SEASONAL DEPENDENCE OF STRATOSPHERIC TEMPERATURE-VARIATIONS

Stratospheric temperatures show distinct trends, not necessarily monotonically upward or downward. At the North Pole, trends were large only during winter and spring and were different for different months; downward for November, December, mixed for January and upward for February, March and April. For the 10 degrees-90 degrees N belt, the trends were variable viz, downward during 1971-1975, upward during 1975-1978 and downward again from 1978 onwards up to date, opposite to the upward trend of ground temperature in the Northern hemisphere in recent years. Twelve-monthly running averages revealed strong QBO (quasi-biennial oscillation). For the North Pole, the QBO showed colder (lower) temperatures during 50-mb wind QBO westerly phase maxima. For the 10 degrees-90 degrees N belt, the QBO was similar for 30 mb and 50 mb but the QBO phases did not match well with 50-mb wind QBO phases.