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Blocking in the ECMWF model: Sensitivity to resolution and model physics

Blocking in the ECMWF model: Sensitivity to resolution and model physics. Antje Weisheimer Thomas Jung Tim Palmer. Outline Resolution dependent blocking frequency The ATHENA project T159 vs T511 vs T1279 The roles of topography and the mean state of the flow

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Blocking in the ECMWF model: Sensitivity to resolution and model physics

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  1. Blocking in the ECMWF model: Sensitivity to resolution and model physics Antje Weisheimer Thomas Jung Tim Palmer

  2. Outline • Resolution dependent blocking frequency • The ATHENA project • T159 vs T511 vs T1279 • The roles of topography and the mean state of the flow • T511 with low resolution topography • Impact of the mean state/systematic error • Physical parameterisations and blocking • Statistics of blocking in the IFS model from 2005-2009 • Seasonal re-forecasts of the summer 2003 over Europe

  3. Outline • Resolution dependent blocking frequency • The ATHENA project • T159 vs T511 vs T1279 • The roles of topography and the mean state of the flow • T511 with low resolution topography • Impact of the mean state/systematic error • Physical parameterisations and blocking • Statistics of blocking in the IFS model from 2005-2009 • Seasonal re-forecasts of the summer 2003 over Europe

  4. 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)]

  5. Blocking frequency: T159 reanalysis T159 T511 T1279 T2047 1960-2007

  6. Blocking frequency: T159vsT511 reanalysis T159 T511 T1279 T2047 1960-2007

  7. Blocking frequency: T159vsT511vsT1279 reanalysis T159 T511 T1279 T2047 1960-2007

  8. Outline • Resolution dependent blocking frequency • The ATHENA project • T159 vs T511 vs T1279 • The roles of topography and the mean state of the flow • T511 with low resolution topography • Impact of the mean state/systematic error • Physical parameterisations and blocking • Statistics of blocking in the IFS model from 2005-2009 • Seasonal re-forecasts of the summer 2003 over Europe

  9. Blocking frequency: T511 with T159 topography reanalysis T159 T511 T1279 T2047 1980-2007

  10. Blocking frequency: T511 with T159 topography reanalysis T159 T511 T511topoT159 1980-2007

  11. reanalysis T159 T511 T511topoT159 T159meanT511 • T159 with T511 mean state 1980-2007

  12. reanalysis T159 T511 T511topoT159 T511topoT159meanT511 • T511topoT159 with T511 mean state 1980-2007

  13. reanalysis T159 T511 T511topoT159 T511topoT159meanT159 • T511topoT159 with T159 mean state 1980-2007

  14. Blocking 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)

  15. Outline • Resolution dependent blocking frequency • The ATHENA project • T159 vs T511 vs T1279 • The roles of topography and the mean state of the flow • T511 with low resolution topography • Impact of the mean state/systematic error • Physical parameterisations and blocking • Statistics of blocking in the IFS model from 2005-2009 • Seasonal re-forecasts of the summer 2003 over Europe

  16. Major changes to the IFS model from 2005 to 2009 model date of modifications cycle 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

  17. reanalysis CY33R1 CY32R3 CY29R2-32R2 • Statistics of blocking in the IFS model from 2005-2009 1962-2005 primarily impact of convection scheme (and turbulent orographic form drag) Jung et al., QJ (2010)

  18. The European heat wave of the summer 2003 Seasonal retrospective forecasts initialised in May: The current operational System 3 (CY31R1) neutral T2m wet precip neutral Z500

  19. The European heat wave of the summer 2003 Seasonal retrospective forecasts initialised in May: CY33R1 very warm T2m very dry precip positive Z500

  20. The European heat wave of the summer 2003 Seasonal retrospective forecasts initialised in May: Impact of the land-surface scheme T2m precip Z500

  21. 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

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