Stationary wave and surface radiative effects weaken and delay the
near-surface response to stratospheric ozone depletion
Abstract
An intermediate complexity moist General Circulation Model is used to
investigate the factor(s) controlling the magnitude of the surface
impact from Southern Hemisphere springtime ozone depletion. In contrast
to previous idealized studies, a model with full radiation is used,
which allows focus on the full range of feedbacks between incoming
ultraviolet radiation and temperature variations. In addition, the model
can be run with a varied representation of the surface, from a zonally
uniform aquaplanet to a highly realistic configuration. The model
captures the positive Southern Annular Mode response to ozone depletion
evident in observations and comprehensive models in December through
February. It is shown that while synoptic waves dominate the long-term
poleward jet shift, the initial response includes changes in planetary
waves which simultaneously moderate the polar cap cooling (i.e., a
negative feedback), but also constitute nearly half of the initial
momentum flux response that shifts the jet polewards. Enhanced
ultraviolet absorption at the surface due to the ozone hole drives an
additional negative feedback on the poleward jet shift. The net effect
is that stationary waves and surface radiative effects weaken the
circulation response to ozone depletion, and also delay the response
until summer rather than spring when ozone depletion peaks.