CMAQv5.0 Windblown Dust

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Jeff Young

This work is based on Tong, et al.

With help from Prakash Bhave, for the wind-blown dust we developed an independent PM distribution for fine (J-mode) and coarse (K-mode) aerosols. The speciation profiles were developed by George Pouliot using the EPA SPECIATE database.

                                  Species Names       Speciation Factors
 Compound                   Fine Mode  Coarse Mode  Fine Mode  Coarse Mode 
  Sulfate                    'ASO4J',   'ASO4K'      0.02250,   0.02655
  Nitrate                    'ANO3J',   'ANO3K'      0.00020,   0.00160
  Chlorine                   'ACLJ',    'ACLK '      0.00945,   0.01190
  Ammonium                   'ANH4J'     ----        0.00005,   0.0
  Sodium                     'ANAJ'      ----        0.03935,   0.0
  Calcium                    'ACAJ'      ----        0.07940,   0.0
  Magnesium                  'AMGJ'      ----        0.0,       0.0
  Potassium                  'AKJ'       ----        0.03770,   0.0
  Organic Carbon             'APOCJ'     ----        0.01075,   0.0
  Non-Carbon Organic Matter  'APNCOMJ'   ----        0.00430,   0.0
  Elemental Carbon           'AECJ'      ----        0.0,       0.0
  Iron                       'AFEJ'      ----        0.03355,   0.0
  Aluminum                   'AALJ'      ----        0.05695,   0.0
  Silicon                    'ASIJ'      ----        0.19425,   0.0
  Titanium                   'ATIJ'      ----        0.00280,   0.0
  Manganese                  'AMNJ'      ----        0.00115,   0.0
  Water                      'AH2OJ'     ----        0.00541,   0.0
  Other                      'AOTHRJ'    ----        0.50219,   0.0
  Non-Anion Dust              ----      'ASOIL'      0.0,       0.95995

The dust particles are distributed within four size ranges: 0.1-1.0, 1.0-2.5, 2.5-5.0, 5.0-10.0 micrometers (μm) (TONG), with the mass distributed as 3, 17, 41, and 39% within the bins. The first two ranges can be considered the fine mass bin and the last two the coarse mass. Thus, the generated wind-blown dust mass is split 20% for fine and 80% for coarse. The fine and coarse mode geometric mean diameters are computed from these splits based on the two 2-bin weighted averages of the geometric means: 1.3914 μm for the fine mode and 5.2590 μm for the coarse. The fine and coarse mode geometric standard deviations are set to 2.0 for both.

The module currently uses the BELD USGS land use classifications 'USGS_shrubland ', 'USGS_shrubgrass', and 'USGS_sprsbarren' as desert land from which wind-blown dust might occur. It also uses an optional erodible agricutural land type, along with a list of 18 crops and a crop activity database which contains each crop's gridded dates for the activities of 'begin planting', 'end planting' and 'end harvesting' to simulate the space-time locations of potential wind-blown dust from these sources.

Following a parametrization based on work by Dale Gillette and others (see the references in Tong, et al.), wind-blown dust occurs over erodible land if rain < 1/100 in., soil moisture is less than a saturation limit for the particular soil type, and the surface friction velocity exceeds a threshold value based on the land type ("desert" + optional "ag"). Dynamic transport factors are used to modulate the locally generated dust emissions rates to account for effects within or above the canopy.

This version requires the following inputs (the BELD3 data can be created using the Spatial Allocator -

      File                                   Program Units
beld3_12US1_459X299_output_a.ncf (12km)    DUST_EMIS, tfbelow, cropcal
beld3_12US1_459X299_output_tot.ncf (12km)  DUST_EMIS, tfbelow
grid_cro_2d                                DUST_EMIS, cropcal
met_cro_2d                                 DUST_EMIS, cropcal

If the optional erodible agricultural land is used, then the following IOAPI files are required for the gridded times of the relevant crop activities: CROPMAP01, CROPMAP04, CROPMAP08. These files are read by cropcal to produce the potential wind blown dust emissions from agricultural activity.

These files are created by a preprocessor, calmap, which must use the BELD landuse files and longitude, latitude data (GRID_CRO_2D), as well as the ASCII files:

  CPCALED.txt - Crop Activity Calendar by State
  USSTATE.txt - US States' two-character names
  states.f    - a Fortran function procedure that locates the State from the
                input longitude and latitude of the grid cell center.

calmap generates 8 IOAPI "CROPMAP" (gridded calendar) files, of which only 3 are used by cropcal: "Begin Planting," "End Planting" and "End Harvesting."

Obviously, the erodible agricultural land option would be valid only for domains within the contiguous US.


Daniel Q. Tong, George E. Bowker, Shan He, Daewon W. Byun, Rohit Mathur, Dale A. Gillette, "Development of a Windblown Dust Module within the Community Multi-scale Air Quality (CMAQ) Model: Description and Preliminary Applications in the Continental United States," submitted to the Journal of Geophysical Research, June, 2011