glacialMelt-method: Method: Ablation model

In glacierSMBM: Glacier Surface Mass Balance Model

Description

A model to calculate melting of supraglacial snow and firn, bare glacier ice and debris covered glacier ice.

Details

Glacier ablation comprises melting of bare and debris-covered ice as well as melting of supraglacial snow and firn. Depending on the glacier surface classification as defined in 'iceMask', 'snowMask' and 'debrisMask', the melt rate for each pixel is quantified using the functions iceMelt, snowMelt and debrisCoveredIceMelt. For more information please refer to the applied melting functions, the examples below or the original publication (Groos et al., submitted, Equations 10-16).

Value

An object of class 'RasterStack' consisting of four individual 'RasterLayers':

1. Melt rate of supraglacial snow and firn as calculated by snowMelt

2. Melt rate of bare ice as calculated by iceMelt

3. Melt rate of debris covered ice as calculated by debrisCoveredIceMelt

4. Sum of 1-3

To access the individual 'RasterLayers', use subset.

If more than one 'RasterLayer' is stored in the input 'RasterStacks', the output 'RasterStack' returns the "mean" or "sum" (depending on 'outType') of snow melt, ice melt and debris covered ice melt.

Note

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

• 'airT' (for every time step)

• 'netRad' (for every time step)

• 'airDensity' (stationary or for every time step)

• 'glacierMask' (stationary or for every time step)

• 'iceMask' (stationary or for every time step)

• 'snowMask' (stationary or for every time step)

• 'debrisMask' (stationary or for every time step)

• 'debrisThickness' (stationary or for every time step)

If 'inRadSW' and 'inRadLW' are provided instead of 'netRad', the energy-balance at the atmosphere-debris interface is calculated taking the 'debrisAlbedo' and 'thermalEmissivity' of the debris layer into account.

A default value (constant in space and time) is given for each additional argument like 'windSpeed', 'relativeHumidity' and 'thermalConductivity'. 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 'disWindSpeed', 'disRelativeHumidity' and 'disThermalConductivity'. In this case, the general parameter is ignored.

File format of written ouput: GeoTIFF.

Author(s)

Alexander R. Groos ([e-mail])

References

Collier, E., Moelg, T., Maussion, F., Scherer, D., Mayer, C., and Bush, A.B.G. (2013). High-resolution interactive modelling of the mountain glacier-atmosphere interface: an application over the Karakoram. The Cryosphere Discussions 7, 103-144.

Evatt, G.W., Abrahams, D., Heil, M., Mayer, C., Kingslake, J., Mitchell, S.L., Fowler, A.C., and Clark, C.D. (2015). Glacial melt under a porous debris layer. Journal of Glaciology 61, 825-836.

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.

Hock, R. (2003). Temperature index melt modelling in mountain areas. Journal of Hydrology 282, 104-115.

Hock, R. (2005). Glacier melt: a review of processes and their modelling. Progress in Physical Geography 29, 362-391.

See Also

snowMelt, iceMelt, debrisCoveredIceMelt

Examples

# Load the provided RasterLayer objects as exemplary
# input for the function
data(airTemperature_30m_daily, netRad_30m_daily,
    airDensity_30m_daily, glacierMask_30m, iceMask_30m,
    firnMask_30m, debrisMask_30m, debrisThickness_30m,
    package = "glacierSMBM")
# Individual RasterLayer objects should be loaded or
# created using the function raster()

# Include RasterLayer in RasterStack
AirTemperature_30m_daily <- stack(airTemperature_30m_daily * 1.01)
NetRad_30m_daily <- stack(netRad_30m_daily)
AirDensity_30m_daily <- stack(airDensity_30m_daily)
GlacierMask_30m <- stack(glacierMask_30m)
IceMask_30m <- stack(iceMask_30m)
FirnMask_30m <- stack(firnMask_30m)
DebrisThickness_30m <- stack(debrisThickness_30m)
DebrisMask_30m <- stack(debrisMask_30m)

## Not run: 
# Calculate ablation using standard settings
output <- glacialMelt(airT = AirTemperature_30m_daily,
    netRad = NetRad_30m_daily, airDensity = AirDensity_30m_daily,
    glacierMask = GlacierMask_30m, iceMask = IceMask_30m,
    snowMask = FirnMask_30m, debrisMask = DebrisMask_30m,
    debrisThickness = DebrisThickness_30m)

# Plot output
plot(output, main = c("snow melt", "bare ice melt",
    "debris covered ice melt","total ablation"),
    legend.args=list(text='Melt (m d-1)', side=3, line=1.5))

## End(Not run)

# Calculate ablation using modified setting (e.g. input
# temperature in celsius instead of kelvin and
# increased thermal conductivity)

# Therefore exemplarily convert temperature from
# kelvin to degree celsius
airTcelsius <- AirTemperature_30m_daily - 273.15

# Include RasterLayer in RasterStack
airTcelsius <- stack(airTcelsius)

## Not run: 
output <- glacialMelt(airT = airTcelsius, netRad =
    NetRad_30m_daily, airDensity <- AirDensity_30m_daily,
    glacierMask = GlacierMask_30m, iceMask = IceMask_30m,
    snowMask = FirnMask_30m, debrisMask = DebrisMask_30m,
    debrisThickness = DebrisThickness_30m, tUnit = "C",
    thermalConductivity = 1.5)

# Plot output
plot(output, main = c("snow melt", "bare ice melt",
    "debris covered ice melt","total ablation"),
    legend.args=list(text='Melt (m d-1)', side=3, line=1.5))

## End(Not run)

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