TRACKING OF WATER VAPOUR CONTRIBUTING TO PRECIPITATION EVENTS OVER THE EASTERN ITALIAN ALPS A. Bertò*, A. Buzzi** and D. Zardi* * University of Trento, Italy ** ISAC-CNR, Bologna,Italy ICAM/MAP Meeting May, Brig

BRIG THE PROJECT AQUAPAST Are there appreciable climatic changes in the precipitations patterns over Trentino? What are the main precipitation patterns? Can we trace back the origin of precipitating water? METHODS 1.MEASUREMENTS: ISOTOPIC CONTENTS OF  D AND  18 O IN precipitation water samples speleothemes from cave stalagmites 2. SIMULATIONS of recent precipitating systems evolution

FLEXTRA (Stohl & Wotawa, 1995) is a Lagrangian Model Petterson (1940) scheme INTERPOLATION: Types of trajectories: 3D, isentropic, isobaric and iso-eta. TRAJECTORY COMPUTATION (1) y x trajectory HORIZONTAL = BICUBIC VERTICAL = POLINOMIAL IN TIME = LINEAR

TRAJECTORY COMPUTATION (2) ALPS APPENNINE ALPS APPENNINE COHERENT ENSEMBLE OF TRAJECTORIES ENDING POINTS ON A 3D GRID: 0.5°  0.5° horizontal resolution 200 m vertical resolution 5  4  23=460 number of trajectories COHERENT ENSEMBLE OF TRAJECTORIES ENDING POINTS ON A 3D GRID: 0.5°  0.5° horizontal resolution 200 m vertical resolution 5  4  23=460 number of trajectories 5 DAY-3D-BACKTRAJECTORIES: Δt computation ~ 30 minutes Output time step = 3 hours COHERENT ENSEMBLE OF TRAJECTORIES ENDING POINTS ON A 3D GRID: 0.5°  0.5° horizontal resolution 200 m vertical resolution 5  4  23=460 number of trajectories 5 DAY-3D-BACKTRAJECTORIES: Δt computation ~ 30 minutes Output time step = 3 hours DOMAIN (5°,-70°) (80°,65°)

TRAJECTORY COMPUTATION (3) INPUT FIELDS FROM ECMWF (MARS ARCHIVE) : u v w to integrate trajectories p T Q PV to interpolate along computed trajectories 4D-VAR ANALYSIS ECMWF : T L 511, 60 levels observations RESOLUTION : Regular grid 0.5°  0.5° 60  vertical levels  t = 3 hours (P. White, ECMWF Training Courses 2003) Cost function J to minimize

EXAMPLE OF BACK-TRAJECTORIES TRAJECTORIES ENDING ON TRENTINO AT 03:00 OF 25/11/2002 ?

FROM TRAJECTORIES TO PATTERNS: CLUSTERING PHYSICAL SPACE r(t)=[x(t),y(t),z(t)] r (t 0 ) r (t 1 ) r (t 2 ) r (t 3 )r (t 4 ) y x PHASE SPACE TRAJECTORIES AGGLOMERATIVE PROCEDURE (CAPE ET AL., 2000) 1.Minimum average-linkage distance 2.Gather together two clusters in a cluster PATTERNS

NO OUTLIERS “Sudden breaks”: merging of significantly different clusters “ROOT MEAN SQUARE DEVIATION” FROM TRAJECTORIES TO PATTERNS: TRAJECTORY CLUSTERING DENDROGRAM

SELECTION OF EVENTS SELECTED 10 INTENSE PRECIPITATION EVENTS ( ) DOMINANT SYNOPTIC SYSTEMS: from SW PRECIPITATION depending on DIFFERENT TRAJECTORY PATTERNS: Synoptic cyclonic forcing Orographic effects Rain gauge networks in Trentino (Rigon, Bertoldi & Salvaterra, 2002) MEDIUM AND HIGH LEVEL FLOW LOW LEVEL FLOW MEDIUM AND HIGH LEVEL FLOW LOW LEVEL FLOW

CASE STUDY (24-26 November 2002) Precipitation from rain gauge measurements (A.Doff, Master Degree under way) METEOSAT: INFRARED CHANNEL (22-27/11/2002)

EVOLUTION OF BACK-TRAJECTORY CLUSTERS TRAJECTORIES ENDING AT 03:00 UTC 25/11/2002

EVOLUTION OF BACK-TRAJECTORY CLUSTERS TRAJECTORIES ENDING AT 03:00 UTC 25/11/ CLUSTERS DETECTED : 1.2 high-level clusters from West Atlantic 2.2 clusters from East Atlantic 3.2 clusters from Sahara 4.1 clusters flowing over Adriatic Sea

SIGNIFICANT CONTRIBUTION TO PRECIPITATION: 1.From area east to Morocco coast 2.From Tyrrhenian Sea TIME EVOLUTION OF BACK-TRAJECTORY CLUSTERS SIGNIFICANT CONTRIBUTION TO PRECIPITATION: 1.From area east to Morocco coast SIGNIFICANT CONTRIBUTION TO PRECIPITATION: 1.From area east to Morocco coast 2.From Tyrrhenian Sea 3.From Adriatic Sea TRAJECTORIES ENDING AT 03:00 UTC 25/11/2002

SPECIFIC HUMIDITY ALONG TRAJECTORIES 25/11/ :00

SPECIFIC HUMIDITY ALONG TRAJECTORIES 25/11/ :00

 e ALONG TRAJECTORY CLUSTERS 25/11/ :00

CONCLUSIONS CLUSTER ANALYSIS OF TRAJECTORIES ALLOWS TO DETERMINE THE ORIGIN OF PRECIPITATING WATER PRELIMINARY RESULT: EVAPORATION OVER MEDITERRANEAN AND EASTERN ATLANTIC PROVIDE THE MOST RELEVANT CONTRIBUTION FUTURE DEVELOPMENTS USE OF A MESOSCALE ATMOSPHERIC MODEL TO COMPUTE HIGH RESOLUTION FIELDS  HIGH RESOLUTION TRAJECTORIES UNDERSTAND PRECIPITATION DISTRIBUTION DETECTED BY RAIN GAUGES COMPARE RESULTS OF TRAJECTORY CLUSTERING WITH FINDINGS FROM ISOTOPIC ANALYSIS

THANK YOU FOR KIND ATTENTION !!

PV ALONG TRAJECTORY CLUSTERS 25/11/ :00