diff --git a/doc/source/tech_note/Glacier/CLM50_Tech_Note_Glacier.rst b/doc/source/tech_note/Glacier/CLM50_Tech_Note_Glacier.rst index 4c15ebbf56..81c017276e 100644 --- a/doc/source/tech_note/Glacier/CLM50_Tech_Note_Glacier.rst +++ b/doc/source/tech_note/Glacier/CLM50_Tech_Note_Glacier.rst @@ -113,7 +113,7 @@ The default behaviors for the world's glacier and ice sheet regions are describe Multiple elevation class scheme ------------------------------- -The glacier land unit contains multiple columns based on surface elevation. These are known as elevation classes, and the land unit is referred to as *glacier\_mec*. (As described in section :numref:`Glacier regions`, some regions have only a single elevation class, but they are still referred to as *glacier\_mec* land units.) The default is to have 10 elevation classes whose lower limits are 0, 200, 400, 700, 1000, 1300, 1600, 2000, 2500, and 3000 m. Each column is characterized by a fractional area and surface elevation that are read in during model initialization, and then possibly overridden by CISM as the run progresses. Each *glacier\_mec* column within a grid cell has distinct ice and snow temperatures, snow water content, surface fluxes, and SMB. +The glacier land unit contains multiple columns based on surface elevation. These are known as elevation classes, and the land unit is referred to as *glacier\_mec*. (As described in section :numref:`Glacier regions`, some regions have only a single elevation class, but they are still referred to as *glacier\_mec* land units.) The default is to have 10 elevation classes whose lower limits are 0, 200, 400, 700, 1000, 1300, 1600, 2000, 2500, and 3000 m. Each column is characterized by a fractional area and surface elevation that are read in during model initialization, and then possibly overridden by CISM as the run progresses. Each *glacier\_mec* column within a grid cell has distinct ice and snow temperatures, snow water content, surface fluxes, and SMB. In CLM6 users can optionally specify using :ref:`Sturm et al. (1997)` or :ref:`Jordan (1991)` parameterizations for snow thermal conductivity over glacier land units (see Chapter :numref:`rst_Soil and Snow Temperatures`), with Sturm (1997) set as the default. The atmospheric surface temperature, potential temperature, specific humidity, density, and pressure are downscaled from the atmosphere's mean grid cell elevation to the *glacier\_mec* column elevation using a specified lapse rate (typically 6.0 deg/km) and an assumption of uniform relative humidity. Longwave radiation is downscaled by assuming a linear decrease in downwelling longwave radiation with increasing elevation (0.032 W m\ :sup:`-2` m\ :sup:`-1`, limited to 0.5 - 1.5 times the gridcell mean value, then normalized to conserve gridcell total energy) :ref:`(Van Tricht et al., 2016)`. Total precipitation is partitioned into rain vs. snow as described in Chapter :numref:`rst_Surface Characterization, Vertical Discretization, and Model Input Requirements`. The partitioning of precipitation is based on the downscaled temperature, allowing rain to fall at lower elevations while snow falls at higher elevations. diff --git a/doc/source/tech_note/Lake/CLM50_Tech_Note_Lake.rst b/doc/source/tech_note/Lake/CLM50_Tech_Note_Lake.rst index 88cb77d737..acc3f0dc1c 100644 --- a/doc/source/tech_note/Lake/CLM50_Tech_Note_Lake.rst +++ b/doc/source/tech_note/Lake/CLM50_Tech_Note_Lake.rst @@ -485,7 +485,7 @@ The overall thermal conductivity :math:`\tau _{i}` for layer *i* with ice mass-f \tau _{i} =\frac{\tau _{ice,eff} \tau _{liq,i} }{\tau _{liq,i} I_{i} +\tau _{ice} \left(1-I_{i} \right)} . -The thermal conductivity of snow, soil, and bedrock layers above and below the lake, respectively, are computed identically to those for vegetated land units (Chapter :numref:`rst_Soil and Snow Temperatures`), except for the adjustment of thermal conductivity for frost heave or excess ice (:ref:`Subin et al., 2012a, Supporting Information`). +The thermal conductivity of snow, soil, and bedrock layers above and below the lake, respectively, are computed identically to those for vegetated land units (Chapter :numref:`rst_Soil and Snow Temperatures`), except for the adjustment of thermal conductivity for frost heave or excess ice (:ref:`Subin et al., 2012a, Supporting Information`). In CLM6 users can optionally specify using :ref:`Sturm et al. (1997)` or :ref:`Jordan (1991)` parameterizations for snow thermal conductivity over lakes (see Chapter :numref:`rst_Soil and Snow Temperatures`), with :ref:`Sturm et al. (1997)` set as the default. .. _Radiation Penetration: diff --git a/doc/source/tech_note/References/CLM50_Tech_Note_References.rst b/doc/source/tech_note/References/CLM50_Tech_Note_References.rst index 58ab424a81..879677c9c2 100644 --- a/doc/source/tech_note/References/CLM50_Tech_Note_References.rst +++ b/doc/source/tech_note/References/CLM50_Tech_Note_References.rst @@ -279,6 +279,10 @@ Dai, Y., Dickinson, R.E., and Wang, Y.-P. 2004. A two-big-leaf model for canopy Dai, A., and Trenberth, K.E. 2002. Estimates of freshwater discharge from continents: Latitudinal and seasonal variations. J. Hydrometeor. 3:660-687. +.. _Damseauxetal2025: + +Damseaux, A., Matthes, H., Dutch, V.R., Wake, L., and Rutter, N. 2025. Impact of snow thermal conductivity schemes on pan-Arctic permafrost dynamics in the Community Land Model version 5.0, The Cryosphere, 19, 1539–1558, DOI:10.5194/tc-19-1539-2025. + .. _Darmenovaetal2009: Darmenova, K., Sokolik, I.N., Shao, Y., Marticorena, B. and Bergametti, G., 2009. Development of a physically based dust emission module within the Weather Research and Forecasting (WRF) model: Assessment of dust emission parameterizations and input parameters for source regions in Central and East Asia. Journal of Geophysical Research: Atmospheres, 114(D14). DOI:10.1029/2008JD011236. @@ -339,6 +343,10 @@ Drewniak, B., Song, J., Prell, J., Kotamarthi, V.R., and Jacob, R. 2013. Modelin Dunfield, P., Knowles, R., Dumont, R. and Moore, T.R., 1993. Methane Production and Consumption in Temperate and Sub-Arctic Peat Soils - Response to Temperature and Ph. Soil Biology & Biochemistry 25:321-326. +.. _Dutchetal2022: + +Dutch, V.R., Rutter, N., Wake, L., Sandells, M., Derksen, C., Walker, B., Hould Gosselin, G., Sonnentag, O., Essery, R., Kelly, R., Marsh, P., King, J., Boike, J. 2022. Impact of measured and simulated tundra snowpack properties on heat transfer, The Cryosphere, 16, 4201–4222, doi:10.5194/tc-16-4201-2022. + .. _EntekhabiEagleson1989: Entekhabi, D., and Eagleson, P.S. 1989. Land surface hydrology parameterization for atmospheric general circulation models including subgrid scale spatial