Abstract
Abstract. We introduce and evaluate aerosol simulations with the global aerosol–climate model ECHAM6.3–HAM2.3, which is the aerosol component of the fully coupled aerosol–chemistry–climate model ECHAM–HAMMOZ. Both the host atmospheric climate model ECHAM6.3 and the aerosol model HAM2.3 were updated from previous versions. The updated version of the HAM aerosol model contains improved parameterizations of aerosol processes such as cloud activation, as well as updated emission fields for anthropogenic aerosol species and modifications in the online computation of sea salt and mineral dust aerosol emissions. Aerosol results from nudged and free-running simulations for the 10-year period 2003 to 2012 are compared to various measurements of aerosol properties. While there are regional deviations between the model and observations, the model performs well overall in terms of aerosol optical thickness, but may underestimate coarse-mode aerosol concentrations to some extent so that the modeled particles are smaller than indicated by the observations. Sulfate aerosol measurements in the US and Europe are reproduced well by the model, while carbonaceous aerosol species are biased low. Both mineral dust and sea salt aerosol concentrations are improved compared to previous versions of ECHAM–HAM. The evaluation of the simulated aerosol distributions serves as a basis for the suitability of the model for simulating aerosol–climate interactions in a changing climate.
Highlights
The increase in the positive radiative forcing of anthropogenic greenhouse gases and tropospheric ozone is partly offset by aerosols imposing a negative radiative forcing (Boucher et al, 2013; Myhre et al, 2013)
For a general overview of the performance of the ECHAM6.3–HAM2.3 aerosol simulation, the simulated global AOT distributions for the CLIM, nudged wind fields (NUDGE), and Global Fire Assimilation System (GFAS) experiments are compared with collocated retrievals from the MODerate-resolution Imaging Spectroradiometer (MODIS) Aqua satellite instrument for the example year 2007 (Fig. 3)
The aerosol part ECHAM6.3– HAM2.3 is evaluated against a standard set of aerosol observations including AOT and AE from sun photometer measurements, particle size distribution, and in situ measurements of mass concentrations of different aerosol species including aircraft measurements
Summary
The increase in the positive radiative forcing of anthropogenic greenhouse gases and tropospheric ozone is partly offset by aerosols imposing a negative radiative forcing (Boucher et al, 2013; Myhre et al, 2013). The latest version of the ECHAM–HAMMOZ model (version ECHAM6.3–HAM2.3–MOZ1.0) combines the most recent versions ECHAM (ECHAM6; Stevens et al, 2013), the aerosol module HAM2 (Zhang et al, 2012), and the atmospheric trace gas chemistry module MOZ (described in Rast et al, 2014). The HAM and MOZ modules share a common interface with ECHAM6 and consistent representation of common processes (e.g., emissions and deposition of trace gases and aerosols, as well as cloud microphysics) and the associated routines. The details of the chemistry module MOZ and evaluation of the ECHAM6.3–HAM2.3–MOZ1.0 model configuration are described in Schultz et al (2018). Cloud processes and cloud–aerosol interactions, as well as direct radiative forcing simulated in ECHAM6.3–HAM2.3, are evaluated in a companion study by Neubauer et al (2019). The aerosol microphysical processes can be described by the sectional or bin aerosol scheme SALSA in the ECHAM6.3–HAM2.3–SALSA configuration, which is described in Kokkola et al (2008, 2018)
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