The signal of sudden stratospheric warmings in surface climate

Abstract

Long term conditions in the atmosphere are changing. Because of this, many of the atmospheric processes that have been studied during the last century will change. Sudden stratospheric warmings (SSWs), which occur in the polar stratosphere, are a prime example of processes that indicate the top down relationship between the stratosphere and troposphere. The frequency of SSWs is believed to change with rising temperatures. SSWs are thought to cause cold air outbreaks over the continents in the northern hemisphere, leading to potential damages to infrastructure and increased health risks. To better understand what future atmospheric conditions infer concerning SSWs, past variations need to be understood. As of now, the record of SSWs start at 1958 due to limitations in stratospheric measurements. The goal of this thesis is to identify regions and surface climate variables sensitive to SSWs. Spatial correlations demonstrate a positive correlation between winter temperatures and the occurrence of SSWs in northeastern North America and Africa and southern Asia. A negative connection between winter temperature and the occurrence of SSWs is displayed in northern Eurasia. A more detailed regional analysis revealed that mean winter temperatures in northeastern North America during SSW years exceeds the 10th percentile of monthly temperatures during non-SSW years. During SSW years winter mean temperatures in northern Fennoscandia are only slightly lower than during non-SSW years. Tree ring data from northeastern North America are suggested as possible proxy data for a winter temperature reconstruction that could be used in the detection of historical SSWs.