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

**URL:** <https://forum.ecmwf.int/t/is-surface-solar-radiation-downwards-the-best-proxy-for-photosynthetically-active-radiation/2597>\
**Category:** C3S - Datasets and Usage\
**Tags:** era5\
**Created:** [25 April 2024 13:20 UTC](https://forum.ecmwf.int/t/is-surface-solar-radiation-downwards-the-best-proxy-for-photosynthetically-active-radiation/2597 "2024-04-25T13:20:22Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Simone\_Bianchi](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/s/e79b87/32.png) [@Simone\_Bianchi](https://forum.ecmwf.int/u/Simone_Bianchi)\
**Post date:** [25 April 2024 13:20 UTC](https://forum.ecmwf.int/t/is-surface-solar-radiation-downwards-the-best-proxy-for-photosynthetically-active-radiation/2597/1 "2024-04-25T13:20:22Z")

</div>

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!