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The effect of non‐uniform radiative damping on the zonal‐mean dynamics of the extratropical middle atmosphere
Author(s) -
Semeniuk K.,
Shepherd T. G.
Publication year - 2002
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1256/00359000260498888
Subject(s) - diabatic , extratropical cyclone , atmospheric sciences , radiative transfer , polar vortex , atmosphere (unit) , middle latitudes , environmental science , climatology , radiative flux , radiative cooling , radiative equilibrium , lapse rate , physics , stratosphere , meteorology , geology , adiabatic process , quantum mechanics , thermodynamics
The effect of spatial and temporal variations in the radiative damping rate on the response to an imposed forcing or diabatic heating is examined in a zonal‐mean model of the middle atmosphere. Attention is restricted to the extratropics, where a linear approach is viable. It is found that regions with weak radiative damping rates are more sensitive in terms of temperature to the remote influence of the diabatic circulation. The delay in the response in such regions can mean that ‘downward’ control is not achieved on seasonal time‐scales. A seasonal variation in the radiative damping rate modulates the evolution of the response and leaves a transient‐like signature in the annual mean temperature field. Several idealized examples are considered, motivated by topical questions. It is found that wave drag outside the polar vortex can significantly affect the temperatures in its interior, so that high‐latitude, high‐altitude gravity‐wave drag is not the only mechanism for warming the southern hemisphere polar vortex. Diabatic mass transport through the 100 hPa surface is found to lag the seasonal evolution of the wave drag that drives the transport, and thus cannot be considered to be in the downward control regime. On the other hand, the seasonal variation of the radiative damping rate is found to make only a weak contribution to the annual mean temperature increase that has been observed above the ozone hole. Copyright © 2002 Royal Meteorological Society.