The sensitivity study on typhoon track prediction from variation of the initial field

Jong-Seok Kim Gi-Sung Ban•

The 73rd Weather Group

Republic of Korea Air Force

The sensitivity study on typhoon track prediction from variation of the initial

field

The 73rd Weather Group ROKAF

2 2/19

Background• There are two principal Factors affecting typhoon track

: One is Variation of synoptic field around a typhoon

and the other is transformation of typhoon structure

• Field error of typhoon environmental area result in

track forecast error increase as forecast time is extended - these factor is not a accurate, resulting these generate errors in typhoon track forecast.

Introduction

Object• try to improve Korea Air Force typhoon track forecast• Improved model initial field is composed of typhoon area applying FDDA and typhoon environmental area using analysis field at initial time


3 3/19

Configuration of KAF-TYP

Model Version

Horizontal Dimension(Resolution)

Time Integration

Vertical layer

Forecast time

Implicit Physics Scheme

Cumulus Parameterization

Planetary Boundary Layer

Radiation Parameterization

MM5 Version 3.5

121 X 141 (36km)

90 sec

23 Sigma Layer

84hr

Reisner II

Kain-Fritsch

MRF

RRTM

Initial DataGDAPS 1.875 ˚(-12hr, -6hr, 00hr)

NOAA Weekly Mean SSTTyphoon Data (-12hr, -6hr, 00hr)


4 4/19

JMA typhoon bogussing

method to insert artificial typhoon in the initial field for every 6hr in 12hr

Typhoon Bogussing Analysis Field(-12hr)

BogussingBogussing

Bogussing Field(-12hr)Analysis Field(-6hr)

BogussingBogussing

Bogussing Field(-6hr)Analysis Field(00hr)

BogussingBogussing

Bogussing Field(00hr)

Configuration of KAF-TYP(Continued)

initial field applied FDDA about wind field every 6hr

in 12hr.

FDDA FDDA Field(-12hr)

FDDAFDDA

FDDA Field(-6hr)

FDDAFDDA

FDDA Field(00hr)

FDDAFDDA


5 5/19

An issue of KAF-TYP

• compared the model initial field(FDDA) with analysis field at same time

A clear Difference on typhoon environmental area At the initial field applying FDDA on whole domain Reinforce of the inner typhoon structure is prominent As forecast time is extended, Analysis error generated in initial time increase, 48hr typhoon track forecast error is amplified

Analysis Field(00hr) FDDA Field for 12hr(00hr)


6 6/19

Environmental area : Analysis Field of initial time

(00hr)

Typhoon area is replaced of an artificial typhoon

(every 6hr in 12hr)

An artificial typhoon is combined with the revised environmental area

: Improved initial Field

Improvement of KAF-TYP To improve initial Field of KAF-TYP to reduce analysis field • Reinforce typhoon structure (by using the typhoon bogussing and FDDA)

• Reduce analysis field error to typhoon environmental area


7 7/19

CTRL

EXP1

NEW

Method of Bogussing

12hr

NO (analysis field)

FDDA Time

12hr

NO

Typhoon area : 12hr FDDA + 12hr BogussingEnvironmental area : (No FDDA) analysis Field

Methodology Experimental Design

Typhoon data explanation

• Typhoon developed on Northwest Pacific on May-October 2004

• There are 20 typhoons in this period and we operated model by 159 times

CTRL means applied whole model domain by FDDA.

NEW means using improved initial field was divided inner and outer typhoon

area.


8 8/19

1200/16/08/2004

12hr

24hr

36hr

48hr

60hr

72hr

CTRL(km)

174.2

279.7

366.1

356.2

386.6

489.4

NEW(km)

105.6

104.8

214.0

283.8

332.3

256.9Surface Chart

Case Study 1

Track Forecast ErrorTrack Forecast

2004-081612


9 9/19

NEWNEWCTRLCTRL

1200/16/08/2004

5880 5880

Case Study 1 (Continued)

Initial Field of 00hr : 500hPa Geopotential Height


10 10/19

1200/18/08/2004

NEWNEWCTRLCTRL

1008 1008


Field of 48hr Forecast : Sea Level Pressure


11 11/19

NEWNEWCTRLCTRL

5880 5880


Field of 48hr Forecast:500hPa Geopotential Height

1200/18/08/2004


12 12/19

Case Study 2

1200/02/09/2004

12hr

24hr

36hr

48hr

60hr

72hr

CTRL(km)

50.0

33.0

91.1

138.9

191.5

197.5

NEW(km)

50.0

33.0

22.1

83.3

118.3

114.6

0000/03/09/2004

12hr

24hr

36hr

48hr

60hr

72hr

CTRL(km)

14.2

88.9

179.3

239.5

291.7

388.3

NEW(km)

33.0

88.9

104.3

207.1

211.1

299.0

1200/03/09/2004

12hr

24hr

36hr

48hr

60hr

72hr

CTRL(km)

60.9

72.5

155.6

174.8

312.4

368.4

NEW(km)

60.9

89.9

122.3

147.3

220.0

298.5

0000/04/09/2004

12hr

24hr

36hr

48hr

60hr

72hr

CTRL(km)

12.0

85.9

174.8

312.4

403.8

694.5

NEW(km)

23.0

85.9

147.3

236.3

234.5

470.3

1200/04/09/2004

12hr

24hr

36hr

48hr

60hr

72hr

CTRL(km)

27.5

39.9

142.6

254.6

546.3

1279.2

NEW(km)

27.5

39.9

97.8

155.0

374.9

971.6

0000/05/09/2004

12hr

24hr

36hr

48hr

60hr

72hr

CTRL(km)

44.0

29.0

83.7

216.8

533.2

472.2

NEW(km)

40.1

62.1

103.8

148.6

383.9

437.1Surface Chart

Track Forecast ErrorTrack Forecast

2004-090500


13 13/19

1200/02/09/2004

NEWNEWCTRLCTRL

58805880


Initial Field of 00hr : 500hPa Geopotential Height


14 14/19

1200/05/09/2004

NEWNEWCTRLCTRL

5880 5880


Field of 72hr Forecast:500hPa Geopotential Height


15 15/19

246.4

326.8

428.6

188.7

84.4

141.412.312.3

35.635.6

50.250.2

46.446.4

Result

Mean Track Forecast Error• Typhoon developed on May-October 2004

New case shows more advenced resultthan CTRL as time going up (specially after 36 hr)

New case will offer better forecast result

suppose NEW case will offer better forecast data to forecasters


16 16/19

Case using initial field applying FDDA

only on typhoon area(NEW) than whole domain(CTRL)

Advancement of 48hr typhoon track forecast

Improvement of track forecast for pre-grade cyclone

Analysis error of environmental area is more reduced

Simulation of typhoon environmental field is improved

Conclusion


17 17/19

Using high resolution data(AVN 1˚X1˚, GDAPS 0.56˚X0.56 ˚)

Analyze typhoon track forecast depend on initial field resolution

Furthermore, with advancement of bogussing method

will study of reducement typhoon track forecast error

by varying intensity

Will try to improve typhoon track forecast

Future Work


18 18/19

Thank you

The sensitivity study on typhoon track prediction from variation of the initial field

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