### 2.11.2.5. Flow Diagram of Leaf Flux Calculations:[¶](#flow-diagram-of-leaf-flux-calculations "Permalink to this headline")

PHS runs nested in the loop that solves for sensible and latent heat fluxes and temperature for vegetated surfaces (see section [2.5.3](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Fluxes/CLM50_Tech_Note_Fluxes.html#sensible-and-latent-heat-fluxes-and-temperature-for-vegetated-surfaces)). The scheme iterates for convergence of leaf temperature (\\(T\_l\\)), transpiration water stress (\\(\\beta\_t\\)), and intercellular CO2 concentration (\\(c\_i\\)). PHS is forced by maximum transpiration (absent water stress, \\(\\beta\_t=1\\)), whereby we first solve for assimilation, stomatal conductance, and intercellular CO2 with \\(\\beta\_{t,sun}\\) and \\(\\beta\_{t,shade}\\) both set to 1. This involves iterating to convergence of \\(c\_i\\) (see section [2.9.4](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Photosynthesis/CLM50_Tech_Note_Photosynthesis.html#photosynthesis)).

Next, using the solutions for \\(E\_{sun,max}\\) and \\(E\_{shade,max}\\), PHS solves for \\(\\psi\\), \\(\\beta\_{t,sun}\\), and \\(\\beta\_{t,shade}\\). The values for \\(\\beta\_{t,sun}\\), and \\(\\beta\_{t,shade}\\) are inputs to the photosynthesis routine, which now solves for attenuated photosynthesis and stomatal conductance (reflecting water stress). Again this involves iterating to convergence of \\(c\_i\\). Non-linearities between \\(\\beta\_t\\) and transpiration require also iterating to convergence of \\(\\beta\_t\\). The outermost level of iteration works towards convergence of leaf temperature, reflecting leaf surface energy balance.

![Image 2: ../../_images/phs_iteration_schematic.svg](https://escomp.github.io/ctsm-docs/versions/master/html/_images/phs_iteration_schematic.svg)

Figure 2.11.2 Flow diagram of leaf flux calculations[¶](#id14 "Permalink to this image")
