Concept of an ice cloud microphysics module of intermediate complexity for application in numerical weather prediction

The deliverable will describe an ice cloud parameterisation for a weather model, in this case the ICON weather model, that allows: 1) ice supersaturation in clear sky, 2) that initiates cirrus formation only at certain degrees of supersaturation (temperature dependent, homogeneous nucleation), 3) that does consume the excess water vapour (i.e. the fraction above saturation) not instantaneously but following its thermodynamic force (that is, the crystal growth rate is proportional to the degree of supersaturation); this allows to have supersaturation within clouds as observed, and4) point 3 above works in the same way at subsaturation, i.e. the rate of crystal sublimation is proportional to the degree of subsaturation, such that cirrus clouds can survive for a while at subsaturated conditions, as observed.The deliverable will also report on tests of this new parameterisation within offline-runs of ICON for several situations.Linked to T2.3.