Mesospheric Heating Due to Convectively Excited Gravity Waves—A Case Study

Abstract

A series of at least daily rocket soundings of the mesosphere at Wallops Island, Virginia (37°50′N, 75°29′W), in August and September 1976 reveal near simultaneity between rapid temperature rises and tropospheric convection in the form of squall lines. A multilevel numerical model is developed to test the hypothesis that the convection and warnings are related via internal gravity waves. Some features of the model are: 1) the wave energy source is expressed in terms of cloud-base mass flux, plume diameter and buoyant updraft velocity; and 2) the turbulent-viscous gravity wave dissipation is limited to above 55 km and is parameterized on the basis of findings by Hines (1965). Significant findings are: 1) mesospheric heating rates of the same order as those observed result for reasonable values of the convective parameters and in situ dissipation time scales; 2) only gravity waves confined to a well-defined wavelength and frequency interval are able to propagate upward to mesospheric altitudes; 3) heating rates are strongly dependent on plume diameter and updraft velocity; and 4) for a given cloud-base mass flux, heating rates are optimized for a plume updraft velocity of 10 m s⁻¹.