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Diagnosing the MJO in the ECMWF forecast system Research and model changes to improve the MJO prediction A cautionary tale!

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Research at ECMWF concerning the simulation of the Madden - Julian Oscillation Adrian Tompkins Peter Bechtold, Judith B - PowerPoint PPT Presentation


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Research at ECMWF concerning the simulation of the Madden - Julian Oscillation Adrian Tompkins Peter Bechtold, Judith Berner, Laura Ferranti, Thomas Jung, Frederic Vitart, Nils Wedi. Diagnosing the MJO in the ECMWF forecast system Research and model changes to improve the MJO prediction

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slide1

Research at ECMWF concerning the simulation of the Madden - Julian OscillationAdrian TompkinsPeter Bechtold, Judith Berner, Laura Ferranti, Thomas Jung, Frederic Vitart, Nils Wedi

  • Diagnosing the MJO in the ECMWF forecast system
  • Research and model changes to improve the MJO prediction
  • A cautionary tale!
1 mjo as a weather diagnostic
1. MJO as a weather diagnostic
  • ECMWF currently produces
    • 10 day forecast (uncoupled) at T799 (25 km) L91 resolution
    • Monthly forecast (coupled) at T159 L62
    • 6-month seasonal forecast (coupled) at T95L40 resolution
  • The prediction of the MJO is becoming a benchmark diagnostic, at least for the monthly and seasonal forecasts.
  • Previous work (Jung and Tompkins 2003) showed that ECMWF model (recent versions) has a eastward propagating signal, but phase speed too fast: Convectively Coupled Kelvin Wave.
mjo previous work

850hPA Zonal Wind

NCEP reanalysis ECMWF operational Analysis

MJO previous work

Signal visible in unfiltered data

Time

MJO

Zhang

2005

slide4

GPCP Precipitation

Operations 24hr forecast

Zhang

2005

Time

MJO

24 hr forecasts of the mjo
24 hr Forecasts of the MJO?

Tomorrow will see scattered showers in the north… and in the south there will be some MJO

what of longer term forecasts internal web pages for monitoring of mjo in monthly forecasts
What of longer term forecasts?Internal Web-pages for monitoring of MJO in Monthly Forecasts
and the latest forecast from 2 nd march 2006 is

1st Feb

And the latest forecast from 2nd March 2006 is…

200 hPa Velocity Potential anomaly

10S/10N

1st Mar

same seen in eof analysis of velocity potential
Same seen in EOF analysisof Velocity Potential

Vitart et al. 2003:

MJO variance decreases during the first 10d by as much as 50%

slide11

ERA40-Reanalysis

Spectral Analysis of 40 Winter Integrations

Model: IFS CY28R3

Q: Is there a crucial physically process (feedback) missing in the model or are waves being damped?

2 further mjo research 2 a berner palmer stochastic superclusters
2. Further MJO Research2(a): Berner & Palmer: Stochastic superclusters

Moncrieff,2004

Develop of a multi-scale cellular automaton (MSCA) for organized convection that captures the subgrid-scale forcing not represented by conventional parameterizations.

  • Potential to reduce systematic error by better representation of MJO (connect to ENSO)
  • Potential of improved skill of medium- to extended-range weather forecasts by better representation of tropical variability (Ferranti et al.,1990)
stochastic super clusters ssc as part of organized convection super gridscale

Stochastic super clusters (SSC) as part of organized convection (super-gridscale)

smooth

scale

Cartoon of idealized forcing pattern

Smoothed CAPE

Non-local, quasi-random,state-dependent

slide14

200hPA Velocity Potential for 6 month Forecast

Analysis

Control

SSC

Work in Progress: But clear impact on propagating signals

2 b nils wedi theorizes on the importance of the zonal mean flow influenced by the extra tropics
2(b). Nils Wedi: Theorizes on the importance of the zonal mean flow, influenced by the extra-tropics?

Average for Ensemble of forecasts

50 days

Sinusoidal zonal

mean wind oscillation

enforced in the tropics

Control: No 50 day peak.

