Abstract
Abstract. The UPSCALE (UK on PRACE: weather-resolving Simulations of Climate for globAL Environmental risk) project constructed and ran an ensemble of HadGEM3 (Hadley Centre Global Environment Model 3) atmosphere-only global climate simulations over the period 1985–2011, at resolutions of N512 (25 km), N216 (60 km) and N96 (130 km) as used in current global weather forecasting, seasonal prediction and climate modelling respectively. Alongside these present climate simulations a parallel ensemble looking at extremes of future climate was run, using a time-slice methodology to consider conditions at the end of this century. These simulations were primarily performed using a 144 million core hour, single year grant of computing time from PRACE (the Partnership for Advanced Computing in Europe) in 2012, with additional resources supplied by the Natural Environment Research Council (NERC) and the Met Office. Almost 400 terabytes of simulation data were generated on the HERMIT supercomputer at the High Performance Computing Center Stuttgart (HLRS), and transferred to the JASMIN super-data cluster provided by the Science and Technology Facilities Council Centre for Data Archival (STFC CEDA) for analysis and storage. In this paper we describe the implementation of the project, present the technical challenges in terms of optimisation, data output, transfer and storage that such a project involves and include details of the model configuration and the composition of the UPSCALE data set. This data set is available for scientific analysis to allow assessment of the value of model resolution in both present and potential future climate conditions.
Highlights
The development of the Met Office Unified ModelTM (MetUM) in recent years has yielded a traceable hierarchy of model resolutions from the N96L85 grid1, with 130 km horizontal resolution at 50◦ N and 85 vertical levels spanning the lower 85 km of the atmosphere, used in standard climate simulations to N512L70, 25 km at 50◦ N with 70 levels again spanning 0–85 km, used in global weather forecasting
Parallelisation within the MetUM has traditionally been achieved through the decomposition of the globe into rectangular latitude–longitude domains, each assigned to one Message Passing Interface (MPI) process
Recent improvements in the MetUM have reduced the frequency of Grid Point Storms (GPS) at resolutions such as N216, but the frequency of occurrence in the GA3 present climate ensemble was around one failure every nine months, improving to one in 19 months in the Global Atmosphere 4 (GA4) configurations
Summary
The development of the Met Office Unified ModelTM (MetUM) in recent years has yielded a traceable hierarchy of model resolutions from the N96L85 grid, with 130 km horizontal resolution at 50◦ N and 85 vertical levels spanning the lower 85 km of the atmosphere, used in standard climate simulations to N512L70, 25 km at 50◦ N with 70 levels again spanning 0–85 km, used in global weather forecasting. Recent work on the MetUM (Malcolm et al, 2010; Selwood, 2012) has significantly improved its computational performance and scalability to the point where it is possible to conceive of running ensembles of multi-decadal climate simulations at weather forecast resolution. A set of N512 runs with an updated scientific configuration, Global Atmosphere 4 (GA4) (Walters et al, 2013), were performed for present climate conditions to explore a number of sensitivities These sensitivities included entrainment rates and the dynamics and radiation time steps. The settings of the GA4 configuration are described in Walters et al (2013), but the major difference to our runs, based on GA3, is the use of the Reynolds SST climatology rather than OSTIA
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