A Double Peak in the Timing of California's Photosynthesis as Observed from Space
Abstract
Photosynthesis is the process by which plants and other organisms use sunlight to synthesize carbon dioxide and water to glucose and oxygen. Accurate knowledge of gross primary productivity (GPP) through photosynthesis is crucial for understanding the land-atmosphere carbon exchange. The recently launched TROPOMI instrument features the required spectral resolution and signal-to-noise ratio to retrieve light emitted from chlorophyll during photosynthesis (termed Solar-Induced chlorophyll Fluorescence: SIF), which has been shown to be a powerful proxy for photosynthesis. Here we show results from an oversampling/down-scaling method to obtain near-daily 500-m resolution from 2018 to present using TROPOMI SIF data over California. We find a strong correspondence with estimates of GPP from multiple AmeriFlux sites across different biomes in California. TROPOMI SIF data indicates a double peak in the timing of California's photosynthesis in both 2018 and 2019, a feature that is not present in the MODIS vegetation indices (NDVI, EVI, or NIRv). We further decompose the spatio-temporal patterns in the TROPOMI SIF data based on land cover and climate, indicating distinct processes responsible for the double peak in photosynthesis. This is corroborated by an EOF/PC analysis. Initial results are promising for near-daily estimation of GPP at high spatial resolution.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B13H2588T
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0480 Remote sensing;
- BIOGEOSCIENCES