Abstract. Chemistry plays an indispensable role in investigations of the atmosphere;
however, many climate models either ignore or greatly simplify atmospheric
chemistry, limiting both their accuracy and their scope. We present the
development and evaluation of the online global atmospheric chemical model
BCC-GEOS-Chem v1.0, coupling the GEOS-Chem chemical transport model (CTM) as
an atmospheric chemistry component in the Beijing Climate Center atmospheric
general circulation model (BCC-AGCM). The GEOS-Chem atmospheric chemistry
component includes detailed tropospheric
HOx–NOx–volatile organic compounds–ozone–bromine–aerosol chemistry and online dry and wet
deposition schemes. We then demonstrate the new capabilities of
BCC-GEOS-Chem v1.0 relative to the base BCC-AGCM model through a 3-year
(2012–2014) simulation with anthropogenic emissions from the Community
Emissions Data System (CEDS) used in the Coupled Model Intercomparison
Project Phase 6 (CMIP6). The model captures well the spatial distributions
and seasonal variations in tropospheric ozone, with seasonal mean biases of
0.4–2.2 ppbv at 700–400 hPa compared to satellite observations and within 10 ppbv at the surface to 500 hPa compared to global ozonesonde observations. The
model has larger high-ozone biases over the tropics which we attribute to an
overestimate of ozone chemical production. It underestimates ozone in the
upper troposphere which is likely due either to the use of a simplified
stratospheric ozone scheme or to biases in estimated
stratosphere–troposphere exchange dynamics. The model diagnoses the global
tropospheric ozone burden, OH concentration, and methane chemical lifetime
to be 336 Tg, 1.16×106 molecule cm−3, and 8.3 years, respectively, which is consistent with recent multimodel assessments. The
spatiotemporal distributions of NO2, CO, SO2, CH2O, and
aerosol optical depth are generally in agreement with satellite
observations. The development of BCC-GEOS-Chem v1.0 represents an important
step for the development of fully coupled earth system models (ESMs) in
China.
Diagnosing the transition layer at extratropical latitudes using MLS O<sub>3</sub> and MOPITT CO analyses
