FORest Canopy Atmosphere Transfer (FORCAsT) 2.0: model updates and evaluation with observations at a mixed forest site

Details

• Journal Title:
  Geoscientific Model Development
• Personal Author:
  Wei, Dandan ; Alwe, Hariprasad D. ; Millet, Dylan B. ; Bottorff, Brandon ; Lew, Michelle ; Stevens, Philip S. ; Shutter, Joshua D. ; Cox, Joshua L. ; Keutsch, Frank N. ; Shi, Qianwen ; Kavassalis, Sarah C. ; Murphy, Jennifer G. ; Vasquez, Krystal T. ; Allen, Hannah M. ; Praske, Eric ; Crounse, John D. ; Wennberg, Paul O. ; Shepson, Paul B. ; Bui, Alexander A. T. ; Wallace, Henry W. ; Griffin, Robert J. ; May, Nathaniel W. ; Connor, Megan ; Slade, Jonathan H. ; Pratt, Kerri A. ; Wood, Ezra C. ; Rollings, Mathew ; Deming, Benjamin L. ; Anderson, Daniel C. ; Steiner, Allison L.
• NOAA Program & Office:
  OAR (Oceanic and Atmospheric Research)
• Description:
  The FORCAsT (FORest Canopy Atmosphere Transfer) model version 1.0 is updated to FORCAsT 2.0 by implementing five major changes, including (1) a change to the operator splitting, separating chemistry from emission and dry deposition, which reduces the run time of the gas-phase chemistry by 70 % and produces a more realistic in-canopy profile for isoprene; (2) a modification of the eddy diffusivity parameterization to produce greater and more realistic vertical mixing in the boundary layer, which ameliorates the unrealistic simulated end-of-day peaks in isoprene under well-mixed conditions and improves daytime air temperature; (3) updates to dry deposition velocities with available measurements; (4) implementation of the Reduced Caltech Isoprene Mechanism (RCIM) to reflect the current knowledge of isoprene oxidation; and (5) extension of the aerosol module to include isoprene-derived secondary organic aerosol (iSOA) formation. Along with the operator splitting, modified vertical mixing, and dry deposition, RCIM improves the estimation of first-generation isoprene oxidation products (methyl vinyl ketone and methacrolein) and some second-generation products (such as isoprene epoxydiols). Inclusion of isoprene in the aerosol module in FORCAsT 2.0 leads to a 7 % mass yield of iSOA. The most important iSOA precursors are IEPOX and tetrafunctionals, which together account for >86 % of total iSOA. The iSOA formed from organic nitrates is more important in the canopy, accounting for 11 % of the total iSOA. The tetrafunctionals compose up to 23 % of the total iSOA formation, highlighting the importance of the fate (i.e., dry deposition and gas-phase chemistry) of later-generation isoprene oxidation products in estimating iSOA formation.
• Keywords:
  General Medicine
• Source:
  Geoscientific Model Development, 14(10), 6309-6329
• DOI:
  https://doi.org/10.5194/gmd-14-6309-2021
• ISSN:
  1991-9603
• Format:
  PDF
• Publisher:
  Copernicus GmbH
• Document Type:
  Journal Article
• Funding:
  Grant no. NA18OAR4310116
• License:
  https://creativecommons.org/licenses/by/4.0/
• Rights Information:
  CC BY
• Compliance:
  Library
• Main Document Checksum:
  urn:sha256:aa99f29ef4b9402b375c79a52d8a0b2d118552725ffcaa6dcbb2d791fc02e732
• Download URL:
  https://repository.library.noaa.gov/view/noaa/58418/noaa_58418_DS1.pdf
• File Type:
  [PDF - 1.03 MB ]