Development and evaluation of a new regionalcoupled atmosphere-ocean model in the North Seaand Baltic Sea

摘要

A new regional coupled model system for the North Sea and the Baltic Sea is developed, which is composed ofthe regional setup of ocean model NEMO, the Rossby Centre regional climate model RCA4, the sea ice modelLIM3 and the river routing model CaMa-Flood. The performance of this coupled model system is assessed usinga simulation forced with ERA-Interim reanalysis data at the lateral boundaries during the period 19792010.Compared to observations, this coupled model system can realistically simulate the present climate. Since theactive coupling area covers the North Sea and Baltic Sea only, the impact of the ocean on the atmosphere overEurope is small. However, we found some local, statistically significant impacts on surface parameters like 2mair temperature and sea surface temperature (SST). A precipitation-SST correlation analysis indicates that bothcoupled and uncoupled models can reproduce the airsea relationship reasonably well. However, the coupledsimulation gives slightly better correlations even when all seasons are taken into account. The seasonalcorrelation analysis shows that the airsea interaction has a strong seasonal dependence. Strongest discrepanciesbetween the coupled and the uncoupled simulations occur during summer. Due to lack of airsea interaction, inthe Baltic Sea in the uncoupled atmosphere-standalone run the correlation between precipitation and SST is toosmall compared to observations, whereas the coupled run is more realistic. Further, the correlation analysisbetween heat flux components and SST tendency suggests that the coupled model has a stronger correlation. Ouranalyses show that this coupled model system is stable and suitable for different climate change studies.