Project 3: Spatjal verifjcatjon of precipitatjon over the Alps during - PowerPoint PPT Presentation

Project 3: Spatjal verifjcatjon of precipitatjon over the Alps during MesoVICT-I Alvarez, Mao, Miesner, Petersen, Willemet Observatjons : • Vienna Enhanced Resolutjon Analysis (VERA) • Interpolatjon of observatjons to a regular grid in mountainous terrain Models : • Swiss COSMO-2 model • Canadian Meteorological Centre CMCGEMH (outdated version) Domain :

Methods (I) : Fractjon Skill Score Answers the questjon  “ What are the spatjal scales at which the forecast resembles the observatjons? • How forecast skill varies with neighbourhood size • The smallest neighbourhood size that can be used to give suffjciently accurate forecasts • Do higher resolutjon NWP provide more accurate forecasts on scales of interest 1 Target skill 0.5 chosen CAWR.gov.au /projects/verifjcatjon

Methods (II) : Contjguous Rain Areas (CRA) Answers the questjon “ What is the locatjon error of the (spatjal) forecast, and how does the total error break down into components due to incorrect locatjon, volume, and fjne scale structure?” Observed Forecast Users choose • threshold to defjne objects [1mm/h], and • patuern-matching functjon [R-verifjcatjon package default] CAWR.gov.au /projects/verifjcatjon

Summer convectjve situatjon in the northern Alpine in August 2007 Evening 7 th Evening 8 th Night 6/7 th mesoVICT whitepaper

19 UTC 07/08/2017 Lead: 13 hours OBSERVATIONS Fractjons Skill Score (FSS) Fractjons Skill Score (FSS) Neighborhood size No skill ! Neighborhood size F F S S S S 1 2 5 10 1 2 5 10 1 25 (mm/h) Neighborhood size (grid squares) (mm/h) Neighborhood size (grid squares) Field resolutjon: 8 km

19 UTC 07/08/2017 Lead: 13 hours OBSERVATIONS No matches in CRA Error Displacement 61 % -8 % Volume 0% 1 % Patuern 40% 107 % Dominant components of the errors are displacement and patuern errors

10 UTC 08/08/2017 Lead: 4 hours OBSERVATIONS Fractjons Skill Score (FSS) Fractjons Skill Score (FSS) Neighborhood size Neighborhood size F F S S S S 1 2 5 10 1 2 5 10 1 25 (mm/h) (mm/h) Neighborhood size (grid squares) Neighborhood size (grid squares)

10 UTC 08/08/2017 Lead: 4 hours OBSERVATIONS c b a c b a Dominant components of the errors are displacement and patuern errors

14 UTC 08/08/2017 Lead: 8 hours OBSERVATIONS Fractjons Skill Score (FSS) Fractjons Skill Score (FSS) Neighborhood size Neighborhood size F F S S S S 1 2 5 10 1 2 5 10 1 25 Neighborhood size (grid squares) (mm/h) (mm/h) Neighborhood size (grid squares)

14 UTC 08/08/2017 Lead: 8 hours OBSERVATIONS b a a b Dominant components of the errors are displacement and patuern errors

Conclusions • Applying several forecast verifjcatjon metric is recommended ! FSS • Showed how skill varies with neighborhood size • Varying skill for difgerent rainfall thresholds and over tjme CRA • Strength: error decomposed into  Displacement  Volume  Patuern • Weakness: patuern matching functjon and threshold must be carefully chosen  default might not suffjce