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1 | Redirecting to URL 'https://iland.boku.ac.at/svn/iland/tags/release_1.0/src/core/watercycle.cpp': |
1 | Redirecting to URL 'https://iland.boku.ac.at/svn/iland/tags/release_1.0/src/core/watercycle.cpp': |
2 | /********************************************************************************************
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2 | /********************************************************************************************
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3 | ** iLand - an individual based forest landscape and disturbance model
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3 | ** iLand - an individual based forest landscape and disturbance model
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4 | ** http://iland.boku.ac.at
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4 | ** http://iland.boku.ac.at
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5 | ** Copyright (C) 2009- Werner Rammer, Rupert Seidl
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5 | ** Copyright (C) 2009- Werner Rammer, Rupert Seidl
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6 | **
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6 | **
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7 | ** This program is free software: you can redistribute it and/or modify
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7 | ** This program is free software: you can redistribute it and/or modify
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8 | ** it under the terms of the GNU General Public License as published by
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8 | ** it under the terms of the GNU General Public License as published by
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9 | ** the Free Software Foundation, either version 3 of the License, or
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9 | ** the Free Software Foundation, either version 3 of the License, or
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10 | ** (at your option) any later version.
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10 | ** (at your option) any later version.
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11 | **
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11 | **
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12 | ** This program is distributed in the hope that it will be useful,
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12 | ** This program is distributed in the hope that it will be useful,
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13 | ** but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 | ** but WITHOUT ANY WARRANTY; without even the implied warranty of
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14 | ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 | ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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15 | ** GNU General Public License for more details.
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15 | ** GNU General Public License for more details.
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16 | **
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16 | **
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17 | ** You should have received a copy of the GNU General Public License
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17 | ** You should have received a copy of the GNU General Public License
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18 | ** along with this program. If not, see <http://www.gnu.org/licenses/>.
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18 | ** along with this program. If not, see <http://www.gnu.org/licenses/>.
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19 | ********************************************************************************************/
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19 | ********************************************************************************************/
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20 | 20 | ||
21 | #include "global.h"
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21 | #include "global.h"
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22 | #include "watercycle.h"
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22 | #include "watercycle.h"
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23 | #include "climate.h"
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23 | #include "climate.h"
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24 | #include "resourceunit.h"
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24 | #include "resourceunit.h"
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25 | #include "species.h"
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25 | #include "species.h"
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26 | #include "model.h"
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26 | #include "model.h"
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27 | #include "helper.h"
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27 | #include "helper.h"
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28 | #include "modules.h"
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28 | #include "modules.h"
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29 | 29 | ||
30 | /** @class WaterCycle
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30 | /** @class WaterCycle
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31 | @ingroup core
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31 | @ingroup core
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32 | simulates the water cycle on a ResourceUnit.
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32 | simulates the water cycle on a ResourceUnit.
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33 | The WaterCycle is simulated with a daily time step on the spatial level of a ResourceUnit. Related are
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33 | The WaterCycle is simulated with a daily time step on the spatial level of a ResourceUnit. Related are
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34 | the snow module (SnowPack), and Canopy module that simulates the interception (and evaporation) of precipitation and the
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34 | the snow module (SnowPack), and Canopy module that simulates the interception (and evaporation) of precipitation and the
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35 | transpiration from the canopy.
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35 | transpiration from the canopy.
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36 | The WaterCycle covers the "soil water bucket". Main entry function is run().
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36 | The WaterCycle covers the "soil water bucket". Main entry function is run().
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37 | 37 | ||
38 | See http://iland.boku.ac.at/water+cycle
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38 | See http://iland.boku.ac.at/water+cycle
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39 | */
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39 | */
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40 | 40 | ||
41 | WaterCycle::WaterCycle() |
41 | WaterCycle::WaterCycle() |
42 | {
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42 | {
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43 | mSoilDepth = 0; |
43 | mSoilDepth = 0; |
44 | mLastYear = -1; |
44 | mLastYear = -1; |
45 | }
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45 | }
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46 | 46 | ||
47 | void WaterCycle::setup(const ResourceUnit *ru) |
47 | void WaterCycle::setup(const ResourceUnit *ru) |
48 | {
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48 | {
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49 | mRU = ru; |
49 | mRU = ru; |
50 | // get values...
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50 | // get values...
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51 | mFieldCapacity = 0.; // on top |
51 | mFieldCapacity = 0.; // on top |
52 | const XmlHelper &xml=GlobalSettings::instance()->settings(); |
52 | const XmlHelper &xml=GlobalSettings::instance()->settings(); |
53 | mSoilDepth = xml.valueDouble("model.site.soilDepth", 0.) * 10; // convert from cm to mm |
