Winter temperature variability during warming and cooling periods in the conterminous United States, 1947-1992

Much literature has reported on the concept of increased surface temperatur e variability during cool periods, although analyses on temperature records have rendered inconsistent results. In addition, temperature variability d uring transition periods has been rarely investigated. This study examines temperature variability during wintertime cooling (1947-1977) and warming ( 1978-1992) periods for the conterminous United States to determine both whe ther temperature variability is different during warming or cooling periods , and whether the change in variability is supported by midtropospheric cir culation conditions. Our results indicate that regions with high temperatur e variability are mostly found below the troughs in the midtropospheric pre ssure fields. The direction of change in temperature variability correspond ing to cooling or warming conditions, however, varied spatially. For the so utheastern and northeastern United States, winter temperatures were more va riable during the cooling period than during the warming period, while the northern and central Great Plains had greater temperature variability durin g the warming period than the cooling period. Similar spatial patterns are also found for the changes in the variability of geopotential height fields . Such spatial patterns in the temperature and height variability during wa rming and cooling periods may be related to the dominant midtropospheric ci rculation patterns, such as the different phases of the Pacific-North Ameri can teleconnection pattern, and the El Nino/Southern Oscillation events. It is concluded that the response of interannual temperature variability to c limatic changes is determined by the variation in circulation patterns, and therefore, not spatially uniform.