OSTI ID:
- 4122183
- Journal Information:
- J. Geophys. Research, Journal Name: J. Geophys. Research Vol. Vol: 65
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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