Draft plan (3)
LR 20 July 2007


HARMONIE radiation comparison


The aim of the model comparison experiment is to compare and validate
HIRLAM-ALARO-AROME radiation parametrizations over complex
terrain. The experiment should give information to understand the
relative importance in mesoscale models of

1) advanced radiation transfer parametrizations in clear sky
   (provided by the ECMWF radiation scheme within AROME)

2) accurate handling of cloud-radiation interactions

3) improved treatment of radiation surface-interactions, including
   sloping surface parametrizations.


Participating models

HARMONIE, to call radiation schemes of

AROME (ECMWF)
ALARO
HIRLAM

HIRLAM  to create boundary data


Radiation parametrizations

HIRLAM  and ECMWF schemes  called from AROME
with and without orographic radiation parametrization


Suggested experiment domain

Iceland, with a resolution 2.75 km/60 (90) levels,
nested into a HIRLAM 17 km/40 levels analyses
over an Arctic area (which are nested to ERA-40 analyses).


Period of comparison and observation data

Summer 1996 during Vatnajökull observation campaign Oerlemans et al., 1999.

Good sides using this data set:
+ summer with sufficient solar radiation, also low solar angles
+ frequent optically thick PBL clouds
+ glacier/bare land - no vegetation
+ local circulations exist, possibly related to radiation differences also
+ good surface-based observations with all radiation components, some soundings
+ well documented, much studied, interested people around
+ lateral boundary conditions in Iceland are simple over ocean, exist already

Bad sides using this data set
- cloud observations not very comprehensive
- surface description in Hirlam not very accurate, i.e. snow and ice quite approximate
- behaviour of HIRLAM surface data assimilation is not very well understood yet
- Iceland is outside of the most accurate surface elevation data (SRTM), 1 x 1 km available
- somewhat old data, not many possibilities e.g. for satellite data usage

Orography and orography-related parameters in fine resolution model

Mean orography and orographic radiation parameters created from
high-resolution orography data (hydro1k) for AROME/SURFEX Lambert
coordinates, with external programmes.
Optionally MSO-SSO parameters also (fur further use)


Diagnostics and parameters to be compared and validated

- components of surface energy balance, inluding (5) radiation fluxes
- two meter temperature and humidity
- three-dimensional tendencies of temperature
- three-dimensional radiation fluxes


Observation data for comparisons

- Observation campaign data, Oerlemans et al., 1999. See also
recent experiments by Rontu et al., ICAM 2007
(manuscript for Met.Atm.Phys/ ICAM 2007 issue in preparation)


Reporting

- HIRLAM/ALADIN ASM08 -> further a journal paper?


Remaining questions

- Surface analysis? First approximation:
  use interpolated 17 km HIRLAM analysis from boundaries, containing surface analysis or
  with ALADIN/AROME way of downscaling?
- Parametrizations of momentum fluxes (turbulent, MSO, SSO fluxes)? Suggestion:
  first as in AROME, concentrating in radiation only; in next step implement the new
  HIRLAM way?



Todo

- Plan the general structure of the HARMONIE experiments

- Plan nesting of AROME to HIRLAM boundaries

- Create needed climate files for AROME/SURFEX

- Generate the subgrid-scale orography parameters for the AROME/SURFEX grid

- Formulate the call of HIRLAM, ALARO and ECMWF radiation scheme in HARMONIE

- Formulate the call of orographic radiation after radiation scheme

- Gather more observational data for comparison

- Define parameters and methods for diagnostics


Possible persons

Laura/Ulf/Sami/Sander
Risto and Friedl?
Eric B / Francois B ?
Radmila?
Carlos Geijo/Nastya?