53 | mSoilDepth = xml.valueDouble("model.site.soilDepth", 0.) * 10; // convert from cm to mm |
54 | double pct_sand = xml.valueDouble("model.site.pctSand"); |
54 | double pct_sand = xml.valueDouble("model.site.pctSand"); |
55 | double pct_silt = xml.valueDouble("model.site.pctSilt"); |
55 | double pct_silt = xml.valueDouble("model.site.pctSilt"); |
56 | double pct_clay = xml.valueDouble("model.site.pctClay"); |
56 | double pct_clay = xml.valueDouble("model.site.pctClay"); |
57 | if (fabs(100. - (pct_sand + pct_silt + pct_clay)) > 0.01) |
57 | if (fabs(100. - (pct_sand + pct_silt + pct_clay)) > 0.01) |
58 | throw IException(QString("Setup Watercycle: soil composition percentages do not sum up to 100. Sand: %1, Silt: %2 Clay: %3").arg(pct_sand).arg(pct_silt).arg(pct_clay)); |
58 | throw IException(QString("Setup Watercycle: soil composition percentages do not sum up to 100. Sand: %1, Silt: %2 Clay: %3").arg(pct_sand).arg(pct_silt).arg(pct_clay)); |
59 | 59 | ||
60 | // calculate soil characteristics based on empirical functions (Schwalm & Ek, 2004)
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60 | // calculate soil characteristics based on empirical functions (Schwalm & Ek, 2004)
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61 | // note: the variables are percentages [0..100]
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61 | // note: the variables are percentages [0..100]
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62 | mPsi_ref = -exp((1.54 - 0.0095*pct_sand + 0.0063*pct_silt) * log(10)) * 0.000098; // Eq. 83 |
62 | mPsi_ref = -exp((1.54 - 0.0095*pct_sand + 0.0063*pct_silt) * log(10)) * 0.000098; // Eq. 83 |
63 | mPsi_koeff_b = -( 3.1 + 0.157*pct_clay - 0.003*pct_sand ); // Eq. 84 |
63 | mPsi_koeff_b = -( 3.1 + 0.157*pct_clay - 0.003*pct_sand ); // Eq. 84 |
64 | mRho_ref = 0.01 * (50.5 - 0.142*pct_sand - 0.037*pct_clay); // Eq. 78 |
64 | mRho_ref = 0.01 * (50.5 - 0.142*pct_sand - 0.037*pct_clay); // Eq. 78 |
65 | mCanopy.setup(); |
65 | mCanopy.setup(); |
66 | 66 | ||
67 | mPermanentWiltingPoint = heightFromPsi(-4000); // maximum psi is set to a constant of -4MPa |
67 | mPermanentWiltingPoint = heightFromPsi(-4000); // maximum psi is set to a constant of -4MPa |
68 | if (xml.valueBool("model.settings.waterUseSoilSaturation",false)==false) { |
68 | if (xml.valueBool("model.settings.waterUseSoilSaturation",false)==false) { |
69 | mFieldCapacity = heightFromPsi(-15); |
69 | mFieldCapacity = heightFromPsi(-15); |
70 | } else { |
70 | } else { |
71 | // =-EXP((1.54-0.0095* pctSand +0.0063* pctSilt)*LN(10))*0.000098
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71 | // =-EXP((1.54-0.0095* pctSand +0.0063* pctSilt)*LN(10))*0.000098
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72 | double psi_sat = -exp((1.54-0.0095 * pct_sand + 0.0063*pct_silt)*log(10.))*0.000098; |
72 | double psi_sat = -exp((1.54-0.0095 * pct_sand + 0.0063*pct_silt)*log(10.))*0.000098; |
73 | mFieldCapacity = heightFromPsi(psi_sat); |
73 | mFieldCapacity = heightFromPsi(psi_sat); |
74 | if (logLevelDebug()) qDebug() << "psi: saturation " << psi_sat << "field capacity:" << mFieldCapacity; |
74 | if (logLevelDebug()) qDebug() << "psi: saturation " << psi_sat << "field capacity:" << mFieldCapacity; |
75 | }
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75 | }
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76 | 76 | ||
77 | mContent = mFieldCapacity; // start with full water content (in the middle of winter) |
77 | mContent = mFieldCapacity; // start with full water content (in the middle of winter) |
78 | if (logLevelDebug()) qDebug() << "setup of water: Psi_ref (kPa)" << mPsi_ref << "Rho_ref" << mRho_ref << "coeff. b" << mPsi_koeff_b; |
78 | if (logLevelDebug()) qDebug() << "setup of water: Psi_ref (kPa)" << mPsi_ref << "Rho_ref" << mRho_ref << "coeff. b" << mPsi_koeff_b; |
79 | mCanopyConductance = 0.; |
79 | mCanopyConductance = 0.; |
80 | mLastYear = -1; |
80 | mLastYear = -1; |
81 | 81 | ||
82 | // canopy settings
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82 | // canopy settings
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83 | mCanopy.mNeedleFactor = xml.valueDouble("model.settings.interceptionStorageNeedle", 4.); |
83 | mCanopy.mNeedleFactor = xml.valueDouble("model.settings.interceptionStorageNeedle", 4.); |
84 | mCanopy.mDecidousFactor = xml.valueDouble("model.settings.interceptionStorageBroadleaf", 2.); |
84 | mCanopy.mDecidousFactor = xml.valueDouble("model.settings.interceptionStorageBroadleaf", 2.); |
85 | mSnowPack.mSnowTemperature = xml.valueDouble("model.settings.snowMeltTemperature", 0.); |
85 | mSnowPack.mSnowTemperature = xml.valueDouble("model.settings.snowMeltTemperature", 0.); |
86 | }
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86 | }
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87 | 87 | ||
88 | /** function to calculate the water pressure [saugspannung] for a given amount of water.
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88 | /** function to calculate the water pressure [saugspannung] for a given amount of water.
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89 | returns water potential in kPa.
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89 | returns water potential in kPa.
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90 | see http://iland.boku.ac.at/water+cycle#transpiration_and_canopy_conductance */
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90 | see http://iland.boku.ac.at/water+cycle#transpiration_and_canopy_conductance */
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91 | inline double WaterCycle::psiFromHeight(const double mm) const |
91 | inline double WaterCycle::psiFromHeight(const double mm) const |
92 | {
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92 | {
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93 | // psi_x = psi_ref * ( rho_x / rho_ref) ^ b
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93 | // psi_x = psi_ref * ( rho_x / rho_ref) ^ b
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94 | if (mm<0.001) |
94 | if (mm<0.001) |
95 | return -100000000; |
95 | return -100000000; |
96 | double psi_x = mPsi_ref * pow((mm / mSoilDepth / mRho_ref),mPsi_koeff_b); |
96 | double psi_x = mPsi_ref * pow((mm / mSoilDepth / mRho_ref),mPsi_koeff_b); |
97 | return psi_x; // pis |
97 | return psi_x; // pis |
98 | }
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98 | }
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99 | 99 | ||
100 | /// calculate the height of the water column for a given pressure
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100 | /// calculate the height of the water column for a given pressure
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101 | /// return water amount in mm
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101 | /// return water amount in mm
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102 | /// see http://iland.boku.ac.at/water+cycle#transpiration_and_canopy_conductance
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102 | /// see http://iland.boku.ac.at/water+cycle#transpiration_and_canopy_conductance
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103 | inline double WaterCycle::heightFromPsi(const double psi_kpa) const |
103 | inline double WaterCycle::heightFromPsi(const double psi_kpa) const |
104 | {
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104 | {
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105 | // rho_x = rho_ref * (psi_x / psi_ref)^(1/b)
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105 | // rho_x = rho_ref * (psi_x / psi_ref)^(1/b)
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106 | double h = mSoilDepth * mRho_ref * pow(psi_kpa / mPsi_ref, 1./mPsi_koeff_b); |
106 | double h = mSoilDepth * mRho_ref * pow(psi_kpa / mPsi_ref, 1./mPsi_koeff_b); |
107 | return h; |
107 | return h; |
108 | }
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108 | }
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109 | 109 | ||
110 | /// get canopy characteristics of the resource unit.
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110 | /// get canopy characteristics of the resource unit.
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111 | /// It is important, that species-statistics are valid when this function is called (LAI)!
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111 | /// It is important, that species-statistics are valid when this function is called (LAI)!