Also Work in Progress

2 c changes for 30r2 summer 2006

Era 40

2(c): Changes for 30R2 (summer 2006)
  • Model physics is updates 1 or 2 times a year
  • Monitored for impact on wave activity
  • Changes to clouds, that increase upper tropospheric ice amounts and increase convective organisation through radiative feedback, appear to impact wave propagation

Control

NewScheme

slide17

Amalgation of 10day forecasts: Velocity potential at 200 hPa

Analysis

30r1 Current operations

30r2 Summer 2006

slide18

Impact on monthly forecast less dramatic

Velocity Potential at 200 hPa.Forecast starting on 31 December 1992

Control

New Scheme

Analysis

4 a cautionary tale wave sensitivity in gcms
4. A Cautionary Tale: Wave sensitivity in GCMs
  • Convective organisation improved the propagating convective signal
  • What about water vapour feedback with convection?
  • Local moistening can “precondition” the atmosphere, making it favourable for future convection, organising convection

MOIST

DRY

DRY

a whole range of targeted sensitivity tests
A whole range of targeted sensitivity tests
  • Boundary Layer Theta_e
  • Entrainment into Updraughts

ENHANCE/INHIBIT

RAINFALL EVAPORATION

ENHANCE

ENTRAINMENT

FACTOR

  • For example:
  • Increase entrainment factor
  • Input zonal mean humidity to convection scheme
  • For example:
  • Coverage from 5% to 30%
  • Double evaporation rate
  • Increase RH limit from 80% to 100%
effect on convective precipitation
Effect on Convective Precipitation

Increase entrainment into convection parametrized updraughts

Instead of enhancing parametrized convection in moist areas and supressing in dry areas..

25 days

25 days

…the scheme is supressed and the grid-scale takes over!!!

increasing large scale activity increases peak power k 1 2 3 15 days p 120 days

Increasing gridscale activity

Increasing Large-scale activity increases peak power (K=1,2,3 15 days<p<120 days)

Increasing power in convectively coupled mode

Normalized Peak Power of 200 hPa Vel Pot

large scale precipitation in kelvin wave
Large-scale precipitation in Kelvin Wave

temperature

Large Scale Circulation

  • Latent heating (from cloud scheme) directly in phase with upward motion by construction. Changes in cloud scheme have large influence on incidence of grid-scale convection
convective scale precipitation in kelvin wave
Convective-scale precipitation in Kelvin Wave

Large Scale Circulation

qe

  • The convection parameterization is not so constrained, and responds to PBL theta_e, CAPE, (humidity). Can provide heating out of phase, possibly damping the wave.
slide25

EOF1

EOF2

Linking the convective parametrization mass-flux closure to mid-tropospheric motion as well as CAPE strengthens propagating modes

but…

Justifiable?

Forecast Scores?

200 hPa Velocity Potential Anomaly

Grid-scale rainfall anomaly

Convective

Parametrization rainfall anomaly

conclusions
Conclusions
  • A whistle-stop tour of MJO at ECMWF, no vertical structure discussion
  • Prediction of MJO falls of rapidly after the 5 to 10 day forecast range
    • Crucial physical mechanism missing?
    • Signal strongly damped by model?
    • Coupling & resolution do not have strong zero-order impact
  • ECMWF research into MJO for long term improvements:
    • Stochastic supercluster forcing (missing mesoscale organisation)
    • Extra-tropical influence on wavenumber zero
    • Participation in the Aqua-Planet Experiment (model intercomparison)
  • Model physics changes monitored for their MJO (and wave) impact
    • Recent enhancement of (convectively detrained) ice leads to increased convective organisation and MJO-like improvements – radiative feedback?
  • Warning about interpreting results from GCMs
    • Physics alters balance of grid-scale/parametrized convection
    • Grid-scale convection in phase with waves and enhances convectively coupled Kelvin wave activity
slide27
The latest Aqua Planet resultsFrom Mike Blackburn & the Aqua-Planet Experiment in which ECMWF in participating

That’s all, thank you!

slide28

Coupling

effect

T159 versus T95

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