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

Wednesday, May 14, 2014 - 07:00
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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 blocking length and the distribution of surface temperature, precipitation and flow patterns of blocking as identified by a composite blocking index. Systematic improvements in blocking are reside in the frequency of blocking events. CAM3 underestimates significantly the occurrence of wintertime blocking over Europe while CAM4 and CAM5 successively improve 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 (turbulent mountain stress, microphysics and shallow convection) to specific improvements in remote teleconnection patterns occurring at prior time-lags to blocking events. We will further highlight the impact resolution and coupling on our range of blocking measures. There is clearly a significant interest in how blocking will change in a future climate and this talk will present initial results on predicted future blocking changes in the range of CESM models.

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