VARIATIONS IN DEW-POINT TEMPERATURES IN THE SOUTHERN UNITED STATES

Atmospheric humidity as measured by dew-point temperatures is an important component of the climate of the southern United States. The South experiences the country's highest dew-point temperatures throughout the year. A gradient is established between moist air along the Gulf and Atlantic coasts inland toward the drier areas of northwestern Texas. This gradient is strongest in winter and weakest in summer when consistent southerly circulation maintains humid conditions throughout the region. Interannual variability also is largest in the winter and smallest in summer. Dew-point temperatures are strongly related to air temperatures in the non-summer season, but are more fundamentally linked to air mass and circulation changes. Recent increases in southerly flow in the spring and autumn seasons have led to a significant increase in dew-point temperatures in many portions of the region. However, there is no evidence at this time to suggest that increased evaporation from greenhouse warming has altered dew-point temperatures in the southern United States.