Relationship between the quantum yields of fluorescence (Ft) and photosystem II (Fv/Fm) sampled Picea glauca needles in Alaska (A) and Abies grandis needles in Idaho (B). Modeled (A) and observed (B) irradiance is indicated by the coloration of points; grey points in individual sampling period panels show observations from all periods for reference. Plots of sampling periods aligned with the timing of satellite overpasses are outlined in green (A) and blue (B) boxes, respectively.
In situ measurements of needle-level chlorophyll fluorescence and other irradiance products are now available.
Predicted spatially contiguous solar-induced chlorophyll fluorescence (SIF) across the United States for August 1 - 16, 2015. Areas of high SIF are in red, and areas of low SIF are in blue. Agricultural areas, like the U.S. Midwestern corn belt, often have a high rate of photosynthetic production which results in high SIF.
High-resolution, global, estimates of SIF based on data from the OCO-2 satellite serve as a proxy for rates of terrestrial photosynthesis.