A study of simulation and prediction of extratropical cyclones over the Northern Hemisphere partⅠ: Verification of simulation performance of the 6 CMIP5 coupled models

Simulation performance of the 6 CMIP5 (Coupled Model Intercomparison Project Phase 5) coupled models, in terms of activity frequency, numbers, central pressure, life span, traveling distance, and deepening rate of extratropical cyclones (ECs) over the Northern Hemisphere, were validated by comparing with the ERA-40 reanalysis data of European Centre for Medium-Range Weather Forecasting (ECMWF) during 1958—2001. The analysis result shows that: (1) the frequency distributions of life span, deepening rate and traveling distance of the ECs are found to be realistic in all the 6 models, and the linear reducing trend of central pressure of the ECs can be simulated by the models; while some system bias exist between simulation results and ERA-40, mainly including longer lifetime and slower deepening rate in simulations. (2) All the 6 models can reproduce the 2 main EC activity areas, and, among them, there are 5 models which overestimate the EC activity frequency over the eastern Europe-central Asia, central Siberian-western Siberian and eastern Asia continent, and all the models underestimate activity frequency over the region from northern Europe to central Siberian. And, (3) both the number of the total processes and strong ECs simulated by the models are less than the ERA-40 results. The simulated decadal oscillation periods of cyclone processes are slightly longer, and the simulated decadal oscillations of central pressure are weaker. From the above, it can be seen that the CMIP5 coupled models can reproduce main features of EC activity over the Northern Hemisphere during the 44 years, but some regional and systematic deviations still remain.