The Dynamical Core, Physical Parameterizations, and Basic Simulation Characteristics of the Atmospheric Component AM3 of the GFDL Global Coupled Model CM3

Abstract

The Geophysical Fluid Dynamics Laboratory (GFDL) has developed a coupled general circulation model (CM3) for the atmosphere, oceans, land, and sea ice. The goal of CM3 is to address emerging issues in climate change, including aerosol-cloud interactions, chemistry-climate interactions, and coupling between the troposphere and stratosphere. The model is also designed to serve as the physical system component of earth system models and models for decadal prediction in the near-term future-for example, through improved simulations in tropical land precipitation relative to earlier-generation GFDL models. This paper describes the dynamical core, physical parameterizations, and basic simulation characteristics of the atmospheric component (AM3) of this model. Relative to GFDL AM2, AM3 includes new treatments of deep and shallow cumulus convection, cloud droplet activation by aerosols, subgrid variability of stratiform vertical velocities for droplet activation, and atmospheric chemistry driven by emissions with advective, convective, and turbulent transport. AM3 employs a cubed-sphere implementation of a finite-volume dynamical core and is coupled to LM3, a new land model with ecosystem dynamics and hydrology. Its horizontal resolution is approximately 200 km, and its vertical resolution ranges approximately from 70 m near the earth's surface to 1 to 1.5 km near the tropopause and 3 to 4 km in much of the stratosphere. Most basic circulation features in AM3 are simulated as realistically, or more so, as in AM2. In particular, dry biases have been reduced over South America. In coupled mode, the simulation of Arctic sea ice concentration has improved. AM3 aerosol optical depths, scattering properties, and surface clear-sky downward shortwave radiation are more realistic than in AM2. The simulation of marine stratocumulus decks remains problematic, as in AM2. The most intense 0.2% of precipitation rates occur less frequently in AM3 than observed. The last two decades of the twentieth century warm in CM3 by 0.328C relative to 1881-1920. The Climate Research Unit (CRU) and Goddard Institute for Space Studies analyses of observations show warming of 0.568 and 0.528C, respectively, over this period. CM3 includes anthropogenic cooling by aerosol-cloud interactions, and its warming by the late twentieth century is somewhat less realistic than in CM2.1, which warmed 0.668C but did not include aerosol-cloud interactions. The improved simulation of the direct aerosol effect (apparent in surface clear-sky downward radiation) in CM3 evidently acts in concert with its simulation of cloud-aerosol interactions to limit greenhouse gas warming.

Internal variability in simulated and observed tropical tropospheric temperature trends

“…For simulations, we use historical and RCP4.5 runs from 44 different GCMs from the CMIP5 archive [Taylor et al, 2012;Bi et al, 2013;Xin et al, 2013;Ji et al, 2014;von Salzen et al, 2013;Meehl et al, 2012;Hurrell et al, 2012;Scoccimarro et al, 2011;Voldoire et al, 2013;Rotstayn et al, 2010;Hazeleger et al, 2010;Li et al, 2013;Delworth et al, 2006;Donner et al, 2011;Schmidt et al, 2014;Smith et al, 2010;Collins et al, 2011;Jones et al, 2011;Volodin et al, 2010;Dufresne et al, 2013;Hourdin et al, 2013;Sakamoto et al, 2012;Watanabe et al, 2010Watanabe et al, , 2011Giorgetta et al, 2013;Yukimoto et al, 2012;Bentsen et al, 2013], and from the 100 realization single-model large ensemble of the MPI-ESM [Giorgetta et al, 2013]. The large ensemble uses the model version MPI-ESM1.1 in low resolution (LR) configuration, with resolution T63 and 47 vertical levels in the atmosphere and 1.5 ∘ resolution and 40 vertical levels in the ocean.…”

Development of a parameterization of black carbon aging for use in general circulation models

“…A simple approach using constant values of the conversion rate from hydrophobic BC to hydrophilic BC, such as 24 or 36 h, has been widely used in several GCM studies (e.g., Cooke and Wilson, 1996;Cooke et al, 1999Cooke et al, , 2002Lohmann et al, 1999;Koch, 2001;Chung and Seinfeld, 2002;Bellouin et al, 2011;Donner et al, 2011;Lamarque et al, 2012), although the conversion rate is considered to vary depending on atmospheric conditions and concentrations of chemical species during the aging process. Previously, Koch (2001) and Wilson et al (2001) calculated the variable conversion rates of BC aging depending on the condensation of sulfuric acid (H 2 SO 4 ), produced from gas-phase oxidation of sulfur dioxide (SO 2 ).…”

“…Considering the τ coag. BC values over the source regions and the time scale over which air parcels are transported outside a source domain in GCMs, the coagulation effects over the source regions can be implicitly treated in the emission process of BC, such as assuming 80 % hydrophobic and 20 % hydrophilic for initially emitted BC particles, which were widely used in previous studies (e.g., Cooke et al, 2002;Chung and Seinfeld, 2005;Donner et al, 2011;Skeie et al, 2011). On the other hand, considering that most domains in GCMs are outside the source regions, the use of a constant conversion time, such as 20 days (i.e., δ in Eq.…”

Characterizing Surface and Air Temperature in the Baltic Sea Coastal Area Using Remote Sensing Techniques and Gis

“…3. The model utilizes Grell-Devenyi ensemble parameterization scheme [10], Ferrier operational microphysics scheme [8], Noah Land Surface Model physics scheme [2] unified by NCEP/NCAR/AFWA and GFDL radiation scheme [7]. Initialization and boundary conditions data is retrieved from GFS model downloaded from NCEP online services which also provide SST in their RTG_SST_HR product i.e.…”