Running a climate model in forecast mode to identify the source of tropical climate errors: With specific reference to the dry bias error over the Maritime Continent in an atmosphere only GCM

The Maritime Continent has been identified as a region of major climatic importance on both local and global scales. It is therefore essential that the region is sufficiently represented in general circulation models (GCMs) in order to correctly reproduce observed regional climatology and ultimately global circulation. However the region represents a major modelling challenge. The systematic underestimation of precipitation over the Maritime Continent region is a problem experienced in the UK Met Office atmosphere only GCM, along with several other global models. In order to identify the source of the model errors, a 'Spin-up' technique is used, similar to the NWP-inspired approach being used by PCMDI's CAPT project, where the first 5 days of climate integrations of a 52 member ensemble are analysed. Results show that the model errors over the Indo-Pacific region spin-up within the first 4 days of model integrations. This is a very useful tool, as it allows a much clearer analysis of the model atmosphere, without the complications of feedback mechanisms, reactions that occur over much longer timescales. Analysis of this initial period lets us observe how and why the model errors develop, making the source of the errors easier to pin-point.