The New GFDL Global Atmosphere and Land Model AM2–LM2: Evaluation with Prescribed SST Simulations

Abstract

The configuration and performance of a new global atmosphere and land model for climate research developed at the Geophysical Fluid Dynamics Laboratory (GFDL) are presented. The atmosphere model, known as AM2, includes a new gridpoint dynamical core, a prognostic cloud scheme, and a multispecies aerosol climatology, as well as components from previous models used at GFDL. The land model, known as LM2, includes soil sensible and latent heat storage, groundwater storage, and stomatal resistance. The performance of the coupled model AM2–LM2 is evaluated with a series of prescribed sea surface temperature (SST) simulations. Particular focus is given to the model's climatology and the characteristics of interannual variability related to E1 Niño– Southern Oscillation (ENSO). One AM2–LM2 integration was performed according to the prescriptions of the second Atmospheric Model Intercomparison Project (AMIP II) and data were submitted to the Program for Climate Model Diagnosis and Intercomparison (PCMDI). Particular strengths of AM2–LM2, as judged by comparison to other models participating in AMIP II, include its circulation and distributions of precipitation. Prominent problems of AM2– LM2 include a cold bias to surface and tropospheric temperatures, weak tropical cyclone activity, and weak tropical intraseasonal activity associated with the Madden–Julian oscillation. An ensemble of 10 AM2–LM2 integrations with observed SSTs for the second half of the twentieth century permits a statistically reliable assessment of the model's response to ENSO. In general, AM2–LM2 produces a realistic simulation of the anomalies in tropical precipitation and extratropical circulation that are associated with ENSO.

Oxygen and indicators of stress for marine life in multi-model global warming projections

“…In a fully coupled state, the model includes components for ocean (MOM-4 Griffies et al, 2004), atmosphere (AM2.1) and terrestrial biosphere (LM3 Anderson et al, 2004). LM3 is based on potential vegetation, so no land use is included.…”

TransCom continuous experiment: comparison of <sup>222</sup>Rn transport at hourly time scales at three stations in Germany

“…We found reasonable correlation between the radiosonde and ECMWF BLHs except at Sigmaringen which had relatively few radiosondes available in [2002][2003]. The local low level inversion studied in the SLOPE experiments Fiedler et al, 2000) was not used in this study because the horizontal scale of the low level inversion may be smaller than the grid interval of the meteorological data used.…”

“…1 at 20 m above the ground. The meteorological conditions during summer in Freiburg and at Schauinsland have characteristics of complex terrain, as studied in SLOPE Fiedler et al, 2000) and are different from typical continental sites. During winter, the meteorological situation is characterized by low, persistent stratus decks associated with stable conditions (Dentener et al, 1999).…”

“…One could explain the horizontal gradient by assuming higher exhalation rate around Freiburg due to soil type, but this cannot explain the vertical gradient. One alternative explanation is the local low level inversion resulting from a cold air pool from the Rhine valley Fiedler et al, 2000). There are two inversion layers over the Schauinsland region in SLOPE, one at 2 km and a lower one at 1 km.…”

“…Temperature of the site was used to include the site effect. The Schauinsland Ozone Precursor Experiment (SLOPE) conducted in June 1996 Fiedler et al, 2000) demonstrated the formation of a cold air pool and the build-up of local low level inversions during daytime on clear summer days in this area; this feature has not been taken into account in the evaluations of low resolution models.…”