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
The 73rd Weather Group ROKAF
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)
The 73rd Weather Group ROKAF
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
The 73rd Weather Group ROKAF
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)
The 73rd Weather Group ROKAF
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
The 73rd Weather Group ROKAF
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.
The 73rd Weather Group ROKAF
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
The 73rd Weather Group ROKAF
9 9/19
NEWNEWCTRLCTRL
1200/16/08/2004
5880 5880
Case Study 1 (Continued)
Initial Field of 00hr : 500hPa Geopotential Height
The 73rd Weather Group ROKAF
10 10/19
1200/18/08/2004
NEWNEWCTRLCTRL
1008 1008
Case Study 1 (Continued)
Field of 48hr Forecast : Sea Level Pressure
The 73rd Weather Group ROKAF
11 11/19
NEWNEWCTRLCTRL
5880 5880
Case Study 1 (Continued)
Field of 48hr Forecast:500hPa Geopotential Height
1200/18/08/2004
The 73rd Weather Group ROKAF
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
The 73rd Weather Group ROKAF
13 13/19
1200/02/09/2004
NEWNEWCTRLCTRL
58805880
Case Study 2 (Continued)
Initial Field of 00hr : 500hPa Geopotential Height
The 73rd Weather Group ROKAF
14 14/19
1200/05/09/2004
NEWNEWCTRLCTRL
5880 5880
Case Study 2 (Continued)
Field of 72hr Forecast:500hPa Geopotential Height
The 73rd Weather Group ROKAF
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
The 73rd Weather Group ROKAF
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
The 73rd Weather Group ROKAF
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
The 73rd Weather Group ROKAF
18 18/19
Thank you