### 2.8.7.2. Subdivision[¶](#subdivision "Permalink to this headline")

The snow layers are subdivided when the layer thickness exceeds the prescribed maximum thickness \\(\\Delta z\_{\\max }\\) with lower and upper bounds that depend on the number of snow layers ([Table 2.8.2](#table-snow-layer-thickness)). For example, if there is only one layer, then the maximum thickness of that layer is 0.03 m, however, if there is more than one layer, then the maximum thickness of the top layer is 0.02 m. Layers are checked sequentially from top to bottom for this limit. If there is only one snow layer and its thickness is greater than 0.03 m ([Table 2.8.2](#table-snow-layer-thickness)), the layer is subdivided into two layers of equal thickness, liquid water and ice contents, and temperature. If there is an existing layer below the layer to be subdivided, the thickness \\(\\Delta z\_{i}\\), liquid water and ice contents, \\(w\_{liq,\\; i}\\) and \\(w\_{ice,\\; i}\\), and temperature \\(T\_{i}\\) of the excess snow are combined with the underlying layer according to equations -. If there is no underlying layer after adjusting the layer for the excess snow, the layer is subdivided into two layers of equal thickness, liquid water and ice contents. The vertical snow temperature profile is maintained by calculating the slope between the layer above the splitting layer (\\(T\_{1}\\) ) and the splitting layer (\\(T\_{2}\\) ) and constraining the new temperatures (\\(T\_{2}^{n+1}\\), \\(T\_{3}^{n+1}\\) ) to lie along this slope. The temperature of the lower layer is first evaluated from

(2.8.55)[¶](#equation-8-62 "Permalink to this equation")\\\[T'\_{3} =T\_{2}^{n} -\\left(\\frac{T\_{1}^{n} -T\_{2}^{n} }{{\\left(\\Delta z\_{1}^{n} +\\Delta z\_{2}^{n} \\right)\\mathord{\\left/ {\\vphantom {\\left(\\Delta z\_{1}^{n} +\\Delta z\_{2}^{n} \\right) 2}} \\right.} 2} } \\right)\\left(\\frac{\\Delta z\_{2}^{n+1} }{2} \\right),\\\]

then adjusted as,

(2.8.56)[¶](#equation-8-63 "Permalink to this equation")\\\[\\begin{split}\\begin{array}{lr} T\_{3}^{n+1} = T\_{2}^{n} & \\qquad T'\_{3} \\ge T\_{f} \\\\ T\_{2}^{n+1} = T\_{2}^{n} +\\left(\\frac{T\_{1}^{n} -T\_{2}^{n} }{{\\left(\\Delta z\_{1} +\\Delta z\_{2}^{n} \\right)\\mathord{\\left/ {\\vphantom {\\left(\\Delta z\_{1} +\\Delta z\_{2}^{n} \\right) 2}} \\right.} 2} } \\right)\\left(\\frac{\\Delta z\_{2}^{n+1} }{2} \\right) & \\qquad T'\_{3} <T\_{f} \\end{array}\\end{split}\\\]

where here the subscripts 1, 2, and 3 denote three layers numbered from top to bottom. After layer subdivision, the node depths and layer interfaces are recalculated from equations and.
