Boundary conditions

Ozone

Climatological ozone volume mixing ratio (ppmv) at the upper 3 levels of TM3 (above 50 hPa) are taken from [Fortuin and Kelder, 1998] and read in from o3vmr.d. The climatology is based upon ozone sonde and SBUV measurements over the period 1979-1990.
Monthly mean zonal mean overhead ozone distributions derived from TOMS and the ozone climatology are used in the photolysis calculations in TM. These are read in from o3du.d. Both ozone data files are calculated with program o3clim.

Methane

Lower boundary condition at the surface

Monthly methane mixing ratios at ground level orginate from TM2 work reported in [Hein, 1994]. They are read in from zch4.d which is calculated by program zch4. In TM3 these surface concentrations are scaled to expected ones for each year. For 1979 to 2000 (32 years) the scale factors are:

Year	Scale factor
1979	0.9516
1980	0.961013
1981	0.970531
1982	0.980201
1983	0.990023
1984	1.00000
1985	1.00728
1986	1.01541
1987	1.02210
1988	1.02963
1989	1.03971
1990	1.04626
1991	1.04955
1992	1.05743
1993	1.05834
1994	1.06116
1995	1.06350
1996	1.06665
1997	1.07174
1998	1.07937
1999	1.08250
2000	1.088

These scale factors are based upon NOAA South Pole FLASK measurements from 1984-2000. The 1979-1983 data are based on [Houweling, 2000].
Before 1979 a polynomial fit to ice core data ([Etheridge et al., 1998]? is used to set the scaling factor: They calculated smoothed yearly methane concentrations for the Antarctic, Arctic and global mean. The used assumption to calculate global means was that the interhemispheric exchange does not vary much and neither the proportion of sources on the NH, so that the latitudinal profile remains more or less constant. This gave that the global mean is the Antarctic concentration plus 37 difference bewteen Arctic (Greenland) and Antartic values. The analysis made by [Etheridge et al., 1998] also indicates that the growth rate of methane sources will drop to zero by 2006 .... The analysis is however rather crude.
dt=YYYY-1800
scalefactor=0.462361+0.00295083 dt-3.91697e-05 dt2 + 2.11858e-07 dt3 After 2000 they are assumed to grow by 0.5 %/year.

Upper boundary condition at 10 hPa

Methane mixing ratios at the top of the model (10 hPa) are also prescribed according to CLAES/UARS monthly mean zonal mean observations. These are read in from zsch4.d.

Nitrate

Monthly mean zonal mean HNO3:03 ratios at 10 hPa derived from UARS instruments (Bregman pers. comm. 1997) are read in from uars_ratio.d. Note that HNO3:O3 is more or less constant during vertical descent in the mid-latitude stratosphere, at least well above the tropopause (Murphy..). The original data in file uars_hno3_o3_ratio_10hPa.d seem to be for 1992. These data are interpolated to the TM grid by program uars_ratio called by script non_annual.