Evaluations of Uncertainty and Sensitivity in Soil Moisture Modeling on the Tibetan Plateau

SitesLocationsStudy periodsElevationsLand surface typesAnduo(91.625°E, 32.241°N)6/16-6/22 (1998)4700 mAlpine meadowMs3478(91.715°E, 31.926°N)9/1-9/16 (1998)5063 mAlpine meadowMs3637(91.657°E, 31.017°N)8/1-8/31 (1998)4533 mAlpine meadowGaiZe(84.050°E, 32.300°N)5/1-5/31 (1998)4420 mAlpine desertShiQuanHe(80.080°E, 32.500°N)7/1-7/31 (1998)4278 mAlpine desert

Sensitivity analysis framework for model parameter combinations based on the CNOP-P approach.

Table 2.

The physical parameters and their default, minimum and maximum values for the TP sites in the CoLM. Def = Default value; Min = Minimum value; Max = Maximum Value.

IndexParameterPhysical meaningCategoryDefMinMaxP01porsl(up)Porosity of upper soil, fraction of soil mass that is voidsoil0.430.250.75P02porsl(low)Porosity of lower soil, fraction of soil mass that is voidsoil0.450.250.75P03phi0(up)Minimum soil suction of upper soil (mm)soil207.3550.0500.0P04phi0(low)Minimum soil suction of lower soil (mm)soil288.9350.0500.0P05bsw(up)Clapp and Hornberger “b” parameter of upper soilsoil5.772.510.0P06bsw(low)Clapp and Hornberger “b” parameter of lower soilsoil8.322.510.0P07hksati(up)Saturated hydraulic conductivity of upper soil (mm/s)soil0.00420.0011.0P08hksati(low)Saturated hydraulic conductivity of lower soil (mm/s)soil0.00280.0011.0P09sqrtdiInverse square root of the leaf dimension (m^-1/2)canopy5.02.57.5P10sltiSlope of the low temperature inhibition functioncanopy0.20.10.3P11shtiSlope of the high temperature inhibition functioncanopy0.30.150.45P12trdaTemperature coefficient of the conductance-photosynthesis modelcanopy1.30.651.95P13trdmTemperature coefficient of the conductance-photosynthesis modelcanopy328.0300.0350.0P14tropTemperature coefficient of the conductance-photosynthesis modelcanopy298.0250.0300.0P15extknCoefficient for leaf nitrogen allocationcanopy0.50.50.75P16zlndRoughness length for the soil surface (m)soil0.010.0050.015P17zsnoRoughness length for snow (m)snow0.00240.00120.0036P18csoilcDrag coefficient for soil under the canopysoil0.0040.0020.006P19dewmxMaximum ponding of the leaf area (mm)canopy0.10.050.15P20wtfactFraction of the shallow groundwater areasoil0.30.150.45P21caprTuning factor of the soil surface temperaturesoil0.340.170.51P22cnfacCrank Nicholson factorsoil0.50.250.5P23ssiIrreducible water saturation of snowsnow0.00330.030.04P24wimpFactor for controlling whether water is impermeablesoil0.050.010.1P25pondmxMaximum ponding depth for the soil surface (mm)soil10.05.015.0P26smpmaxWilting point potential (mm)canopy−1.5e + 5−2.0e + 5−1.0e + 5P27smpminRestriction for the minimum soil potential (mm)soil−1.0e + 8−1.0e + 8−9.0e + 7P28trsmx0Maximum transpiration for vegetation (mm/s)canopy0.00020.00010.01

The reference states of SSM simulated by using the default parameter values (a) as well as the maximal uncertainties in the simulated SSM due to errors from all 28 selected parameters at different TP sites during different simulation periods in terms of absolute changes (b).

The variations (left column) in ET (a, mm day⁻¹), R_sur (c, mm day⁻¹) and subsurface soil moisture (e, m³ m⁻³) relative to their respective reference states (right column) of ET (b, mm day⁻¹), R_sur (d, mm day⁻¹), subsurface soil moisture (f, m³ m⁻³) caused by the CNOP-P-type parameter errors associated with all 28 parameters at different TP sites during different simulation periods.

The sensitivity ranks of all 28 parameters based on the single-parameter sensitivity analyses using the CNOP-P approach (a) and the OAT method (b) at different TP sites. Numbers “1”, “2”, “3”, and “4” on colored boxes label the 4 most sensitive parameters (in order of sensitivity) at each site.

The maximal uncertainties in the simulated SSM due to errors from the most sensitive and important 4-parameter combinations identified by using the CNOP-P approach as well as errors from the 4 most sensitive parameters determined by using the OAT method: (a) in terms of absolute changes, (b) in terms of percentage changes.

Table 3.

The most sensitive parameter combinations at different TP sites identified by using the sensitivity analysis framework based on the CNOP-P approach.

SiteThe most sensitive parameter combinationAnduoP01, P02, P03, P05Ms3478P01, P02, P03, P04Ms3637P01, P02, P03, P04GaiZeP01, P02, P03, P05ShiQuanHeP01, P02, P04, P05

The reductions in the uncertainties of the simulated SSM at different TP sites, which are represented by $τ,$ caused by the different decreased extents (as indicated by $α$ ) of three types of parameter error: CNOP, CNOP_Single, and OAT.

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DOI: https://doi.org/10.1080/16000870.2019.1704963 | Journal eISSN: 3035-9554

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Language: English

Page range: 1704963 - 1704963

Published on: Jan 1, 2020

Published by: Stockholm University Press

In partnership with: Paradigm Publishing Services

Keywords:

surface soil moisture,

Tibetan Plateau,

CNOP-P,

uncertainty and sensitivity analysis,

CoLM

© 2020 Fei Peng, Mu Mu, Guodong Sun, published by Stockholm University Press
This work is licensed under the Creative Commons Attribution 4.0 License.

Volume 72 (2020): Issue 1

Evaluations of Uncertainty and Sensitivity in Soil Moisture Modeling on the Tibetan Plateau

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