The Impact of the Antarctic Ozone Hole on the Mesospheric Circulation and Temperature

Figure 1. Changes in (a) temperature, (b) zonal wind, and (c) gravity wave momentum forcing over the period 1960-2006 averaged over the months of November and December simulated by WACCM. Results from four realizations of WACCM have been averaged to make the plot. [High resolution image]

The loss of ozone that has occurred in the Antarctic lower stratosphere during each spring since1980 is known as the ozone hole. Dynamical impacts of the ozone loss include a cooling in the lower stratosphere and changes in the stratospheric winds in the high southern latitudes during spring and summer. The wind changes affect the propagation of waves from the lower to the upper atmosphere. Some of the gravity waves that are generated in the troposphere propagate vertically through the stratosphere and into the mesosphere. Dissipation of these waves in the upper mesosphere (75-90 km) has a large effect on the circulation and temperature there. Through their effect on the vertical propagation of gravity waves, the stratospheric wind changes associated with the ozone hole can indirectly affect the mesospheric temperature.

Simulations with the Whole Atmosphere Community Climate Model (WACCM) reproduce the onset of the Antarctic ozone hole. The model simulations of the associated changes in stratospheric temperature and winds are larger in magnitude but similar in morphology to observations. The figure shows the simulated zonally averaged changes in temperature, zonal wind, and gravity wave momentum forcing over the period 1960-2006. The stratospheric changes are evident; strongest signals are at 70 hPa (temperature) and 20 hPa (wind). The large negative change in gravity wave forcing in the mesosphere has led to a weaker circulation and warming in the SH polar temperature near 65-80 km. The increase in temperature near the SH summer mesopause has implications for the presence of polar mesospheric clouds.

References

Smith, A.K., R.R. Garcia, D.R. Marsh, D.E. Kinnison, and J.H. Richter, Simulations of the response of mesospheric circulation and temperature to the Antarctic Ozone hole, Geophys. Res. Lett., in press, 2010.