Light

Figure 1. The snow-covered landscape of central Hokkaido in mid-March 2024 when the growth potential was 0 but the DLI was fine. In a recent ATC Doublecut discussing light and temperature, I mentioned that I’d calculate potential DLI for the recording location, check the actual DLI for the recording location, and share that information.

A question that comes up again and again is whether the PACE Turf growth potential (GP) would be improved by also accounting for light. Grass growth—plant growth of any type, actually—is influenced by more than temperature.

I was in Tokyo on June 14. When I looked out the hotel window just after sunrise, it was cloudy. When I walked to a harborside restaurant for a working lunch, it was noticeably cloudy.

I’ll start with a tautology. Warm-season grass species grow, and are used as turfgrasses, in locations with warm temperatures. Where it gets interesting is the interaction of light—specifically the photosynthetically active radiation (PAR)—with temperature, and with water supply or drought stress.

The NASA POWER agroclimatology dataset provides information on a global grid of 0.5° by 0.5°. The Global DLI app uses the nasapower R package to get global solar radiation data from NASA POWER.

You’ve seen the Global DLI app that uses satellite data from the NASA POWER Agroclimatology dataset to show a summary of photosynthetically active radiation—expressed as the daily light integral, or DLI—for the past year at any location.

I made a Global DLI app to generate summary charts of DLI for anywhere in the world. This app uses the nasapower R package to get satellite data from the NASA POWER Agroclimatology dataset.

A previous post showed photosynthetically active radiation (PAR) data in units of daily totals—the daily light integral (DLI). That post included a chart with a locally smoothed regression line through it.

I’ve been using the NASA POWER agroclimatology data for a few projects. I get the data using the convenient nasapower R package by Adam Sparks. There is also a web-based map data access viewer.

The PPFD (photosynthetic photon flux density) every 5 minutes for a day, week, month, and year at Corvallis looks like this. I’m not so interested in the PPFD when the temperatures are too cold or too hot for photosynthesis.