Brief summary of GLOMAP-mode: global size-resolved aerosol microphysics
The UKCA aerosol scheme is a simplified version of the GLobal Model of Aerosol Processes (GLOMAP) (e.g. Spracklen et al., 2005). GLOMAP is designed to simulate the aerosol particle size distribution and represents the key microphysical processes (nucleation, coagulation, condensation and cloud processing) which control it.
The simpler GLOMAP version used in UKCA, called GLOMAP-mode, simulates these processes within a two-moment modal aerosol dynamics approach (number and mass in each mode), which requires much fewer transported tracers (typically 15 to 30) than the original bin-resolved GLOMAP scheme which requires 100-200 transported tracers for a multi-component simulation (e.g. Spracklen et al, 2008).
The dynamically evolving particle size distribution in UKCA leads to improved simulation of the number concentration of the sub-set of particles that interact with the clouds (cloud condensation nuclei, or CCN).
The incorporation of the UKCA aerosol in HadGEM3 will represent a step-change in the capability of the UK climate model to simulated aerosol indirect effects on climate.
A recent publication in Geoscientific Model Development (Mann et al, 2010) describes GLOMAP-mode in detail and presents evaluation of the model in the chemical transport model against a wide range of observations.
Spracklen, D. V., Pringle, K. J., Carslaw, K. S., et al.: A global off-line model of size-resolved aerosol microphysics: I. Model development and prediction of aerosol properties, Atmos. Chem. Phys., 5, 2227--2252, doi:10.5194/acp-5-2227-2005, 2005.
Spracklen, D. V., Carslaw, K. S., Kulmala, M., et al.: Contribution of particle formation to global cloud condensation nuclei concentrations, Geophys. Res. Lett., 35, L06808, doi:10.1029/2007GL033038, 2008.
Mann, G. W., Carslaw, K. S., Spracklen, D. V., et al.: Description and evaluation of GLOMAP-mode: a modal global aerosol microphysics model for the UKCA composition-climate model. Geosci. Model Dev., 3, 519-551, 2010.
For more details about the GLOMAP-mode aerosol scheme and the interface to the rest of UKCA and other parts of the UM, please contact Graham Mann (NCAS, University of Leeds) email@example.com.