Investigating the relationship between tropical precipitation and water vapor in a cloud resolving model

In a recent analysis of satellite data in the tropics, Peters and Neelin (2006) found a steep power-law increase of precipitation as a function of column integrated water vapor. The increase occurs at a critical value of the water vapor that is associated with a sharp peak in precipitation variance. Similar behavior was also seen in a simple two layer model (Muller et al. (2009)). In a more in depth analysis of the satellite data, Neelin et al. (2009) found a Gaussian core shaped probability distribution function of column intergrated water vapor for precipitating points with exponential tails.

In this project, we investigate the relationship between water vapor, precipitation, and precipitation variance using a cloud resolving model. We verify the existence of a sharp peak in precipitation variance where the precipitation starts to increase, and compare the probability distribution of column integrated water vapor to the results reported in Neelin et al. (2009).