Heavy Precipitation at the Alpine South Side and Saharan Dust over

Central Europe: A Predictability Study using TIGGE

Lars Wiegand, Arwen Twitchett, Conny Schwierz & Peter Knippertz

11th EMS Annual Meeting, Berlin, 12–16 Sept. 2011

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Outline

Motivation

Upper-Level Development Forecast performance

Analysis uncertainty

High-Impact Weather Saharan dust storm

Heavy precipitation at the Alpine south side

Conclusions

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Motivation

2008/05/27 10 UTC 2008/05/27 13 UTC

Motivation

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Gorner glacier August 2008 with dust from the May event

Motivation

Motivation

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

flooding on the Alpine south side of Switzerland & Italy

Lago Maggiore rose by 10 cm in 24 hours

Motivation

4-dayprecipitation sum

26–29 May 2008

mm

source: ENSEMBLE gridded rain gauge data

Motivation

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

DATA

Thorpex Interactive Grand Global Ensemble

(TIGGE)

10 forecasting centres: Australia, Brazil, China,

Canada, ECMWF, France, Japan, Korea, UK, USA

~500 multi-model ensemble members per day

Exciting new dataset for operational forecasting

and research

Motivation

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Upper-level potential vorticity

Upper-Level Development

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Upper-Level Development

Upper-level potential vorticity

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Upper-Level Development

Upper-level potential vorticity

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Upper-Level Development

Upper-level potential vorticity

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Upper-Level Development

Upper-level potential vorticity

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Upper-Level Development

Upper-level potential vorticity

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Upper-Level Development

region of interest (29°-55°N, 15°W-2°E)

Upper-level potential vorticity

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Root mean square errors (RMSEs)

ECMWF_europe

BoM_australia

CMA_china

CMC_canada

CPTEC_brazil

JMA_japan

KMA_korea

NCEP_usa

UKMO_uk

calculated with ECMWF analysis

Upper-Level Development

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

ECMWF_europe

BoM_australia

CMA_china

CMC_canada

CPTEC_brazil

JMA_japan

KMA_korea

NCEP_usa

UKMO_uk

calculated with every center’s own analysis

Upper-Level Development

Root mean square errors (RMSEs)

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

RMSE/spread comparison

Upper-Level Development

non-dispersivemodels

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

RMSE/spread comparison

Upper-Level Development

under dispersivemodels

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Saharan dust outbreak RGB composite: purple color = dust from 2008/05/26: 09UTC – 23UTC

High Impact Weather

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Saharan dust outbreak RGB composite: purple color = dust from 2008/05/26: 09UTC – 23UTC

High Impact Weather

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

925-hPa wind fields

High Impact Weather

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Diagnostic approach

High Impact Weather

€

PDU =U 3 1−U t

U

⎛

⎝ ⎜

⎞

⎠ ⎟ 1−U t

2

U 2

⎛

⎝ ⎜

⎞

⎠ ⎟

PDU = 0

for U > Ut

for U < Ut

Define “Potential dust uplift” (PDU)

Set dust emission threshold: Ut = 10 m s–1 at 925hPa

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Potential dust uplift forecast

High Impact Weather

analyses

10

3m

3s-

3 P

DU

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

High Impact Weather

analyses

10

3m

3s-

3 P

DU

Potential dust uplift forecast

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

High Impact Weather

analyses

10

3m

3s-

3 P

DU

Potential dust uplift forecast

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

High Impact Weather

analyses

10

3m

3s-

3 P

DU

Potential dust uplift forecast

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Precipitation observation

High Impact Weather

4-day precipitation sum

06 UTC 26 – 06 UTC 29 May 2008

mm

source: ENSEMBLE (gridded rain gauges data)

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Precipitation forecast

High Impact Weather

observed precipitation

(ENSEMBLE data set)

mm

in 4

days

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

High Impact Weather

observed precipitation

(ENSEMBLE data set)

mm

in 4

days

Precipitation forecast

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

High Impact Weather

observed precipitation

(ENSEMBLE data set)

mm

in 4

days

Precipitation forecast

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

High Impact Weather

observed precipitation

(ENSEMBLE data set)

mm

in 4

days

Precipitation forecast

Motivation Upper-Level Development High Impact Weather Conclusions

Wiegand et al. – Alpine Precipitation & dust over central Europe

Conclusions TIGGE offers interesting new insight into multi-model ensemble

prediction.

Case study of unusual weather event in May 2008.

Forecast performance metrics sensitive to analysis used.

Some TIGGE models with under-dispersive behaviour.

Winds for dust mobilization over Sahara general

underpredicted but spread rather large.

Heavy precipitation at Alpine south side fairly well forecast on

regional scale.

Multi model approach increases skill!

More in a recently published paper in Weather & Forecasting

Conclusions