1 / 20

WGSF links with WGNE, WGCM, TFSL

WGSF links with WGNE, WGCM, TFSL. WGNE – Working Group on numerical experimentation, it is responsible in WCRP for the development of the atmospheric component of climate models. WGCM –

reuben
Download Presentation

WGSF links with WGNE, WGCM, TFSL

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. WGSF links with WGNE, WGCM, TFSL WGNE – Working Group on numerical experimentation, it is responsible in WCRP for the development of the atmospheric component of climate models WGCM – Working Group on coupled modelling, responsible for the development of requirements for the comprehensive model tools which allow for the realistic present and forced climate simulations WGCM/CLIVAR WGOMD – Working Group on Ocean Model Development – ocean modelling for climate diagnostics and for further coupling with atmospheric models

  2. AMIP & CMIP AMIP1/AMIP2 – Comprehensive validation and intercomparison of atmospheric models ran with the standard requirements and forcing functions. 23 modelling groups, fluxes are still poorly validated, SURFA… CMIP1/CMIP2 – establishing a validation framework for the coupled models ran with the standard perfomance, both PC and SR

  3. Where is the role of WGSF? • WGNE, WGCM, WGOMD: • forcing functions for ocean/atmosphere • modelling; • assessments of the strengths and • weaknesses of particular NWP flux products; • flux fields/forcing formulations for ocean • reanalyses;

  4. Sources of the global- and basin-scale flux field products:

  5. A typical NWP air-sea flux product Operational atmospheric GCM Data assimilation system Short-term forecast: 1 to 6 hours SST analysis • Prognostic variables: • (time-step forecasts) • air temperature (2m), • specific humidity (2m), • wind speed (10m), • sea level pressure, • cloud cover Physical parameterizations • Diagnostic variables: • (time-step averages) • sensible heat, • Latent heat, • SW radiation, • LW radiation, • wind stress Our choice Fluxes, recomputed from NWP prognostic variables Directly use the fluxes, diagnosed by the NWP

  6. Challenges for WGSF • Global/regional energy budgets; • Parameterizations, their assessments and • validation; • Use of NWP for estimation of sampling errors • in VOS and satellite fluxes; • Role of fluxes in driving climate system, in • particular, the extent to that surface fluxes • can help to establish predictability limits; • Variability studies, climate modes, key-regions • and key-processes.

  7. Global ocean heat balance derived from different data sources The largest variations are observed for the latent flux and net SW (up to 20 W/m2) Global heat balance in VOS products is imbalanced by 30 W/m2 (ocean gets more heat), while in the NWP products imbalances are within ±5W/m2.

  8. Example: sources of biases in NWP precipitation • Strong impact of the spin-up on precipitation in short-range forecasts; • Running precipitation parameterizations on reduced Gaussian grid; • An incorrect parameterization of horizontal moisture diffusion, • unrealistic cloud-top cooling and unrealistically high oceanic albedo • in NCEP1 (all three have been corrected along in NCEP2); • Gibbs oscillations in the orography of NCEP1 (was smoothed in • NCEP2). Different data assimilation inputs: • NCEP1 – Radiosondes, the dropsondes and pibals, marine and • continental winds from different sources • NCEP2 – Xie and Arkin (1997) five day mean rainfall for tor • adjustment of soil moisture • ERA-40 – VTPR (Vertical Temperature Profile Radiometer) and TOVS • (Television Infrared Operational Satellite (TIROS) Operational • Vertical Sounder) starting from 1972 and ERS winds (from 1991)

  9. Sampling biases in VOS fluxes

  10. Kushnir et al. (2002), Lisa Goddard: analysis of 10 GCM integrations forced with global SST  ratio of SST-determined SLP variance (potential predictability) Dan Hodson and Rowan Sutton, 2002: Six simulations with the HadAM3 AGCM of the period 1871-1999  The internal SLP variability vs the SST-forced response

  11. The ERA-40-WAM system • Operational ECMWF system (IFS) • TL159, 60 layers • 3DVAR: • COADS, GTS, satellites, hist. data, .... • interactive determination of Charnock parameter (= sea • surface roughness) • coupled to WAM (1.5°) • => Waves Global mean SWH ERA40-WAM (by courtesy of Andreas Sterl and Sofia Caires)

  12. GEWEX: • Provides Guidance on How to Initialize Land Surface • Proposes/Implements Diagnostic Studies and Numerical • experiments: Understanding Land Surface Feedbacks • CliC: • Provides Guidance on How to Initialize Cryosphere • Proposes/Implements Diagnostic Studies and Numerical • experiments • CLIVAR: • Provides Guidance on How to Initialize Ocean • Proposes/Implements Diagnostic Studies and Numerical • experiments • SPARC: • Provides Guidance on How to Prescribe Atmospheric composition • Provides Guidance on How to Initialize Stratosphere • Proposes/Implements Diagnostic Studies and Numerical • experiments Task Force for Seasonal Prediction: Interactive Atmosphere-Ocean-Land-Ice Prediction Experiment

  13. Interactive Atmosphere-Ocean-Land-Ice Prediction Experiment • Predictability Diagnostic (Example) • Limit of Predictability when the Forecast Ensemble Distribution same as Total Forecast Climate Distribution Free Running Model PDF Initial Condition (t=0) PDF t=limit of Predictability?

  14. Previous climate New climate More record extreme rainfall and flooding Probability of occurrence Moderate Dry Wet IPCC, 2001

  15. TSSL and WGSF TSSL - is established to facilitate multidisciplinary study of the sea level change (JSC-26, special topic) Surface fluxes, first of all E-P, affecting water balance, and ocean heat/fresh water uptakes, affecting steric changes, is a critical factor of sea-level variability

  16. STERIC SEA LEVEL TRENDS (1955-1995) Cabanes et al., 2001

  17. Topex/Poseidon (1993-1998) SEA LEVEL TRENDS FOR 1993-1998 (mm/yr) Upper map : Observed (Topex/Poseidon) Bottom map: Computed (thermal expansion) Thermal expansion (1993-1998) - -27 mm/yr +27 Cabanes et al., 2001

  18. WGSF Target actions: • SURFA; • AMIP parameterization testbed – cross- • pollination of parameterizations developed • from field experiments and used in NWP; • NWP fluxes and biases and in VOS/satellite • flux products; • Ocean reanalyses – • (i) better established forcing functions, • (ii) tools and requirements for the • reanalyses output diagnostics; • Climate modes and predictability limits; • TFSL – assessment of the role of sea-air • fluxes.

More Related