Update a and b for sea level rise

Update a and b parameters for sea level rise

update_ab_SLR(v, SLR_m, control_volume)

Arguments

v	Vector of length 4 containing log parameter values: log(a), log(b), log(d), and log(C_d)
SLR_m	vector of sea level rise in meters
control_volume	set to "channel" or "gw"

Value

Returns the parameter vector v with updated a and b for a given sea level rise and d set to NA.

Details

For a given sea level rise and initial v1 (parameters), this function updates a and b as a2 = a1 / R_V and b_2 = b_1 R_E / R_V, where R_E and R_V are determined from get_ganges_SLR_ratios. Because v contains logged values, this is calculated as:

• log(a2) = log(a1) - log(R_V)

• log(b2) = log(b1) + log(R_E) - log(R_V)

Examples

library(ggplot2)

# get updated v with sea level rise of 0.5 m
v_orig <- ganges_params$param
v_slr_chan <- update_ab_SLR(v_orig, SLR_m = 0.5, "channel")
v_slr_gw <- update_ab_SLR(v_orig, SLR_m = 0.5, "gw")

# replace original value of d to create a dummy simulation
v_slr_chan[3] <- v_orig[3]
v_slr_gw[3] <- v_orig[3]

# simulate salinity under original and new parameters
Q_df <- ganges_streamflow[ganges_streamflow$group == "Treaty avg",]
Q_df$S_ppm_orig <- sim_salin_annual(Q_df, v_orig)
Q_df$S_ppm_slr_chan <- sim_salin_annual(Q_df, v_slr_chan)
Q_df$S_ppm_slr_gw <- sim_salin_annual(Q_df, v_slr_gw)

# plot the results
ggplot(Q_df) +
  geom_line(aes(date, S_ppm_orig, color = "orig")) +
  geom_line(aes(date, S_ppm_slr_chan, color = "slr 0.5 m (chan)")) +
  geom_line(aes(date, S_ppm_slr_gw, color = "slr 0.5 m (gw)")) +
  ylab("Salinity, ppm")