Package net.simplace.sim.components.soil.temperature

Class SnowCoverCalculator

java.lang.Object
net.simplace.sim.model.FWSimComponent
net.simplace.sim.components.soil.temperature.SnowCoverCalculator
All Implemented Interfaces:
net.simplace.sim.util.FWSimFieldContainer
public class SnowCoverCalculator extends net.simplace.sim.model.FWSimComponent
Calculates the snow cover, first soil layer temperature and biomass on ground factor depending on climate and soil conditions.

Snow Cover

Snow Cover is calculated using the formula:

\[ \begin{eqnarray} DST0=(1.-BCV) \cdot DST + BCV \cdot STMP0 \end{eqnarray} \]

Snow Cover calculation

If the soil surface is not bare, the surface temperature can be affected considerably by the amount of cover (crop residue or snow). This effect can be simulated by combining the estimated bare surface temperature for the day with the previous day's temperature in the second soil layer (the top 10 mm layer is considered too thin for this purpose).

where DST0 is the final estimate of soil surface temperature in °C and BCV is a lagging factor for simulating residue and snow cover effects on surface temperature. The value of BCV is 0.0 for bare soil and approaches 1.0 as cover increases, as expressed in the equation

\[ \begin{eqnarray} BCV &=& max(SNOF,BCV') \\ BCV' &=& \frac{CV}{CV+exp(5.34-2.40 \cdot CV)} \\ SNOF &=& \frac{SNO}{SNO+exp(2.30-0.220 \cdot SNO)} \end{eqnarray} \]

where

  • CV is the sum of above ground biomass and crop residue in t ha-1 and
  • SNO is the water content of the snow cover in mm.

Snow melt

If snow is present, it may be melted on days when the second soil layer temperature exceeds 0 oC. Snow is melted as a function of the snow pack temperature using the equation

\[ \begin{eqnarray} SML &=& max(0.,X1 \cdot (1.52+.54 \cdot F \cdot SNPKT)) \quad \text{for} \quad 0.0 \lt SML \lt SNO \\ SNPKT & =& .3333 \cdot (2. \cdot X2+TX) \\ X1 &=& \sqrt{TMX \cdot RA} \\ X2 &=& min(DST0,STMP(2)) \\ F &=& TSNO/(TSNO+exp(5.34-2.395 \cdot TSNO)) \end{eqnarray} \]

where

  • SML is the snowmelt rate in mm d-1,
  • SNO is the snow present in mm of water,
  • STMP is the temperature in oC of soil layer 2,
  • SNPKT is the snow pack temperature in oC,
  • DST0 is the soil surface temperature in oC, and
  • TSNO is the age of the snow pack in d.

The equations for estimating STMP and DST0 are presented in the soil temperature section. Melted snow is treated the same as rainfall for estimating runoff volume and percolation, but rainfall energy is set to 0.0 and peak runoff rate is estimated by assuming uniformly distributed rainfall for a 24-h duration.

Snow evaporation

EAJ is a soil cover index. The value of EAJ ranges from 0 to 1.0 according to the equation

\[ \begin{eqnarray} EAJ & = & exp(-X1) \\ X1 & = & max(0.4 \cdot SMLA,0.1 \cdot (CV+.1)) \end{eqnarray} \]

where

  • CV is the weight of all above ground plant material in t ha-1.

Reference:

Williams, J.R., Izaurralde, C.A., 2005. The APEX model, Blackland Research Center Reports, Vol. 2. Blackland Research Center, USDA, Temple, Texas, USA

Author:
Andreas Enders, Gunther Krauss

Component Variables

Content TypeNameDescriptionData TypeUnitMin ValueMax ValueDefault Value
constantcAlbedoAlbedo, if not set it will be initializedDOUBLE10.01.00.0
constantcCarbonContentCarbon content of upper soil layerDOUBLE%0.520.00.5
constantcInitialAgeOfSnowInitial age of snowINT%0-0
constantcInitialSnowWaterContentInitial snow water contentDOUBLE%0.01500.00.0
constantcSnowIsolationFactorAStatic part of the snow isolation index calculationDOUBLE10.010.02.3
constantcSnowIsolationFactorBDynamic part of the snow isolation index calculationDOUBLE10.01.00.22
inputiCropResiduesCrop residues plus above ground biomassDOUBLEg/m20.020000.0-
inputiDoInitializeSwitch to re-initialize the model with initial values.BOOLEAN1--false
inputiLeafAreaIndexLeaf area indexDOUBLEm2/m20.010.0-
inputiPotentialSoilEvaporationPotenial EvaporationDOUBLEmm0.012.00.0
inputiRAINRain amountDOUBLEmm0.060.00.0
inputiRadiationGlobal Solar radiationDOUBLEMJ/m20.02000.0-
inputiSoilTempArraySoil Temp array of last dayDOUBLEARRAY°C-15.035.0-
inputiTempMaxDaily maximum air temperatureDOUBLE°C-40.050.0-
inputiTempMinDaily minimum air temperatureDOUBLE°C-40.050.0-
stateAgeOfSnowAge of snowINTd0-0
stateSnowWaterContentSnow water contentDOUBLEmm0.01500.00.0
stateSoilSurfaceTemperatureSoil surface temperatureDOUBLE°C-40.070.00.0
raterAgeOfSnowRatedaily age of snow change rateINT1--0
raterSnowWaterContentRatedaily snow water content change rateDOUBLEmm/d-1500.01500.00.0
raterSoilSurfaceTemperatureRatedaily soil surface temperature change rateDOUBLEdegree_Celsius_per_day-40.070.00.0
outSnowIsolationIndexSnow isolation indexDOUBLE10.01.00.0

