“Consolidation of the Surface-to-Atmosphere Transfer-scheme: ConSAT Priority Task “Consolidation of the Surface-to-Atmosphere Transfer-scheme: ConSAT COSMO Matthias Raschendorfer Sibiu 2013

Aim of the 1-year PT Finalizing already started and several times delayed work regarding the SAT-scheme: Implementation (and validation) of already prepared modifications of the SAT-scheme expected to improve the simulation of the diurnal cycle of near surface variables, such as surface fluxes, as well as 2m- and 10m-diagnostics and the representation of the stable boundary layer Setting up the SAT scheme (in relation to turbulence and numerical surface coupling) as a part of the common more clearly arranged physic package for COSMO and ICON Adaption the SC framework to the current version of the COSMO code and preparation for common use as a testbed for this and following development Documentation of the whole implementation This special implementation work is directed to the originating developer. The work should also prepare a basis for further investigation of the SAT scheme and the diurnal cycle problem COSMO-SMC Matthias Raschendorfer 2013

The task is integrated in the continuous process of model improvement: Detection of crucial processes , being badly represented by the model Conditional verification of 3D-forecast runs against observations and assimilation data. Component testing of specific parameterization by means of COSMO-SC. Maxing out the existing formulations together with existing extensions 1) Determination of optimal parameter values based on component testing 2) Statistical hyper-parameterization expressing so long not considered dependencies by empirical corrections Analysis and revision of related parameterizations and numerical procedures Implementation of revised formulations into the code Validation of the modifications Reporting and documentation of the modified parameterizations 1-st ConSAT task The 1-year task ConSAT deals with the implementation of a first revised version of the SAT-scheme starting at step IV in the process loop. Well defined follow-up actions according the process loop are desired (next maybe related to steps I to III) The rather extensive ConSAT plan is a guideline for the whole development process COSMO-SMC Matthias Raschendorfer 2013

Prepared measures to be implemented (step IV): This ConSAT task: Implementing the ICON-version of the turbulence-and SAT-code into COSMO including the revision of numerical security limits in the turbulence model (used by the SAT scheme) Changing the vertical profile functions used in the calculation of transfer resistances in case of stable stratification to those fitting better to the constant flux solution of the turbulence model. Expressing the transfer resistances without using the lowest diffusion coefficient above the CFL as an interpolation node, what may currently cause a damping of the diurnal amplitude the transfer resistances Extension of the profile function towards an universal one that includes the laminar limit, thus getting rid of using a virtual laminar layer (and the parameter rlam_heat). Revision of near surface diagnostics in particular with respect to their applicability at grid points with a large roughness length. Introduction of a rigid canopy layer less strongly coupled to the soil Presumably for a later ConSAT task: COSMO-SMC Matthias Raschendorfer 2013

Calculation of the transport resistances: The current scheme in COSMO explicitly considers the roughness layer resistance for scalars: applying and an effective SAI value for the whole roughness layer using the laminar length scale and a proper scaling factor for scalars assuming for , it can be written: Can be expressed by surface layer variables only, increasing sensitivity on thermal stratification The current scheme in COSMO explicitly considers the free atmospheric resistance: applying a linear -profile between level (top of the roughness layer) and level (top of the lowest model layer) using the atmospheric height and the stability parameter it can be written: new branch DWD Matthias Raschendorfer May.2013

COSMO-SMC Matthias Raschendorfer 2013

Remarks and conclusions: The proposed task is more or less an example how to apply the general strategy of improving parameterizations, and is first of all an opportunity to implement already prepared modifications in order to get a consolidated SAT-scheme Later tasks are possible, based on this consolidation Parameter estimation for separated processes Introduction a vertically resolved roughness layer Various issues of future science plan COSMO-SMC Matthias Raschendorfer 2013

Transfer scheme and 2m-values with respect to a SYNOP lawn: Effective velocity scale profile Mean GRID box profile SYNOP station lawn profile upper boundary of the lowest model layer from turbulence-scheme linear interpolated logarithmic Prandtl-layer profile unstable stable lowest model main level (expon. roughness-layer profile) Prandtl layer lower boundary of the lowest model layer roughness layer no storage capacity laminar layer Exponential roughness layer profile is valid for the whole grid box, but it is not present at a SYNOP station turbulence-scheme DWD Matthias Raschendorfer CLM-Training Course