Difference between pages "GLOMAP-mode in UKCA linked to Stratospheric Chemistry (StratChem)" and "Direct effect from GLOMAP-mode aerosol to the Edwards-Slingo radiation scheme"

Revision as of 13:01, 18 February 2011

The UKCA model is configured into the HadGEM3 climate model with a double call to the radiation scheme to allow the direct radiative effect from the GLOMAP-mode aerosol to be calculated online in the model.

For the existing CLASSIC aerosol scheme used in HadGEM2-ES and previous HadGEM versions, the aerosol is considered as an external mixture of different aerosol types (sulphate, biomass, soot, biogenic and sea-salt). Then, for the direct aerosol forcing, the optical properties from each of these types was considered separately. The interface to the Edwards-Slingo radiation scheme used in HadGEM is based on look-up tables (from Mie calculations) for the optical properties of each particle type as a function of relative humidity.

In contrast to CLASSIC, GLOMAP-mode assumes each mode consists of an internal mixture of the different aerosol components (e.g. sulphate, black carbon and organic carbon). The water content is evaluated within this assumption using the ZSR algorithm (Stokes and Robinson, 1966), using water activity data from Jacobson et al. (1996).

Whereas the look-up tables for the CLASSIC aerosol scheme were based only on relative humidity and wavelength; for GLOMAP-mode, the information on mean particle radius and composition for each of the internally-mixed size modes is used. A volume-average mixing rule is used over the components present (including water) to calculate the real and imaginary parts of the refractive index. The particle size determines the Mie parameter in relation to the wavelength. The look-up tables have been calculated based on the integrals across each of the spectral bands for the short-wave and long-wave used by HadGEM.

For more details about the interface to the Edwards-Slingo radiation scheme and the calculations of the optical properties of the aerosol, please contact Nicolas Bellouin (UK Met Office) nicolas.bellouin@metoffice.gov.uk.

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+The UKCA model is configured into the HadGEM3 climate model
-This configuration involves an extension to the UKCA Stratospheric Chemistry
+with a double call to the radiation scheme to allow the
-(StratChem) scheme to additionally include stratospheric aerosol-precursor chemistry.
+direct radiative effect from the GLOMAP-mode aerosol to be
+calculated online in the model.
+For the existing CLASSIC aerosol scheme used
-In addition to the 36 advected tracers in StratChem, 8 extra gas phase tracers
+in HadGEM2-ES and previous HadGEM versions,
-are added for the aerosol chemistry (DMS, SO2, SO3, H2SO4, MSA, CS2, COS, H2S).
+the aerosol is considered as an external
-The sulphur chemistry scheme is essentially that from Weisenstein et al (1997)
+mixture of different aerosol types (sulphate,
-including updates from WMO (2006).
+biomass, soot, biogenic and sea-salt).
+Then, for the direct aerosol forcing, the optical properties
+from each of these types was considered separately.
+The interface to the Edwards-Slingo radiation scheme used
+in HadGEM is based on look-up tables (from Mie calculations)
+for the optical properties of each particle type
+as a function of relative humidity.
+In contrast to CLASSIC, GLOMAP-mode assumes each mode
-In this configuration, H2SO4 in the aerosol phase has a non-zero vapour
+consists of an internal mixture of the different aerosol
-pressure in the stratosphere, calculated following Ayers et al (1980).
+components (e.g. sulphate, black carbon and organic carbon).
-The GLOMAP-mode aerosol routines have been modified to calculate this
+The water content is evaluated within this assumption using
-vapour pressure and allow evaporation or condensation of
+the ZSR algorithm (Stokes and Robinson, 1966), using water activity data from Jacobson et al. (1996).
-sulphuric acid depending on
-the atmospheric conditions, with the Kelvin effect included according
-to the mean radius calculated by GLOMAP-mode.
-The nucleation mechanism of Vehkamakki et al (2002) which is applicable
-to both tropospheric and stratospheric conditions has also been added.
+Whereas the look-up tables for the CLASSIC aerosol scheme were
-As for the StratChem chemistry, this extended scheme (StratChem+Aero) uses the
+based only on relative humidity and wavelength; for GLOMAP-mode, the
-sparse-matrix Newton-Raphson solver.
+information on mean particle radius and composition for each
+of the internally-mixed size modes is used.  A volume-average
+mixing rule is used over the components present (including water)
+to calculate the real and imaginary parts of the refractive
+index. The particle size determines the Mie parameter in
+relation to the wavelength.   The look-up tables have been
+calculated based on the integrals across each of the
+spectral bands for the short-wave and long-wave used by HadGEM.
+For more details about the interface to the Edwards-Slingo
-Ayers, G. P., Gillett, R. W. and Gras, J. L. et al (1980)
+radiation scheme and the calculations of the optical properties
-On the vapor pressure of sulfuric acid,
+of the aerosol, please contact Nicolas Bellouin (UK Met Office)
-Geophys. Res. Lett., vol. 7, no. 6, pp. 433-436, 1980.
+nicolas.bellouin@metoffice.gov.uk.
-WMO (2006): SPARC Assessment of Stratospheric Aerosol Properties,
-Ed. L. Thomason and T. Peter.
-Vehkamakki, H., Kulmala, M., Napari, I. et al (2002):
-An improved parameterization for sulfuric acid - water nucleation
-rates for tropospheric and stratospheric conditions, J. Geophys. Res.,
-vol 107, D22, doi:10.1029/2002JD002184, 2002.
-Weisenstein, D. K., Yue, G. K., Ko, M. K. W. et al.: A two-dimension model
-of sulfur species and aerosol, J. Geophys. Res., vol. 102, D11, pp. 13,019-13,035.