50 Evaluation of the New Version of Stratospheric Chemistry Module …
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In our updated module the composition of aqueous HNO 3 –H 2 SO 4 stratospheric
aerosol is calculated non-iteratively by using the model by [3]. Additionally, the
solubility of HCl, HOCl, and HBr in STS is calculated using the effective Henry’s
law constants [3, 5, 6].
In addition to new bromine species, we have also included the halogen emissions
in order to be able to study a steady state situation. For chlorine species we used the
GEIA inventory, and included the emissions of CH 3 Cl, HCl, Cl, CH 3 CCl 3 , CFC11, and CFC-12. In order to cover the most important ozone depletion substances,
we also included CCl 4 (CFC-10). Also, since the GEIA inventory covers only one
year, we scaled the CFC and CH 3 CCl 3 (methyl chloroform) emissions using the
known yearly estimates based, e.g., on the AFEAS data [1]. These emission estimates
typically extended up to year 2000. For the following years the emissions of CFC-12,
CCl 4 , and methyl chloroform was decreased to zero by year 2010, in accordance with
the Montreal Protocol. For CFC-11, whose production was essentially zero already
in 2000, we release yearly 7.5% of the still existing “banks” of CFC-11 (mainly
in closed cell foams), which was about 950 Gg in 1999 [1]. In addition to CH 3 Cl
emissions from GEIA, which covers emissions from sea and biomass burning, we
included terrestrial emissions of 2330 Gg [9].
We included bromine emissions from sea-salt, which contains approximately
0.223% of bromine [8], and should cover at least 90% of all the bromine emissions to the atmosphere. Currently the bromine sea-salt emissions are in the form
of Br 2 . Additionally, we release CH 3 Br due to biomass burning (23 Gg), terrestial
(18 Gg), and from the sea (32 Gg) [9]. Other standard emissions are taken from the
MACCity emission inventory.
50.3 Results
The preliminary simulations that cover yearly changing CFC-, and CH 3 CCl 3 -
emissions, extend from year 1942–2017. Any emissions prior to 1942 is released
during the first year of simulation. These simulations have a spatial resolution of
2° and they use ERA_interim for meteorology, which is simply copied from years
1980–2017 to cover also the years 1942–1979. CFC emissions included in the model
produce reasonable concentrations of these gases. For example, the average mixing
ratios for CFC-11, CFC-12, and CCl 4 in 2011 are 253, 522, and 88 ppt, respectively.
These are in line with the tropospheric measurements [9].
Our simulations clearly indicate that the ozone depletion above Antarctic is sensitive to the amount of active chlorine that originates mainly from CFCs and methyl
chloroform due to the photolysis. With current emissions the total ozone column
above the Antarctic has a thickness that is consistent with the observations. This is
illustrated in Fig. 50.1, where monthly averaged total ozone column is shown for
October 2011 (output of the zoomed run with 1° resolution).
319
In our updated module the composition of aqueous HNO 3 –H 2 SO 4 stratospheric
aerosol is calculated non-iteratively by using the model by [3]. Additionally, the
solubility of HCl, HOCl, and HBr in STS is calculated using the effective Henry’s
law constants [3, 5, 6].
In addition to new bromine species, we have also included the halogen emissions
in order to be able to study a steady state situation. For chlorine species we used the
GEIA inventory, and included the emissions of CH 3 Cl, HCl, Cl, CH 3 CCl 3 , CFC11, and CFC-12. In order to cover the most important ozone depletion substances,
we also included CCl 4 (CFC-10). Also, since the GEIA inventory covers only one
year, we scaled the CFC and CH 3 CCl 3 (methyl chloroform) emissions using the
known yearly estimates based, e.g., on the AFEAS data [1]. These emission estimates
typically extended up to year 2000. For the following years the emissions of CFC-12,
CCl 4 , and methyl chloroform was decreased to zero by year 2010, in accordance with
the Montreal Protocol. For CFC-11, whose production was essentially zero already
in 2000, we release yearly 7.5% of the still existing “banks” of CFC-11 (mainly
in closed cell foams), which was about 950 Gg in 1999 [1]. In addition to CH 3 Cl
emissions from GEIA, which covers emissions from sea and biomass burning, we
included terrestrial emissions of 2330 Gg [9].
We included bromine emissions from sea-salt, which contains approximately
0.223% of bromine [8], and should cover at least 90% of all the bromine emissions to the atmosphere. Currently the bromine sea-salt emissions are in the form
of Br 2 . Additionally, we release CH 3 Br due to biomass burning (23 Gg), terrestial
(18 Gg), and from the sea (32 Gg) [9]. Other standard emissions are taken from the
MACCity emission inventory.
50.3 Results
The preliminary simulations that cover yearly changing CFC-, and CH 3 CCl 3 -
emissions, extend from year 1942–2017. Any emissions prior to 1942 is released
during the first year of simulation. These simulations have a spatial resolution of
2° and they use ERA_interim for meteorology, which is simply copied from years
1980–2017 to cover also the years 1942–1979. CFC emissions included in the model
produce reasonable concentrations of these gases. For example, the average mixing
ratios for CFC-11, CFC-12, and CCl 4 in 2011 are 253, 522, and 88 ppt, respectively.
These are in line with the tropospheric measurements [9].
Our simulations clearly indicate that the ozone depletion above Antarctic is sensitive to the amount of active chlorine that originates mainly from CFCs and methyl
chloroform due to the photolysis. With current emissions the total ozone column
above the Antarctic has a thickness that is consistent with the observations. This is
illustrated in Fig. 50.1, where monthly averaged total ozone column is shown for
October 2011 (output of the zoomed run with 1° resolution).