Climate

(These parameters apply to the Soil Moisture method. For the Simplified Coefficient Method, see Simplified Coefficient Method, Climate; for the MABIA Method, see MABIA, Climate; for the Plant Growth Method, see Plant Growth Model Method, Climate.)

Depending on the setting in General: Basic Parameters, the values for all of these variables (except latitude) can either be entered once for each catchment and will apply to all the land use branches within that catchment, or they will be entered separately for each branch within each catchment. This second option might be necessary if there is a large variation in the elevation among different land uses within a catchment. Alternatively, the catchment could be divided into several different catchment nodes according to elevation, so that the climate within each catchment did not vary by land use.

Precipitation

The monthly precipitation time series can either be read in from a file or entered in manually.

Temperature

The weighted mean of high and low temperature on a monthly basis.

Humidity

The average monthly relative humidity.

Wind

The average monthly wind speed.

Cloudiness Fraction

Fraction of daytime hours with no clouds (0.0=completely overcast, 1.0=no clouds). If blank, will default to 1 (no clouds).

Latitude

The latitude in degrees.  Note: The value for Latitude will be filled in automatically if the catchment was created in Catchment Delineation Mode.

Freezing Point

Solid water threshold for snow accumulation (defaults to -5 degrees Celsius).

Melting Point

Liquid water threshold for snow melt (defaults to +5 degrees Celsius).

Albedo Lower Bound

Albedo is calculated by WEAP as a broken linear function of snow accumulation and timestep length between Albedo Lower Bound and Albedo Upper Bound.  Albedo = Albedo Lower Bound when snow accumulation = 0.  The default value for Albedo Lower Bound is 0.15, but you can enter a different value.  Only used if Albedo variable is blank.

Albedo Upper Bound

Albedo is calculated by WEAP as a broken linear function of snow accumulation and timestep length between Albedo Lower Bound and Albedo Upper Bound.  Albedo = Albedo Upper Bound when snow accumulation is at or above 10 mm * number of days in the timestep.  The default value for Albedo Upper Bound is 0.25, but you can enter a different value.  Only used if Albedo variable is blank.

Albedo

Override default calculation for albedo and set its value directly.  If blank, WEAP will calculate albedo as a linear function of snow accumulation -- a linear interpolation between Albedo Lower Bound and Albedo Upper Bound.

Initial Snow

The initial value for snow accumulation at the beginning of the first month of the simulation.

Snow Accumulation Gauge

Historic data of snow accumulation (snowpack), to be used in calibration.  Measured in melt water equivalent (MWE) depth.  For calibrating, see the "Snow Accumulation vs. Gauge" report, or use the PEST Calibration Wizard.

See also: Soil Moisture Method Calculation Algorithm

Entered on: Data View, Branch: Catchments, Category: Climate, Tabs: Precipitation, Temperature, Humidity, Wind, Melting Point, Freezing Point, Latitude, Initial Snow.