1 / 29

Numerical Weather Prediction Models

Numerical Weather Prediction Models. Prepared by C. Tubbs, P. Davies, Met Office UK Revised, delivered by P. Chen, WMO Secretariat SWFDP-Eastern Africa Training Workshop Bujumbura, Burundi, 11-22 November 2013. NWP Model Formulation. Different types of model Model Characteristics

remy
Download Presentation

Numerical Weather Prediction Models

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. Numerical Weather Prediction Models Prepared by C. Tubbs, P. Davies, Met Office UK Revised, delivered by P. Chen, WMO Secretariat SWFDP-Eastern Africa Training Workshop Bujumbura, Burundi, 11-22 November 2013

  2. NWP Model Formulation • Different types of model • Model Characteristics • General strengths and weaknesses of NWP models

  3. Types of atmospheric model • Climatological • Global Climate Models (GCM’s) • Hindcasts and forecasts • Climate change – global warming • Non-operational weather forecasting models

  4. Types of atmospheric model • Long-term and seasonal • Coupled ocean-atmosphere models • Aims to infer climate from indicators such as Sea Surface Temperature (El Nino) • Forecasts issued by ECMWF every month • Typically based on ensemble methods

  5. Types of atmospheric model • Global NWP models • Operational forecasting models • Run twice to four times daily • Generally short- to medium-range (typically t+144h) • Global output coverage (datasets) • Hi-res “deterministic” vs EPS

  6. Types of atmospheric model • Limited Area Models (mesoscale/LAMs) • Add local detail to broad picture from global model • Take boundary conditions from global • Higher resolution, so better representation of small scale events • Shorter forecast range (typically t+48h) • Careful (especially if approaching cloud-scale!): kinematic effects vs dynamical processes

  7. Types of atmospheric model • Very-short-range (<12h) incl. Nowcasting • Nowcasting aims to give best forecast for time period of <4-6h hours lead-time • Blend of model and observational data • e.g. UK Met Office uses the NIMROD system • Specific applications • Atmospheric Dispersion • Air quality • Lee-wave forecasting models

  8. ? T574L64 ~27km ? ? EPS 50 members +1 control ? Models ? forecast range / max. lead-time ? t+144h ? ? domain ? « Anticipated advances in NWP, and the growing technology gap in weather forecasting » (2013) http://www.wmo.int/pages/prog/www/swfdp/Meetings/documents/Advances_NWP.pdf See Annex II for NWP systems

  9. ECMWF Global High-Res. IFS • Horizontal resolution of T1279 (16km), 91 vertical levels • 240h forecast range (10 days ahead) • 4-D VAR Global EPS – Ensemble Prediction System • 50 members, T319 (65km), 62 levels T= spectral truncation

  10. NCEP National Centers for Environmental Prediction (Washington, USA) • GFS (Global Forecasting System) model – T574 L64 (27km, 2010), T1148 (18km, planned 2013), and • GEPS ensemble model – 42 members, T190 (70km)

  11. Met Office UK Global model “UM” • Horizontal resolution of 25 km and L70 vertical levels • 4 times daily • Run out to t+144h • 4DVar MOGREPS-15 (UM) Global 23 members, 60km, L70

  12. UK Met Office • Africa LAM – retired October 2013

  13. UK Met Office Lake Victoria LAM • 4 km horizontal resolution, 70 vertical levels • Available via password protected website http://www.metoffice.gov.uk/weather/africa/lam/ • Username is afr_nms and password is uk_alam • Intermittent data assimilation • Run to t+48h

  14. Strengths & Weaknesses of NWP models

  15. Strengths & Weaknesses • There are generic problems common to most NWP • If we know about these we can account for them in our initial verification • Most problems are related to resolution

  16. NWP Strengths • Convection • General area of convection is well captured • Extra-tropical latitudes • Model is much better here • Frontal systems are well represented • Orographically enhanced rainfall better than Global Model

  17. Generic Problems • Inaccurate Initial Conditions • Lack of data • Imperfect data assimilation • Resolution • Horizontal resolution may cause small scale features to be missed • Vertical profile may not capture full detail e.g. inversions, localised temperature advection

  18. Generic Problems • Orography • Generally flattened – less steep and less high • Some features completely omitted • Orography in LAMs is better than in global models but still not perfect

  19. Generic Problems • Lateral Boundary Conditions • Only a problem for LAM’s • Spin up problems when transposing low resolution data onto a high resolution grid • Potential problems at edge of domain

  20. NWP Weaknesses • Tropical Convection • Representation of diurnal cycle is poor • Convection initiated too early and is too widespread • 0600-1200 ppn accumulation frames contain much spurious ppn but can indicate areas of activity • Fails to develop large scale, long-lived mesoscale convective systems

  21. NWP convection switched on….

  22. NWP convection switched off….

  23. Questions & Answers

More Related