The Norwegian Earth System Model, NorESM1-M – Part 1: Description and basic evaluation of the physical climate

TLDR

The NorESM family is based on CCSM4 but differs by using an isopycnic ocean coordinate and advanced chemistry–aerosol–cloud–radiation interaction schemes; the lower‑resolution and biogeochemical cycling variants are not covered in this paper. This paper presents the core NorESM1‑M model and outlines its intended use, with further performance analysis and scenario projections detailed in a companion study. NorESM1‑M operates at ~2° horizontal resolution for atmosphere and land and ~1° for ocean and ice, with lower‑resolution and biogeochemical cycling variants also available, and the study evaluates its stability, mean state, and internal variability using CMIP5 experiments. The assessment shows that NorESM1‑M is stable, reproduces a realistic mean state, and exhibits internal variability consistent with CMIP5 experiments, while detailed performance and scenario projections are reported in a companion paper. Abstract.

Abstract

Abstract. The core version of the Norwegian Climate Center's Earth System Model, named NorESM1-M, is presented. The NorESM family of models are based on the Community Climate System Model version 4 (CCSM4) of the University Corporation for Atmospheric Research, but differs from the latter by, in particular, an isopycnic coordinate ocean model and advanced chemistry–aerosol–cloud–radiation interaction schemes. NorESM1-M has a horizontal resolution of approximately 2° for the atmosphere and land components and 1° for the ocean and ice components. NorESM is also available in a lower resolution version (NorESM1-L) and a version that includes prognostic biogeochemical cycling (NorESM1-ME). The latter two model configurations are not part of this paper. Here, a first-order assessment of the model stability, the mean model state and the internal variability based on the model experiments made available to CMIP5 are presented. Further analysis of the model performance is provided in an accompanying paper (Iversen et al., 2013), presenting the corresponding climate response and scenario projections made with NorESM1-M.