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112 | void WaterCycle::getStandValues() |
112 | void WaterCycle::getStandValues() |
113 | {
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113 | {
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114 | mLAINeedle=mLAIBroadleaved=0.; |
114 | mLAINeedle=mLAIBroadleaved=0.; |
115 | mCanopyConductance=0.; |
115 | mCanopyConductance=0.; |
116 | const double ground_vegetationCC = 0.02; |
116 | const double ground_vegetationCC = 0.02; |
117 | double lai; |
117 | double lai; |
118 | foreach(const ResourceUnitSpecies *rus, mRU->ruSpecies()) { |
118 | foreach(const ResourceUnitSpecies *rus, mRU->ruSpecies()) { |
119 | lai = rus->constStatistics().leafAreaIndex(); |
119 | lai = rus->constStatistics().leafAreaIndex(); |
120 | if (rus->species()->isConiferous()) |
120 | if (rus->species()->isConiferous()) |
121 | mLAINeedle+=lai; |
121 | mLAINeedle+=lai; |
122 | else
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122 | else
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123 | mLAIBroadleaved+=lai; |
123 | mLAIBroadleaved+=lai; |
124 | mCanopyConductance += rus->species()->canopyConductance() * lai; // weigh with LAI |
124 | mCanopyConductance += rus->species()->canopyConductance() * lai; // weigh with LAI |
125 | }
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125 | }
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126 | double total_lai = mLAIBroadleaved+mLAINeedle; |
126 | double total_lai = mLAIBroadleaved+mLAINeedle; |
127 | 127 | ||
128 | // handle cases with LAI < 1 (use generic "ground cover characteristics" instead)
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128 | // handle cases with LAI < 1 (use generic "ground cover characteristics" instead)
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- | 129 | /* The LAI used here is derived from the "stockable" area (and not the stocked area).
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- | 130 | If the stand has gaps, the available trees are "thinned" across the whole area. Otherwise (when stocked area is used)
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- | 131 | the LAI would overestimate the transpiring canopy. However, the current solution overestimates e.g. the interception.
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- | 132 | If the "thinned out" LAI is below one, the rest (i.e. the gaps) are thought to be covered by ground vegetation.
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- | 133 | */
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129 | if (total_lai<1.) { |
134 | if (total_lai<1.) { |
130 | mCanopyConductance+=(ground_vegetationCC)*(1. - total_lai); |
135 | mCanopyConductance+=(ground_vegetationCC)*(1. - total_lai); |
131 | total_lai = 1.; |
136 | total_lai = 1.; |
132 | }
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137 | }
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133 | mCanopyConductance /= total_lai; |
138 | mCanopyConductance /= total_lai; |
134 | 139 | ||
135 | if (total_lai < Model::settings().laiThresholdForClosedStands) { |
140 | if (total_lai < Model::settings().laiThresholdForClosedStands) { |
136 | // following Landsberg and Waring: when LAI is < 3 (default for laiThresholdForClosedStands), a linear "ramp" from 0 to 3 is assumed
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141 | // following Landsberg and Waring: when LAI is < 3 (default for laiThresholdForClosedStands), a linear "ramp" from 0 to 3 is assumed
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137 | // http://iland.boku.ac.at/water+cycle#transpiration_and_canopy_conductance
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142 | // http://iland.boku.ac.at/water+cycle#transpiration_and_canopy_conductance
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138 | mCanopyConductance *= total_lai / Model::settings().laiThresholdForClosedStands; |
143 | mCanopyConductance *= total_lai / Model::settings().laiThresholdForClosedStands; |
139 | }
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144 | }
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140 | if (logLevelInfo()) qDebug() << "WaterCycle:getStandValues: LAI needle" << mLAINeedle << "LAI Broadl:"<< mLAIBroadleaved << "weighted avg. Conductance (m/2):" << mCanopyConductance; |
145 | if (logLevelInfo()) qDebug() << "WaterCycle:getStandValues: LAI needle" << mLAINeedle << "LAI Broadl:"<< mLAIBroadleaved << "weighted avg. Conductance (m/2):" << mCanopyConductance; |
141 | }
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146 | }
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142 | 147 | ||
143 | /// calculate responses for ground vegetation, i.e. for "unstocked" areas.
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148 | /// calculate responses for ground vegetation, i.e. for "unstocked" areas.
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144 | /// this duplicates calculations done in Species.
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149 | /// this duplicates calculations done in Species.
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145 | /// @return Minimum of vpd and soilwater response for default
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150 | /// @return Minimum of vpd and soilwater response for default
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146 | inline double WaterCycle::calculateBaseSoilAtmosphereResponse(const double psi_kpa, const double vpd_kpa) |
151 | inline double WaterCycle::calculateBaseSoilAtmosphereResponse(const double psi_kpa, const double vpd_kpa) |
147 | {
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152 | {
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148 | // constant parameters used for ground vegetation:
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153 | // constant parameters used for ground vegetation:
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149 | const double mPsiMin = 1.5; // MPa |
154 | const double mPsiMin = 1.5; // MPa |
150 | const double mRespVpdExponent = -0.6; |
155 | const double mRespVpdExponent = -0.6; |
151 | // see SpeciesResponse::soilAtmosphereResponses()
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156 | // see SpeciesResponse::soilAtmosphereResponses()
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152 | double water_resp; |
157 | double water_resp; |
153 | // see Species::soilwaterResponse:
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158 | // see Species::soilwaterResponse:
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154 | const double psi_mpa = psi_kpa / 1000.; // convert to MPa |
159 | const double psi_mpa = psi_kpa / 1000.; // convert to MPa |
155 | water_resp = limit( 1. - psi_mpa / mPsiMin, 0., 1.); |
160 | water_resp = limit( 1. - psi_mpa / mPsiMin, 0., 1.); |
156 | // see species::vpdResponse
|
161 | // see species::vpdResponse
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157 | 162 | ||
158 | double vpd_resp; |
163 | double vpd_resp; |
159 | vpd_resp = exp(mRespVpdExponent * vpd_kpa); |
164 | vpd_resp = exp(mRespVpdExponent * vpd_kpa); |
160 | return qMin(water_resp, vpd_resp); |
165 | return qMin(water_resp, vpd_resp); |
161 | }
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166 | }
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162 | 167 | ||
163 | /// calculate combined VPD and soilwaterresponse for all species
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168 | /// calculate combined VPD and soilwaterresponse for all species
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164 | /// on the RU. This is used for the calc. of the transpiration.
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169 | /// on the RU. This is used for the calc. of the transpiration.
