Fragments of the chemically perturbed vortex air mass may persist throughout the summer and have been observed in the lower stratosphere. After the final warming, the circulation in the zonal mean winds remains as easterlies in the lower stratosphere, signaling the onset of the summer circulation. Thus no strong diabatic descent of high-PV air follows the event and the vortex does not recover. As during midwinter, the strong planetary activity in spring disrupts the vortex, but the warmer stratospheric temperatures that follow the warming are much closer to the radiative equilibrium temperature. Solar heating of the polar ozone layer increases toward equinox, thus reducing the ability of the strong IR cooling to restore the temperature gradient. ‘The rapidly changing length of day around the equinoxes might disturb the circadian and sleep-wake rhythms and change mood and activity in vulnerable individuals.The polar vortex typically lasts until the spring equinox in the NH and up to 2 months or more past the spring equinox in the SH.‘Note that day length is at a minimum at the start of winter, at a maximum at the start of summer, and is 12 hours at the spring and fall equinoxes.’.‘The Harvest Moon, therefore, occurs within several days of September 23, the fall equinox.’.
#Equinox definition full#
‘He relied on the formula adopted by the Church two centuries before, the Easter shall fall on the first Sunday after the first full moon after the spring of the equinox.’.
Such dates carry an importance in many European and European-derived calendars.’
‘Anyone who says day and night is equal on the equinox hasn't bothered to let facts get in the way of theory.’.‘‘An equinox is when night and day are equal,’ he said.’.‘The lengths of the hours were equal around the equinoxes but the rest of the time they could vary considerably.’.