The Influence of the Madden-Julian Oscillation (MJO) on the weather of Alaska

The Madden-Julian Oscillation (MJO) is the primary mode of large-scale intraseasonal variability in the tropics. Previous and ongoing work has explored the influences of the MJO on precipitation along the U.S. West Coast. This work indicates that the atmospheric circulation anomalies associated with the MJO extend into the high latitudes of the Pacific Ocean and North America. Because of the magnitudes of these anomalies, the MJO has a statistically robust effect on important elements of the weather of Alaska and its environs. The MJO is diagnosed based on time series of the principal components of the two leading EOF modes of the 850 mb zonal wind in the tropics. The weather of Alaska, the northern Bering Sea and the Beaufort Sea is diagnosed based on sea-level pressure, precipitation and 925 mb temperature distributions. The source of data in both cases is daily averages from the NCEP/NCAR Reanalysis for the period of 1979 to 2001. The seasons considered are winter and spring. The weather elements of special interest are cyclonic storm passages, with their attendant mild temperatures and significant precipitation, and the development and propagation of continental and arctic anticyclones, with their accompanying cold-air outbreaks. Our assessment of the MJO's modulation of Alaska weather takes into account the seasonal cycle and the state of climate modes such as the Arctic Oscillation, since these factors help determine the mean flow and hence the high latitude response to the MJO.