U.K. HiGEM: The New U.K. High-Resolution Global Environment Model—Model Description and Basic Evaluation

Abstract

This paper describes the development and evaluation of the UK's new high resolution global coupled model, HiGEM, which is based on the latest climate configuration of the Met Office Unified Model, HadGEM1. In HiGEM, the horizontal resolution has been increased to 1.25 • x 0.83 • in longitude and latitude for the atmosphere, and 1/3 • x 1/3 • globally for the ocean. Multi-decadal integrations of HiGEM, and the lower resolution HadGEM, are used to explore the impact of resolution on the fidelity of climate simulations.Generally SST errors are reduced in HiGEM. Cold SST errors associated with the path of the North Atlantic drift improve, and warm SST errors are reduced in upwelling stratocumulus regions where the simulation of low level cloud is better at higher resolution. The ocean model in HiGEM allows ocean eddies to be partially resolved, which dramatically improves the representation of sea surface height variability. In the Southern Ocean, most of the heat transports in HiGEM is achieved by resolved eddy motions which replaces the parametrised eddy heat transport in the lower resolution model. HiGEM is also able to more realistically simulate small-scale features in the windstress curl around islands and oceanic SST fronts, which may have implications for oceanic upwelling and ocean biology.Higher resolution in both the atmosphere and the ocean allows coupling to occur on small spatial scales. In particular the small scale interaction recently seen in satellite imagery between the atmosphere and Tropical instability waves in the Tropical Pacific ocean is realistically captured in HiGEM. Tropical instability waves play a role in improving the simulation of the mean state of the Tropical Pacific which has important implications for climate variability.In particular all aspects of the simulation of ENSO (spatial patterns, the timescales at which ENSO occurs, and global teleconnections) are much improved in HiGEM.2

Using satellite and reanalysis data to evaluate the representation of latent heating in extratropical cyclones in a climate model

“…The model evaluated in this study is HiGEM1.2 (Shaffrey et al 2009), which is part of the UK Met Office Hadley Centre Global Environmental Model (HadGEM) family of models and is based on the HadGEM1 model. HiGEM is a higher resolution version of HadGEM1, in both atmosphere and ocean, which has been amended in certain respects.…”

“…The atmosphere has 38 vertical levels with a model top at 39 km. Detailed description of the model formulation can be found in Shaffrey et al (2009, Martin et al (2006), McLaren et al (2006) and references therein.…”

“…The ability of a state-of-the-art climate model, HiGEM (Shaffrey et al 2009), to reproduce latent heating in ETCs is assessed using data from the ERA-Interim (ERAI) renalysis (Dee et al 2011;Simmons et al 2007) and the ISCCP Schiffer 1991, 1999) and CloudSat (Stephens et al 2002) datasets. This framework also allows an assessment of ETC structure in ERAI relative to the observational datasets.…”

High-resolution global climate modelling: the UPSCALE project, a large-simulation campaign

“…The role of resolution in different physical processes in the climate system is not necessarily the same Demory et al, 2014;Schiemann et al, 2014). For example, due to the local Rossby radius of deformation a 1/3 • resolution ocean model cannot resolve the most important processes, eddies, while at 60 km the atmosphere can Shaffrey et al, 2009;Demory et al, 2014). Coarse-resolution simulations can produce representative data for global mean properties, but their limitations for studying regional effects and temporal variability are becoming more obvious Shaffrey et al, 2009;Scaife et al, 2011;Delworth et al, 2012;Kinter et al, 2013).…”

Scale space methods for climate model analysis

“…[28] To evaluate the performance of these models, we use two observational data sets: the ERA Interim reanalysis data set, spanning 1989-2009 [Dee et al, 2011], and the Global Precipitation Climatology Project (GPCP) [Adler et al, 2003] precipitation data set for 1979-2009. ERA-INT reanalysis is available on a uniform latitude-longitude grid with a resolution of 1.5 ı , while the GPCP grid has a resolution of 2.5 ı .…”