Using Atmospheric Models and Ensembles on a Variety of Time and ...

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Using Atmospheric Models and Ensembles on a Variety of Time and ...

ong>Usingong> ong>Atmosphericong> ong>Modelsong> ong>andong> ong>Ensemblesong> on a

Variety of Time ong>andong> Spatial Scales to Improve

Predictions of Song>andong>y, Storm Surge, ong>andong> Future

Changes in Coastal Storms

Dr. Brian A. Colle

School of Marine ong>andong> ong>Atmosphericong> Sciences


Outline

• What was unusual about Song>andong>y from a

meteorological perspective?

• Storm Surge Forecast Issues – Motivation for

ensembles ong>andong> multi-model approaches

• Collaboration with Penn State on simulations

of Song>andong>y using Ensemble Kalman Filter

(EnKF) data assimilation

• Future (next 100 years) changes East coast

storms (Oct-March) from an ensemble of

global climate models


Upper-Level Flow Differences

1938 Long Islong>andong> Express Hurricane Song>andong>y 2012


How Rare Was Song>andong>y??

(Hall ong>andong> Sobel (GRL 2013) – 1 in 700 yr storm??

Song>andong>y

Scileppi ong>andong> Donnelly, 2007, Geochem. Geophys. Geosys.


Courtesy of Mel Shapiro

Scatterometer

observed winds

at 0600 UTC 29

Oct 2012

L


knots

L

Scatterometer

Winds at

1200 UTC 29

Oct 2012


Obs water

level

NOAA ong>andong> Stevens

Inst 46-h forecast


Stony Brook (ADCIRC) Surge Forecasts using 12-km MM5

Obs

29/12

27/12

29/00

28/00

28/12


12-km

MM5 run

starting at

1200 UTC

28 Oct

Valid:

2200 UTC

29 Oct

* NYC


Benefits of Multi-Model Surge Predictions (Brier

Skill relative to SBSS CTL – DiLiberto et al. 2011)

ALL-Bias Correct

ENS3-

Bias

correct

ENS 3 (Best SBSS

member , NWS, Stevens)

ALL (5 SBSS, NWS,

Stevens)

SBSS (5

members)


To Better Estimate of ong>Atmosphericong> Forcing

ong>andong> Uncertainty: Ensemble WRF Simulations

ong>Usingong> 60-member EnKF (Assimilates Aircraft

Doppler ong>andong> In Situ-- Zhang et al. 2011)

Courtesy of Dr. Fuqing Zhang

Wind speed in kts


WRF Model Simulation (3-km grid spacing)


Observed Surface Wind Comparison vs 3-km WRF

Simulation of Hurricane Song>andong>y at Long>andong>fall.

at 1200 UTC 29 October 2012

Satellite Obs

3-km WRF


But how will coastal flooding

events change as we go into the

future?

-As the climate changes, the frequency, intensity ong>andong> track of cyclones will must

change.

-We can use general circulation models (GCM's) as part of the Coupled Model

Intercomparison Project (CMIP5) to determine long term variability in the weather

using grid spacing of 0.5 to 3 degrees.

Source:

http://www.climatewizard.o

rg/Climate_ong>Modelsong>_ong>andong>_Sc

enarios/Climate_ong>Modelsong>.ht

ml


Cyclone frequency ong>andong> intensity (Oct-March) were tracked within 13 GCM's

along the East Coast of the U.S. (Colle et al. 2013)


East Coast Region Future

Change in 6-h Deepening Rates

Number change per cool season in EC-L

% Change in the number of 850

hPa wind bins for MPI ong>andong> MRI

models (10 deg around cyclone)

% change per cool season in EC-L


Summary

• A blocking high to the northeast helped steer

Song>andong>y to the coast. This pattern is not that

unusual during the Fall season, but it is rare to be

coupled with a tropical/hybrid storm.

• Song>andong>y’s wind field was highly asymmetric – can

not use a simplified or deterministic wind field.

• Large surge forecast uncertainty with Song>andong>y’s

track. ong>Usingong> multi-model surge predictions can

improve accuracy of water levels.

• Global CMIP5 models suggest there may be a

period during the mid-21 st century with more

intense Fall-Spring storms.

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