RT Journal Article
T1 Extratropical age of air trends and causative factors in climate projection simulations
A1 Sacha , Petr
A1 Eichinger, Roland
A1 Garny, Hella
A1 Pišoft, Petr
A1 Dietmüller, Simone
A1 De La Torre Ramos, Laura
A1 Plummer, David A.
A1 Jöckel, Patrick
A1 Morgenstern, Olaf
A1 Zeng, Guang
A1 Butchart, Neal
A1 Añel Cabanelas, Juan Antonio
K1 2501 Ciencias de la Atmósfera
K1 2502 Climatología
AB Climate model simulations show an acceleration of theBrewer–Dobson circulation (BDC) in response to climate change. While thegeneral mechanisms for the BDC strengthening are widely understood, thereare still open questions concerning the influence of the details of the wave driving. Mean age of stratospheric air (AoA) is a useful transportdiagnostic for assessing changes in the BDC. Analyzing AoA from a subset ofChemistry–Climate Model Initiative part 1 climate projection simulations, wefind a remarkable agreement between most of the models in simulating thelargest negative AoA trends in the extratropical lower to middlestratosphere of both hemispheres (approximately between 20 and 25 geopotential kilometers (gpkm) and 20–50∘ N and S). We show that the occurrence of AoA trend minima in those regions is directlyrelated to the climatological AoA distribution, which is sensitive to anupward shift of the circulation in response to climate change. Also otherfactors like a reduction of aging by mixing (AbM) and residual circulationtransit times (RCTTs) contribute to the AoA distribution changes by wideningthe AoA isolines. Furthermore, we analyze the time evolution of AbM and RCTT trends in the extratropics and examine the connection to possible driversfocusing on local residual circulation strength, net tropical upwelling andwave driving. However, after the correction for a vertical shift of pressurelevels, we find only seasonally significant trends of residual circulationstrength and zonal mean wave forcing (resolved and unresolved) without aclear relation between the trends of the analyzed quantities. This indicatesthat additional causative factors may influence the AoA, RCTT and AbMtrends. In this study, we postulate that the shrinkage of the stratospherehas the potential to influence the RCTT and AbM trends and thereby causeadditional AoA changes over time.
PB Atmospheric Chemistry and Physics
SN 16807324
YR 2019
FD 2019-06-07
LK http://hdl.handle.net/11093/4289
UL http://hdl.handle.net/11093/4289
LA eng
NO Atmospheric Chemistry and Physics, 19(11): 7627-7647 (2019)
NO Czech Science Foundation (GACˇ R) | Ref. 16- 01562J
DS Investigo
RD 28-sep-2023