This study explores how global precipitation and tropospheric water vapor content vary on the interdecadal/long-term time scale during 1979-2009, in particular to what extent the spatial structures of their variations relate to the changes in surface temperature. Satellite- and station-based observations are applied. EOF analyses indicate that the first two modes of global precipitation and water vapor content anomalies are in general related to the El Niņo-Southern Oscillation (ENSO). The spatial patterns of their third modes resemble the corresponding linear fits estimated at each grid point during the time period.

An EOF analysis of long-record (1949-2009) sea surface temperature (SST) anomalies within the Pacific basin (60oN-60oS) is further made. The first and third modes are dominated by the ENSO variations, while the second SST mode shows a strong shift around 1998/1999. This sudden shift indicates the existence of a climate regime change associated with the Pacific Decadal Variability (PDV) as suggested in past studies. Therefore, the linear changes/trends in both precipitation and tropospheric water vapor during 1988-2009 may result from a combined impact of global surface warming and PDV. It is further suggested that this combined impact shapes the spatial structure of linear changes/trends in these two components during the time period. In particular, in the tropical central-eastern Pacific, a band of increases along the equator in both precipitation and water vapor sandwiched by strong decreases south and north of it are likely caused by opposite effects from global-mean surface warming and PDV-related regional cooling. Furthermore, the PDV-related SST changes in the tropical Pacific tend to be the major reason for flattening/leveling in the time series of both global and tropical mean precipitation and tropospheric water vapor during the past decade.