Blocking in the ECMWF model:

Sensitivity to resolution and model physics

Antje Weisheimer

Thomas Jung

Tim Palmer

Blocking in the ECMWF model Reading University 15 Dec 2010

Outline

1. Resolution dependent blocking frequency

• The ATHENA project

• T159 vs T511 vs T1279

2. The roles of topography and the mean state of the flow

• T511 with low resolution topography

• Impact of the mean state/systematic error

3. Physical parameterisations and blocking

• Statistics of blocking in the IFS model from 2005-2009

• Seasonal re-forecasts of the summer 2003 over Europe

Blocking in the ECMWF model Reading University 15 Dec 2010

Outline

1. Resolution dependent blocking frequency

• The ATHENA project

• T159 vs T511 vs T1279

2. The roles of topography and the mean state of the flow

• T511 with low resolution topography

• Impact of the mean state/systematic error

3. Physical parameterisations and blocking

• Statistics of blocking in the IFS model from 2005-2009

• Seasonal re-forecasts of the summer 2003 over Europe

Blocking in the ECMWF model Reading University 15 Dec 2010

Project ATHENA: High Resolution Global Climate Simulations

… to determine the feasibility of using high-end computing resources to simulate climate variability and global climate change and to test the benefit of employing

very high resolutions for weather and climate models.

• NSF offered dedicated use of the NSF Cray XT-4 Athena supercomputer in Oak Ridge, Tennessee, from Oct 2009 -March 2010

• international team of over 30 people from six institutions on three continents

• 900 TB of output, >90% level of utilization of the resource, general data availability in 2011

ECMWF: 13-month atmospheric climate integrations from 1960(1989)-2007 with IFS CY36R1

T159 (~120km) T511 (~ 40km) T1279 (~ 16km)[T2047 (~ 10km)]

Blocking in the ECMWF model Reading University 15 Dec 2010

Blocking frequency: T159

1960-2007

reanalysisT159T511T1279T2047

Blocking in the ECMWF model Reading University 15 Dec 2010

Blocking frequency: T159 vs T511

1960-2007

reanalysisT159T511T1279T2047

Blocking in the ECMWF model Reading University 15 Dec 2010

Blocking frequency: T159 vs T511 vs T1279

1960-2007

reanalysisT159T511T1279T2047

Blocking in the ECMWF model Reading University 15 Dec 2010

Outline

1. Resolution dependent blocking frequency

• The ATHENA project

• T159 vs T511 vs T1279

2. The roles of topography and the mean state of the flow

• T511 with low resolution topography

• Impact of the mean state/systematic error

3. Physical parameterisations and blocking

• Statistics of blocking in the IFS model from 2005-2009

• Seasonal re-forecasts of the summer 2003 over Europe

Blocking in the ECMWF model Reading University 15 Dec 2010

Blocking frequency: T511 with T159 topography

1980-2007

reanalysisT159T511T1279T2047

Blocking in the ECMWF model Reading University 15 Dec 2010

Blocking frequency: T511 with T159 topography

1980-2007

reanalysisT159T511T511topoT159

Blocking in the ECMWF model Reading University 15 Dec 2010

T159 with T511 mean state

1980-2007

reanalysisT159T511T511topoT159T159meanT511

Blocking in the ECMWF model Reading University 15 Dec 2010

1980-2007

reanalysisT159T511T511topoT159T511topoT159meanT511

T511topoT159 with T511 mean state

Blocking in the ECMWF model Reading University 15 Dec 2010

1980-2007

reanalysisT159T511T511topoT159T511topoT159meanT159

T511topoT159 with T159 mean state

INSTITUT CATALÀ DE CIÈNCIES DEL CLIMABlocking frequency in seasonal forecasts

Northern Hemisphere DJF blocking frequency for 1-month lead seasonal hindcasts for the ECMWF, Météofrance, Met Office, IfM and

INGV forecast systems over the period 1981-2005 compared to ERA40/ERA-Int (black solid). Results are for the Tibaldi and Molteni index (reversal of the meridional gradient of Z500). 95% confidence

intervals are shown.

Standard index Systematic error removed

courtesy F. Doblas-Reyes see also Doblas-Reyes et al., JGR (2002)

Blocking in the ECMWF model Reading University 15 Dec 2010

Outline

1. Resolution dependent blocking frequency

• The ATHENA project

• T159 vs T511 vs T1279

2. The roles of topography and the mean state of the flow

• T511 with low resolution topography

• Impact of the mean state/systematic error

3. Physical parameterisations and blocking

• Statistics of blocking in the IFS model from 2005-2009

• Seasonal re-forecasts of the summer 2003 over Europe

Blocking in the ECMWF model Reading University 15 Dec 2010

Major changes to the IFS model from 2005 to 2009

model date of modificationscycle introduction

CY29R2 Jun 2005

CY30R1 Feb 2006 vertical resolution L60 L91

CY31R1 Sep 2006 turbulent orographic form drag scheme

System 3 for operational seasonal forecasting (T159L60)

CY32R2 Jun 2007 new radiation scheme (SW, cloud radiation interaction,

MODIS albedo), retuning of GWD

CY32R3 Nov 2007 convection (entrainment and deep convection closure),

vertical diffusion, new land-surface module H-TESSEL

CY33R1 Jun 2008 retuning + bugfix

Blocking in the ECMWF model Reading University 15 Dec 2010

reanalysisCY33R1CY32R3CY29R2-32R2

1962-2005

primarily impact of convection scheme (and turbulent orographic form drag)

Statistics of blocking in the IFS model from 2005-2009

Jung et al., QJ (2010)

Blocking in the ECMWF model Reading University 15 Dec 2010

The European heat wave of the summer 2003

T2m

precip

Z500

Seasonal retrospective forecasts initialised in May: The current operational System 3

(CY31R1)

neutral

wet

neutral

Blocking in the ECMWF model Reading University 15 Dec 2010

T2m

precip

Z500

The European heat wave of the summer 2003

Seasonal retrospective forecasts initialised in May: CY33R1

very warm

very dry

positive

Blocking in the ECMWF model Reading University 15 Dec 2010

T2m

precip

Z500

The European heat wave of the summer 2003

Seasonal retrospective forecasts initialised in May: Impact of the land-surface scheme

Blocking in the ECMWF model Reading University 15 Dec 2010

Conclusions

Blocking is model resolution dependent.

• improved blocking statistics for horizontal resolution increase from T159 (~120km) to T511 (~40km)

• future work will investigate blocking on different time scales ( M. Matsueda’s talk)

Model topography needs to be resolved at a sufficiently high resolution.

Reducing the systematic errors of the mean flow is important but not necessarily easier than getting blocking itself right.

• improved blocking for “low-res” (T159) simulations with “high-res” (T511) mean state

Model representation of physical processes is essential too.

• recent changes to the convection parametrisation had major positive impact on blocking frequency

• critical role of land surface scheme on summer 2003 atmospheric circulation