  • Nested Class Summary

    Nested classes/interfaces inherited from class net.simplace.sim.model.FWSimComponent

    net.simplace.sim.model.FWSimComponent.TEST_STATE

  • Field Summary

    Fields inherited from class net.simplace.sim.model.FWSimComponent

    iFieldMap, iFrequence, iInputMap, iJexlRule, iMasterComponentGroup, iName, iOrderNumber, isComponentGroup, iSimComponentElement, iSimModel, iVarMap

  • Constructor Summary

    Constructors
    Constructor
    Description
    SnowCoverCalculator()
    Empty constructor used by class.forName()

  • Method Summary

    Modifier and Type
    Method
    Description
    protected net.simplace.sim.model.FWSimComponent
    clone(net.simplace.sim.util.FWSimVarMap aVarMap)
     
    HashMap<String,net.simplace.sim.util.FWSimVariable<?>>
    createVariables()
    create the FWSimVariables as interface for this SimComponent
    HashMap<String,net.simplace.sim.util.FWSimVariable<?>>
    fillTestVariables(int aParamIndex, net.simplace.sim.model.FWSimComponent.TEST_STATE aDefineOrCheck)
    called for single component test to check the components algorithm.
    protected void
    init()
    initializes the fields by getting input and output FWSimVariables from VarMap
    protected void
    process()
    process the algorithm and write the results back to VarMap
    protected void
    reInitialize()
     

    Methods inherited from class net.simplace.sim.model.FWSimComponent

    addVariable, bind, checkCondition, createSimComponent, createSimComponent, createSimComponent, createSimComponent, doProcess, getConstantVariables, getContentType, getCreateFormXML, getDescription, getEditFormXML, getFieldMap, getFrequence, getFrequenceRuleScript, getInputs, getInputVariables, getMasterComponentGroup, getName, getOrderNumber, getOutputVariables, getVariable, getVariableField, getVarMap, initialize, isConditionCheck, isVariableAvailable, performLinks, performLinks, readInputs, removeVariable, reset, runComponentTest, setVariablesDefault, toComponentLinkingXML, toDocXML, toGroupXML, toOutputDefinitionXML, toResourcesDataXML, toResourcesDefinitionXML, toString, toXML, writeVarInfos

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

  • Constructor Details

    • SnowCoverCalculator

      public SnowCoverCalculator()
      Empty constructor used by class.forName()

  • Method Details

    • createVariables

      public HashMap<String,net.simplace.sim.util.FWSimVariable<?>> createVariables()
      create the FWSimVariables as interface for this SimComponent
      Specified by:
      createVariables in interface net.simplace.sim.util.FWSimFieldContainer
      Specified by:
      createVariables in class net.simplace.sim.model.FWSimComponent
      See Also:
      • FWSimComponent.createVariables()

    • init

      protected void init()
      initializes the fields by getting input and output FWSimVariables from VarMap
      Specified by:
      init in class net.simplace.sim.model.FWSimComponent
      See Also:
      • FWSimComponent.init()

    • reInitialize

      protected void reInitialize()

    • process

      protected void process()
      process the algorithm and write the results back to VarMap
      Specified by:
      process in class net.simplace.sim.model.FWSimComponent
      See Also:
      • FWSimComponent.process()

    • fillTestVariables

      public HashMap<String,net.simplace.sim.util.FWSimVariable<?>> fillTestVariables(int aParamIndex, net.simplace.sim.model.FWSimComponent.TEST_STATE aDefineOrCheck)
      called for single component test to check the components algorithm. aParamIndex: Used to set up different test cases. Start with 0 - result check with 1 aso
      Specified by:
      fillTestVariables in class net.simplace.sim.model.FWSimComponent
      See Also:
      • net.simplace.sim.util.FWSimFieldContainer#fillTestVariables(int aParamIndex, TEST_STATE aDefineOrCheck)

    • clone

      protected net.simplace.sim.model.FWSimComponent clone(net.simplace.sim.util.FWSimVarMap aVarMap)
      Specified by:
      clone in class net.simplace.sim.model.FWSimComponent
      See Also:
      • FWSimComponent.clone(net.simplace.sim.util.FWSimVarMap)