1. “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

2. 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

3. 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

4. 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

5. 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

6. COSMO-SMC
Matthias Raschendorfer
2013

7. 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

8. 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