THE IMPACT OF TELECONNECTION PATTERNS ON AIR MASS FREQUENCY AND CHARACTER IN NORTH AMERICAN WINTERS

Advisor:  Laurence S. Kalkstein

Committee:  Daniel J. Leathers, Roger G. Barry 

ABSTRACT

Air masses are important indicators of spatially large-scale thermal and moisture conditions. The advection of air masses across North America is largely determined by the movement of ridge-trough systems. Teleconnection patterns are known to influence the positioning of these systems, though the relationship between teleconnections and air mass dynamics is yet to be fully understood. This investigation is aimed at identifying the impact of four teleconnection patterns [El Niño/ Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Pacific North American pattern (PNA), and North Atlantic Oscillation (NAO)] on the November-March frequency and character of 11 air masses (identified by the Spatial Synoptic Classification) in the United States and Canada over the past 50 years.

Positive and negative teleconnection phases are identified and within-air mass mean frequencies are calculated for each pattern regime. Normal winter synoptic conditions are defined by the mean air mass frequencies for all years of record. The differences between positive or negative teleconnection phase frequencies and normal frequencies are computed for each air mass type and evaluated for statistical significance. Frequency differences are then spatially interpolated in a GIS across North America and examined for regional trends.

Results indicate that all four teleconnections significantly impact air mass frequency across North America. ENSO and the PNA appear to influence greater frequency changes, with more spatial cohesion, than the PDO and NAO. Further, impacts over western North America are greater than those in the east. The Dry Moderate, Dry Polar, Dry Polar-, Moist Moderate, and Moist Polar air masses exhibit the greatest frequency departures during teleconnection regimes.