Relationships between global precipitation and surface temperature on interannual and longer timescales (1979-2006)

Associations between global and regional precipitation and surface temperature anomalies on interannual and longer timescales are explored for the period of 1979-2006 using the GPCP precipitation product and the NASA-GISS surface temperature data set. Positive (negative) correlations are generally confirmed between these two variables over tropical oceans (lands). ENSO is the dominant factor in these interannual tropical relations. Away from the tropics, particularly in the Northern Hemisphere mid-high latitudes, this correlation relationship becomes much more complicated with positive and negative values of correlation tending to appear over both ocean and land, with a strong seasonal variation in the correlation patterns. Relationships between long-term linear changes in global precipitation and surface temperature are also assessed. Most intense long-term, linear changes in annual-mean rainfall during the data record tend to be within the tropics. For surface temperature however, the strongest linear changes are observed in the Northern Hemisphere mid-high latitudes, with much weaker temperature changes in the tropical region and Southern Hemisphere. Finally, the ratios between the linear changes in zonal-mean rainfall and temperature anomalies over the period are estimated. Globally, the calculation results in a +2.3%/degrees C precipitation change, although the magnitude is sensitive to small errors in the precipitation data set and to the length of record used for the calculation. The long-term temperature-precipitation relations are also compared to the interannual variations of the same ratio in a zonally averaged sense and are shown to have similar profiles, except for over tropical land areas.