Simulation and Projection of Northern Hemisphere Blockings In CMIP5 Models

Abstract

The frequencies of atmospheric blocking are analyzed as simulated in 16 models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) over North Hemisphere especially over key regions where blocking highs influencing China (the Ural, Baikal and Okhotsk), and the Representative Concentration Pathway 4.5 (RCP4.5) integrations are used to examine projected future changes in a warmer climate. Comparison with reanalysis data reveals that the frequencies of North Atlantic-Eurasia blocking are significantly underestimated throughout the year, however, multi-model mean generally overestimates the blocking frequency over high-latitude of Pacific. Ural blocking, Lake Baikal and Okhotsk Sea blocking frequencies are found to be mainly underestimated especially during the cold season. The RCP4.5 integrations show a heavily reduced for blocking frequency over North Atlantic and higher latitude of Eurasia in 2044-2099, but high-latitude blocking over Atlantic and Pacific presents a small increase. A significant increase of the Ural blocking is found. In contrast to the trend of blocking index for RCP4.5 path in the second half of the 21st, the increasing trend from 2006 to 2050 is distinct, the blocking increasing trend is more significant in summer than in winter over the three regions.