air quality assessment & management
Reference and User Manual
AirWare   On-line Reference Manual
  Release Level 6.2
  Release Date 2013 09
  Revision Level 1.0
Last modified on:   Friday, 6-Dec-13 14:07 CET

Dust entrainment: model parameters

The dust entrainment model estimates non-pyrogenic dust emission from natural surfaces as a function of wind speed, land cover/vegetation, soil characteristics, and soil moisture, as well as slope and aspect of the surface;

The DUST emission model works as a pre-processor for the CAMx fate and transport model, and generates hourly dust (non-pyrogenic) emission matrices. PM10 emission is split into PM2.5 and PM10 using a constant factor PM2.5/PM10=0.89 according to ARB Speciation for Combustion.

This parameter is defined in the location setup table of default parameters.

The model basic concepts, assumptions and equations are described in a separate page on dust model basics.

The default parameter values are defined in the location setup configuration TABLE accessible for system administrators as part of the system administration menu (restricted access). These parameters are used for all forecats runs, ansd as the default setting for interactive scenarios (CAMx standard and super-scenarios, DUST sensitivity analysis runs). For the latter, selected parameters can be editied "locally", only affecting the sensitivity runs.

DUST model parameters

The are 14 parameters for the model available (an additional two define display and export options):

  • Calibration_factor: Calibration factor: a global multiplier to correct (observed) bias over the entire model domain and a given 24 hour scenario, can be used for calibration or automatic corrections (dynamic data assimilation).
  • City_sealed_surface: defines the area for dust deposition and re-entrainment within cities (global default; city landuse parameters could be used for an individual configuration of re-entrainment source areas);)
  • Wind threshsold speeds: wind thresholds: three separate threshold values (minimum speed) for the erosion/entrainment process; below this speed, no "passive" dust emissions will be generated: defined as: Coarse_soil_wind_threshold, Heavy_soil_wind_threshold, Med_soil_wind_threshold.
  • Mine_dust_source_area: the percentage of the total area of an (open cast) mine for dust entrainment (global default); could be replaced by landcover parameter for individual mines.
  • Soil_moisture_multiplier: Soil moisture dependency slope parameters, that defines the slope of a linear function between the threshold and a (theoretical) zero soil moisture level.
  • Soil_moisture_threshold: Soil moisture threshold (common for all soil fractions): soil moisture (expressed as % of water in the uppermost 20 cm soil layer, estimated by MM5 at hourly resolution.)
  • Unpaved_road_width: together with the actual length of unpaved roads in each grid cell (1 km2) defines the area (%) for passive dust entrainment from unpoaved roads; defined explicitly, as the satellite (vegetation data) resolution may not allow detection of smaller roads.
  • Urban_uncultivated_area: defines the percentage of urban space subject to wind erosion; global default, can be overaloaded with individual city land use/land cover data.
  • Weibull_cutoff: the exponential Weibull function is open-ended; a cutoff (expressed in multiples of the average hourly wind speed at each cell) is defined for computational efficiency;
  • Weibull_shape_parameter: Weibull function shape parameter;
  • Wind_exponent: expresses the dependency of erosion on wind speed, e.g., quadratic;
  • Wind_multiplier: designed to correct bias in the average wind speed estimates, e.g., depending on MM5 resolution.

These parameters can be edited:

Please note that values from the location setup TABLE will be read before any new forecast run, and overload any values changed in the mean time. Any values defined at the sensitivity analysis page are temporary, designed for the "local" rerun of the emission model. To propagate any changes to a CAMx scenario with optionally several nested domains (that should be kept consistent), a button Sync on the sensitivity analysis page can be used to synchronize DUST parameters over the CAMx scenarios/domains.

Application level defaults

User defined values that are part of location set up include:

  • unpaved_road_width
  • urban_uncultivated_area
  • mine_dust_source_area
  • city_sealed_surface

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