Seasonal Analysis of Historical Air Mass Persistance Across the United States, 1955-2015

The persistence of synoptic air masses is related to a number of environmental risks to human health, including lower atmospheric pollution, dust, and pollen concentrations and prolonged oppressive heat and humidity. From a climate dynamics perspective, air mass persistence also reflects variability in the dynamical nature of the middle latitude atmosphere. Here, a historical analysis of synoptic air mass persistence across the continental United States is presented to portray spatial and temporal variability and trends in air mass residence times. Historical daily air mass calendars for 144 locations across the United States for the 60-year period 1955 through 2015 were extracted from the Spatial Synoptic Classification database. The data were stratified by season and a 60-year climatology of seasonal air mass occurrence was created for each location. The historical daily air mass data were then translated into a record of residence time, or the length of consecutive days that a synoptic air mass type was in place at a location. The historical record of seasonal air mass residence times, or persistence, were then analyzed for spatial variability across the United States and for temporal variability and trends. The results contribute synoptic meteorological evidence in support of climate change study while also portraying changes in the risks to human health that stem from synoptic atmospheric stagnation.