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165 | inline double WaterCycle::calculateSoilAtmosphereResponse(const double psi_kpa, const double vpd_kpa) |
170 | inline double WaterCycle::calculateSoilAtmosphereResponse(const double psi_kpa, const double vpd_kpa) |
166 | {
|
171 | {
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167 | double min_response; |
172 | double min_response; |
168 | double total_response = 0; // LAI weighted minimum response for all speices on the RU |
173 | double total_response = 0; // LAI weighted minimum response for all speices on the RU |
169 | double total_lai_factor = 0.; |
174 | double total_lai_factor = 0.; |
170 | foreach(const ResourceUnitSpecies *rus, mRU->ruSpecies()) { |
175 | foreach(const ResourceUnitSpecies *rus, mRU->ruSpecies()) { |
171 | if (rus->LAIfactor()>0.) { |
176 | if (rus->LAIfactor()>0.) { |
172 | // retrieve the minimum of VPD / soil water response for that species
|
177 | // retrieve the minimum of VPD / soil water response for that species
|
173 | rus->speciesResponse()->soilAtmosphereResponses(psi_kpa, vpd_kpa, min_response); |
178 | rus->speciesResponse()->soilAtmosphereResponses(psi_kpa, vpd_kpa, min_response); |
174 | total_response += min_response * rus->LAIfactor(); |
179 | total_response += min_response * rus->LAIfactor(); |
175 | total_lai_factor += rus->LAIfactor(); |
180 | total_lai_factor += rus->LAIfactor(); |
176 | }
|
181 | }
|
177 | }
|
182 | }
|
178 | 183 | ||
179 | if (total_lai_factor<1.) { |
184 | if (total_lai_factor<1.) { |
180 | // the LAI is below 1: the rest is considered as "ground vegetation"
|
185 | // the LAI is below 1: the rest is considered as "ground vegetation"
|
181 | total_response += calculateBaseSoilAtmosphereResponse(psi_kpa, vpd_kpa) * (1. - total_lai_factor); |
186 | total_response += calculateBaseSoilAtmosphereResponse(psi_kpa, vpd_kpa) * (1. - total_lai_factor); |
182 | }
|
187 | }
|
183 | 188 | ||
184 | // add an aging factor to the total response (averageAging: leaf area weighted mean aging value):
|
189 | // add an aging factor to the total response (averageAging: leaf area weighted mean aging value):
|
185 | // conceptually: response = min(vpd_response, water_response)*aging
|
190 | // conceptually: response = min(vpd_response, water_response)*aging
|
186 | if (total_lai_factor==1.) |
191 | if (total_lai_factor==1.) |
187 | total_response *= mRU->averageAging(); // no ground cover: use aging value for all LA |
192 | total_response *= mRU->averageAging(); // no ground cover: use aging value for all LA |
188 | else if (total_lai_factor>0. && mRU->averageAging()>0.) |
193 | else if (total_lai_factor>0. && mRU->averageAging()>0.) |
189 | total_response *= (1.-total_lai_factor)*1. + (total_lai_factor * mRU->averageAging()); // between 0..1: a part of the LAI is "ground cover" (aging=1) |
194 | total_response *= (1.-total_lai_factor)*1. + (total_lai_factor * mRU->averageAging()); // between 0..1: a part of the LAI is "ground cover" (aging=1) |
190 | 195 | ||
191 | DBGMODE(
|
196 | DBGMODE(
|
192 | if (mRU->averageAging()>1. || mRU->averageAging()<0. || total_response<0 || total_response>1.) |
197 | if (mRU->averageAging()>1. || mRU->averageAging()<0. || total_response<0 || total_response>1.) |
193 | qDebug() << "water cycle: average aging invalid. aging:" << mRU->averageAging() << "total response" << total_response << "total lai factor:" << total_lai_factor; |
198 | qDebug() << "water cycle: average aging invalid. aging:" << mRU->averageAging() << "total response" << total_response << "total lai factor:" << total_lai_factor; |
194 | ); |
199 | ); |
195 | 200 | ||
196 | //DBG_IF(mRU->averageAging()>1. || mRU->averageAging()<0.,"water cycle", "average aging invalid!" );
|
201 | //DBG_IF(mRU->averageAging()>1. || mRU->averageAging()<0.,"water cycle", "average aging invalid!" );
|
197 | return total_response; |
202 | return total_response; |
198 | }
|
203 | }
|
199 | 204 | ||
200 | 205 | ||
201 | /// Main Water Cycle function. This function triggers all water related tasks for
|
206 | /// Main Water Cycle function. This function triggers all water related tasks for
|
202 | /// one simulation year.
|
207 | /// one simulation year.
|
203 | /// @sa http://iland.boku.ac.at/water+cycle
|
208 | /// @sa http://iland.boku.ac.at/water+cycle
|
204 | void WaterCycle::run() |
209 | void WaterCycle::run() |
205 | {
|
210 | {
|
206 | // necessary?
|
211 | // necessary?
|
207 | if (GlobalSettings::instance()->currentYear() == mLastYear) |
212 | if (GlobalSettings::instance()->currentYear() == mLastYear) |
208 | return; |
213 | return; |
209 | DebugTimer tw("water:run"); |
214 | DebugTimer tw("water:run"); |
210 | WaterCycleData add_data;
|
215 | WaterCycleData add_data;
|
211 | 216 | ||
212 | // preparations (once a year)
|
217 | // preparations (once a year)
|
213 | getStandValues(); // fetch canopy characteristics from iLand (including weighted average for mCanopyConductance) |
218 | getStandValues(); // fetch canopy characteristics from iLand (including weighted average for mCanopyConductance) |
214 | mCanopy.setStandParameters(mLAINeedle, |
219 | mCanopy.setStandParameters(mLAINeedle, |
215 | mLAIBroadleaved, |
220 | mLAIBroadleaved, |
216 | mCanopyConductance); |
221 | mCanopyConductance); |
217 | 222 | ||
218 | // main loop over all days of the year
|
223 | // main loop over all days of the year
|
219 | double prec_mm, prec_after_interception, prec_to_soil, et, excess; |
224 | double prec_mm, prec_after_interception, prec_to_soil, et, excess; |
220 | const Climate *climate = mRU->climate(); |
225 | const Climate *climate = mRU->climate(); |
221 | const ClimateDay *day = climate->begin(); |
226 | const ClimateDay *day = climate->begin(); |
222 | const ClimateDay *end = climate->end(); |
227 | const ClimateDay *end = climate->end(); |
223 | int doy=0; |
228 | int doy=0; |
224 | double total_excess = 0.; |
229 | double total_excess = 0.; |
225 | for (; day<end; ++day, ++doy) { |
230 | for (; day<end; ++day, ++doy) { |
226 | // (1) precipitation of the day
|
231 | // (1) precipitation of the day
|
227 | prec_mm = day->preciptitation; |
232 | prec_mm = day->preciptitation; |
228 | // (2) interception by the crown
|
233 | // (2) interception by the crown
|
229 | prec_after_interception = mCanopy.flow(prec_mm, day->temperature); |