variability. J. Climate 2:816-831. @@ -1404,6 +1412,10 @@ Strahler, A.H., Muchoney, D., Borak, J., Friedl, M., Gopal, S., Lambin, E., and Stull, R.B. 1988. An Introduction to Boundary Layer Meteorology. Kluwer Academic Publishers, Dordrecht. +.. _Sturmetal1997: + +Sturm, M., Holmgren, J., Konig, M., and Morris, K. 1997. The thermal conductivity of seasonal snow. Journal of Glaciology 43:26-41. + .. _Subinetal2012a: Subin, Z.M., Riley, W.J. and Mironov, D. 2012a. Improved lake model for climate simulations, J. Adv. Model. Earth Syst., 4, M02001. DOI:10.1029/2011MS000072. diff --git a/doc/source/tech_note/Soil_Snow_Temperatures/CLM50_Tech_Note_Soil_Snow_Temperatures.rst b/doc/source/tech_note/Soil_Snow_Temperatures/CLM50_Tech_Note_Soil_Snow_Temperatures.rst index f5a2965f69..f98446795a 100644 --- a/doc/source/tech_note/Soil_Snow_Temperatures/CLM50_Tech_Note_Soil_Snow_Temperatures.rst +++ b/doc/source/tech_note/Soil_Snow_Temperatures/CLM50_Tech_Note_Soil_Snow_Temperatures.rst @@ -723,38 +723,55 @@ where S_{r,\, i} =\left(\frac{w_{liq,\, i} }{\rho _{liq} \Delta z_{i} } +\frac{w_{ice,\, i} }{\rho _{ice} \Delta z_{i} } \right)\frac{1}{\theta _{sat,\, i} } =\frac{\theta _{liq,\, i} +\theta _{ice,\, i} }{\theta _{sat,\, i} } \le 1. -Thermal conductivity :math:`\lambda _{i}` (W m\ :sup:`-1` K\ :sup:`-1`) for snow is from :ref:`Jordan (1991) ` + +Thermal conductivity :math:`\lambda _{i}` (W m\ :sup:`-1` K\ :sup:`-1`) for snow in CLM6.0 is modified from :ref:`Sturm et al. (1997)`, as applied by :ref:`Dutch et al. (2022)` and :ref:`Damseaux et al. (2025)`. The Sturm function uses the bulk density of snow to determine the thermal conductivity of snow layer (:math:`_{i}`) as: .. math:: :label: 6.87 - \lambda _{i} =\lambda _{air} +\left(7.75\times 10^{-5} \rho _{sno,\, i} +1.105\times 10^{-6} \rho _{sno,\, i}^{2} \right)\left(\lambda _{ice} -\lambda _{air} \right) + \lambda _{i} = \left\{ + \begin{array}{lr} + 0.023 + 0.234(\rho _{sno,\, i} /1000) &\qquad \rho _{sno,\, i} <= 156 \\ + 0.138 - 1.01(\rho _{sno,\, i} /1000) + 3.233(\rho _{sno,\, i} /1000)^2 &\qquad \rho _{sno,\, i} > 156 + \end{array}\right\} -where :math:`\lambda _{air}` is the thermal conductivity of air (:numref:`Table Physical Constants`) and :math:`\rho _{sno,\, i}` is the bulk density of snow (kg m\ :sup:`-3`) + +with the bulk density of snow :math:`\rho _{sno,\, i}` (kg m\ :sup:`-3`) calculated as the mass of ice and liquid water per unit volume of snow layer .. math:: :label: 6.88 \rho _{sno,\, i} =\frac{w_{ice,\, i} +w_{liq,\, i} }{\Delta z_{i} } . + +Previous versions of CLM used the :ref:`Jordan (1991) ` parameterization for snow thermal conductivity, which uses the thermal conductivity of air and the bulk density of snow as: + +.. math:: + :label: 6.89 + + \lambda _{i} =\lambda _{air} +\left(7.75\times 10^{-5} \rho _{sno,\, i} +1.105\times 10^{-6} \rho _{sno,\, i}^{2} \right)\left(\lambda _{ice} -\lambda _{air} \right) + +where :math:`\lambda _{air}` is the thermal conductivity of air (:numref:`Table Physical Constants`) and :math:`\rho _{sno,\, i}` calculated, as in :eq:`6.88`. + +The Sturm (1997) parameterization is used in CLM6 over vegetated, glacier, and lake land units, but users can choose to use the Jordan (1991) parameterization over any of these land units. This can be accomplished through a change to the lnd_in namelist by using