|Climate Models in UJCC|
|Written by Administrator|
|Friday, 05 January 2007|
UJCC climate models
UJCC is making use of a broad group of models in order to systematically explore the role and value of resolution in climate system research: starting with the base N96 AOGCM (HadGEM1), an array of coupled and uncoupled models has been set up, in order to test hypotheses about the global impact of increasingly resolving the fundamental building blocks of climate. This model "matrix" will be an invaluable resource for understanding the impact of resolution in both atmosphere and ocean model components, and will help to guide future model development.
See http://www.higem.nerc.ac.uk/higem_only/validation/hadgem1a/hadgem1a.html for more details of HadGEM1a.
The following figure illustrates the role of resolution in climate modelling. In this figure, model clouds have been drawn with a grey/white colour scale, while precipitation has been overlaid in red. The model-produced information is shown on a global map. The impact of resolution can be discerned by analogy, noticing how the left panels remind us of a picture taken with a cheap digital camera, where the individual pixels are visible; as resolution increases, the pixels are smaller and the image is of higher quality. In climate modelling, at lower resolution, many of the climate elements (e.g. weather fronts, organised convection) are not properly resolved, so that their characteristics are only approximative and their interaction with other climate elements is only partially possible. Their impacts (e.g. high winds, extreme precipitation) are only partially included in the climate simulation. At higher resolution it is possible to see how weather fronts are narrower, how regions of convection seem to have more coherent structure and how large regions of intense precipitation emerge.
The value of high resolution in climate system research
The UJCC team work alongside Japanese scientists at the Earth Simulator Centre and at the University of Tokyo, who have also developed models at high and ultra-high resolution to solve climate problems. It is beneficial to make use of a broad group of models of varying resolution (and model science) in order to explore the role and value of resolution in climate system research, particularly at the regional scale. Because of the way certain processes and feedbacks are modelled, different GCMs may simulate quite different responses to the same forcing. The inter-comparison of models is essential to achieve the most reliable climate simulation, and will also help to guide future model development.
In the first two years, UJCC have made the following contributions to UK climate system research:
HadGEM1: The Hadley Centre's HadGEM1 model, successor to the famous HadCM3, is normally run with an atmospheric resolution of (1.88x1.25, ~135 km in mid-latitudes) and was recently integrated for hundreds of years within the framework of IPCC AR4. In the ocean, this coupled model is integrated with a grid spacing of 1x1 (1x0.333 in the tropics).
With these models established on the ES, two further models combining their resolutions have also been developed.
The HadGEM1 atmospheric resolution model (135km) has been coupled to the HiGEM ocean model (30km). Hadgem1a3rdDegOcnPd status on ES:
Uncoupled models (AMIP2 simulations)
HiGAM1a status on ES:
NUGAM1a status on ES:
|Last Updated ( Monday, 28 May 2007 )|