A changing arctic atmospheric circulation in response to global change, and its influence on future extreme weather and convective potential

• Main Author: Fisel, Brandon Joshua
• Format: Text
• Language: English
• Published: Iowa State University Digital Repository 2018
• Subjects: Atmospheric Sciences; Arctic; Pacific; North Atlantic; Sea ice
• Online Access: https://lib.dr.iastate.edu/etd/16579; https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=7586&context=etd

The Arctic circulation can develop multiple dynamic circulation regimes. Previous results from ensemble simulations for June -- December 2007 suggest that as sea-ice cover wanes (increases) there is a tendency for more 1- (2-)regime behavior. In the first study, we extend the analysis of dynamic circulation regimes to 16 years (1992 -- 2007) using a six-member ensemble of CORDEX WRF simulations to understand the climatology of persistent dynamical regimes over longer time periods. Additionally, we analyze temperature extremes in our simulations to understand how changes in atmospheric circulations associated with persistent regime behavior is more likely to produce extreme behavior. There is a tendency for 1-regime behavior to be preferred more during the transition seasons. December-January-February and June-July-August has the most 2-regime behavior. Additional results presented in this study suggest there is a tendency for more warm (cold) temperature extremes to be favored with 1- (2-)regime behavior. Results suggest that identification of when persistent regime behavior occurs is useful for understanding future Arctic temperature extremes. The regime behavior uncovered through this study also has implications for the future predictability of the Arctic atmospheric circulation as climate changes. In the second paper, we analyze Arctic December-January-February MSLP in reduced spectral nudging RASM simulations, for the 1990 -- 1995 time period. This analysis focuses on the change in Arctic atmospheric circulations along the North Pacific and North Atlantic regions. ERAI Re-Analysis was used to validate our CTRL simulation. Two ensembles consisting of four members were branched from the CTRL simulation, and restarted using perturbed initial conditions. Results showed substantially higher MSLP across the interior of the RASM domain in the reduced nudging simulations, and an improvement in the weakly nudged versus intermediate nudged simulations. In addition, 2-m temperature responses to nudging changes did not correspond in position with the MSLP results, suggesting further work is needed. In the last paper, we analyze July convective potential and heavy convective precipitation produced by four CMIP5 GCMs, for historical (1986 -- 2005) and RCP 8.5 scenario (2081 -- 2100) time periods. Analysis focuses on four analysis regions identified to experience large future atmospheric change. This analysis focuses on common stability indices and convective precipitation. Robust statistics were calculated using the bootstrap resampling technique. We also analyze individual components of the stability indices to understand the physical processes producing changes in Arctic convective potential. Results suggest a future Arctic with less convective potential, however increasing convective precipitation intensity.