canadamodel

Scatterometer use in NWP at Environment and Climate Change Canada

Contents

Physical characteristics

Modelling system: Global Environmental Multiscale (GEM) model (Côté et al. 1998)

Global Deterministic Prediction System (GDPS)

  • Grid-point model (2x2047x683 Yin-Yang horizontal grid) (McTaggart-Cowan et al, 2019)
  • Horizontal resolution: quasi-uniform ~15 km
  • Vertical resolution: 84 levels, hybrid-eta coordinate, lid at 0.1 hPa
  • 10-day forecasts at 00 and 12 Z

Global Ensemble Prediction System (GEPS)

  • Grid-point model (2 x 799 x 267 Yin-Yang horizontal grid) (Lin et al, 2019)
  • Horizontal resolution: ~39 km
  • Vertical resolution: 84 levels, hybrid-eta coordinate, lid at 0.1 hPa
  • 16-day, 20-member (+1 control) forecast ensemble at 00 and 12 Z (32-day on Thursday at 00 Z)

Regional Deterministic Prediction System (RDPS)

  • Grid-point model (1108 x 1082), grid centred on North America (Separovic et al, 2019)
  • Horizontal resolution: ~10 km
  • Vertical resolution: 84 levels, hybrid-eta coordinate, lid at 0.1 hPa
  • 3.5-day forecasts at 00, 06, 12 and 18 Z

Regional Ensemble Prediction System (REPS)

  • Grid-point model (1108 x 1082), grid centred on North America (Patoine, 2019)
  • Horizontal resolution: ~10 km
  • Vertical resolution: 84 levels, hybrid-eta coordinate, lid at 0.1 hPa
  • 3-day, 20-member (+1 control) forecast ensemble, piloted by GEPS (lid at 0.1 hPa)

High Resolution Deterministic Prediction System – National (HRDPS-Nat)

  • Grid-point model (2582 x 1332), grid centred on Canada (Caron et al, 2022)
  • Horizontal resolution: ~2.5 km
  • Vertical resolution: 62 levels, hybrid-eta coordinate, lid at 1 hPa
  • 2-day forecasts at 00, 06, 12 and 18 Z

Data assimilation method

Global Deterministic Prediction System

  • 4DEnVar, 6-hr data assimilation window (Buehner et al 2013)
  • Increment resolution: 0.33º x 0.33º
  • Vertical resolution: 84 levels, lid at 0.1 hPa
  • Analysis times (T): 00, 06, 12, 18 Z
  • Time window: T ± 3 hrs, divided into twenty four 15-min intervals
  • Time constraints (data cut-off time and model runtime):
    • Early analysis and forecast: T+3 hrs, forecast at 00 and 12Z only
    • Update analysis: T+7 hrs at 00, 06, 12 and 18Z

Global Ensemble Prediction System

  • LETKF, 256 members partitioned into 8 sub-ensembles, stochastic parameter perturbation, 6-hr data assimilation window (Buehner, 2020)
  • Increment resolution: 0.35º x 0.35º
  • Vertical resolution: 84 levels, lid at 0.1 hPa
  • Analysis times (T): 00, 06, 12, 18 Z
  • Time window: T ± 3 hrs, divided into seven 1-hr intervals
  • Time constraints (data cut-off time and model runtime):
    • T+7 hrs at 00, 06, 12 and 18Z

Regional Deterministic Prediction System

  • 4DEnVar, 6-hr data assimilation window (Caron et al, 2016)
  • Increment resolution: 0.33º x 0.33º
  • Vertical resolution: 84 levels, lid at 0.1 hPa
  • Analysis times (T): 00, 06, 12, 18 Z
  • Time window: T ± 3 hrs, divided into twenty four 15-min intervals
  • Time constraints (data cut-off time and model runtime):
    • Early analysis and forecast: T+2 hrs at 00, 06, 12 and 18Z.
    • Update analysis: T+7 hrs at 00, 06, 12 and 18Z.

