snowFall: Function: Snowfall model

Description Usage Arguments Details Value Note Author(s) References See Also Examples

Description

A simple model to derive snowfall from precipitation and air temperature.

Usage

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snowFall(airT, precip, glacierMask,
    snowTransTempThreshold = 274.15, tuningFacPrecip = 1,
    disTuningFacPrecip = stack(), tuningFacAirT = 1,
    disTuningFacAirT = stack(), decimalPlaces = 4,
    outType = "mean", writeOutput = FALSE,
    outputName = "snowfall", tmpCreate = FALSE,
    tmpDir = "", outDir = "", ... )

Arguments

airT

An object of class 'RasterStack'. Distributed air temperature (Kelvin or Celsius). For every time step.

precip

An object of class 'RasterStack'. Distributed precipitation (m). For every time step.

glacierMask

An object of class 'RasterStack'. Glacier area (1 = glacier, 0 = no glacier). Stationary or for every time step.

snowTransTempThreshold

An object of class 'numeric'. Temperature threshold (same unit as 'airT') for the transition from rain- to snowfall (default = 274.15 Kelvin).

tuningFacPrecip

An object of class 'numeric'. General precipitation tuning factor (<1 = snowfall decrease, 1 = default, >1 = snowfall increase).

disTuningFacPrecip

An object of class 'numeric'. Distributed precipitation tuning factor

(tuningFacPrecip). Stationary or for every time step.

tuningFacAirT

An object of class 'numeric'. General air temperature tuning factor (<1 = temperature decrease, 1 = default, >1 = temperature increase).

disTuningFacAirT

An object of class 'RasterStack'. Distributed air temperature tuning factor ('tuningFacAirT'). Stationary or for every time step.

decimalPlaces

An object of class 'numeric'. Number of decimal places (default = 4).

outType

An object of class 'character'. Type of output to be returned by the function: "mean" (default) snowfall or "sum".

writeOutput

An object of class 'logical'. Determines whether the ouput shall be exported as 'RasterLayer' (TRUE) or not (FALSE, default).

outputName

An object of class 'character'. File name for the output 'RasterLayer(s)' (default = "dcIceMelt").

tmpCreate

An object of class 'logical'. Determines whether a temporary directory should be used (TRUE) or not (FALSE, default). Recommendend if large datasets are processed.

tmpDir

An object of class 'character'. Directory where processing files can be temporarily stored if 'tmpCreate' = TRUE.

outDir

An object of class 'character'. Directory for the output files if 'writeOutput' = TRUE.

...

Further arguments.

Details

A simple empirical air temperature threshold (e.g. 1 degree Celsius) is applied to derive snowfall from precipitation (e.g. Rohrer and Braun, 1994). Snowfall is defined as precipitation below the temperature threshold. For temperatures above the threshold, no precipitation is considered since refreezing and percolation processes have yet not been implemented in 'glacierSMBM'. For more information see Groos et al. (submitted).

Value

An object of class 'RasterLayer' returning the calculated snowfall distribution (m timestep-1).

Note

The following input variables are the requested minimum to run the model:

A default value (constant in space and time) is given for the additional arguments like 'tuningFacPrecip' or 'tuningFacAirT'. If desired, the default parameters can be modified. Furthermore, there is the option to pass distributed values (stationary or for every time step) instead of general values using the related 'dis*'-arguments like 'disTuningFacPrecip' or disTuningFacAirT. In this case, the general parameter is ignored.

File format of written ouput: GeoTIFF.

Author(s)

Alexander R. Groos (alexander.groos@giub.unibe.ch)

References

Groos, A.R., Mayer, C., Smiraglia, C., Diolaiuti, G., and Lambrecht A. (submitted). A first attempt to model region-wide glacier surface mass balances in the Karakoram: findings and future challenges. Geografia Fisica e Dinamica Quaternaria.

Rohrer, M., and Braun, L. (1994). Long-Term Records of Snow Cover Water Equivalent in the Swiss Alps 2. Simulation. Nordic Hydrology 25, 65-78.

See Also

glacialMelt

Examples

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# Load the provided RasterLayer objects as exemplary
# input for the function
# Individual RasterLayer objects should be loaded or
# created using the function raster()
data(airTemperature_30m_daily, precip_30m_daily,
    glacierMask_30m, package = "glacierSMBM")

# Include RasterLayer in RasterStack
AirTemperature_30m_daily <- stack(airTemperature_30m_daily)
Precip_30m_daily <- stack(precip_30m_daily)
GlacierMask_30m <- stack(glacierMask_30m)

# Calculate snow fall from air temperature and total
# precipitation using standard settings
output <- snowFall(airT = AirTemperature_30m_daily,
    precip = Precip_30m_daily, glacierMask = GlacierMask_30m)

# Plot output
plot(output, main = "snow fall",
    legend.args=list(text='Snowfall (m)', side=3, line=1.5))

# Calculate snow fall from air temperature and total
# precipitation using modified settings (e.g. snow transition
# is changed from 1 to 0 degree Celsius) and general
# precipitation tuning factor is set from 1 to 0.8)
output <- snowFall(airT = AirTemperature_30m_daily,
    precip = Precip_30m_daily, glacierMask = GlacierMask_30m,
    tuningFacPrecip = 0.8, snowTransTempThreshold = 273.15)

# Plot output
plot(output, main = "snow fall",
    legend.args=list(text='Snowfall (m)', side=3, line=1.5))

glacierSMBM documentation built on May 2, 2019, 3:42 a.m.