Impacts of wildfire smoke on photosythetically-active radiation in the California Sacramento Valley in Summer 2018: Implications for crop productivity
Abstract
Photosynthetically-active radiation (400-700nm, PAR) is a key determinant of crop productivity. Aerosol scattering and absorption reduce the total PAR reaching the surface, which can decrease productivity. However, aerosol-driven increases in diffuse (scattered) PAR may increase in crop radiation use efficiency (RUE, defined as accumulated biomass per unit radiant energy intercepted) and therefore productivity. The magnitude of this "diffuse radiation fertilization effect" can vary with total PAR and crop type and may depend on aerosol type. The impact of smoke on total and diffuse PAR was examined using data collected at the USDA UV-B Monitoring and Research Program's UC Davis site in Summer 2018. Situated in California's Sacramento Valley, the UC Davis site was frequently influenced by wildfire smoke from the large Carr and Mendocino Complex Fires between July and September. Diffuse and total irradiance measured by two multifilter rotating shadowband radiometers (MFRSRs) at 5 discrete visible wavelengths (415, 500, 610, 665, and 860nm) and 1 near-UV wavelength (368nm) were used to calculate the respective diffuse fractions (DF, defined as diffuse divided by total) on cloud-free days before and during the active fire period. PAR DF was determined by integrating the interpolated spectral DF from the measured DF values. Measurement-derived PAR DF values were consistently higher than those modeled for aerosol-free conditions using the Tropospheric Ultraviolet Visible Model (TUV V5.3.2). Further, aerosol-driven PAR DF enhancements increased with AOD, demonstrating the positive relationship between aerosol scattering and diffuse irradiance. RUEs for two common Sacramento Valley crops (wheat and corn) were calculated using established RUE-DF relationships for both aerosol-free and measurement-based PAR DFs; comparisons of aerosol-free and measured RUEs were performed to assess the impact of smoke on crop productivity.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A23L2977C
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0322 Constituent sources and sinks;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE