HIRLAM - NetFAM
Working meeting on Nordic Temperature Problem
was held 31 January 2005 10:00-16:30, FMI lecture room, 3rd floor
Collecting the facts and problems = short presentations about the old and ongoing work
Stefan Gollvik: Parametrizations over snow and forest surfaces
Sander Tijm: Experiment results from 1D HIRLAM runs
Mihail Sofiev (presented by Pilvi Siljamo): The year 2000 problem of sensible and latent heat fluxes
Laura Rontu: A
wintertime verification picture and Example of
Carl Fortelius (presented by Per Unden): A Sodankylä spring example
Sergei Zilitinkevich: How to parametrize the stable PBL turbulence
Simo Järvenoja: Additional comparisons of predicted and observed temperature and cloudiness. See also Simo's review in Norrköping workshop
Operative Sodankylä-model comparison Saturday
30 January 2005
Definition of the problems and listing the suspected causes
Northern winter problem
In the model, too warm predicted near-surface temperatures in a stable arctic
boundary layer. Differences between observation and forecast of the
order of ten degrees are common. In reality, clear sky, no significant SW
radiation, shallow surface layer with strong surface temperature
inversion over snow covered surface. Relative humidity may be
large but not close to saturation. Observed latent and sensible heat
fluxes are small, in the model generally somewhat larger. Extra clouds/fog
seem to form in HIRLAM.
Northern spring problem
Too cold daytime near-surface temperatures, supressed diurnal cycle.
Differences between observation and forecast of the order of ten
degrees are common. Clear sky cases, magnitude of measured SW radiation and heat
fluxes increase towards summer. At least some snow on ground but typically not on trees, ice
cover on lakes. In the model heat fluxes are often large,
compensate each other and the ratio of sensible (smaller)/latent (larger)
heat is often incorrect. Excessive cloudiness and humidity are frequently
produced by the model.
Further analysis: questions
Comparison of three-dimensional cloudiness: observed and predicted
by the model?
Extra clouds seem to form in HIRLAM - why?
What is the observed height of planetary boundary layer?
Do capping inversions exist, what would be their role in
What is the role of vertical resolution of the model in situations
of very shallow boundary layer?
How does evaporation from vegetation influence in model? Snow and its melting on ground/on trees?
Heat fluxes in forest/low vegetation. Heating of forest, small scale
(equilibrium within tiles - influence on neighbouring areas)
Role of soil moisture/ soil moisture assimilation?
- Correlation between cloud cover and low-level temperature bias
- Influence of the overprediction of weak winds by HIRLAM
Which observational and model data we need to study ?
- cloud condensate content,cloud cover : time/height, maps (cloud, low cloud, fog)
- temperature profiles, moisture (q), wind
- fluxes: latf,senf,radf (all components)
- fog, cloud from SYNOP
- PBLH, capping inversion (from T profiles), types of PBL, relation
to synoptic situation
- snow temperature profiles (heat conduction), canopy temperature in
What data are available for comparisons?
- Sodankylä, Cabauw: profiles, fluxes - routinely compared
with RCR at
- Sodankylä sounding and synop data
- RCR/MBE forecasts from Feb 2004
- Hyytiälä, Värriö, Nopex Uppsala tower data - need to contact
- Helsinki testbed boundary layer data - future: 2005-2007
What additional data we would need
Downwelling long-wave radiation at surface (SLWDN)
- available in Cabauw, Uppsala, the Sodankylä possibilites to be checked (FMI)
To be added to the routine comparisons: SLWDN from model, clouds
from SYNOP observation, absolute humidity along with the present relative humidity values?
Plan for model experiments and comparisons
Observation - model comparisons
A study of factors controlling T2m in Nordic winter conditions.
Systematic comparison of HIRLAM data (analyses, forecasts of RCR 6.3,
RCR 6.4, MBE with Sodankylä obsevations
- started Timo, Zhenia, in contact with Sergei
Next step: the same for Nordic spring conditions
- Timo, Zhenia, in contact with Sergei
Single column experiments
Winter and spring studies related to condensation parametrization
and cloud-LW-radiation interactions, sources and sinks of
moisture in the model
- Sander to contact Bent, Javier, Karl-Ivar
Evaporation from vegetation in the reference HIRLAM (quick temporary
Full model experiments to test suggested developments
Testing of the new surface scheme (snow/forest etc)
- Stefan et al. with support from FMI/RSHU
Surface analysis: snow cover analysis, soil moisture assimilation
- ongoing, Ernesto et al.
Basic studies of particular aspects
Study of wind in stable boundary conditions -> turbulence
- Priit, Laura
Vertical resolution of the HIRLAM - later
Roughness - stability dependence - later
Possible problems in fluxes when used as boundary values for the (moist) turbulence scheme?
Parametrized cloud-radiation interactions, cloud LW emissivity -
Comparisons with LES results
- in contact with Igor Esau, Nansen center
What statistical - diagnostic methods do we need to handle obs/model data?
Standard station verification with advanced tools for analysis (bias
classified according to observed variables etc).
- Tools to be added to reference HIRLAM, FMI
Mast verification - pictures, statistics
- ask Eric Bazile about Arpege - Sodankylä comparisons!
Accumulated diagnostics = tendencies, fluxes
- available in the reference HIRLAM
- Forest 2m temperatures in surface analysis - low vegetation tiles
- Representativeness of (Sodankylä mast) observations?
1. Report on comparison Sodankylä-RCR in stable winter conditions : Technical report/Newsletter/Journal
2. Web page to keep in contact, to see the plans and what people are
Including references for relevant reports/articles
3. Short term HIRLAM code modifications, long-term also
4. 1D winter and spring cases + tools + data for comparison
5. Recommendations for further research
Sodankylä summer school on
boundary layer modelling, 4-14.6.2005
Participants of the meeting at 31 Jan, 2005
contact: laura.rontu at fmi.fi