user_nl_clm. The volumetric heat capacity :math:`c_{i}` (J m\ :sup:`-3` K\ :sup:`-1`) for soil is from :ref:`de Vries (1963) ` and depends on the heat capacities of the soil solid, liquid water, and ice constituents .. math:: - :label: 6.89 + :label: 6.90 c_{i} =c_{s,\, i} \left(1-\theta _{sat,\, i} \right)+\frac{w_{ice,\, i} }{\Delta z_{i} } C_{ice} +\frac{w_{liq,\, i} }{\Delta z_{i} } C_{liq} where :math:`C_{liq}` and :math:`C_{ice}` are the specific heat capacities (J kg\ :sup:`-1` K\ :sup:`-1`) of liquid water and ice, respectively (:numref:`Table Physical Constants`). The heat capacity of soil solids :math:`c_{s,i}` \ (J m\ :sup:`-3` K\ :sup:`-1`) is .. math:: - :label: 6.90 + :label: 6.91 c_{s,i} =(1-f_{om,i} )c_{s,\min ,i} +f_{om,i} c_{s,om} where the heat capacity of mineral soil solids :math:`c_{s,\min,\, i}` (J m\ :sup:`-3` K\ :sup:`-1`) is .. math:: - :label: 6.91 + :label: 6.92 \begin{array}{lr} c_{s,\min ,\, i} =\left(\frac{2.128{\rm \; }\left(\% sand\right)_{i} +{\rm 2.385\; }\left(\% clay\right)_{i} }{\left(\% sand\right)_{i} +\left(\% clay\right)_{i} } \right)\times 10^{6} &\qquad i=1,\ldots ,N_{levsoi} \\ @@ -764,14 +781,14 @@ where the heat capacity of mineral soil solids :math:`c_{s,\min,\, i}` (J m\ :su where :math:`c_{s,bedrock} =2\times 10^{6}` J m\ :sup:`-3` K\ :sup:`-1` is the heat capacity of bedrock and :math:`c_{s,om} =2.5\times 10^{6}` \ J m\ :sup:`-3` K\ :sup:`-1` (:ref:`Farouki 1981 `) is the heat capacity of organic matter. For glaciers and snow .. math:: - :label: 6.92 + :label: 6.93 c_{i} =\frac{w_{ice,\, i} }{\Delta z_{i} } C_{ice} +\frac{w_{liq,\, i} }{\Delta z_{i} } C_{liq} . For the special case when snow is present (:math:`W_{sno} >0`) but there are no explicit snow layers (:math:`snl=0`), the heat capacity of the top layer is a blend of ice and soil heat capacity .. math:: - :label: 6.93 + :label: 6.94 c_{1} =c_{1}^{*} +\frac{C_{ice} W_{sno} }{\Delta z_{1} } @@ -785,14 +802,14 @@ Excess Ground Ice An optional parameterization of excess ground ice melt and respective subsidence based on (:ref:`Lee et al., (2014) `). Initial excess ground ice concentrations for soil columns are derived from (:ref:`Brown et al., (1997) `). When the excess ground ice is present in the soil column, soil depth for a given layer (:math:`z_{i}`) is adjusted by the amount of excess ice in the column: .. math:: - :label: 6.94 + :label: 6.95 z_{i}^{'}=\Sigma_{j=1}^{i} \ z_{j}^{'}+\frac{w_{exice,\, j}}{\rho_{ice} } where :math:`w_{exice,\,j}` is excess ground ice amount (kg m :sup:`-2`) in layer :math:`j` and :math:`\rho_{ice}` is the density of ice (kg m :sup:`-3`). After adjustment of layer depths have been made, all of the soil temperature equations (from :eq:`6.80` to :eq:`6.89`) are calculted based on the adjusted depths. Thermal properties are additionally adjusted (:eq:`6.8` and :eq:`6.8`) in the following way: .. math:: - :label: 6.95 + :label: 6.96 \begin{array}{lr} \theta_{sat}^{'} =\frac{\theta _{liq} }{\theta _{liq} +\theta _{ice} +\theta_{exice}}{\theta_{sat}} \\ @@ -803,7 +820,7 @@ where :math:`w_{exice,\,j}` is excess ground ice amount (kg m :sup:`-2`) in laye Soil subsidence at the timestep :math:`n+1` (:math:`z_{exice}^{n+1}`, m) is then calculated as: .. math:: - :label: 6.96 + :label: 6.97 z_{exice}^{n+1}=\Sigma_{i=1}^{N_{levgrnd}} \ z_{j}^{',\ ,n+1}-z_{j}^{',\ ,n }