The gridded fields of daily precipitation are defined by interpolating
rain-gauge observations obtained from meteorological and hydrological
stations throughout the region. We use new daily precipitation climatology
and interpolate the ratio of the daily precipitation to the climatology at
a resolution of 0.05 degrees, then multiplied each gridded ratio by each
gridded climatology value day-by-day. We then re-gridded the 0.05-degree
analysis to both 0.5-degree and 0.25-degree grids. Details are given in a
paper by Yatagai et al. (2009, 2012)