Unfrozen: Unfozen water in soil

In geocryology/PermafrostTools: PermafrostTools

Description

Computes the proportion of unfozen water and ice in soil as well as the temperature derivative of liquid water content.

Usage

Unfrozen(mat, unfrozen.type = "INTERVAL", unfrozen.par = 0.5)

Arguments

mat	Data frame with relevant ground properties.
unfrozen.type	Character string indicating the type of function to be used; the standard is "INTERVAL". The full options are: "DALLAMICO": Dall’Amico, M., Endrizzi, S., Gruber, S., & Rigon, R. (2011). A robust and energy-conserving model of freezing variably-saturated soil. The Cryosphere, 5(2), 469–484. doi:10.5194/tc-5-469-2011 Typical values of van Genuchten parameters are found in Table 2 of Gubler, S., Endrizzi, S., Gruber, S., & Purves, R. S. (2013). Sensitivities and uncertainties of modeled ground temperatures in mountain environments. Geoscientific Model Development, 6(4), 1319–1336. doi:10.5194/gmd-6-1319-2013 "MOTTAGHY": Mottaghy, D., & Rath, V. (2006). Latent heat effects in subsurface heat transport modelling and their impact on palaeotemperature reconstructions. Geophysical Journal International, 164(1), 236-245. "INTERVAL": Phase change takes place in an interval of specified with (unfrozen.par) below 0C and at a constant rate.
unfrozen.par	Parameter set for the chosen unfrozen water function. "DALLAMICO": unfrozen.par[1]: van Genuchten alpha [mm-1], unfrozen.par[2]: van Genuchten n [-], unfrozen.par[3]: residual water content [m3/m3]. The saturated water content is given by the input (mat$wat) and can thus vary with depth. "MOTTAGHY": unfrozen.par[1]: width of freezing interval [K], unfrozen.par[2]: omega. "INTERVAL" unfrozen.par[1]: width of freezing interval [K].

Details

This function applies invariant freezing parameters with depth and assumes saturated conditions without movement of water.

Value

Returns the input data frame with three columns updated: liq [m3/m3] (liquid water content, relative to soil volume), ice [m3/m3] (ice content, relative to soil volume), and dice [m3/C] (change in ice content, relative to soil volume per degree Celsius). If these columns do not exist in the input data frame, they are created.

Author(s)

Stephan Gruber <[e-mail]>

Examples

mat <- data.frame(Tj  = (-500:200)/100, 
                  wat = rep(0.5,701))

#Mottahgy and Rath (2006) example
mat <- Unfrozen(mat, unfrozen.type = "MOTTAGHY", unfrozen.par = c(0, 0.5))
plot(mat$Tj, mat$dice, type="l", lty = 1, col = "black", ylim =c(0,2),
     xlab = "Temperature [C]", 
     ylab = "Liquid water content (solid), derivation (dashed)")
lines(mat$Tj, mat$liq, lty = 2, col = "black")

#interval function example
mat <- Unfrozen(mat, unfrozen.type = "INTERVAL", unfrozen.par = 1)
lines(mat$Tj, mat$dice, lty = 1, col = "blue")
lines(mat$Tj, mat$liq,  lty = 2, col = "blue")

#Dall'Amico et al. (2011) example, assuming saturated conditions.
mat <- Unfrozen(mat, unfrozen.type = "DALLAMICO", 
                unfrozen.par = c(0.001, 1.4, 0.05))
lines(mat$Tj, mat$dice, lty = 1, col = "red")
lines(mat$Tj, mat$liq,  lty = 2, col = "red")

geocryology/PermafrostTools documentation built on Dec. 20, 2021, 10:40 a.m.