Description and evaluation of GLOMAP-mode: a modal global aerosol microphysics model for the UKCA composition-climate model

摘要

A new version of the Global Model of Aerosol Processes (GLOMAP) is described,which uses a two-moment pseudo-modal aerosol dynamics approach rather than the originaltwo-moment bin scheme. GLOMAP-mode simulates the multi-component globalaerosol, resolving sulfate, sea-salt, dust, black carbon (BC) andparticulate organic matter (POM), the latter including primary and biogenicsecondary POM. Aerosol processes are simulated in a size-resolved mannerincluding primary emissions, secondary particle formation by binaryhomogeneous nucleation of sulfuric acid and water, particle growth bycoagulation, condensation and cloud-processing and removal by dry deposition,in-cloud and below-cloud scavenging. A series of benchmark observationaldatasets are assembled against which the skill of the model is assessed interms of normalised mean bias (b) and correlation coefficient (R).Overall, the model performs well against the datasets in simulatingconcentrations of aerosol precursor gases, chemically speciated particlemass, condensation nuclei (CN) and cloud condensation nuclei (CCN). Surfacesulfate, sea-salt and dust mass concentrations are all captured well, whileBC and POM are biased low (but correlate well). Surface CN concentrationscompare reasonably well in free troposphere and marine sites, but areunderestimated at continental and coastal sites related to underestimation ofeither primary particle emissions or new particle formation. The modelcompares well against a compilation of CCN observations covering a range ofenvironments and against vertical profiles of size-resolved particleconcentrations over Europe. The simulated global burden, lifetime and wetremoval of each of the simulated aerosol components is also examined and eachlies close to multi-model medians from the AEROCOM model intercomparisonexercise.