GFDL's CM2 Global Coupled Climate Models. Part I: Formulation and Simulation Characteristics

Abstract

The formulation and simulation characteristics of two new global coupled climate models developed at NOAA's Geophysical Fluid Dynamics Laboratory (GFDL) are described. The models were designed to simulate atmospheric and oceanic climate and variability from the diurnal time scale through multicentury climate change, given our computational constraints. In particular, an important goal was to use the same model for both experimental seasonal to interannual forecasting and the study of multicentury global climate change, and this goal has been achieved.Two versions of the coupled model are described, called CM2.0 and CM2.1. The versions differ primarily in the dynamical core used in the atmospheric component, along with the cloud tuning and some details of the land and ocean components. For both coupled models, the resolution of the land and atmospheric components is 2°latitude ϫ 2.5°longitude; the atmospheric model has 24 vertical levels. The ocean resolution is 1°in latitude and longitude, with meridional resolution equatorward of 30°becoming progressively finer, such that the meridional resolution is 1/3°at the equator. There are 50 vertical levels in the ocean, with 22 evenly spaced levels within the top 220 m. The ocean component has poles over North America and Eurasia to avoid polar filtering. Neither coupled model employs flux adjustments.The control simulations have stable, realistic climates when integrated over multiple centuries. Both models have simulations of ENSO that are substantially improved relative to previous GFDL coupled models. The CM2.0 model has been further evaluated as an ENSO forecast model and has good skill (CM2.1 has not been evaluated as an ENSO forecast model). Generally reduced temperature and salinity biases exist in CM2.1 relative to CM2.0. These reductions are associated with 1) improved simulations of surface wind stress in CM2.1 and associated changes in oceanic gyre circulations; 2) changes in cloud tuning and the land model, both of which act to increase the net surface shortwave radiation in CM2.1, thereby reducing an overall cold bias present in CM2.0; and 3) a reduction of ocean lateral viscosity in the extratropics in CM2.1, which reduces sea ice biases in the North Atlantic. Both models have been used to conduct a suite of climate change simulations for the 2007 Intergovernmental Panel on Climate Change (IPCC) assessment report and are able to simulate the main features of the observed warming of the twentieth century. The climate sensitivities of the CM2.0 and CM2.1 models are 2.9 and 3.4 K, respectively. These sensitivities are defined by coupling the atmospheric components of CM2.0 and CM2.1 to a slab ocean model and allowing the model to come into equilibrium with a doubling of atmospheric CO 2 . The output from a suite of integrations conducted with these models is freely available online (see http://nomads.gfdl.noaa.gov/).

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.…”

Finding the way to the top: how the composition of oceanic mid-trophic micronekton groups determines apex predator biomass in the central North Pacific

“…Modeled phytoplankton biomass for 4 primary producer groups ('diatoms', 'diazotrophs', 'other large phytoplankton' 5−200 µm, and 'small phytoplankton' 0.2−5 µm) were obtained from the NOAA GFDL prototype Earth System Model (ESM2.1). ESM2.1 links a climate model (CM2.1; Delworth et al 2006, Gnanadesikan et al 2006) to a biogeochemical model, Tracers of Phytoplankton with Allometric Zooplankton (TOPAZ; Dunne et al 2005), and data used represent the IPCC Special Report on Emissions Scenario A2 (for details, see Polovina et al 2011, Howell et al 2013). Clarke (1973), Maynard et al (1975), Childress et al (1980), Hopkins & Gartner (1992), Sutton & Hopkins (1996) Zooplanktivorous micronekton fishes Mesopelagic fishes from the families Myctophidae, Gonostomatidae, Phosichthyidae, Bregmacerotidae, and Sternoptychidae inhabiting waters 200−1000 m. Many are vertical migrators and feed on zooplankton.…”

Using model‐data fusion to interpret past trends, and quantify uncertainties in future projections, of terrestrial ecosystem carbon cycling

“…For the climate change projection, we used downscaled data (Hayhoe et al, 2008) from the regionalized projection of the GFDL-CM global coupled climate-land model (Delworth et al, 2006) driven with socio-economic change scenario A1FI (IPCC, 2007).…”