234 | prec_after_interception = mCanopy.flow(prec_mm, day->temperature); |
230 | // (3) storage in the snow pack
|
235 | // (3) storage in the snow pack
|
231 | prec_to_soil = mSnowPack.flow(prec_after_interception, day->temperature); |
236 | prec_to_soil = mSnowPack.flow(prec_after_interception, day->temperature); |
232 | // save extra data (used by e.g. fire module)
|
237 | // save extra data (used by e.g. fire module)
|
233 | add_data.water_to_ground[doy] = prec_to_soil; |
238 | add_data.water_to_ground[doy] = prec_to_soil; |
234 | add_data.snow_cover[doy] = mSnowPack.snowPack(); |
239 | add_data.snow_cover[doy] = mSnowPack.snowPack(); |
235 | // (4) add rest to soil
|
240 | // (4) add rest to soil
|
236 | mContent += prec_to_soil; |
241 | mContent += prec_to_soil; |
237 | 242 | ||
238 | excess = 0.; |
243 | excess = 0.; |
239 | if (mContent>mFieldCapacity) { |
244 | if (mContent>mFieldCapacity) { |
240 | // excess water runoff
|
245 | // excess water runoff
|
241 | excess = mContent - mFieldCapacity; |
246 | excess = mContent - mFieldCapacity; |
242 | total_excess += excess; |
247 | total_excess += excess; |
243 | mContent = mFieldCapacity; |
248 | mContent = mFieldCapacity; |
244 | }
|
249 | }
|
245 | 250 | ||
246 | double current_psi = psiFromHeight(mContent); |
251 | double current_psi = psiFromHeight(mContent); |
247 | mPsi[doy] = current_psi; |
252 | mPsi[doy] = current_psi; |
248 | 253 | ||
249 | // (5) transpiration of the vegetation (and of water intercepted in canopy)
|
254 | // (5) transpiration of the vegetation (and of water intercepted in canopy)
|
250 | // calculate the LAI-weighted response values for soil water and vpd:
|
255 | // calculate the LAI-weighted response values for soil water and vpd:
|
251 | double interception_before_transpiration = mCanopy.interception(); |
256 | double interception_before_transpiration = mCanopy.interception(); |
252 | double combined_response = calculateSoilAtmosphereResponse( current_psi, day->vpd); |
257 | double combined_response = calculateSoilAtmosphereResponse( current_psi, day->vpd); |
253 | et = mCanopy.evapotranspiration3PG(day, climate->daylength_h(doy), combined_response); |
258 | et = mCanopy.evapotranspiration3PG(day, climate->daylength_h(doy), combined_response); |
254 | // if there is some flow from intercepted water to the ground -> add to "water_to_the_ground"
|
259 | // if there is some flow from intercepted water to the ground -> add to "water_to_the_ground"
|
255 | if (mCanopy.interception() < interception_before_transpiration) |
260 | if (mCanopy.interception() < interception_before_transpiration) |
256 | add_data.water_to_ground[doy]+= interception_before_transpiration - mCanopy.interception(); |
261 | add_data.water_to_ground[doy]+= interception_before_transpiration - mCanopy.interception(); |
257 | 262 | ||
258 | mContent -= et; // reduce content (transpiration) |
263 | mContent -= et; // reduce content (transpiration) |
259 | // add intercepted water (that is *not* evaporated) again to the soil (or add to snow if temp too low -> call to snowpack)
|
264 | // add intercepted water (that is *not* evaporated) again to the soil (or add to snow if temp too low -> call to snowpack)
|
260 | mContent += mSnowPack.add(mCanopy.interception(),day->temperature); |
265 | mContent += mSnowPack.add(mCanopy.interception(),day->temperature); |
261 | 266 | ||
262 | // do not remove water below the PWP (fixed value)
|
267 | // do not remove water below the PWP (fixed value)
|
263 | if (mContent<mPermanentWiltingPoint) { |
268 | if (mContent<mPermanentWiltingPoint) { |
264 | et -= mPermanentWiltingPoint - mContent; // reduce et (for bookkeeping) |
269 | et -= mPermanentWiltingPoint - mContent; // reduce et (for bookkeeping) |
265 | mContent = mPermanentWiltingPoint; |
270 | mContent = mPermanentWiltingPoint; |
266 | }
|
271 | }
|
267 | 272 | ||
268 | 273 | ||
269 | //DBGMODE(
|
274 | //DBGMODE(
|
270 | if (GlobalSettings::instance()->isDebugEnabled(GlobalSettings::dWaterCycle)) { |
275 | if (GlobalSettings::instance()->isDebugEnabled(GlobalSettings::dWaterCycle)) { |
271 | DebugList &out = GlobalSettings::instance()->debugList(day->id(), GlobalSettings::dWaterCycle); |
276 | DebugList &out = GlobalSettings::instance()->debugList(day->id(), GlobalSettings::dWaterCycle); |
272 | // climatic variables
|
277 | // climatic variables
|
273 | out << day->id() << mRU->index() << mRU->id() << day->temperature << day->vpd << day->preciptitation << day->radiation; |
278 | out << day->id() << mRU->index() << mRU->id() << day->temperature << day->vpd << day->preciptitation << day->radiation; |
274 | out << combined_response; // combined response of all species on RU (min(water, vpd)) |
279 | out << combined_response; // combined response of all species on RU (min(water, vpd)) |
275 | // fluxes
|
280 | // fluxes
|
276 | out << prec_after_interception << prec_to_soil << et << mCanopy.evaporationCanopy() |
281 | out << prec_after_interception << prec_to_soil << et << mCanopy.evaporationCanopy() |
277 | << mContent << mPsi[doy] << excess; |
282 | << mContent << mPsi[doy] << excess; |
278 | // other states
|
283 | // other states
|
279 | out << mSnowPack.snowPack(); |
284 | out << mSnowPack.snowPack(); |
280 | //special sanity check:
|
285 | //special sanity check:
|
281 | if (prec_to_soil>0. && mCanopy.interception()>0.) |
286 | if (prec_to_soil>0. && mCanopy.interception()>0.) |
282 | if (mSnowPack.snowPack()==0. && day->preciptitation==0) |
287 | if (mSnowPack.snowPack()==0. && day->preciptitation==0) |
283 | qDebug() << "watercontent increase without precipititaion"; |
288 | qDebug() << "watercontent increase without precipititaion"; |
284 | 289 | ||
285 | }
|
290 | }
|
286 | //); // DBGMODE()
|
291 | //); // DBGMODE()
|
287 | 292 | ||
288 | }
|
293 | }
|
289 | // call external modules
|
294 | // call external modules
|
290 | GlobalSettings::instance()->model()->modules()->calculateWater(mRU, &add_data); |
295 | GlobalSettings::instance()->model()->modules()->calculateWater(mRU, &add_data); |
291 | mLastYear = GlobalSettings::instance()->currentYear(); |
296 | mLastYear = GlobalSettings::instance()->currentYear(); |
292 | 297 | ||
293 | }
|
298 | }
|
294 | 299 | ||
295 | 300 | ||
296 | namespace Water { |
301 | namespace Water { |
297 | 302 | ||
298 | /** calculates the input/output of water that is stored in the snow pack.
