together with an initialization procedure and a model evaluation system. This paper 31 summarizes the lessons learned from MiKlip so far; some are purely scientific, others concern 32 strategies and structures of research that targets future operational use. 33Three prediction-system generations have been constructed, characterized by 34 alternative initialization strategies; the later generations show a marked improvement in 35 hindcast skill for surface temperature. Hindcast skill is also identified for multi-year-mean 36European summer surface temperatures, extra-tropical cyclone tracks, the Quasi-Biennial 37Oscillation, and ocean carbon uptake, among others. Regionalization maintains or slightly 38 enhances the skill in European surface temperature inherited from the global model and also 39 displays hindcast skill for wind-energy output. A new volcano code package permits rapid 40 modification of the predictions in response to a future eruption. 41MiKlip has demonstrated the efficacy of subjecting a single global prediction system 42 to a major research effort. The benefits of this strategy include the rapid cycling through the 43 prediction-system generations, the development of a sophisticated evaluation package usable 44 by all MiKlip researchers, and regional applications of the global predictions. Open research 45 questions include the optimal balance between model resolution and ensemble size, the 46 appropriate method for constructing a prediction ensemble, and the decision between full-47 field and anomaly initialization. 48

ABSTRACT:To determine whether the use of regional climate models improves the representation of climate is a crucial topic in climate modelling. An improvement over coarser scale models is expected especially in areas with complex orography or along coastlines. However, some studies have shown no clear added value for regional climate models. In this study a high-resolution regional climate simulation performed with REMO 5.0 (regional model) over the whole of Europe over the period 1958-1998 is analysed for 2-m temperature over the European Alps and their surroundings called the Greater Alpine region (GAR). The simulation is driven by perfect boundary conditions at the lateral boundaries provided by the ERA40 reanalysis and spectral nudging of the large-scale wind fields towards ERA40 values for the upper layers inside the model domain. The added value of the regional simulation (1/6°resolution) is analysed with respect to the driving reanalysis (1.125°resolution).Both the REMO simulation and the ERA40 reanalysis are validated against different station datasets of monthly and daily mean 2-m temperature. Correlation analysis shows that the temporal variability of temperature is well represented by both REMO and ERA40, whereas both show considerable biases. The REMO bias reaches 3 K in summer in regions known to experience a problem with summer drying in a number of regional models. The comparison of REMO and ERA40 shows that an added value of the former exists for all regions in winter. For the regions surrounding the Alps, the added value is absent in summer, whereas in the inner Alpine subregions with most complex orography, REMO performs better than ERA40 during the whole year. The only moderate value added by REMO in this hindcast set-up may be partly explicable by the fact that meteorological measurements are assimilated in the ERA40 reanalysis but not in the REMO simulation.

Simulations using the ECHAM5/MPI-OM coupled atmosphere-ocean model both with and without the Tibetan Plateau are performed in order to study the large scale effects of orographic forcing on the behaviour of the Asian summer monsoon system. Our analysis emphasises the significant impact of plateau forcing on the atmosphere-ocean interactions. It is argued that, in addition to the orographic forcing of the Tibetan Plateau on the climate of Asia such as sensible heat pumping and thermal insulation, other significant direct processes exist, which link the Asian summer monsoon to the sea surface temperatures in the North Atlantic Ocean. The removal of the Tibetan Plateau modifies the wind-driven ocean circulations over the North Atlantic, which leads to a decrease in the surface heat advection over the North Atlantic Ocean and a decrease in the Atlantic Meridional Overturning Circulation. This, in turn, affects, via teleconnections, both the monsoon rainfall and the position of the intertropical convergence zone.

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