REVIEW OF THE DECADAL OSCILLATION IN THE STRATOSPHERE OF THE NORTHERN-HEMISPHERE

The decadal oscillation of the temperature and geopotential height in the lower stratosphere of the northern hemisphere can be followed back to the early 1950s. During this time it was in phase with the 11-year sunspot cycle. The correlation with the solar cycle is positive and largest in the stratospheric geopotential heights of the subtropics below 10 mbar (approximately 31 km, which is as high as the grid point data reach), especially on the western, ocean-dominated side of the hemisphere. As expected from the hydrostatic equation, it is also evident in the temperatures of the upper troposphere in the same region. There is no large correlation at high latitudes. The correlation with the sunspot cycle is weakest in January-February, but if the data in these months are grouped according to the wind direction in the quasi-biennial oscillation (QBO) of the lower equatorial stratosphere, the positive subtropical correlations in the east years are as high as in all other months. There are, in addition large negative correlations in the Arctic in agreement with the strong teleconnection (negative correlation) between lower and higher latitudes in winter. There is no consistent sign in the weak correlations at middle and lower latitudes in the west years, but in the Arctic the correlation with the solar cycle is highly positive, because those major midwinter warmings that occur in west years of the QBO take place in solar maxima, whereas the years without major warmings are found in solar minima. There is not yet an explanation of the 10-12 year oscillation in the stratosphere.