Project Funding: 2014 - 2016

NRA: 2013 NASA: Suomi National Polar-orbiting Partnership (NPP) Science Team and Science Investigator-led Processing Systems for Earth System Data Records From Suomi NPP   

Funded by NASA

Abstract:
Photo-synthetically available radiation (PAR) at the ocean surface is an important parameter for biological and ecological studies. It controls phytoplankton growth and ultimately regulates the composition and evolution of marine ecosystems. There is a need for a global, long-term, consistent PAR time series to understand biogeochemical cycles of carbon, nutrients, and oxygen and to address important climate and global change issues such as the fate of anthropogenic atmospheric carbon dioxide. In view of this, the proposal overall objective is to develop a science quality standard ocean surface PAR product from VIIRS data. Specific objectives are: (1) to improve the current algorithm used by the Ocean PEATE to generate the VIIRS PAR experimental product, (2) to correct the resulting estimates for differences/biases due to limitations in the modeling and diurnal variability of clouds, and (3) to quantify product accuracy. The algorithm improvements will deal with spectral integration of atmospheric functions, ocean albedo parameterization, specification of aerosol optical properties, extension to observations at large solar zenith angles, and they will take into account, using climatology, diurnal changes in cloudiness, i.e., fractional cloud coverage and optical thickness. Biases between sensors will be determined by comparing PAR estimates obtained from VIIRS with those from MODIS after adjusting the MODIS values for differences with combined estimates from SeawiFS, MODIS-Terra, and MODIS-Aqua. This will require also applying algorithms modifications to SeaWiFS and MODIS. Accuracy of the PAR estimates will be quantified theoretically and in comparisons with in-situ measurements and other radiation products. A PAR ATBD will be developed that accounts for algorithm improvements and specifies accuracy. Implementation of the improved PAR algorithm and routine production and distribution of bias-corrected PAR estimates from VIIRS data and will be accomplished by the NASA-designated SIPS, as currently performed by the NASA OBPG for SeaWiFS and MODIS. Similar procedures and interactions are anticipated. The PAR products from the SIPS and OBPG will be consistent and compatible. The SIPS will allow for multiple data re-processing as the PAR algorithm improves and include routine check of accuracy and control of quality. The project will result in a 4.6 km resolution (equal-area grid) global ocean surface PAR product using NPP VIIRS data. The product will extend into the future the daily, weekly, and monthly PAR record started in 1997 with SeaWiFS and continued with MODIS. A  wide range of research applications will benefit from the long term PAR record, such as primary production and carbon export modeling, ecosystem dynamics and mixed-layer physics, photochemical transformations of dissolved organic matter, and control of stable soluble iron in marine waters. The contribution of the project to understanding the role of the oceans in carbon cycling and climate change, one of NASA objectives in Earth science research, is expected to be very significant. The project is highly responsive to Program Element A.29 in the ROSES-2013 Announcement, which addresses the development of science quality standard data products using Suomi NPP measurements that will enable continuity of key standard Earth system data records from NASA’s EOS Terra, Aqua, and/or Aura satellites, and which lists PAR as one of the key EOS products.

Publications:

Dupouy, C., Rottgers, R., Tedetti, M., Frouin, R., Lantoine, F., Rodier, M., Martias, C., Goutx, M. 2020. Impact of Contrasted Weather Conditions on CDOM Absorption/Fluorescence and Biogeochemistry in the Eastern Lagoon of New Caledonia. Frontiers in Earth Science. 8. DOI: 10.3389/feart.2020.00054

Tan, J., Frouin, R. 2019. Seasonal and Interannual Variability of Satellite-Derived Photosynthetically Available Radiation Over the Tropical Oceans. Journal of Geophysical Research: Oceans. 124(5), 3073-3088. DOI: 10.1029/2019jc014942

More details may be found in the following project profile(s):

• NASA Ocean Biology & Biogeochemistry (OBB) Project Profile