Filters

1996 - 19992

More filters

20192
Reset filters

Settings

Start date: 1990 × End date: 1999 × Publisher: Milton Park : Taylor & Francis ×

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    The feedback of midlatitude waves onto the Hadley cell in a simple general circulation model
    (Milton Park : Taylor & Francis, 1996) Becker, E.; Schmitz, G.; Geprägs, R.
    We present self-consistent comparisons of axissymmetric and 3-dimensional simulations of the tropospheric circulation under idealized physical conditions. These reveal a feedback of transient eddies onto the Hadley circulation which, first, strongly depends on equatorial heating and, second, is in case of realistic heating quite different from prescribed eddy forcing. A quantitative estimation for the eddy-induced mixing of vorticity into the poleward flow of the Hadley cell is given. The proposed relation is in accordance with observations. It is derived from the computational result that eddy momentum flux convergence is of the same order as the equatorward flux of relative vorticity generated by the Hadley circulation. Evaluation of the local budgets of sensible heat gives rise to a clear picture of how the poleward heat transports due to Hadley circulation and transient eddies interlock. This mechanism is found to be essential for an interpretation of the eddy feedback.
  • Thumbnail Image
    Item
    The rôle of orographically and thermally forced stationary waves in the causation of the residual circulation
    (Milton Park : Taylor & Francis, 1999) Becker, E.; Schmitz, G.
    Several experiments performed with an idealized troposphere–stratosphere GCM are comparedto estimate the impact of orography and prescribed local heat sources on the residual circulationin the northern winter stratosphere. It is found that only the combined action of orographicand thermal wave forcing in northern midlatitudes is capable of inducing a residual circulationreaching continuously from tropical to polar latitudes at stratospheric altitudes. Intensificationsof the residual circulation in response to modified forcing of stationary waves are generallyassociated with, firstly, a reduced polar night jet accompanied by enhanced easterlies inlow and summer hemispheric latitudes and, secondly, substantial warming of the polar nightstratosphere completely compensated by cooling in the tropics and subtropics.