The ACCROSS (Atmospheric Composition and Circulation investigated with meteorological Reanalyses, Observational datasets and models for the Study of the Stratosphere and its changes) project is a collaboration between the University of Liège and BIRA-IASB. The main goal of the ACCROSS project was to improve our understanding of the circulation changes in the stratosphere during the past three decades through the use of observation and model simulation time series of selected long-lived tracers.
Within the ACCROSS project, two Ph.D. theses were carried out: one by Maxime Prignon and the other by Daniele Minganti. Maxime Prignon used the total inorganic fluorine in the stratosphere
as a long-lived tracer. The first objective of his thesis was to evaluate the major source of total inorganic fluorine in the stratosphere using groundbased and satellite observations together with model simulations [1]. The main goal was then to investigate long-term changes and the interannual variability of the BDC using satellite and FTIR observations and CTM simulations of total fluorine [2].
The thesis of Daniele Minganti was complementary to Maxime Prignon’s work. Within the common aim set by the ACCROSS project, Daniele Minganti's work used a different long-lived tracer: nitrous oxide (N2O), which, thanks to its relatively simple chemistry, allowed to focus more on the stratospheric dynamics, separating the impact of advection and mixing on its volume mixing ratio.
Before focusing on long-term changes, it was necessary to evaluate the performances of the models to simulate the mean N2O abundances. To this end, Daniele Minganti's work was to evaluate the realism of the BDC in a CCM by investigating and evaluating the climatological abundances of N2O and the impact of the BDC on those abundancies, and comparing them with CTM simulations and a chemical reanalysis [3]. This evaluation set the ground for the second and main objective of Daniele Minganti's thesis: evaluating the changing BDC in the same CCM by studying multi-decadal and decadal changes of N2O in the stratosphere, comparing them with observations and CTM simulations, and calculating the impact of the BDC on those changes.
This investigation used several CTM and CCM simulations as well as groundbased FTIR and satellite observations. Thanks to the model simulations, the impact of the BDC on the N2 O changes can further isolated, by separating the contribution from advection and mixing on those changes [4].
[1] Prignon, M., Chabrillat, S., Minganti, D., O'Doherty, S., Servais, C., Stiller, G., Toon, G. C., Vollmer, M. K., and Mahieu, E.: Improved FTIR retrieval strategy for HCFC-22 (CHClF2), comparisons with in situ and satellite datasets with the support of models, and determination of its long-term trend above Jungfraujoch, Atmos. Chem. Phys., 19, 12309-12324, https://doi.org/10.5194/acp-19-12309-2019, 2019.
[2] Prignon, M., Chabrillat, S., Friedrich, M., Smale, D., Strahan, S. E., Bernath, P. F., et al. (2021). Stratospheric fluorine as a tracer of circulation changes: Comparison between infrared remote-sensing observations and simulations with five modern reanalyses. Journal of Geophysical Research: Atmospheres, 126, e2021JD034995. https://doi.org/10.1029/2021JD034995
[3] Minganti, D., Chabrillat, S., Christophe, Y., Errera, Q., Abalos, M., Prignon, M., Kinnison, D. E., and Mahieu, E.: Climatological impact of the Brewer\u2013Dobson circulation on the N2O budget in WACCM, a chemical reanalysis and a CTM driven by four dynamical reanalyses, Atmos. Chem. Phys., 20, 12609-201312631, doi:10.5194/acp-20-12609-2020, 2020.
[4] Minganti, D., Chabrillat, S., Errera, Q., Prignon, M., Kinnison, D. E., Garcia, R. R., et al. (2022). Evaluation of the N2O rate of change to understand the stratospheric Brewer-Dobson circulation in a Chemistry-Climate Model. Journal of Geophysical Research: Atmospheres, 127, e2021JD036390. https://doi.org/10.1029/2021JD036390
