Start Date/Time: Tuesday, March 18, 2014, 10:30 AM
Ending Date/Time: Tuesday, March 18, 2014, 11:30 AM
Location: PMEL Seminar Room, 7600 Sand Point Way NE, Building 3
Dr. James Overland
Abstract: An apparently increasing number of record-breaking meteorological events have occurred in mid-latitudes during the past decade as well as a large number of recent abrupt climate changes in the Arctic. Opinions differ on whether such recent extreme weather events were related to recent global or Arctic climate change, Pacific or tropical forcing, or simply chaotic random events. Record negative values of the early winter Arctic Oscillation atmospheric circulation index, high pressures over Greenland and warm temperatures (increased geopotential thickness west of Greenland) have been observed in four of the last five early winters, with cold air penetrating into the southeastern United States and a southern location of the jet stream across the Atlantic. So far we have a tantalizing array of possible drivers based on observed correlations, theoretical reasoning and limited model work. Given the recent run of Greenland high pressures and the potential for scientific breakthroughs for improved seasonal forecasting, one should not rule out a possible emergence of a combination of Arctic change, Pacific influences, and chaotic long-wave patterns impacting mid-latitude extreme weather as an important research challenge, but one that will be dominated by uncertainty for the foreseeable future.