Intermediate model for the annual and global evolution of species IMAGES: Intermediate model for the annual and global evolution of species Description of the model The reactive carbon cycle Bottom-up inventories Model results for CO NOx chemistry, modelled NOx columns, comparison with SCIAMACHY NO2 columns Modelling HCHO, comparison with measurements

[X]=number concentration of a compound X Description I [X]=number concentration of a compound X « Box model » N species - N equations Chemical transport model (CTM) N x N1 x N2 x N3 equations N1=number of longitudes N2=number of latitudes N3=number of altitudes operator splitting-less accurate solvers Extends from the surface to the pressure level of 44 mbar, 40 vertical levels, and 5x5 degree horizontal resolution Provides the distribution of 48 chemical species (including non-oxygenated organic e.g. C2H6, C2H4, oxygenated e.g. PAN, MPAN, CH3COOOH, carbonyls e.g. HCHO, CHOCHO, CH3CHO, etc., peroxyradicals e.g. CH3O2, etc.) Short-lived species are not transported in the model

Description II The vertical resolution is higher near the surface Equation 1 is solved numerically by an operator-splitting technique Time step = 1 day, except for the three first days of each month : diurnal cycle calculation Advection is driven by monthly mean climatological fields from ECMWF  short-term wind variability not taken into account – mixing associated with wind variability is comprised in the diffusion term Turbulent mixing in the PBL  diffusion term Vertical transport associated with deep convection Advection  Semi-Lagrangian scheme : suitable for large timesteps

Description III Diffusion equation in 3 dimensions: Kxx, Kyy, Kzz are the zonal, meridional and vertical diffusion coefficients, solve with a implicit Eulerian scheme in each direction Horizontal diffusion coefficients : proportional to the deviations of wind fields Vertical diffusion coefficient : depends on the PBL height Kxx = 106-107 m2/s at mid-latitudes, much smaller values in the tropics, Kyy = factor of two lower than Kxx Kzz values are sufficiently high to allow for rapid exchanges of mass between the surface and the free troposphere

Description IV Deep convection : Treated as an 1-dimensional process Assumption : Ascending motions transport air from the boundary layer to the free troposphere, while subsidence transports air from each level to the adjacent lower level only  derive probabilities from the updraft densities Use updraft fluxes from the ECMWF analyses Chemistry : P is the photochemical production and beta the loss rate For transported species, the quasi-steady state approximation is used, or an Eulerian appoximation when beta is close to zero, for short-lived equilibrium is assumed, iterative procedure

Description V 48 long-lived and 20 short-lived species ~200 chemical reactions, ~30 photolytic reactions (Muller and Stavrakou, 2005) Water vapor, pressure and temperature are specified from ECMWF data Lumping is used to reduce the number of species, e.g. the peroxy radicals formed from ISOP+OH are lumped into one species (MIM is used) J’s are interpolated from values calculated offline using a radiative model J’s depend on the sza, ozone column, surface albedo, T, clouds, and z Heterogeneous reactions on sulphate aerosols N2O5 + SO4  2 HNO3 + SO4, NO3+SO4 HNO3+SO4, HO2+SO40.5 H2O2+SO4, (cloud droplets) N2O5 2HNO3  under construction Wash-out parameterization : uses large-scale and convenctive precipitation from ECMWF, 3-d cloud cover fields and much more  under construction The model is parallelized with OpenMP at 95%. It runs on 2,4,8, and 16 cpus. On the 5x5 grid : 20 min for 1-year simulation

The reactive carbon cycle (units: Tg C/year) deposition deposition 85 30 OH OH, hv OH CH2O CO2 CO CH4 1100 570 360 CO2 340 deposition 100 OH,O3 80 NMVOC (non-methane volatile organic compounds) 250 SOA 200 50 700 100

Bottom-up emissions Global total : 27 Tg N/yr, source: EDGAR v3.3

Global total : 8 Tg N/yr, Yienger and Levy, 1995 Global total : 3 Tg N/yr, Price et al, 1997, Pickering et al, 1998

Bottom-up biogenic emissions MEGAN model coupled with the MOHYCAN canopy model driven by ECMWF fields and accounts for leaf age, soil moisture stress, and past temperature radiation levels (Muller et al., 2008) http://www.aeronomie.be/tropo/inventory.html A newly developed inventory for biogenic emissions is used in this study. It is based on the MEGAN model coupled with a canopy environment model. A detailed description of the inventory is given in the Muller et al., 2007 (not yet submitted) – ask for the preprint if interested ! – and the files at a resolution of 1 degree can be downloaded at this website. Zonally and monthly averaged biogenic emissions from 1995 to 2006 of this database are shown here, and comparison with the Guenther et al., 1995 is provided in the last panel. Large interannual variability and lower emissions by up to 30% with repspect to the G95 database are the two main features of the new inventory.

IMAGES results : CO Mixing ratio

NOx : role, surces and sinks + NO2 NO + O  O3 RO2 O3 + + N2O5 H2O CO, VOC, O3 OH HO2 2HNO3 O3 HNO3

Annually averaged modelled vs. observed NOx column - 2003 SCIAMACHY NO2 column

HCHO chemistry, sources and sinks The most abundant carbonyl in the atmosphere Short-lived - lifetime on the order of a few hours Directly emitted from fossil fuel combustion and biomass burning Also formed as a high-yield secondary product in the CH4, and NMVOC oxidation CH4 NMVOC HO2 OH OH CH3OOH CH3O2 RO2 OH NO HCHO OH CO+2HO2 CO+HO2+H2O CO+H2 deposition

Annually averaged prior NMVOC emissions from biomass burning and biogenic sources - 2003

Annually averaged modelled vs. observed HCHO column - 2003 SCIAMACHY HCHO column

Impact of NMVOCs on O3 mixing ratios July 1997 without NMVOCs with NMVOCs