Remote Teleconnection Influences on Atmospheric Blocking in the Community Earth System Model (CESM)

This presentation will summarize the performance of the family of Community Atmosphere Models (CAM3/CAM4/CAM5) in representing atmospheric high pressure blocking patterns over the Euro-Atlantic and Pacific sectors. All three model versions have a reasonable simulation of the distribution of surface temperature, precipitation and flow patterns of blocking as identified by a composite blocking index. Where systematic improvements in blocking are seen reside in the frequency of blocking events. CAM3 underestimates significantly the occurrence of wintertime blocking over Europe while CAM4 and CAM5 improved on this. The improved distribution of events is even more striking during the Spring. Results will be shown that relate changes to the parameterized physics between CAM3 and CAM4 (mainly deep convection) and CAM4 and CAM5 (microphysics, shallow convection) and the origin regions for teleconnection patterns related to these changes. Additionally, we will highlight the detrimental impact of coupling to an interactive ocean and the mixed response to increasing the atmospheric resolution.