Precipitation and cloud forecasts in two HIRLAM versions (RCR and H635) in September 2004

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Precipitation and cloud forecasts in two HIRLAM
versions (RCR and H635) in September 2004

• Kalle Eerola
• Finnish Meteorological Institute
• kalle.eerola_at_fmi.fi

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Contents

1. Introduction
2. Precipitation verification of European LAMs from
   U.K. Met.Off.
3. Comparison of RCR and H635 forecasts
4. Differences between RCR and H635
5. Accumulated monthly precipitation
6. Verification of T2m, Rh2m and cloudiness
7. Conclusions

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Precipitation verification of European LAMs by
U.K. Met.Off

• Area United Kingdom
• Against UK NIMPROD rain-fall composite
• Time since January 2004
• LAMs
• Aladin (France)
• Hirlam RCR (FMI)
• Lokall MODEL (DWD)
• Met. Off. unified mesoscale Model (U.K.)
• Scores
• FBI - Frequency Bias Index
• gt1 ? overestimates, lt 1 ? underestimates
• ETS Equitable Threat Score
• 0 for random hit, 1 for perfect forecast

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FBI and ETS over UK for different thresholds

• Results since January 2004
• Hirlam RCR at FMI (6.3.0)
• Frequency bias
• All model overestimate weak precipitation
• Hirlam underestimates moderate/strong
  precipitation
• Other models overestimate them
• Equitable Threat Score
• Hirlam very weak rain score lower
• Skill decreases in all model as threshold
  increases

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Results of tests between RCR and Hirlam 6.3.5

• RCR Regular Cycle with the Reference
• RCR Hirlam 6.2.1 changes Hirlam 6.3.0
• Earlier no one ran with reference ? no good idea
  how the reference works
• Operational at FMI
• Resolution 0.2º x 0.2º, 40 levels
• Archived at ECMWF, available for Hirlam community
• Products available for Hirlam community in
  near-real time on WEB-pages
• Available a mod. set to run parallel to RCR (will
  be included into the reference )
• Possible to test against RCR products
• A control run already exists

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Main differences and similarities between RCR and
H635

• Similarities
• H635 uses same observations, boundaries, boundary
  strategies and extra observations as RCR
• Same area and resolution in horizontal and
  vertical
• Differences
• New release of HIRVDA (mainly technical)
• Modified water vapour saturation below freezing
• First Aid Kit by Laura Rontu
• Tanquay-Ritchie scheme of temperature in
  SL-scheme
• Rotation of surface stress vector
• Physics-dynamics coupling
• Modified melting of soil ice
• Smoothed topography

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Monthly precipitation Europe

• Rather similar in RCR and H635, compares well to
  gauge-based analysis
• GPCC The Global Precipitation Climatology
  Centre
• H635 more precipitation than RCR (Scandinavia,
  Alps,)
• H635 has smoother structure
• Smoothed orography
• Tanquay-Ritchie SL changes
• Dynamics-physics coupling

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Monthly precipitation Scandinavia

• Rainy month in Finland observed is 100-300 of
  the normal
• In H635 more precipitation, fits better to
  observed (southern Finland, Kainuu),
• H635 has smoother sctructure

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Convective part of precipitation

• As earlier, the 24-48 hour forecasts, ie. second
  day
• In H635 the structure is much smoother than in
  RCRa
• Smoothed orography
• Tanquay-Ritchie SL changes
• Dynamics-physics coupling
• Especially over the mountains

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Conclusion from precipitation

• H635 produces more precipitation than RCR
• The accumulated monthly precipitation has a
  smoother structure in H635 than in RCR
• Convective part is especially smoother

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Diurnal variation in surface (near-)parameters
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Station verification for EWGLAM stations

• T2m
• At night almost all negative bias removed
• During day negative bias reduced
• RH2m
• Diurnal cycle in RCRa
• In H635 almost unbiased

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At night Bias of T2m, Rh2m and cloudiness
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During day Bias of T2m, Rh2m and cloudiness
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Conclusions I

• U. K. Met. Off. Precipitation verification
• Frequency bias
• All model overestimate weak precipitation
• Hirlam underestimates moderate/strong
  precipitation, while other models overestimate
  them
• Equitable Threat Score
• Hirlam very weak rain score lower
• Skill decreases in all model as threshold
  increases
• Accumulated monthly precipitation
• H635 produces more precipitation than RCR
• The accumulated monthly precipitation has a
  smoother structure in H635 than in RCR
• Convective part is especially smoother

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Conclusions II

• At Night
• T2m negative bias decreased, even positive bias
  in some are
• Rh2m Positive bias (too humid) decreased
• Too dry southern Europe and America
• Cloudiness. Difficult to interpret the results
• Daytime
• T2m
• Cold bias still is in H635 but it is reduced
• In America almost disappeared
• Rh2m
• Positive (too humid bias has reduced in central
  and northern Europe
• Even too much in southern Europe, where in H635
  is now negative bias
• Cloudiness difficult to interpret