GitHub

Diagnostic EDMF equations

This describes the diagnostic EDMF scheme equations and its discretizations. Where possible, we use a coordinate invariant form: the ClimaCore operators generally handle the conversions between bases internally.

Grid-scale variables

  • $\rho$: density in kg/m³, discretized at cell centers.
  • $u^3$: the contravariant 3 component of velocity, discretized at cell faces.
  • $h_{\mathrm{s}}$: moist static energy in J/kg, discretized at cell centers.
  • $q_t$: total specific humidity in kg/kg, discretized at cell centers.
  • $\Phi = g z$: geopotential in m²/s², where $g$ is the gravitational acceleration rate and $z$ is altitude above the mean sea level, discretized at cell centers.
  • $(\nabla \Phi)^3$: the contravariant 3 component of the gradient of geopotential, reconstructed at cell centers.
  • $p$: air pressure, reconstructed at cell centers.

Subgrid-scale variables

  • $\hat{\rho}^j$: effective density in kg/m³. Superscript $j$ represents the sub-domain. $\hat{\rho}^j = \rho^j a^j$ where $\rho^j$ is the sub-domain density and $a^j$ is the sub-domain area fraction. This is discretized at cell centers.
  • $\rho^j$: density in kg/m³, derived from the thermodynamic state, reconstructed at cell centers.
  • $b^{j,3}$: the contravariant 3 component of the buoyancy of updraft, reconstructed at cell centers.

    \[b^{j,3} = - \frac{\rho^j-\rho}{\rho^j} (\nabla \Phi)^3\]

  • $u^{j,3}$: the contravariant 3 component of velocity, discretized at cell faces.
  • $h_{\mathrm{s}}^j$: moist static energy, discretized at cell centers.
  • $q_t^j$: total specific humidity of the sub-domain j, discretized at cell centers.
  • $u^{0,3}$: the contravariant 3 component of the environmental velocity, obtained as the residual:

    \[\rho u^{0, 3} = \rho u^3 - \sum_{j\ne 0} \hat\rho^j u^{j, 3}.\]

Equations and discretizations

Mass

\[\frac{1}{J} \frac{\partial}{\partial \xi^3} \bigl( \hat\rho^j J u^{j, 3} \bigr) = (E^{j0} - \Delta^{j0}) \hat\rho^j\]

This is descritized using the following

\[\frac{1}{J[i-1]} \left( J[i-\frac{1}{2}] \hat\rho^j[i] u^{(j), 3}[i-\frac{1}{2}] -J[i-\frac{3}{2}] \hat\rho^j[i-1] u^{j, 3}[i-\frac{3}{2}] \right) = (E^{j0}[i-1] - \Delta^{j0}[i-1]) \hat\rho^j[i-1]\]

Momentum

\[\frac{1}{J^2} \frac{\partial}{\partial \xi^3} \bigl(\frac{1}{2} J^2 (u^{j, 3})^2 \bigr) = b^{j, 3} + E^{j0}(u^{0,3} - u^{j,3}) - d^{j, 3}\]

This is descritized using the following

\[\frac{1}{2} \frac{1}{J[i-1]^2} \left( J[i-\frac{1}{2}]^2 u^{j, 3}[i-\frac{1}{2}]^2 -J[i-\frac{3}{2}] u^{j, 3}[i-\frac{3}{2}]^2 \right) = - \frac{\rho^{j}[i-1]-\rho[i-1]}{\rho^{j}[i-1]} \nabla^3 \Phi + E^{j0}[i-1](u^{0, 3}[i-\frac{3}{2}] - u^{j, 3}[i-\frac{3}{2}]) - d^{j, 3}[i-1]\]

Total energy

\[\frac{1}{J} \frac{\partial}{\partial \xi^3} ( \hat\rho^j J h_{\mathrm{s}}^j u^{j, 3} ) = - u^{j,3} \cdot b^j_3 + \hat\rho^j \left(E^{j0} h_{\mathrm{s}} - \Delta^{j0} h_{\mathrm{s}}^j\right)\]

This is descritized using the following

\[\frac{1}{J[i-1]} \left( J[i-\frac{1}{2}] \hat\rho^j[i] u^{j, 3}[i-\frac{1}{2}] h_{\mathrm{s}}^j[i] -J[i-\frac{3}{2}] \hat\rho^j[i-1] u^{j, 3}[i-\frac{3}{2}] h_{\mathrm{s}}^j[i-1] \right) = \hat\rho^j[i-1] (E^{(j0)}[i-1] h_{\mathrm{s}}[i-1] - \Delta^{(j0)}[i-1] h_{\mathrm{s}}^j[i-1])\]

Total water

\[\frac{1}{J} \frac{\partial}{\partial \xi^3} \bigl(\hat\rho^j J q_t^j (u^{j, 3} - W_t^j \hat k^3) \bigr) = \hat\rho^j \left(E^{j0} q_t - \Delta^{j0} q_t^j\right)\]

This is descritized using the following

\[\frac{1}{J[i-1]} \left( J[i-\frac{1}{2}] \hat\rho^j[i] u^{j, 3}[i-\frac{1}{2}] q_t^j[i] -J[i-\frac{3}{2}] \hat\rho^j[i-1] u^{j, 3}[i-\frac{3}{2}] q_t^j[i-1] \right) = \hat\rho^j[i-1] (E^{j0}[i-1] q_t[i-1] - \Delta^{j0}[i-1] q_t^j[i-1])\]