Sensitivity of tracer transport to model resolution, prescribed meteorology and tracer lifetime in the general circulation model ECHAM5

• Main Authors: Aghedo, A.M., Rast, S., Schultz, M. G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: EGU 2010
• Subjects: info:eu-repo/classification/ddc/550; J; Sea ice
• Online Access: https://juser.fz-juelich.de/record/9339; https://juser.fz-juelich.de/search?p=id:%22PreJuSER-9339%22

Atmospheric transport of traces gases and aerosols plays an important role in the distribution of air pollutants and radiatively active compounds. For model simulations of chemistry-climate interactions it is important to know how the transport of tracers depends on the geographical resolution of the general circulation model. However, this aspect has been scarcely investigated until now. Here, we analyse tracer transport in the ECHAM5 general circulation model using 6 independent idealized tracers with constant lifetimes, which are released in two different altitudes at the surface and in the stratosphere, respectively. Model resolutions from T21L19 to T106L31 were tested by performing multi-annual simulations with prescribed sea surface temperatures and sea ice fields of the 1990s. The impacts of the tracer lifetime were investigated by varying the globally uniform exponential decay time between 0.5 and 50 months. We also tested the influence of using prescribed meteorological fields (ERA40) instead of climatological sea surface temperature and sea ice fields. Meridional transport of surface tracers decreases in the coarse resolution model due to enhanced vertical mixing, with the exception of the advection into the tropical region, which shows an inconsistent trend between the resolutions. Whereas, the meridional transport of tracers released in the stratosphere was enhanced with higher model resolutions, except in the transport from tropical stratosphere to the Southern Hemisphere, which exhibits an increase trend with increasing model resolution. The idealized tracers exhibit a seasonal cycle, which is modulated by the tracer lifetime. In comparison to the run with prescribed sea surface temperature and sea ice fields, the simulation with prescribed meteorological fields did not exhibit significant change in the meridional transport, except in the exchange of stratospheric tracers between both hemispheres, where it causes about 100% increase. The import of the surface tracers into the stratosphere is ...