CHIRPS is the product of a two part process. First, IR Precipitation (IRP) pentad rainfall estimates are created from satellite data by calculating the percentage of time during the pentad that the IR observations indicate cold cloud tops (<235° K), and converting that value into millimeters of precipitation by means of previously determined local regression with TRMM 3B42 precipitation pentads. The IRP pentads are then expressed as percent of normal by dividing the values by their long-term (1981–2012) IRP means. These unitless values represent variations in time from the long-term mean (below normal, normal, or above normal rainfall). The percent of normal IRP pentad is then multiplied by the corresponding CHPClim pentad to produce an unbiased gridded estimate, with units of millimeters per pentad, called the Climate Hazards Group IR Precipitation (CHIRP). In the second part of the process, stations are blended with the CHIRP data to produce the final product, CHIRPS