|
303 | /** calculates the input/output of water that is stored in the snow pack.
|
299 | The approach is similar to Picus 1.3 and ForestBGC (Running, 1988).
|
304 | The approach is similar to Picus 1.3 and ForestBGC (Running, 1988).
|
300 | Returns the amount of water that exits the snowpack (precipitation, snow melt) */
|
305 | Returns the amount of water that exits the snowpack (precipitation, snow melt) */
|
301 | double SnowPack::flow(const double &preciptitation_mm, const double &temperature) |
306 | double SnowPack::flow(const double &preciptitation_mm, const double &temperature) |
302 | {
|
307 | {
|
303 | if (temperature>mSnowTemperature) { |
308 | if (temperature>mSnowTemperature) { |
304 | if (mSnowPack==0.) |
309 | if (mSnowPack==0.) |
305 | return preciptitation_mm; // no change |
310 | return preciptitation_mm; // no change |
306 | else { |
311 | else { |
307 | // snow melts
|
312 | // snow melts
|
308 | const double melting_coefficient = 0.7; // mm/°C |
313 | const double melting_coefficient = 0.7; // mm/°C |
309 | double melt = qMin( (temperature-mSnowTemperature) * melting_coefficient, mSnowPack); |
314 | double melt = qMin( (temperature-mSnowTemperature) * melting_coefficient, mSnowPack); |
310 | mSnowPack -=melt; |
315 | mSnowPack -=melt; |
311 | return preciptitation_mm + melt; |
316 | return preciptitation_mm + melt; |
312 | }
|
317 | }
|
313 | } else { |
318 | } else { |
314 | // snow:
|
319 | // snow:
|
315 | mSnowPack += preciptitation_mm; |
320 | mSnowPack += preciptitation_mm; |
316 | return 0.; // no output. |
321 | return 0.; // no output. |
317 | }
|
322 | }
|
318 | 323 | ||
319 | }
|
324 | }
|
320 | 325 | ||
321 | 326 | ||
322 | inline double SnowPack::add(const double &preciptitation_mm, const double &temperature) |
327 | inline double SnowPack::add(const double &preciptitation_mm, const double &temperature) |
323 | {
|
328 | {
|
324 | // do nothing for temps > 0°
|
329 | // do nothing for temps > 0°
|
325 | if (temperature>mSnowTemperature) |
330 | if (temperature>mSnowTemperature) |
326 | return preciptitation_mm; |
331 | return preciptitation_mm; |
327 | 332 | ||
328 | // temps < 0°: add to snow
|
333 | // temps < 0°: add to snow
|
329 | mSnowPack += preciptitation_mm; |
334 | mSnowPack += preciptitation_mm; |
330 | return 0.; |
335 | return 0.; |
331 | }
|
336 | }
|
332 | 337 | ||
333 | /** Interception in crown canopy.
|
338 | /** Interception in crown canopy.
|
334 | Calculates the amount of preciptitation that does not reach the ground and
|
339 | Calculates the amount of preciptitation that does not reach the ground and
|
335 | is stored in the canopy. The approach is adopted from Picus 1.3.
|
340 | is stored in the canopy. The approach is adopted from Picus 1.3.
|
336 | Returns the amount of precipitation (mm) that surpasses the canopy layer.
|
341 | Returns the amount of precipitation (mm) that surpasses the canopy layer.
|
337 | @sa http://iland.boku.ac.at/water+cycle#precipitation_and_interception */
|
342 | @sa http://iland.boku.ac.at/water+cycle#precipitation_and_interception */
|
338 | double Canopy::flow(const double &preciptitation_mm, const double &temperature) |
343 | double Canopy::flow(const double &preciptitation_mm, const double &temperature) |
339 | {
|
344 | {
|
340 | // sanity checks
|
345 | // sanity checks
|
341 | mInterception = 0.; |
346 | mInterception = 0.; |
342 | mEvaporation = 0.; |
347 | mEvaporation = 0.; |
343 | if (!mLAI) |
348 | if (!mLAI) |
344 | return preciptitation_mm; |
349 | return preciptitation_mm; |
345 | if (!preciptitation_mm) |
350 | if (!preciptitation_mm) |
346 | return 0.; |
351 | return 0.; |
347 | double max_interception_mm=0.; // maximum interception based on the current foliage |
352 | double max_interception_mm=0.; // maximum interception based on the current foliage |
348 | double max_storage_mm=0.; // maximum storage in canopy |
353 | double max_storage_mm=0.; // maximum storage in canopy |
349 | 354 | ||
350 | if (mLAINeedle>0.) { |
355 | if (mLAINeedle>0.) { |
351 | // (1) calculate maximum fraction of thru-flow the crown (based on precipitation)
|
356 | // (1) calculate maximum fraction of thru-flow the crown (based on precipitation)
|
352 | double max_flow_needle = 0.9 * sqrt(1.03 - exp(-0.055*preciptitation_mm)); |
357 | double max_flow_needle = 0.9 * sqrt(1.03 - exp(-0.055*preciptitation_mm)); |
353 | max_interception_mm += preciptitation_mm * (1. - max_flow_needle * mLAINeedle/mLAI); |
358 | max_interception_mm += preciptitation_mm * (1. - max_flow_needle * mLAINeedle/mLAI); |
354 | // (2) calculate maximum storage potential based on the current LAI
|
359 | // (2) calculate maximum storage potential based on the current LAI
|
355 | double max_storage_needle = mNeedleFactor * (1. - exp(-0.55*mLAINeedle) ); |
360 | double max_storage_needle = mNeedleFactor * (1. - exp(-0.55*mLAINeedle) ); |
356 | max_storage_mm += max_storage_needle; |
361 | max_storage_mm += max_storage_needle; |
357 | }
|
362 | }
|
358 | 363 | ||
359 | if (mLAIBroadleaved>0.) { |
364 | if (mLAIBroadleaved>0.) { |
360 | // (1) calculate maximum fraction of thru-flow the crown (based on precipitation)
|
365 | // (1) calculate maximum fraction of thru-flow the crown (based on precipitation)
|
361 | double max_flow_broad = 0.9 * pow(1.22 - exp(-0.055*preciptitation_mm), 0.35); |
366 | double max_flow_broad = 0.9 * pow(1.22 - exp(-0.055*preciptitation_mm), 0.35); |
362 | max_interception_mm += preciptitation_mm * (1. - max_flow_broad * mLAIBroadleaved/mLAI); |
