Changing spatial structure of the Brewer-Dobson circulation in CCMI simulations - competing role of wave driving
Abstract
The mean age of stratospheric air (AoA) is a useful transport diagnostic and one of the best tools for accessing the Brewer-Dobson circulation (BDC) change. Analyzing AoA output from CCMI REFC2 model simulations we found a remarkable agreement among majority of models in projecting the largest mean age-of-air (AoA) negative trends and changes in localized regions in the extratropical LS on both hemispheres (approximately between 200000 and 250000gpm and 20°- 40°N and 20°- 40°S). The occurrence of those regions are a direct function of the climatological AoA distribution, upward shifting trend of the circulation and of widening of the AoA izolines due to a negative trend in aging by mixing. The negative trend in aging by mixing is primarily caused by the speeding up of the residual circulation in the shallow BDC branch, which is connected with an interplay (not only compensation) between spatial structures and magnitudes of gravity and resolved wave drag leading to strengthening trend of the total drag.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E2691P