WMS:GSSHA Snowmelt Options

From XMS Wiki
Jump to: navigation, search
The GSSHA Snowmelt Options dialog.

The GSSHA Snowmelt Options dialog contains options for how GSSHA handles various aspects of snowmelt within the simulation. The dialog consists of three columns: Parameters, Value, and Units.

The Help button at the bottom of the dialog opens this page in a web browser.

The options are as follows:

  • Snowmelt analysis option – A drop-down list with the following options:
    • "Hybrid energy balance/NWSRFS" – A hybrid method based on both of the other two options.
    • "Energy balance" – A simple method where the amount of heat available is applied to the snowpack and the amount of meltwater is calculated. See the GSSHA Wiki for more details.
    • "Temperature index method" – A method of estimating snowfall accumulation and melting based on the National Weather Service River Forecasting System (NWSRFS) SNOW-17 model. See the GSSHA Wiki for more details. Selecting this option turns on Empirical wind function factor and Liquid water holding capacity fraction at the bottom of the dialog.
  • Vertical flow options – A drop-down list with the following options:
    • "Snap retention" – Uses the SNAP gravity flow model to distribute melt-water vertically through the snow pack and to the overland.
    • "Vertical snow retention" – GSSHA creates multiple melt-waves (up to 6 simultaneous waves) that distribute the melt to the overland.
  • Snow water equivalent map – Turn on this option to activate a drop-down list of all continuous maps in the project.
  • Hydraulic conductivity of the snow pack – A decimal value in meters per second.
  • Reynolds number when flow goes from Darcy to Overland – A unitless decimal value.
  • Maximum melt factor – A decimal value in millimeters per degree Celsius per time step.
  • Minimum melt factor – A decimal value in millimeters per degree Celsius per time step.
  • Dry adiabetic lapse rate – Turn on this option to activate editability of this decimal value in degrees Celsius per kilometer. Also activates editability of Elevation of HMET gage (below).
  • Elevation of HMET gage – A decimal value in meters.
  • Snow cover fraction – A decimal value usually between "0.8" and "1.2".
  • Base temperature to begin melt – A decimal temperature value in degrees Celsius.
  • Fraction of precipitation in the form of rain – A decimal percentage value between "0.0" and "1.0".
  • Snow cover thermal gradient – A decimal percentage value between "0.0" and "1.0".
  • Negative melt factor – A decimal value in millimeters per degree Celsius per time step.
  • Empirical wind function factor – A decimal value in millimeters per millibars per 6 hours.
  • Liquid water holding capacity fraction – A decimal value between "0.0" and "0.4".