Stratospheric and lower Mesospheric Wind Systems in the Equatorial Region

Abstract

Rocket wind data from 25 firings over Thumba (India) have been used in conjunction with similar data from other low latitude stations like Ascension Island, Colon (Panama), Natal (Brazil),Barking Sands (Hawaii) and Somniani (Pakistan), Behaviour of the stratospheric and mesospheric Winds seasonally, in the equatorial region and outside it, has been studied, A strong easterly jet is detected over the equatorial stations in January, with core winds  varying from 35 to 60 mps and height varying from 42 to 50 km, From a synoptic study of the rocket wind data pertaining to 17 March 1965 over Thumba, Ascension Island, U S, Navy ship Croatan at 13°S, 78°W, Barking Sands and Sonmiani, it is inferred that in the equinoctial month of March, the stratospheric wind speed increases with proximity to the equator, with the region of maximum wind speed to the south of the equator; but in the mesosphere the region of maximum wind is to the north of the equator, J et stream in the troposphere (both easterly and westerly) in the Indian region, has been studied in relation to the stratospheric winds over Thumba and Sonmialii and found that there is no obvious relation between the trophspheric jets and the stratospheric wind system, Lack of correlation between the zonal (and also meridional) wind speeds in the stratosphere an a the ozone content above the station, indicates that ozone mixing may be taking place mainly in the vertical. Vertical wind shears have been computed fur rocket flights over Thuillba and Sonmiani and their plots against height reveal that turbulence is larger over Thumba than over Sonmiani. In the equatorial region, there is considerable winds shear in the equinoctial months, which decrease in winter when there is a peak shear in the mesosphere near 52 km. Outside the equatorial region, there is very little seasonal variation in the-windshear, either in the stratosphere or in the mesosphere, The rockets wind data of Thamba  do not indicate oppositely directed winds at each level from one; year to the next, as is shown by the data of Kwajalein. It is, therefore, inferred that the amplitude of the quasi-biennial wave is greater over Kwajalein than over Thumba, contrary to expectation.