Cloud Cover KOE Scheme

Section Author

M. Koehler, DWD

Principles of the KOE Scheme

The cldcov_koe scheme diagnoses the fraction of each grid box covered by cloud and the partitioning of total water into vapour, cloud liquid and cloud ice. It combines a subgrid statistical closure driven by the turbulent saturation-deficit variance and contributions from convective detrainment. It adds a stratocumulus parameterization controlled by lower-tropospheric stability, an in-cloud representation based on the fractional standard deviation (FSD) of in-cloud water, and the dusty cirrus description.

Code Structure

The cldcov_koe scheme is separated from ICON as a granule, for further description see Granule Guidelines. It is called from the cloud cover koe driver (atm_phy_nwp/mo_nwp_cldcov_koe_driver), which gathers the physical state (T, p, geopotential, water-species mixing ratios, convective updraft diagnostics, turbulent variance) from ICON and bundles it into the granule input. Since various cloud cover schemes are implemented in ICON all these schemes are called from the common cloud cover interface (atm_phy_nwp/mo_cldcov_interface), which calls the schemes and post-processes the cloud fields (FSD, ART dusty cirrus).