PAR looks like this

Photosynthetically active radiation (PAR) provides the energy for plants to grow. Unlike temperature or precipitation data, which are readily available, it is less common to see the numbers or charts for PAR.

This is PAR at Corvallis, Oregon, on a day with light cloud cover in June, on a sunny day in August, then for a week, a month, and an entire year.

5 charts of PAR at Corvallis in 2014, from one day up to one year

This is showing instantaneous PAR every 5 minutes. Instantaneous PAR is the amount of photosynthetic light every second, which is called the photosynthetic photon flux density (PPFD). Add up the PPFD for every second from sunrise until sunset, and that makes the daily total of PAR, which is called the daily light integral (DLI).

For more about this, see:

Micah Woods
Micah Woods

Scientist, author, consultant, and founder of the Asian Turfgrass Center