Regional Ensemble Prediction System

  • Currently assimilation is performed by the RDPS (see above)

High Resolution Deterministic Prediction System – National

  • 4DEnVar, 6-hr data assimilation window (Caron et al, 2022)
  • Increment resolution: 0.33º x 0.33º
  • Vertical resolution: 84 levels, lid at 0.1 hPa
  • Analysis times (T): 00, 06, 12, 18 Z
  • Time window: T ± 3 hrs, divided into twenty four 15-min intervals
  • Time constraints (data cut-off time and model runtime):
    • Early analysis and forecast: T+2 hrs at 00, 06, 12 and 18Z
    • Update analysis: T+7 hrs at 00, 06, 12 and 18Z

Scatterometers assimilated

Scat name Product Models assimilated
ASCAT-B/C OSI-SAF Level 2 BUFR 25-km equivalent-neutral wind product produced by KNMI. GDPS, GEPS, RDPS, HRDPS-Nat

Monitoring

External monitoring web pages

Generic Quality Control

Observations exclusion

  • All wind speeds outside range 4-30 m/s

Ambiguity removal

  • Performed a-priori by using solution identified as most probable by the data provider (OSI-SAF/KNMI).

Bias correction

  • 0.2 m/s is subtracted from the retrieved wind speeds (see table below).

Thinning

  • 25-km retrievals thinned to 100 km by selecting observation closest to centre of 100 km x 100 km grid boxes.

Background check

  • Background check applied in GDPS, RDPS and HRDPS-Nat (GEPS assimilates observations background-checked by GDPS). Observation flagged as suspicious when ratio of squared innovation against sum of background and observation error variances is greater than or equal to 8 but smaller than 14, observation is rejected if the ratio is equal to or greater than 14.
  • Variational QC applied in deterministic systems following Gauthier et al. (2003). Applied starting at 6th iteration of the minimization. Observation weight is reduced or observation is discarded if still departing significantly from the updated analyzed state.

Specific Quality Control

Global model

Scat name ASCAT-B/C
Operational since 23 April 2014 (Metop-B), 23 July 2019 (Metop-C)
Observation error std. dev. (U/V) 1.7 m/s
Wind speed range 4-30 m/s *
Bias corrected? Equivalent-neutral wind vectors derived at KNMI using CMOD7 GMF are transformed into real wind vectors by subtracting 0.2 m/s from retrieved wind speeds. The correction corresponds to the global average difference between equivalent-neutral and real, e.g. stability-dependent, wind speeds.
Cross-track cells used All nodes 1-21 and 22-42
QC thresholds Rely on flags determined by data provider (see documentation at https://scatterometer.knmi.nl/publications/)

* The 4 m/s low wind speed threshold is applied “in-house” to eliminate observations characterized by weak winds while the upper 30 m/s threshold follows QC measures applied by the data provider which flags observations above 30 m/s as less reliable.

Observation Operator

Lowest model level

  • Height of lowest model (momentum) level: 20 m
Interpolation

  • Horizontal interpolation of 10-m real wind components calculated on the model grid using Monin-Obukhov formalism with the stability functions of Delage and Girard (1992) for unstable surface layers and Delage (1997) for stable surface layers.
Analysis increments

  • Associated wind analysis increments calculated on a 10-m analysis level from tangent linear/adjoint of the horizontal interpolation operator. Increments at other levels and on other state variables determined through the background error covariance matrix.

History of Changes

  • The list includes the main scatterometer or model changes implemented operationally in the Environment Canada models.
    None.

