PhotoSpec solar-induced fluorescence and meteorological data: Soy, Iowa, 2017

PhotoSpec consists of a 2D scanning telescope to guide reflected radiances into a set of high‐resolution spectrometers (Grossmann et al., 2018) to infer SIF using the solar Fraunhofer line in‐filling technique, similar to all current satellite retrievals. The scanning telescope was placed atop a 7‐m tower, and we calculate a "canopy average" of all viewing angles at a half-hourly time step to match the temporal resolution of flux tower data (following Magney, Frankenberg, et al., 2019).

Because the scanning telescope revisits every measuring point within a half-hour, this canopy average is more representative of a hemispherical sensor with a footprint of a few meters around the tower (an average of all viewing directions). Notably, while the escape ratio and angular dependencies are an important consideration for tower‐based SIF measurements (Zeng et al., 2019), this makes little difference in our study for the canopy structure is relatively stable during the peaking growing season.

More details on PhotoSpec retrievals and instrument specifications can be found in Grossmann et al. (2018) and Magney, Frankenberg, et al. (2019). Relevant publications: He, L., Magney, T., Dutta, D., Yin, Y., Köhler, P., Grossmann, K., … Frankenberg, C. (2020). From the ground to space: Using solar‐induced chlorophyll fluorescence (SIF) to estimate crop productivity.

Geophysical Research Letters, 0–3. doi.org/10.1029/2020GL087474 Magney, T. S., Frankenberg, C., Köhler, P., North, G., Davis, T. S., Dold, C., … Porcar-Castell, A. (2019). Disentangling Changes in the Spectral Shape of Chlorophyll Fluorescence: Implications for Remote Sensing of Photosynthesis. Journal of Geophysical Research: Biogeosciences. doi.org/10.1029/2019JG005029 For more information or higher resolution data please contact Troy Magney: tmagney@ucdavis.edu