Precipitation falls every day somewhere in the U.S. Geospatial data of these daily rainfall amounts is available and was used to generate the 'Ten Years of Accumulating Precipitation' video.
In this video, each daily rainfall data layer is added to the previous day's summed data. Therefore, each day shows the total accumulation of rainfall from the beginning of the animation data (January 1, 1960) to that day.
The hillshaded terrain (the growing hills and mountains) is based on the rainfall data, not on actual physical topography. In other words, hills and mountains are formed by the rainfall distribution itself and grow as the accumulated precipitation grows. High mountains and sharp edges occur where the distribution of precipitation varies substantially across short distances. Wide, broad plains and low hills are formed when the distribution of rainfall is relatively even across the landscape.
The precipitation terrain is similar to (but not the same as) actual terrain in many places because of orography.
To produce the video, an arcpy script was used to create the daily accumulated layers (summed precipitation and the associated hillshaded terrain) and a second arcpy script was used to generate each of the 3,650 (or so) .jpg files that compose the animation.