A calculation has been made of the meridional circulation sufficient to transport heat between the radiational sources and sinks in the stratosphere (15-55 km) and mesosphere (55-80 km). Assuming that the principal heat sources are in the region of the equatorial tropopause and in the mesosphere over the summer pole, with the corresponding heat sinks near the polar tropopause and over the winter pole in the mesosphere, the main circulation patterns are found. Below 30 km there is rising air over the equator with outflow towards both poles and descent towards the tropopause in high latitudes in both hemispheres. At higher levels there is ascent over the summer pole and descent over the winter pole with a well defined flow towards the winter pole above 50 km and a more indeterminate flow pattern between 30 and 50 km. The order of magnitude of the speed of these circulations is m sec-' horizontally and cm sec-' vertically.The calculations were made for the solstices, equinoxes and mid-times between them and several particle trajectories were determined. The results are in agreement with many of the observed physical features of the stratosphere and mesosphere, particularly the distribution of tracer elements.

A calculation has been made of the meridional circulation sufficient to transport heat between the radiational sources and sinks in the stratosphere (15-55 km) and mesosphere (55-80 km). Assuming that the principal heat sources are in the region of the equatorial tropopause and in the mesosphere over the summer pole, with the corresponding heat sinks near the polar tropopause and over the winter pole in the mesosphere, the main circulation patterns are found. Below 30 km there is rising air over the equator with outflow towards both poles and descent towards the tropopause in high latitudes in both hemispheres. At higher levels there is ascent over the summer pole and descent over the winter pole with a well defined flow towards the winter pole above 50 km and a more indeterminate flow pattern between 30 and 50 km. The order of magnitude of the speed of these circulations is m sec-' horizontally and cm sec-' vertically.The calculations were made for the solstices, equinoxes and mid-times between them and several particle trajectories were determined. The results are in agreement with many of the observed physical features of the stratosphere and mesosphere, particularly the distribution of tracer elements.

Ozone photochemistry over Antarctica in summer has been examined using a 1-D model. With diffusive transport alone, the predicted ozone decay rates from the December (summer) solstice to the March (autumn) equinox were found greatly to exceed observed rates. In order to obtain broad agreement between calculated and observed ozone amounts, it was necessary to include the effects of a slow downward mean velocity. The velocities used, a few tens of metres per day. are compatible with a Lagrangian mean circulation pattern derived from thermodynamic considerations and from GCMs.The rates of change of ozone amounts computed for 75"s decrease abruptly following the change from continuous to interrupted photolysis when the sun first sets (in mid-February) after the long polar day of midsummer. In the polar day regime, N , 0 5 concentrations are depressed strongly, and C10N02 concentrations moderately, relative to those in regions subjected to diurnal interruption of photolysis. The effects on the diurnal variations of ozone and other minor constituents are described.

SUMMARYZonal and meridional diffusivities K, , and Kyy have been found at mid-latitudes from the spreads of sets of geostrophic trajectories at levels between 700 mb and 30 mb during each season of 1965. Values have been calculated using the relationship R = e-PT cos 47 for the form of the corresponding Lagrangian autocorrelograms. In addition a similar set of Eulerian data has been analysed to obtain autocorrelograms and by comparison with the trajectory data Eulerian-Lagrangian scale relationships have been obtained.The results show values of K, , ranging from 0-2. lo6 to about 2 0 . lo6 and K,, from 0 2 . lo6 to about 6 . 106 m2 sec-I. In both cases the lowest values are found in the summer stratosphere and the highest in the spring stratosphere and in the upper troposphere in winter. Their distributions principally follow that of the wind variances. Integral time scales are mainly between 5 and 30 hours meridionally and 10 and 50 hours zonally and are greatest in the stratosphere and lowest in the mid-troposphere. The contributions of damping and harmonic effects to these time scales are discussed. Comparison of the Lagrangian and Eulerian time scales indicates a mean value , ! 3 of about 0.6 for their ratio with the meridional values smaller than the zonal values.

SUMMARYThe absorption of solar radiation and the exchange of long-wave terrestrial radiation are computed for the 30 to 90 km region for all latitudes using the climatological mean temperatures given by Murgatroyd (1957). Over most of the earth's surface (approximately 30" in the winter hemisphere to 60" in the summer hemisphere) there is a close approach to radiative equilibrium at all the levels considered. In the polar regions, however, there is a significant departure from radiative equilibrium with excess heating during the summer and excess cooling during the winter.