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
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
• Issues
• Next steps/ targets for next 6 months
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
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
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
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.
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
SCM test-case: with (top) & without physics (bottom)
temperature humidity u-wind v-wind
Relaxation of winds: u-windwith relaxation without relaxation
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
ERA interim data: temperatureactual
SCM without forcing
SCM with forcing
ERA interim data: humidityactual (log)
SCM without forcing
SCM with forcing
ERA interim data: u-windactual
SCM without forcing
SCM with forcing
ERA interim data: v-windactual
SCM without forcing
SCM with forcing
Coupled model: full physics
Coupled model: full physics
Coupled model: radiation, cloud & convection off
Coupled model: radiation, cloud & convection off
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