Characteristics of extreme cold airmasses over the North American subarctic

Past studies have suggested that possible climate change would be most pronounced and perhaps most easily detected in the arctic regions of the globe. Furthermore, since these changes would be amplified during the winter months, it follows that their signature could appear in extreme cold arctic airmasses. To explore this likely possibility, we analyzed NCEP reanalysis surface temperature data spanning a 60-year time period over the source regions for the formation of arctic airmasses in North America, and were able to find variability within the coldest arctic airmasses on a decadal timescale. The variability we observed confirmed that extreme cold arctic airmasses have shown signs of warming at least in terms of surface temperature since the beginning of the data record. Our results strongly support the notion that extreme cold air arctic outbreaks have decreased in frequency and duration over time. In addition, we have examined several atmospheric parameters in an attempt to better understand the vertical structure and depth of extreme cold airmasses. We have identified criteria which could be to help classify cold airmasses in terms of depth and strength, such as lowest kilometer temperature change and inversion height. The understanding that we gain from these parameters among others can be used to further study extreme cold airmasses in the arctic and potentially to evaluate models.