Precipitation and cloud forecasts in two HIRLAM versions
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Precipitation and cloud forecasts in two HIRLAM versions (RCR and H 635) in September 2004 • Kalle Eerola • Finnish Meteorological Institute • kalle. eerola@fmi. fi 20/10/2021 1
Contents 1. Introduction 2. Precipitation verification of European LAMs from U. K. Met. Off. 3. Comparison of RCR and H 635 forecasts 1. Differences between RCR and H 635 2. Accumulated monthly precipitation 3. Verification of T 2 m, Rh 2 m and cloudiness 4. Conclusions 20/10/2021 2
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 • >1 overestimates, < 1 underestimates – ETS – Equitable Threat Score • =0 for random hit, =1 for perfect forecast 20/10/2021 3
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 20/10/2021 4
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 20/10/2021 5
Main differences and similarities between RCR and H 635 • Similarities – H 635 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 20/10/2021 6
Monthly precipitation: Europe • • Rather similar in RCR and H 635, compares well to gauge-based analysis GPCC = The Global Precipitation Climatology Centre H 635 more precipitation than RCR (Scandinavia, Alps, …) H 635 has smoother structure • Smoothed orography • Tanquay-Ritchie SL changes • Dynamics-physics coupling 20/10/2021 7
Monthly precipitation: Scandinavia • • • Rainy month in Finland: observed is 100300% of the normal In H 635 more precipitation, fits better to observed (southern Finland, Kainuu), H 635 has smoother sctructure 20/10/2021 8
Convective part of precipitation • • As earlier, the 24 -48 hour forecasts, ie. second day In H 635 the structure is much smoother than in RCRa – Smoothed orography – Tanquay-Ritchie SL changes – Dynamics-physics coupling • Especially over the mountains 20/10/2021 9
Conclusion from precipitation • H 635 produces more precipitation than RCR • The accumulated monthly precipitation has a smoother structure in H 635 than in RCR • Convective part is especially smoother 20/10/2021 10
Diurnal variation in surface (near-)parameters 20/10/2021 11
Station verification for EWGLAM stations • T 2 m – At night almost all negative bias removed – During day negative bias reduced • RH 2 m – Diurnal cycle in RCRa – In H 635 almost unbiased 20/10/2021 12
At night: Bias of T 2 m, Rh 2 m and cloudiness 20/10/2021 13
During day: Bias of T 2 m, Rh 2 m and cloudiness 20/10/2021 14
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 – H 635 produces more precipitation than RCR – The accumulated monthly precipitation has a smoother structure in H 635 than in RCR – Convective part is especially smoother 20/10/2021 15
Conclusions II • At Night • • • T 2 m: negative bias decreased, even positive bias in some are Rh 2 m: Positive bias (too humid) decreased Too dry: southern Europe and America Cloudiness. Difficult to interpret the results Daytime • T 2 m: • • – – Cold bias still is in H 635 but it is reduced In America almost disappeared Rh 2 m: • Positive (too humid bias has reduced in central and northern Europe • Even too much in southern Europe, where in H 635 is now negative bias Cloudiness: difficult to interpret 20/10/2021 16
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