3 Results
3.1 Implementation and sensitivity tests on a single-point LSM
We first performed a single-point LSM simulation in the fen site in
North Saskatchewan. Two modifications were tested: first, the modified\(F_{\text{sat}}\) formula and, second, a sensitivity test for surface
water dynamics with various storage capacities. Figure 4 shows the\(F_{\text{sat}}\) parameter, energy and water balance in the fen site
simulated by Noah-MP. In Figure 4a, the default \(F_{\text{sat}}\)formula using the exponential function of the water table depth fails to
represent the large magnitude and strong seasonal variation, as shown by
the GIEMS data. The modified formula using the first layer of soil
moisture improves both the magnitude and seasonal cycle of the\(F_{\text{sat}}\) parameter. This larger \(F_{\text{sat}}\) effectively
changes the surface water partitioning, by increasing the surface
runoff, which leaves the grid point water balance, and reducing the
infiltration to soil moisture, which further reduces ET and underground
runoff (Figure 4b). Furthermore, the increased \(F_{\text{sat}}\)reduces latent heat fluxes and enhances sensible heat fluxes from March
to September, with the strongest decrease in July (Figure 4c).
The surface wetland scheme (Section 2.4) collects the increased surface
runoff in wetland storage and allows evaporation to the atmosphere. The
scheme’s contribution to surface water and energy balance depends on its
storage capacity. Figure 4d shows the sensitivity of water storage in a
wetland with four different capacities (WS=0, 5, 50 and 500 mm). When
wetland storage = 5 mm (“WS=5”), the wetland water would be depleted
during the summer, while with larger capacity (WS=50 or 500), the water
storage from the previous year can be sustained through dry seasons.
Greater water-holding capacity allows greater contribution to
evaporation and reduces surface runoff (Figure 4e). The changing storage
capacity has little impact on underground runoff. Moreover, greater
storage capacity also allows greater latent heat flux and less sensible
heat flux. The effect threshold lies between WS=5 and WS=50, as water
may be dried in smaller capacities, while the contribution is similar
between WS=50 and WS=500.