Comparison of mean age of air in ERA5, ERA-Interim, MERRA2 and JRA-3Q using the BASCOE CTM and observations from MIPAS, ACE-FTS, GLORIA-B and CAIRT

We compare stratospheric mean age of air (AoA) derived from four recent reanalyses: ERA5,
ERA-Interim, MERRA2, and JRA-3Q, using the BASCOE chemistry transport model (CTM). AoA
is a transit time of air parcels that move from the troposphere to the stratosphere and is used
as a proxy for circulation speed. Our analysis focuses on long-term trends and differences between the datasets. We compare our findings with previous studies and with satellite observations, including MIPAS and ACE-FTS, as well as GLORIA-B balloon measurements at Kiruna and Timmins, and simulated data from the proposed CAIRT mission for ESA’s Earth Explorer 11.