| Atmospheric water vapor measurements are made from a variety of sources including radiosondes, aircraft, surface observations, and various satellite instruments. The dataset used in this study is an eight-year (1988–1995) total and layered global water vapor data produced under the NASA Water Vapor Project (NVAP). The NVAP dataset is composed of radiosonde, Television and Infrared Operational Satellite (TIROS) Operational Vertical Sounder (TOVS) and Spatial Sensor Microwave/Imager (SSM/I) observation. The distribution of upper-tropospheric precipitable water (UTPW) shows good correlation with total precipitable water (TPW), both spatially and temporally. The fluctuations of UTPW in the tropics show good correlation with El Niño/Southern Oscillation (ENSO) events, especially with the 1988 La Niña. The eruption of Mt. Pinatubo in 1991 has a large impact on the TPW in the Northern Hemisphere (NH) but a small impact on the UTPW. The UTPW from NVAP and National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis datasets show consistency in NH mid-latitudes, but the differences become prominent in the Southern Hemisphere (SH), especially in its cold season. |
