Variability of global upper-tropospheric water vapor derived from satellite infrared observations

Uncertainties in the amount and variability of global atmospheric water vapor content weaken our ability to define the present climate system and lessens our confidence in future predictions of climate change. In particular, the small amount of water vapor in the upper troposphere contributes disproportionately to the Earth´s radiation budget. In this paper, infrared observations of global upper tropospheric water vapor are analyzed to examine variability on seasonal and interannual time scales. Particular attention is given to the intersatellite calibration of the seven instruments used to piece together the time series of observations from 1981-1990 (and extending the record through 1993 by IGARSS). A method for identifying and removing the intersatellite biases is discussed and implemented. Analysis of the adjusted time series shows upper troposphere water vapor variability related to the seasonal cycle of the monsoon circulations and interannual variability related to El Nino/Southern Oscillation warm and cold events