- 2016. American Geophysical Union. All Rights Reserved. In this study, we show that the well-documented exponential increase in the precipitation-water vapor (P-r) curve over tropical oceans also applies to tropical land but that the land curve starts its exponential increase at smaller values of column moisture than over ocean. We demonstrate that daytime surface heating contributes to this characteristic shape of the land P-r curves. There is also significant geographical variation in the shape of the P-r curve within land and ocean regions, with the Amazon, the Maritime Continent, and the eastern edges of oceans as distinct outliers. We further show that convective and stratiform rain intensities exhibit a pickup that is separate from the corresponding rain areas in the tropical P-r curve while shallow convective rain has a yet another pickup. These variations of the P-r curve characteristics likely represent geographical variations of environmental controls on storm life cycle.