12. September 2008 Jährliches Treffen SWA - GKSS Page 1 An attempt to homogeneously describe 60...

12. September 2008Jährliches Treffen SWA - GKSS

An attempt to homogeneously describe 60 years statistics of TC

activity in E Asia, 1948-2007

Hans von Storch and Frauke Feser1Institute for Coastal Research, GKSS Research Center,

Germany2clisap-Klimacampus, University of Hamburg, Germany


Applications: past and future marine weather in N Europe

Globale development(NCEP)

Dynamical DownscalingREMO or CLM

Simulation with barotropicmodel of North Sea

Cooperation with a variety of governmental agencies and with a number of private companies

downscaling cascade for constructing variable

regional and local marine weather statistics


Downscaling SE Asian marine weather

• We have implemented the dynamical downscaling approach for SE Asian marine weather.

• The key question is – will we master the description of typhoons?

• Done: Case studies and seasons – formation of typhoons induced by large scale dynamics and NOT by initial values.

• Presently under examination: Continuous 6-decade simulations constrained by NCEP global re-analyses.

Feser, F.,and H. von Storch, 2008: Regional modelling of the western Pacific typhoon season 2004, Meteor. Z. 17 (3), 1-10. DOI: 10.1127/0941-2948/2008/0282Feser, F., and H. von Storch, 2008: A dynamical downscaling case study for typhoons in SE Asia using a regional climate model. Mon. Wea. Rev. 136, 1806-1815


A case study:

Simulating tropical storm Winnie (August 1997)with a regional a climate model

-Sensitivity to spectral nudging

-Sensitivity to horizontal resolution

with regional atmospheric model CLM;

initiated at or close to 1. August 1997(about 10 days prior to formation)


Core pressure development


12 TCs in Seaso

n 2004only 10

were found in

CLM simulationFollowing Zhang et

al., 2007. Meteor. Atmos. Phys.


D ianmu M indule Ranamin M egi Chaba A er e S ongda M ear i M a- on T okage

880

900

920

940

960

980

1000

T r opical Cyclones in 2 0 0 4M inimum cor e pr essur e (hPa)

Best T r ack J M AN CE P/ N CA R r e- analysisCLM 0 .5 r esolut ionCL M 0 .5 / 0 .165 doubel nest ing


Complete simulation of 1948-2007using CLM with 0.5º grid resolutionand NCEP/NCAR reanalysis

Spectral nudging of scales larges than about 800 km.

Results are new; thus may be subject to future revisions!


1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

15

20

25

30

35

40

Annual number o f T Cs dow nscaled

linear fit

11-year running m ean

best track

linear fit

11 year running m ean

Criteria have subjectively been selected so that the mean number of TCs detected in the simulation is about equal to the mean number given in the best track data.


1960 1980 2000

- 15

- 10

- 5

0

5

10

15A nnual T C countB ias CL M vs B est T r ack

CLM - Best T r ack11 year r unning mean


???????????


Beide Datensätze: JMA Best Track und NCEP Re-Analyse

sind inhomogen!

JMA best track

NCEP/NCAR

Southern Hemisphere

Northern Hemisphere


Conclusions• (Some) typhoons can be described by regional

atmospheric models run in the climate mode.• But, downscaled (simulated) TCs are too weak in terms

of core pressure, maximum pressure fall and maximum sustained wind.

• We need better data for validation.• Preliminary results concerning change- Strong year-to-year variability- Little decadal variability- No overall trend in numbers- Slight upward trends in minimum pressure and max

wind since 1990s.

12. September 2008 Jährliches Treffen SWA - GKSS Page 1 An attempt to homogeneously describe 60...

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