Radiation measurements at ICOS ecosystem stations

Abstract

Solar radiation is a key driver of energy and carbon fluxes in natural ecosystems. Radiation measurements are essential for interpreting ecosystem scale greenhouse gases and energy fluxes as well as many other observations performed at ecosystem stations of the Integrated Carbon Observation System (ICOS). We describe and explain the relevance of the radiation variables that are monitored continuously at ICOS ecosystem stations and define recommendations to perform these measurements with consistent and comparable accuracy. The measurement methodology and instruments are described including detailed technical specifications. Guidelines for instrumental set up as well as for operation, maintenance and data collection are defined considering both ICOS scientific objectives and practical operational constraints. For measurements of short-wave (solar) and long wave (infrared) radiation components, requirements for the ICOS network are based on available well-defined state-of-the art standards (World Meteorological Organization, International Organization for Standardization). For photosynthetically active radiation measurements, some basic instrumental requirements are based on the performance of commercially available sensors. Since site specific conditions and practical constraints at individual ICOS ecosystem stations may hamper the applicability of standard requirements, we recommend that ICOS develops mid-term coordinated actions to assess the effective level of uncertainties in radiation measurements at the network scale.

Effect of droughts on future weathering rates in Sweden

“…Monthly averages of these data were lower than the monthly data used in previous ForSAFE modelling (e.g. Kronnäs et al, 2019), but comparison with modelled PAR data from SMHI (Landelius et al, 2001), and measured PAR data from the ICOS network (Carrara et al, 2018) showed that the ECLAIRE data were on the right level and that the older data (which were downscaled from a global model in a simpler way) had most likely not been adjusted enough for the effect of cloudiness.…”

Temperature effects on the global patterns of photosynthetic quantum efficiency

“…To estimate fAPAR from measured below canopy PPFD we used the following calculation 65 : Where, PPFD IN is the incoming photosynthetic photon flux density at the top of the canopy, PPFD OUT is the outgoing photosynthetic photon flux density, PPFD_BC IN is the incoming photosynthetic photon flux density below the canopy. All PPFD measurements are in μmol m -2 s -1 .…”

The Flux You Say?: Comments on “The Integrated Carbon Observation System in Europe”

“…Both hillsides have 11° slopes like the ICOS ecosystem station Renon (Feigenwinter et al 2010) and are exposed to the same ϕp, with a 45° solar zenith angle. However, when scaled to a unit surface and compared with what perfectly leveled sensors would measure (|ϕp| cos[45°])-as specified by ICOS protocols (Carrara et al 2018)-this geometry yields solar fluxes that are 17% greater on the grassland (|ϕp| cos[34°]), and 21% reduced on the forest (|ϕp| cos[56°]). The need to measure radiative fluxes with sensors that are aligned, not horizontally but parallel to the ecosystem surface, is easily overlooked when conflating F and ϕ.…”