Relationships between tropospheric water vapor and surface temperature as observed by radiosondes

Using radiosonde data from 50 stations for 1973–1990, we quantify relationships between surface air temperature ( T s ) and precipitable water vapor ( W ) for different time scales. Monthly mean observations are fairly well described by an equation of the form ln W = A + B T s , but the coefficients A and B depend on the T s range considered. At high T s , the relationship is poor. This relationship and relationships between sea surface temperature ( SST ) and W based on satellite microwave observations over oceans are in remarkably good agreement over restricted SST ranges. Monthly and annual anomalies of W and T s are well correlated only outside the tropics, but on longer time scales, there is some evidence of positive trends in both W and T s at most of the stations studied. Thus the relationship between W and T s depends on the time scales and geographic region considered.