367 | max_interception_mm += preciptitation_mm * (1. - max_flow_broad * mLAIBroadleaved/mLAI); |
363 | // (2) calculate maximum storage potential based on the current LAI
|
368 | // (2) calculate maximum storage potential based on the current LAI
|
364 | double max_storage_broad = mDecidousFactor * (1. - exp(-0.5*mLAIBroadleaved) ); |
369 | double max_storage_broad = mDecidousFactor * (1. - exp(-0.5*mLAIBroadleaved) ); |
365 | max_storage_mm += max_storage_broad; |
370 | max_storage_mm += max_storage_broad; |
366 | }
|
371 | }
|
367 | 372 | ||
368 | // (3) calculate actual interception and store for evaporation calculation
|
373 | // (3) calculate actual interception and store for evaporation calculation
|
369 | mInterception = qMin( max_storage_mm, max_interception_mm ); |
374 | mInterception = qMin( max_storage_mm, max_interception_mm ); |
370 | 375 | ||
371 | // (4) limit interception with amount of precipitation
|
376 | // (4) limit interception with amount of precipitation
|
372 | mInterception = qMin( mInterception, preciptitation_mm); |
377 | mInterception = qMin( mInterception, preciptitation_mm); |
373 | 378 | ||
374 | // (5) reduce preciptitaion by the amount that is intercepted by the canopy
|
379 | // (5) reduce preciptitaion by the amount that is intercepted by the canopy
|
375 | return preciptitation_mm - mInterception; |
380 | return preciptitation_mm - mInterception; |
376 | 381 | ||
377 | }
|
382 | }
|
378 | 383 | ||
379 | /// sets up the canopy. fetch some global parameter values...
|
384 | /// sets up the canopy. fetch some global parameter values...
|
380 | void Canopy::setup() |
385 | void Canopy::setup() |
381 | {
|
386 | {
|
382 | mAirDensity = Model::settings().airDensity; // kg / m3 |
387 | mAirDensity = Model::settings().airDensity; // kg / m3 |
383 | }
|
388 | }
|
384 | 389 | ||
385 | void Canopy::setStandParameters(const double LAIneedle, const double LAIbroadleave, const double maxCanopyConductance) |
390 | void Canopy::setStandParameters(const double LAIneedle, const double LAIbroadleave, const double maxCanopyConductance) |
386 | {
|
391 | {
|
387 | mLAINeedle = LAIneedle; |
392 | mLAINeedle = LAIneedle; |
388 | mLAIBroadleaved=LAIbroadleave; |
393 | mLAIBroadleaved=LAIbroadleave; |
389 | mLAI=LAIneedle+LAIbroadleave; |
394 | mLAI=LAIneedle+LAIbroadleave; |
390 | mAvgMaxCanopyConductance = maxCanopyConductance; |
395 | mAvgMaxCanopyConductance = maxCanopyConductance; |
391 | 396 | ||
392 | // clear aggregation containers
|
397 | // clear aggregation containers
|
393 | for (int i=0;i<12;++i) mET0[i]=0.; |
398 | for (int i=0;i<12;++i) mET0[i]=0.; |
394 | 399 | ||
395 | }
|
400 | }
|
396 | 401 | ||
397 | 402 | ||
398 | 403 | ||
399 | /** calculate the daily evaporation/transpiration using the Penman-Monteith-Equation.
|
404 | /** calculate the daily evaporation/transpiration using the Penman-Monteith-Equation.
|
400 | This version is based on 3PG. See the Visual Basic Code in 3PGjs.xls.
|
405 | This version is based on 3PG. See the Visual Basic Code in 3PGjs.xls.
|
401 | Returns the total sum of evaporation+transpiration in mm of the day. */
|
406 | Returns the total sum of evaporation+transpiration in mm of the day. */
|
402 | double Canopy::evapotranspiration3PG(const ClimateDay *climate, const double daylength_h, const double combined_response) |
407 | double Canopy::evapotranspiration3PG(const ClimateDay *climate, const double daylength_h, const double combined_response) |
403 | {
|
408 | {
|
404 | double vpd_mbar = climate->vpd * 10.; // convert from kPa to mbar |
409 | double vpd_mbar = climate->vpd * 10.; // convert from kPa to mbar |
405 | double temperature = climate->temperature; // average temperature of the day (°C) |
410 | double temperature = climate->temperature; // average temperature of the day (°C) |
406 | double daylength = daylength_h * 3600.; // daylength in seconds (convert from length in hours) |
411 | double daylength = daylength_h * 3600.; // daylength in seconds (convert from length in hours) |
407 | double rad = climate->radiation / daylength * 1000000; //convert from MJ/m2 (day sum) to average radiation flow W/m2 [MJ=MWs -> /s * 1,000,000 |
412 | double rad = climate->radiation / daylength * 1000000; //convert from MJ/m2 (day sum) to average radiation flow W/m2 [MJ=MWs -> /s * 1,000,000 |
408 | 413 | ||
409 | // the radiation: based on linear empirical function
|
414 | // the radiation: based on linear empirical function
|
410 | const double qa = -90.; |
415 | const double qa = -90.; |
411 | const double qb = 0.8; |
416 | const double qb = 0.8; |
412 | double net_rad = qa + qb*rad; |
417 | double net_rad = qa + qb*rad; |
413 | 418 | ||
414 | //: Landsberg original: const double e20 = 2.2; //rate of change of saturated VP with T at 20C
|
419 | //: Landsberg original: const double e20 = 2.2; //rate of change of saturated VP with T at 20C
|
415 | const double VPDconv = 0.000622; //convert VPD to saturation deficit = 18/29/1000 |
420 | const double VPDconv = 0.000622; //convert VPD to saturation deficit = 18/29/1000 |
416 | const double latent_heat = 2460000.; // Latent heat of vaporization. Energy required per unit mass of water vaporized [J kg-1] |
421 | const double latent_heat = 2460000.; // Latent heat of vaporization. Energy required per unit mass of water vaporized [J kg-1] |
417 | 422 | ||
418 | double gBL = Model::settings().boundaryLayerConductance; // boundary layer conductance |
423 | double gBL = Model::settings().boundaryLayerConductance; // boundary layer conductance |
419 | 424 | ||
420 | // canopy conductance.
