Overview of GABLS achievements
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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 bert holtslag thanks to bob beare

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

www.met.wau.nl/gabls.html


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Example:Mean model bias for the 2 meter temperaturein present winter climate (30 years)Courtesy,Geert Lenderink, KNMI

Also impact

on diurnal cycle


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Mean model difference in 2 meter temperature for January 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

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

enhanced mixing

What can we learn from fine-scale modeling (LES)?

How do operational models compare?


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

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


Mean potential temperature of les models after nine hours of cooling

Mean potential temperature of LES modelsafter nine hours of cooling

Significant spread in results, but convergence at highresolution (Sensitivity to sub-grid model)

Beare et al, 2005


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Comparison of Single-Column Models with LES (Cuxart et al, 2005)

GABLS 1D

Intercomparison

Resolution (most) operational models is set to 6.25 m!


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Momentum Fluxes

Heat Fluxes


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

a

(u ms-1)

’Ekman spirals’ (Svensson+Holtslag, 2005)

LES

Operational

Research-Meso

Research


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Boundary-layer height and surface angle

LES consistent with Cabauw data!


Why do operational models need enhanced mixing

Why do Operational Models need Enhanced Mixing?

To prevent ‘runaway’ surface cooling

To have sufficient ‘Ekman pumping’

To compensate for model errors

However,

Atmospheric Boundary Layer pays the price!


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

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


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Second GABLS model intercomparison experiment

About 20 models by 15 groups

Coordinated by

Gunilla Svensson

Department of meteorology,

Stockholm university


Intercomparison of 1d models on basis of cases99 for a period of 2 5 days focus on pbl

Intercomparison of 1D models on basis of CASES99 for a period of 2.5 days (focus on PBL)

Prescribed surface temperature

Also same initial conditions and forcings for wind and humidity


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Potential temperature

Preliminary Results

+24 h forecasts


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Potential temperature

Preliminary Results

+36 h forecasts


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Potential temperature

Preliminary Results

+48 h forecasts


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Wind speed

Preliminary Results

+24 h forecasts


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Wind speed

Preliminary Results

+32 h forecasts


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Wind speed

Preliminary Results

+36 h forecasts


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Wind speed

Preliminary Results

+40 h forecasts


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Friction velocity


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Sensible heat flux


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Boundary-layer height


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

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?


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

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


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

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


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Thanks to all the participating scientists within GABLS (about 50) and our colleagues for providing inputs, model runs, advice, et cetera


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Int.

turb

Fully

turb

Non-

turb

Example:

Results with a

1D high resolution

ABL model

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)


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Int.

turb

Fully

turb

Non-

turb


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Int.

turb

Fully

turb

Non-

turb


Overview of gabls achievements as relevant for loco bert holtslag thanks to bob beare

Wind and temperature profiles


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