Wave propagation and amplification along the surface of discontinuity between air masses of different atmospheric static stabilities: A case study of West African tropospheric air masses

Summary A linearised inviscid form of the hydrodynamical equations is solved in shear, with the aid of a two-layer model of the atmosphere, for waves generated along the boundary between the air masses. Results show that some modes, generated by assuming different atmospheric static stabilities for the two layers of air, propagate and amplify with time; the static stability has been given a novel definition in units of height.A case study, in pressure co-ordinates, of typical tropospheric air masses in West Africa reveals that the mode with the largest growth rate of 1.6 per hour propagates in an East-West (E-W) direction along the surface of discontinuity between the (monsoon) southwesterlies and the (dry) northeasterlies with a phase speed of 7.7 m s^–1, a period of 3.6 hours and a wavelength of 100 km. Similar study inz co-ordinate reveals a mode with a growth rate of 1.8 per hour in an E-W direction, with a phase speed of 8.0 m s^–1, a period of 3.5 hours and a wavelength of 100 km.With 2 Figures