A high positive correlation is found between the isotopic composition of atmospheric water vapor and both the specific and relative humidities at Palisades, New York, during the growing season. This relationship is explained in terms of the meteorological setting. In general, the lowest ΔD values occur when cool, dry Canadian air that is stable aloft moves southeastward, while much higher values occur in hot, more humid air that is unstable aloft. The highest ΔD values approach the local groundwater value and occur when the surface is stably stratified. |