Is "Surface solar radiation downwards" the best proxy for "Photosynthetically active radiation"?

I need an estimate of light available to tree growth in Northern Europe. I am thinking to downloand “ERA5-Land monthly averaged data from 1950 to present” and use “Surface solar radiation downwards” as predictor for a tree growth model. Do you think it is the better representation of total direct + diffuse light incident in a particular area and available for plant growth? Bonus question: wow can I transform it in Photosynthetically Active Radiation? Thanks!