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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,

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


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

Also impact

on diurnal cycle


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


State of the Art 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)

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?


GABLS 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars) 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 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)of LES modelsafter nine hours of cooling

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

Beare et al, 2005


C 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)omparison of Single-Column Models with LES (Cuxart et al, 2005)

GABLS 1D

Intercomparison

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


Momentum Fluxes 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)

Heat Fluxes


a 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)

(u ms-1)

’Ekman spirals’ (Svensson+Holtslag, 2005)

LES

Operational

Research-Meso

Research


Boundary-layer height and surface angle 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)

LES consistent with Cabauw data!


Why do operational models need enhanced mixing
Why do Operational Models need Enhanced Mixing? 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)

To prevent ‘runaway’ surface cooling

To have sufficient ‘Ekman pumping’

To compensate for model errors

However,

Atmospheric Boundary Layer pays the price!


Summary 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars) 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 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars) 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 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)for a period of 2.5 days (focus on PBL)

Prescribed surface temperature

Also same initial conditions and forcings for wind and humidity


Potential temperature 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)

Preliminary Results

+24 h forecasts


Potential temperature 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)

Preliminary Results

+36 h forecasts


Potential temperature 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)

Preliminary Results

+48 h forecasts


Wind speed 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)

Preliminary Results

+24 h forecasts


Wind speed 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)

Preliminary Results

+32 h forecasts


Wind speed 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)

Preliminary Results

+36 h forecasts


Wind speed 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)

Preliminary Results

+40 h forecasts


Friction velocity 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)


Sensible heat flux 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)


Boundary-layer height 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)


What next in GABLS? 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)

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 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)-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 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)-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 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)within GABLS (about 50) and our colleagues for providing inputs, model runs, advice, et cetera


Int. 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)

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)


Int. 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)

turb

Fully

turb

Non-

turb


Int. 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)

turb

Fully

turb

Non-

turb


Wind and temperature profiles 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)


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