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Current status: IN-HOUSE TESTING

Code is (pretty much) frozen but currently we are evaluating the air-sea exchange of a number of compounds, including acetaldehyde (CH3CHO), acetone (CH3COCH3), methyl nitrate (CH3ONO2), and organohalogens (e.g. CHBr3, CH2Br2), using a combination of airborne, ship-borne and satellite observations. 

Point of contact: Siyuan Wang | NCAR



BRIEF INTRODUCTION

An Online Air-Sea Interface for Soluble Species (OASIS) is developed for CESM | CAM-Chem to calculate the bi-directional oceanic fluxes of trace gases of interest, which is mainly based on the two-layer model as previously described. 1 The air-sea flux is calculated from the concentration gradient across the air-sea interface, as well as the transfer velocities on the air-side (kair, in s-1) and water-side (kwater, in s-1). kair is mainly based on the NOAA COARE algorithm, 2 with the addition of the still air diffusive flux adjustment. 3 kwater is based on Nightingale et al. 4 In addition, the bubble-mediated transfer 5 is included in the air-sea exchange module, in which the fractional coverage of actively breaking whitecaps is parameterized based on previous study. 6 The bubble-mediated transfer is optional, i.e. user can switch this on or off in $caseroot/user_nl_cam.


USER INPUT

Surface seawater concentration (nanomoles per liter) of the species of interest and surface seawater salinity (parts per thousand) need to be provided in $caseroot/user_nl_cam. For example:

$CASEROOT/user_nl_cam

0

1

2

3

4

bubble_mediated_transfer = .FALSE.
ocean_salinity_file = '/$your_directory/$salinity_file.nc'
csw_specifier = 'Species_1 -> Scaling_Factor * /$your_directory/$seawater_concentration_for_Species_1_in_nanomole_per_liter.nc',
                'Species_2 -> Scaling_Factor * /$your_directory/$seawater_concentration_for_Species_2_in_nanomole_per_liter.nc'
csw_type = 'SERIAL‘

The chemistry package reads in seawater concentration data from netCDF files. Each tracer species is read from its own file as directed by the namelist variable CSW_SPECIFIER (Line 2-3). This is similar to emis_specifierSCALING_FACTOR (Line 2 and 3) is exactly what it looks like. This is optional. Default (omit) is1.0. CSW_TYPE (Line 4): type of time interpolation of seawater concentration datasets specified. Valid values: CYCLICAL,SERIAL,INTERP_MISSING_MONTHS,FIXED.

The seawater concentration fields can be read in as time series of data, cycle over a given year, or be fixed to a given date. For example, to specify cycle year of the seawater concentration data:

$CASEROOT/user_nl_cam

4

5

csw_type = 'CYCLICAL‘
csw_cycle_yr = 2016




(Webpage currently under construction)

(This wiki architecture unfortunately doesn't appear to be entirely mobile-friendly)


REFERENCES

  1. Johnson, M. T. (2010). A numerical scheme to calculate temperature and salinity dependent air-water transfer velocities for any gas. Ocean Sci.6(4), 913–932.
  2. Jeffery, C. D., Robinson, I. S., & Woolf, D. K. (2010). Tuning a physically-based model of the air–sea gas transfer velocity. Ocean Modelling31(1), 28–35.
  3. Mackay, D., & Yeun, A. T. K. (1983). Mass transfer coefficient correlations for volatilization of organic solutes from water. Environmental Science & Technology17(4), 211–217.
  4. Nightingale, P. D., Malin, G., S, L. C., Watson, A. J., Liss, P. S., Liddicoat, M. I., et al. (2000). In situ evaluation of air‐sea gas exchange parameterizations using novel conservative and volatile tracers. Global Biogeochemical Cycles14(1), 373–387.
  5. Asher, W., & Wanninkhof, R. (1998). The effect of bubble‐mediated gas transfer on purposeful dual‐gaseous tracer experiments. Journal of Geophysical Research: Oceans, 103(C5), 10555–10560. 
  6. Soloviev, A., & Schluessel, P. (2002). A Model of Air-Sea Gas Exchange Incorporating the Physics of the Turbulent Boundary Layer and the Properties of the Sea Surface. Washington DC American Geophysical Union Geophysical Monograph Series, 141–146.


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