Universality and Scale Invariance in Hourly Rainfall
  We show that the hourly rainfall rate distribution can be described by a simple power law to a good approximation. We show that the exponent of the distribution in tropics is universal and is equal to $1.13\pm 0.11$. At higher latitudes the exponent increases and is found to lie in the range 1.3-1.6. 
Pankaj Jain, Suman Jain and Gauher Shaheen