|
425 | // canopy conductance.
|
421 | // The species traits are weighted by LAI on the RU.
|
426 | // The species traits are weighted by LAI on the RU.
|
422 | // maximum canopy conductance: see getStandValues()
|
427 | // maximum canopy conductance: see getStandValues()
|
423 | // current response: see calculateSoilAtmosphereResponse(). This is basically a weighted average of min(water_response, vpd_response) for each species
|
428 | // current response: see calculateSoilAtmosphereResponse(). This is basically a weighted average of min(water_response, vpd_response) for each species
|
424 | double gC = mAvgMaxCanopyConductance * combined_response; |
429 | double gC = mAvgMaxCanopyConductance * combined_response; |
425 | 430 | ||
426 | 431 | ||
427 | double defTerm = mAirDensity * latent_heat * (vpd_mbar * VPDconv) * gBL; |
432 | double defTerm = mAirDensity * latent_heat * (vpd_mbar * VPDconv) * gBL; |
428 | 433 | ||
429 | // with temperature-dependent slope of vapor pressure saturation curve
|
434 | // with temperature-dependent slope of vapor pressure saturation curve
|
430 | // (following Allen et al. (1998), http://www.fao.org/docrep/x0490e/x0490e07.htm#atmospheric%20parameters)
|
435 | // (following Allen et al. (1998), http://www.fao.org/docrep/x0490e/x0490e07.htm#atmospheric%20parameters)
|
431 | // svp_slope in mbar.
|
436 | // svp_slope in mbar.
|
432 | //double svp_slope = 4098. * (6.1078 * exp(17.269 * temperature / (temperature + 237.3))) / ((237.3+temperature)*(237.3+temperature));
|
437 | //double svp_slope = 4098. * (6.1078 * exp(17.269 * temperature / (temperature + 237.3))) / ((237.3+temperature)*(237.3+temperature));
|
433 | 438 | ||
434 | // alternatively: very simple variant (following here the original 3PG code). This
|
439 | // alternatively: very simple variant (following here the original 3PG code). This
|
435 | // keeps yields +- same results for summer, but slightly lower values in winter (2011/03/16)
|
440 | // keeps yields +- same results for summer, but slightly lower values in winter (2011/03/16)
|
436 | double svp_slope = 2.2; |
441 | double svp_slope = 2.2; |
437 | 442 | ||
438 | double div = (1. + svp_slope + gBL / gC); |
443 | double div = (1. + svp_slope + gBL / gC); |
439 | double Etransp = (svp_slope * net_rad + defTerm) / div; |
444 | double Etransp = (svp_slope * net_rad + defTerm) / div; |
440 | double canopy_transpiration = Etransp / latent_heat * daylength; |
445 | double canopy_transpiration = Etransp / latent_heat * daylength; |
441 | 446 | ||
442 | // calculate reference evapotranspiration
|
447 | // calculate reference evapotranspiration
|
443 | // see Adair et al 2008
|
448 | // see Adair et al 2008
|
444 | const double psychrometric_const = 0.0672718682328237; // kPa/degC |
449 | const double psychrometric_const = 0.0672718682328237; // kPa/degC |
445 | const double windspeed = 2.; // m/s |
450 | const double windspeed = 2.; // m/s |
446 | double net_rad_mj_day = net_rad*daylength/1000000.; // convert W/m2 again to MJ/m2*day |
451 | double net_rad_mj_day = net_rad*daylength/1000000.; // convert W/m2 again to MJ/m2*day |
447 | double et0_day = 0.408*svp_slope*net_rad_mj_day + psychrometric_const*900./(temperature+273.)*windspeed*climate->vpd; |
452 | double et0_day = 0.408*svp_slope*net_rad_mj_day + psychrometric_const*900./(temperature+273.)*windspeed*climate->vpd; |
448 | double et0_div = svp_slope+psychrometric_const*(1.+0.34*windspeed); |
453 | double et0_div = svp_slope+psychrometric_const*(1.+0.34*windspeed); |
449 | et0_day = et0_day / et0_div; |
454 | et0_day = et0_day / et0_div; |
450 | mET0[climate->month-1] += et0_day; |
455 | mET0[climate->month-1] += et0_day; |
451 | 456 | ||
452 | if (mInterception>0.) { |
457 | if (mInterception>0.) { |
453 | // we assume that for evaporation from leaf surface gBL/gC -> 0
|
458 | // we assume that for evaporation from leaf surface gBL/gC -> 0
|
454 | double div_evap = 1. + svp_slope; |
459 | double div_evap = 1. + svp_slope; |
455 | double evap_canopy_potential = (svp_slope*net_rad + defTerm) / div_evap / latent_heat * daylength; |
460 | double evap_canopy_potential = (svp_slope*net_rad + defTerm) / div_evap / latent_heat * daylength; |
456 | // reduce the amount of transpiration on a wet day based on the approach of
|
461 | // reduce the amount of transpiration on a wet day based on the approach of
|
457 | // Wigmosta et al (1994). see http://iland.boku.ac.at/water+cycle#transpiration_and_canopy_conductance
|
462 | // Wigmosta et al (1994). see http://iland.boku.ac.at/water+cycle#transpiration_and_canopy_conductance
|
458 | 463 | ||
459 | double ratio_T_E = canopy_transpiration / evap_canopy_potential; |
464 | double ratio_T_E = canopy_transpiration / evap_canopy_potential; |
460 | double evap_canopy = qMin(evap_canopy_potential, mInterception); |
465 | double evap_canopy = qMin(evap_canopy_potential, mInterception); |
461 | 466 | ||
462 | // for interception -> 0, the canopy transpiration is unchanged
|
467 | // for interception -> 0, the canopy transpiration is unchanged
|
463 | canopy_transpiration = (evap_canopy_potential - evap_canopy) * ratio_T_E; |
468 | canopy_transpiration = (evap_canopy_potential - evap_canopy) * ratio_T_E; |
464 | 469 | ||
465 | mInterception -= evap_canopy; // reduce interception |
470 | mInterception -= evap_canopy; // reduce interception |
466 | mEvaporation = evap_canopy; // evaporation from intercepted water |
471 | mEvaporation = evap_canopy; // evaporation from intercepted water |
467 | 472 | ||
468 | }
|
473 | }
|
469 | return canopy_transpiration; |
474 | return canopy_transpiration; |
470 | }
|
475 | }
|
471 | 476 | ||
472 | } // end namespace |
477 | } // end namespace |
473 | 478 |