The photosynthetically active radiation (PAR) changes at a location by time of year and by cloud cover. This animated chart shows what the average photosynthetic photon flux density (PPFD) would be for every 5 minute interval in clear sky conditions, and also shows what the actual PPFD was. Adding up the PPFD from every second gives the total PAR for a day -- the daily light integral (DLI). This chart shows potential DLI under clear sky conditions, as well as actual DLI.