Interactive chemistry in CAM : Interactive chemistry in CAM Jean-François Lamarque, D. Kinnison S. Walters and the WACCM group
Atmospheric Chemistry Division
NCAR
Goal : Goal Provide a flexible framework for the study of chemistry-climate interactions in CCSM
Focus on the troposphere and stratosphere
Computational approach : Computational approach Chemical scheme is input in a preprocessor that creates a set of subroutines added to the standard CAM
Reads a set of external files (for emissions, deposition velocities and photolysis rates)
Uses the finite volume dynamical core for the advection of tracers
Convective and diffusive transport of tracers is considered
Main features : Main features Photolysis and chemical reactions solved with an implicit/explicit set of solvers
Lookup table photolysis rates, including cloud correction (but not aerosols)
Wet (first-order loss linked to precipitation in CAM) and dry removal
Surface emissions (fixed, monthly averages)
Lightning NO production linked to convection in CAM
Current status : Current status Implementation in WACCM of combined tropospheric (valid for regional and global scale chemistry) and stratospheric chemistry (including PSCs) : 105 species, over 300 chemical reactions
Simulations performed with 52 levels, extending up to 85 km.
Stratosphere-troposphere flux is explicitly calculated
Horizontal resolution of 2x2.5
25 years of present-day simulations, using climatological SST
Performance : Performance In the present configuration, inclusion of chemistry (including transport of tracers) approximately doubles the cost of the equivalent WACCM simulation; this ratio will be a little worse for CAM
On bluesky, 96 CPUs, 1 year in 2 days
Mid-tropospheric ozone : Mid-tropospheric ozone
Mid-tropospheric ozone : Mid-tropospheric ozone
Model evaluation : Model evaluation Comparison with tropospheric and stratospheric observations
Comparison with TOMS total ozone column
Comparison with observations (1) : Comparison with observations (1) Barrow, Alaska Black sea, Romania Mauna Loa, Hawaii Halley station, Antarctica Red : model results
Blue : observations Month
Comparison with observations (2) : Comparison with observations (2) Ozone mixing ration (ppbv) Month
Comparison with observations (3) : Comparison with observations (3) NOx = NO + NO2
Comparison with observations (4) : Comparison with observations (4)
Summary : Summary Working version of interactive tropospheric/stratospheric chemistry
Analysis of results indicate a good overall representation of the chemistry in the atmosphere
Biases are similar to the ones found in MOZART results, on which the chemistry is based
Next steps (1) : Next steps (1) Develop a CAM version (requires the addition of upper-boundary conditions); expected to happen within a month
Inclusion of aerosols (ammonium, sulfate, sea-salt, dust,organic and black carbon; X.X. Tie, P. Hess N. Mahowald and P. Rasch)
Better representation of wet removal (P. Hess and P. Rasch)
Interactions with CLM (deposition; emissions of BVOCs (C. Wiedinmyer and S. Levis); soil NO)
Next steps (2) : Next steps (2) Interactive calculation of photolysis rates
Development of a variety of chemical packages for ease of use
Coupling with ocean biogeochemistry
Coupling between the nitrogen and the carbon cycle through CLM (P. Thornton)
Interactive emissions from wetlands