Variability of cold-season temperatures in the Mackenzie Basin

Abstract

The Mackenzie River Basin exhibits extremely large interannual variability in its cold-season atmospheric temperatures while some of the strongest warming signals in the Northern Hemisphere have also been observed over the Basin. To understand these observed thermal characteristics and behavior of the region, the atmospheric enthalpy budget for the Basin during 1970-99 was studied using the NCEP reanalysis dataset. Adiabatic warming associated with mean subsidence was found to be more important than net horizontal temperature advection in governing the heat budget during the cold-season. Processes responsible for the development of extreme warm/cold winters were investigated in conjunction with the composite atmospheric heat budget and large-scale atmospheric conditions that prevailed during the anomalous winters. The large temperature variability is linked to the interactions between the North Pacific airflow and the regional environment, notably the Western Cordillera. Understanding the mechanisms responsible for winter temperature variability facilitates the interpretation of temperature trends and offers an explanation of the cold-season temperature bias found in some climate modeling results. © 2008 Springer-Verlag Berlin Heidelberg.