RELATIONSHIPS BETWEEN GEOPOTENTIAL HEIGHTS AND TEMPERATURE IN THE SOUTH-EASTERN US DURING WINTERTIME WARMING AND COOLING PERIODS

This paper discusses the relationship between geopotential heights and mean winter surface temperature and the characteristics of interannua l variability in the south-eastern USA during cooling and warming peri ods from 1946 to 1992. Data from 83 Historical Climatology Network sta tions in 12 south-eastern states were examined Factor analysis was use d to separate the south-east into three climatic regions. These region s were then matched with both 500 hPa and 700 hPa pressure heights dur ing two periods: the 1946-1976 cooling period and the 1976-1992 warmin g period. The degree of association between geopotential heights and s urface temperature was greater during the cooling period than during t he warming period Possible influences may lie with differential temper ature modification effects of the Gulf of Mexico and Atlantic Ocean, a s well as soil moisture variability. The amount of geopotential height variability, as measured by standard deviations, was also compared be tween the cooling and warming periods, and was significantly greater d uring the cooling period. This explains a similar pattern in the surfa ce temperature variability. A possible cause is the susceptibility of troughs to prolongation and amplification during cold winters. Both re sults suggest that not only is it difficult to determine the forcing m echanisms that cause short-term variability, but that the influence of the forcing mechanisms may not be consistent between cooling and warm ing periods as well.