References

Buehner M., and Co-authors, 2013: Four-dimensional ensemble-variational data assimilation for global deterministic weather prediction. Nonlin. Processes Geophys., 20, 669-682, doi:10.5194/npg-20-669-2013.
Buehner, M., 2020: Local ensemble transform Kalman filter with cross validataion. Monthly Weather Review, 148, 2265– 2282.
Caron, J.-F., and Co-authors, 2016: Changes to the Regional Deterministic Prediction System (RDPS) from version 4.2.0 to version 5.0.0 – Description of changes and forecast performance up to 48h. Canadian Meteorological Centre Technical Note. Available on request from Environment and Climate Change Canada, Centre Meteorologique Canadien, division du developpement, 2121 route Transcanadienne, 4e etage, Dorval, Quebec, H9P1J3 or via the following link:
http://collaboration.cmc.ec.gc.ca/cmc/cmoi/product_guide/docs/lib/technote_rdps-500_20160907_e.pdf
Caron, J.-F. and Co-authors, 2022: Changes from version 5.2.0 to version 6.0.0 of the High Resolution Deterministic Prediction System – National domain (HRDPS-NAT). Canadian Meteorological Centre Technical Note. Available on request from Environment and Climate Change Canada, Centre Météorologique Canadien, division du développement, 2121 route Transcanadienne, 4e étage, Dorval, Quebec, H9P-1J3 or via the following link: https://collaboration.cmc.ec.gc.ca/cmc/cmoi/product_guide/docs/tech_notes/technote_hrdps-600_e.pdf
Côté, J., S. Gravel, A. Méthot, A. Patoine, M. Roch, and A. Staniforth, 1998: The operational CMC-MRB Global Environmental Multiscale (GEM) model: Part I – Design considerations and formulation. Mon. Wea. Rev., 126, 1373-1395.
Delage, Y. and C. Girard, 1992: Stability functions correct at the free convection limit and consistent for both the surface and Ekman layers. Bound.-Layer Meteor., 58, 19-31.
Delage, Y., 1997: Parameterising sub-grid scale vertical transport in atmospheric models under statically stable conditions. Bound.-Layer Meteor., 82, 23-48.
Gauthier, P., C. Chouinard and B. Brasnett, 2003: Quality Control: Methodology and Applications. In Data Assimilation for the Earth System. R. Swinbank, V. Shutyaev and W. A. Lahoz editors, Kluwer Academic Publishers, 388 pp.
Lin, H. and Co-authors, 2019: Upgrade of the Global Ensemble Prediction System (GEPS) from version 5.0.0 to version 6.0.0. Canadian Meteorological Centre Technical Note. Available on request from Environment and Climate Change Canada, Centre Météorologique Canadien, division du développement, 2121 route Transcanadienne, 4e étage, Dorval, Québec, H9P-1J3 or via the following link:
https://collaboration.cmc.ec.gc.ca/cmc/cmoi/product_guide/docs/tech_notes/technote_geps-600_e.pdf
McTaggart-Cowan, R. and Co-authors, 2019: Changes from version 6.1.0 to version 7.0.0 of the Global Deterministic Prediction System (GDPS). Phase 2: Changes to the atmospheric and oceanic model. Canadian Meteorological Centre Technical Note. Available on request from Environment and Climate Change Canada, Centre Météorologique Canadien, division du développement, 2121 route Transcanadienne, 4e étage, Dorval, Quebec, H9P-1J3 or via the following link:
https://collaboration.cmc.ec.gc.ca/cmc/cmoi/product_guide/docs/tech_notes/technote_gdps-700_e.pdf
Patoine, A., 2019: Regional Ensemble Prediction System (REPS) Version 3.0.0. Summary of changes with respect to version 2.4.0 and validation. Canadian Meteorological Centre Technical Note. Available on request from Environment and Climate Change Canada, Centre Météorologique Canadien, division du développement, 2121 route Transcanadienne, 4e étage, Dorval, Québec, H9P-1J3 or via the following link: https://collaboration.cmc.ec.gc.ca/cmc/cmoi/product_guide/docs/tech_notes/technote_reps-300_20190703_e.pdf
Separovic, L. and Co-authors, 2019: Changes to the Regional Deterministic Prediction System (RDPS) from version 6.0.0 to version 7.0.0. Canadian Meteorological Centre Technical Note. Available on request from Environment and Climate Change Canada, Centre Météorologique Canadien, division du développement, 2121 route Transcanadienne, 4e étage, Dorval, Québec, H9P-1J3 or via the following link: https://collaboration.cmc.ec.gc.ca/cmc/cmoi/product_guide/docs/tech_notes/technote_rdps-700_20190703_e.pdf