Overview of GABLS achievements as relevant for LOCO Bert Holtslag Thanks to Bob Beare, Joan Cuxart, Gunilla Svensson and many others…. GEWEX Atmospheric Boundary Layer Study: Towards a better representation of the Atmospheric Boundary Layer in Weather and Climate models
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Overview of GABLS achievements
as relevant for LOCO
Thanks to Bob Beare,
Joan Cuxart, Gunilla Svensson
and many others…
GEWEX Atmospheric Boundary Layer Study:
Towards a better representation of the Atmospheric Boundary Layer in Weather and Climate models
on diurnal cycle
State of the Art
for stable boundary layers
Large bias and sensitivity to model formulation
(at least over Land and Ice!)
Operational models typically like
What can we learn from fine-scale modeling (LES)?
How do operational models compare?
GABLS first inter comparison case
Simple shear driven case (after Kosovic and Curry, 2000)
Prescribed surface cooling 0.25 K/h (over ice) for 9 hours to quasi- equilibrium; no surface and radiation scheme
Geostrophic wind 8 m/s, latitude 73N
Significant spread in results, but convergence at highresolution (Sensitivity to sub-grid model)
Beare et al, 2005
Comparison of Single-Column Models with LES (Cuxart et al, 2005)
Resolution (most) operational models is set to 6.25 m!
’Ekman spirals’ (Svensson+Holtslag, 2005)
Boundary-layer height and surface angle
LES consistent with Cabauw data!
To prevent ‘runaway’ surface cooling
To have sufficient ‘Ekman pumping’
To compensate for model errors
Atmospheric Boundary Layer pays the price!
Summary First model intercomparisonLarge variation among 1D models, but all operational models show too strong mixing!Details in Turbulence Schemes do matter!8 papers are currently acceptedfor special issue in Boundary Layer Meteorology, to appear in 2005/6
Second GABLS model intercomparison experiment
About 20 models by 15 groups
Department of meteorology,
Prescribed surface temperature
Also same initial conditions and forcings for wind and humidity
+24 h forecasts
+36 h forecasts
+48 h forecasts
+24 h forecasts
+32 h forecasts
+36 h forecasts
+40 h forecasts
Sensible heat flux
What next in GABLS?
Further analysis and intercomparison
of the 1D models for CASES99 (Diurnal Cycle)
Intercomparison of LES and 1D models
for specific stable cases
Coupling of models to Land Surface
But HOW and by WHOM?
Theme 1: Stable boundary layers -Experience with coupled land/atmosphere models for stable boundary layers in other regions of the world -Ideas for parameterizations that specifically aim at a proper representation of the land/atmosphere couplingGert Jan SteeneveldExperiences with the (coupled) boundary-layer modelling of the three day-night period in CASES99Break Zbig SorbjanParameterizations of very stable boundary layers, derived from CASES99Joan CuxartMesoscale simulations of Stable Boundary LayersBob BeareLarge Eddy Simulations of an evening transition
Theme 2: Coupled boundary layer experiments and feedbacks-Observational means for diagnosing land-atmosphere interaction-SCM experiments with cloud and pbl feedbacks for other places in the world -Ideas for parameterizations that specifically aim at a proper representation of the land/atmosphere coupling Michael EkSCM experiments at CabauwAnne McCabeModeling the stable boundary layer and the role of land surface heterogeneityFrank BeyrichSome recent results on land/atmosphere interaction and ABL structure over the LITFASS areaFred Bosveld and Peter BaasClassification of low level jets at Cabauw
Thanks to all the participating scientists within GABLS (about 50) and our colleagues for providing inputs, model runs, advice, et cetera
Results with a
1D high resolution
fully coupled to
Land Surface for
3 different nights
using dynamic forcings
and local surface characteristics
Steeneveld, van de Wiel, Holtslag, 2005 (J.Atmos. Sci, in press)
Wind and temperature profiles