Stratospheric Cooling and Perturbation of the Meridional Flow During the Solar Eclipse of 7 March 1970

Abstract

Eight ARCAS meteorological rockets were fired from Wallops Island (38N, 75W) before, during and after the total solar eclipse of 7 March 1970. Detailed temperature and wind data were acquired to an altitude of about 65 km. Pressures and densities were derived by hydrostatic integration of the corrected temperature profiles. A time-height cross section of the temperature data (smoothed to suppress small-scale detail) shows significant cooling mainly in the layer 40–60 km. Maximum amplitude of the temperature perturbation is about 9K, near 50 km. Maximum pressure variation, amounting to a decrease of at least 7%, occurred about one scale height higher, near 58 km. The ARCAS wind observations are independent of the thermodynamic measurements; a time-height analysis of the winds shows a large amplification of the meridional flow, which is found to be consistent with the observed pressure changes. Derivatives in the perturbation equation of motion are evaluated with the aid of a space-time transformation based on the speed of the eclipse shadow. Consistency between the wind and thermodynamic data is indicated by approximately a three-fold increase, with altitude, of both the observed perturbation wind and the geostrophic wind specified by the perturbation model. Evidence supporting the observed temperature variation includes not only the ARCAS wind data, but also Pitot-probe and balloon measurements at Wallops Island and falling-sphere eclipse measurements in Florida. The cooling rate observed in the eclipse exceeds computed cooling rates at 50 km.