The utility of long-term reconstructions with

regional climate models

Hans von Storch, Frauke Feser, Ralf Weisse and Lars

Bärring

The Third Workshop on Regional Climate Modeling for Monsoon System (RCM)17-21 February 2004, East-West Center, University of Hawaii, Honolulu,

The purpose of regional models is not to validate and improve them by making them more complex but to apply them in building of new knowledge about the real world.

Long term reconstruction

• Use of model SN-REMO (REMO + spectral nudging operating on wind above 850 hPa) – details, recall Feser‘s talk

• Forcing with NCEP re-analyses 1958-2002

• Gridding: 50 km• Time step stored: 1 hourly• Area: Europe• Data freely available

Quality of reconstruction

• Is difficult to assess since specific high-resolution analyses hardly exist.

• Comparison with local data always questionable.

• Use of „integrating“ variables such as storm surges and wave heights yield favorable results.

• Wind data likely of high quality over sea – not over land.

Marcos Garcia Sotilla, 2003

Assimilated into NCEP(Atlantic)

Not assimilated into NCEP (Ionic Sea)

Wind speed at two bouys

20-year return values of wind speed, * based on daily 1992-97 data (color codes)

Southern North Sea

Extreme wind speeds

* plus from station data in NL (numbers in black)

Insa

Mei

nke,

per

s. c

omm

.

Accuracy of ISCCP estimates: about 10%

Applications

1. Assessment of changing storminess 2. Storm surges 3. Ocean wave conditions 4. Long-range pollution –

examples: gasoline lead and benzapyren

5. Commercial applications – Wind energy planning and shipbuilding

6. Emergency planning – risk of coastal oil spills

Stormcount 1958-2001

Weis

se , p

ers

. co

mm

.

C/year

t t

High tides in Helgoland (SE North Sea) in January 1995

Try

gve A

spelie

n, G

KSS

Ess

elb

orn

, pers

. co

mm

.

The Helgoland case of wave conditions in Oct 1998

Buoy at 54o 9’ N, 7o 52’ E, depth 22m(data available 1.10.1998 – 20.10 1998, every 3 hours)

Radar (WAMOS) 54º10’N, 7º53’E, depth 7m(data available 9.10.1998-31.10.1998)

Model output vs radar and buoy measurements

Lid

ia G

asl

ikova,

pers

. co

mm

.

Significant wave height

Wave mean direction (coming from)

Comparison of significant wave height from ERS (Meteomer) and HIPOCAS hindcast for the Southern North Sea for 1993.

Comparison with Satellite Data

Ocean wave height

reconstruction Solid: HIPOCAS RCM/NCEP reconstruction

Dashed: WASA/DNMI SLP reconstruction

Red: Local observations

50%, 90%, 95% and 99%iles.

Estimatedlead emissions(from Pacyna and Pacyna, 2000)

1955

19951955

1975

deposition

Calculated depositions

1995

model estimate

Estimated lead depositions into the Baltic Sea, compared to analyses based on observational evidence

0

20

40

60

80

100

120

140

160

1982 1984 1986 1988 1990 1992 1994 1996

time [a]

lead

lo

ad [

t a

-1]

lead loads at Schnackenburg/D

simulated lead loads river Elbe

Estimated transport in the Elbe river

Further Applications• Assessment of oil drifts in case of coastal accidents

• Assessment of fatigue in ships and off-shore constructions (with FGS Flensburg)

• Planning of harbor constructions (Jade Port)

• Planning of off-shore wind energy (commercial)

• Assessment of coastal defense measures (ALR)

• Wave conditions in the Elbe estuary.

Ulrich Callies, GKSS

source

Conclusions

• Regional models can be used to reconstruct detailed weather in the past decades by downscaling global re-analyses.

• In particular information about marine wind can be used for assessing past developments and contemporary risk assessments.

Mean monthly

precipitation [mm/month]

for 1999.

REMO

Frauke F

ese

r, p

ers

. co

mm

.

NCEP