A Diagnostic part of the SPARC Chemistry-Climate Model Validation Activity CCMVal

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Latitudinal gradients of long-lived tracers

PROCESS: Subtropical and polar mixing barriers

Useful information on subtropical and polar mixing barriers can be obtained from instantaneous snapshots of tracer fields, which makes the model-measurement comparison straightforward. For this purpose there is a wealth of high-quality observational data available. A simple check on the degree of isolation is provided by the sharpness of latitudinal gradients of long-lived species (CH₄, N₂O, CFC-11).

Diagnostic

Variables

Examples

Figure 1. Climatological zonal-mean CH4 mixing ratios from the CCMs and HALOE in ppmv.  Latitudinal profiles at 50 hPa in March (left) and October (right). The grey area shows HALOE plus and minus 1 standard deviation (s) about the climatological zonal mean (from Eyring et al., 2006, their Figure 5).	Figure 2. Absolute value of the zonal-mean latitudinal gradient of N2O for October in the CMAM model. The dark colors show low latitudinal gradients of N2O, while the bright colors show large latitudinal gradients representing jumps in the mixing ratio across a mixing barrier (from Sankey and Shepherd, 2003, their Figure 7)

Correlative data

• SPARC reference climatologies (CH₄ and N₂O)
• A stratospheric climatology for O₃, H₂O, CH₄, NO_x, HCl and HF derived from HALOE measurements (Reference: Grooß and Russell III,  2005)

References

1. Eyring, V., N. Butchart, D. W. Waugh, H. Akiyoshi, J. Austin, S. Bekki, G. E. Bodeker, B. A. Boville, C. Brühl, M. P. Chipperfield, E. Cordero, M. Dameris, M. Deushi, V. E. Fioletov, S. M. Frith, R. R. Garcia, A. Gettelman, M. A. Giorgetta, V. Grewe, L. Jourdain, D. E. Kinnison, E. Mancini, E. Manzini, M. Marchand, D. R. Marsh, T. Nagashima, P. A. Newman, J. E. Nielsen, S. Pawson, G. Pitari, D. A. Plummer, E. Rozanov, M. Schraner, T. G. Shepherd, K. Shibata, R. S. Stolarski, H. Struthers, W. Tian, and M. Yoshiki, Assessment of temperature, trace species and ozone in chemistry-climate model simulations of the recent past, J. Geophys. Res., 111, D22308, doi:10.1029/2006JD007327, 2006.
2. Grooß, J. -U. and J. M. Russell III,  2005: Technical note: A stratospheric climatology for O₃, H₂O, CH₄, NO_x, HCl and HF derived from HALOE measurements,  Atmos. Chem. Phys., 5, 2797-2807.
3. Sankey, D., and T.G. Shepherd, 2003: Correlations of long-lived chemical species in a middle atmosphere general circulation model. J. Geophys. Res., 108, 10.1029/2002JD002799.

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