coupled model data assimilation:
DESCRIPTION
Coupled Model Data Assimilation:. Building an idealised coupled system Polly Smith, Amos Lawless, Alison Fowler* School of Mathematical and Physical Sciences, University of Reading, UK * funded by NERC. Outline. Objectives Tasks & progress I ssues Next steps/ targets for next 6 months. - PowerPoint PPT PresentationTRANSCRIPT
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Coupled Model Data Assimilation:
Building an idealised coupled system
Polly Smith, Amos Lawless, Alison Fowler*
School of Mathematical and Physical Sciences, University of Reading, UK
* funded by NERC
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Outline
• Objectives
• Tasks & progress
• Issues
• Next steps/ targets for next 6 months
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Objective
To use an idealised system to gain a greater theoretical understanding of the coupled atmosphere-ocean data assimilation problem:
• explore different approaches to coupled 4D-Var data assimilation using a single-column, coupled atmosphere-ocean model
• help guide the design/ implementation of coupled DA methods within full 3D operational scale systems
• strong-constraint incremental 4D-Var
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Building the idealised systemTask 1: develop an idealised, single-column, coupled atmosphere-ocean model with a strong-constraint incremental 4D-Var assimilation scheme.
For this we need a model that
• is simple and quick to run• is able to represent realistic atmosphere-ocean coupling
Atmosphere:• ECMWF single column model (SCM)
Ocean:• single column KPP (K-Profile Parameterisation) mixed-layer
ocean model
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SCM:
• based on the IFS code• includes a full set of physical parameterisations • we will use a stripped down version
- adiabatic component (+ vertical diffusion?) • also want option to use full physics in later experiments
KPP model:
• developed at UoR• already within the SCM code but never been used• currently only works when full SCM physics scheme is
switched on
coupling through surface fluxes and SST
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Progress so far· Successfully compiled and ran the SCM test-case provided by
ECMWF.
· Simplified the SCM code to remove physical parameterisations.
· Tested the simplified atmospheric model using real data.
· Coupled the KPP ocean code to the full-physics SCM and successfully ran a test case for the coupled atmosphere-ocean model.
· Produced draft documentation for the models.
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Issues• Lack of documentation
• Choice of suitable test-case(s), creation of input file
• Prescription of model forcing
ocean: surface fluxes of heat, moisture & momentum, compute using bulk formulae of Large & Yeager
atmosphere: vertical velocity, geostrophic u & v winds, horizontal advection tendencies.
• Relaxation
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SCM test-case: with (top) & without physics (bottom)
temperature humidity u-wind v-wind
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Relaxation of winds: u-windwith relaxation without relaxation
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Issues• Lack of documentation
• Choice of suitable test-case(s), creation of input file
• Prescription of model forcing
ocean: surface fluxes of heat, moisture & momentum, compute using bulk formulae of Large & Yeager
atmosphere: vertical velocity, geostrophic u & v winds, horizontal advection tendencies.
• Relaxation
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ERA interim data: temperatureactual
SCM without forcing
SCM with forcing
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ERA interim data: humidityactual (log)
SCM without forcing
SCM with forcing
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ERA interim data: u-windactual
SCM without forcing
SCM with forcing
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ERA interim data: v-windactual
SCM without forcing
SCM with forcing
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Coupled model: full physics
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Coupled model: full physics
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Coupled model: radiation, cloud & convection off
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Coupled model: radiation, cloud & convection off
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Next steps• Initial results with simple coupled atmosphere-ocean model
expected by end of January 2013.
• Development of prototype 4D-Var system - tangent linear and adjoint modelspreliminary results by April/May 2013.
• Exploration of different coupling strategies being implemented in the ECMWF system - identical twin experiments