A comparison between HadCM3 integrations for coupled ocean-atmosphere processes and european climate (COAPEC) using Beowulf (UM version 4.5) and Cray T3E (UM version 4.4)

This report documents a comparison between two long integrations of HadCM3 which have been performed for COAPEC: one on a Cray T3E using Unified Model version 4.4, the other on a Beowulf cluster using UM version 4.5. A detailed comparison of difference plots between the two models shows a number of statistically significant differences in some fields, but these are small in magnitude, and both models are judged to be equally valid for scientific use for climate studies. Data are available from both runs at the NCAS/British Atmospheric Data Centre, and can be supplied to the research community.