Trends in the Northern Midlatitude Rossby Wave in a Future Climate

Enhanced Arctic warming in recent decades has occurred in part due to anthropogenic climate change. This phenomenon is known as Arctic amplification (AA), and has received considerable attention in recent literature. Furthermore, numerous studies have analyzed the effects AA may have on Northern mid-latitude circulation and weather patterns, including what these effects may be and if they will occur. One effect studied is how the phase speed of planetary-scale mid-latitude waves (i.e., Rossby waves) may change in a future climate during each season as a result of AA. However, many climate models have shown disagreement in their results and many authors state the result is method dependent. In addition, trends in the types of waves (i.e., high and low- frequency) have yet to be analyzed. This study seeks to analyze trends by season in the phase speed of high and low-frequency Rossby waves over the global Northern mid-latitudes using a wavenumber-frequency power spectrum applied to five climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) for the high emissions scenario (i.e., RCP8.5). Results show that for all seasons and both wave frequencies, the change in power has a decadal oscillation from 1950 to 2099, which is approximately consistent amongst the models. This study also works to determine a potential mechanism responsible for the decadal variations by conducting a preliminary test through the regression of background zonal wind against both high and low-frequency power trends.