Atmos. Chem. Phys. Discuss., 5, 7309-7340, 2005
www.atmos-chem-phys-discuss.net/5/7309/2005/
doi:10.5194/acpd-5-7309-2005
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Convective damping of buoyancy anomalies and its effect on lapse rates in the tropical lower troposphere
I. Folkins
Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, B3H 3J5, Canada

Abstract. In actively convecting regions of the tropics, lapse rates in the lower troposphere (2.0 km to 5.2 km) vary with height in a way which is inconsistent with both reversible moist adiabatic and pseudoadiabatic assumptions. It is argued that this anomalous behavior arises from the tendency for the divergence of a convective buoyancy anomaly to be primarily offset by the collective divergence of all other updrafts and downdrafts within one Rossby radius of deformation. (Ordinarily, convective divergences are at least partially offset by an induced radiative divergence in the background atmosphere.) If convective divergences are balanced purely by other convective divergences, it would force the vertical clear sky radiative mass flux to be independent of altitude. This is consistent with what is observed at several radiosonde locations in the Western Tropical Pacific between 2.0 and 5.2 km. It is conjectured, that at tropical locations where SST's exceed 27°C over a region whose horizontal extent exceeds the local Rossby radius, this condition on the clear sky radiative mass flux serves to partially constrain the range of physically allowed mean temperature and moisture profiles in the lower troposphere.

Citation: Folkins, I.: Convective damping of buoyancy anomalies and its effect on lapse rates in the tropical lower troposphere, Atmos. Chem. Phys. Discuss., 5, 7309-7340, doi:10.5194/acpd-5-7309-2005, 2005.
 
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