Atmospheric Blocking in Community Earth System Model Large Ensemble 2

Weather patterns in different parts of the globe are significantly affected by atmospheric blocking, a phenomenon that can cause extreme weather events such as heatwaves, cold spells, flash floods, wildfires, and prolonged droughts. Despite its crucial impact, current climate models have limitations in accurately representing blocking events. Thus, assessing blocking representation in climate models is essential for understanding potential changes in extreme weather events under the influence of climate change.
In this study, we assessed the representation of Northern Hemispheric (NH) Atmospheric Blocking in the Community Earth System Model Large Ensemble 2 (LENS2) which comprises 100 Ensemble Members. Results show substantial progress in blocking representation with improved fidelity and minimal bias when compared with ERA5 and NCEP DOE Reanalysis 2 as a reference datasets.
Future simulations of LENS2 confirm a projected decrease of blocking frequency in the NH by ~11% for Winter, and an increase in Summer by ~12% under the SSP370 emission scenario. We also suggest a potential of studying less persistent blocking conditions for better understanding of the onset mechanism of blocking.

Keywords: Atmospheric Blocking, CESM Large Ensemble 2