Photosynthetically Active Radiation (PAR) refers to the spectrum of light that plants can use for photosynthesis (400-700 nm). An estimation of the available useful radiation for plant life in a given area can be used to optimize the design of urban green features such as green roofs or walls. The amount of PAR that reaches an area in a full 24-hour day is called the Daily Light Integral (DLI). This is an essential metric to consider when designing urban ecosystems that ensure long term health and functionality of green infrastructure.
DLI in Orbital Stack is presented as the daily sum of moles of PAR photons per meter squared. This quantifies the total amount of photosynthetically active radiation (PAR) received over a day. A “mole” is a standard unit that represents a specific quantity of particles – in this case, photons. One mole corresponds to approximately 6.022 x 10²³ photons. PAR energy density may reach as high as 60 mol/m² in an Arizona summer, or be less than 5 mol/m² per day during a London winter.
For plant life to remain healthy, the ideal DLI level is typically in the range of 5-20 mol/m² per day. The exact value depends on the specific plant species and growth stage, nutrient level, and other environmental factors such as humidity and temperature.
What is it measuring?
The DLI color scale indicates the daily number of moles of PAR photons received per meter squared of surface area.
What options can I specify?
There are no user specifications for DLI. Results for each calendar month are generated by default.