平成 28 年度
三重大学大学院 生物資源学研究科
修士論文

結合系『黒潮→台風⇔大気』がもたらす台風の U ターン
A “Kuroshio-typhoon-atmosphere” couple system causes the Uturn of a typhoon

Weather and Climate Dynamics Division
Graduate school of Bioresources
Mie University515M209
Momoko Horiguchi
Supervisor: Prof.Yoshihiro Tachibana

1

ABSTRACT
Typhoon Ma-on landed of Tokushima prefecture on 20 July 2011, then moved southward until
July 22.Focusing on the characteristic course of this typhoon, we conducted a verification using
a numerical model. When the typhoon is strong, the typhoon does not go southward but goeseast, but when the typhoon is weak, the typhoon goes southward. Comparing the atmosphericenvironment around the typhoon at this time, the result of both calculations was a place where
north wind dominates as a whole, but when the typhoon was strong, there was a high pressureanomaly on the east side of the typhoon compared to the weak typhoon. It was shown that thesouth wind was excited. From this, it was shown that the stronger the typhoon, the more distantthe effect is to the surroundings. From the results of data assimilation, the developing ofdisturbance and the strengthening of trough were seen on the Kuroshio Extension. In
assimilation of the observation, low pressure anomaly was observed on the Kuroshio Extension
compared to REF. It is thought that the disturbance captured by the observation developed on theKuroshio Extension. From the results of the two analyzes, the remote influence of the typhoonand the development of the disturbance occurred on the Kuroshio Extension, which supported
the southward movement of the typhoon.

2Contents

1. Introduction .......................................................................................................................... 4
2. Data and Methods ................................................................................................................. 6
2.1 Model configuration ............................................................................................................ 62.2 Data assimilation ................................................................................................................ 8
3. Result .................................................................................................................................. 10
3.1 Calculation results of the model ....................................................................................... 10
3.2 Analysis results of data assimilation ............................................................................... 12
4. Discussion and conclusion .................................................................................................. 13
Acknowledgements ................................................................................................................. 15Reference ................................................................................................................................. 16
List of Table ............................................................................................................................ 18
Figure Captions ...................................................................................................................... 183

1. Introduction
The course of typhoons is determined by two factors, large-scale flow and typhoon’s ownflow. Although the typhoon itself has a flow toward the northwest due to the beta effect and soon, Chan and Williams (1987) showed that the movement by his own flow is extremely slow and
it is common to be flushed by the wind of the upper layer. Therefore, many studies have been
made to determine the course by the influence of the surrounding atmospheric pressure field, but
the contents that the typhoon itself affects the surroundings there are few studies on the influenceof the typhoon itself on. Research on typhoons by remote effect, there are things that the remoteinfluence affects the correlation magnitude atmospheric field and the one that influences thetyphoon's own route.Kawamura and Ogasawara (2006) and Yamada and Kawamura (2007)

showed the influence of the typhoon around the surrounding area. These studies show that atyphoon strengthens the anticyclone in remote way. However, these studies do not mention therelationship between the enhanced anticyclone and the course of the typhoon. As a previous
study, Katsube and Inatsu (2016) describes the relationship between the strength of the typhoonand its course.
Typhoon Ma-on landed of Tokushima prefecture on 20 July 2011, then moved southward until
July 22. Typhoons moving southwards for two days near Japan are unprecedented. This4

movement is different from the movement of westerly jet and Pacific Ocean anticyclone and it isalso different from typhoon's own flow.
In this research, we focus on the path like U-turn of Margon. The aim in this research is toclarify whether or not the remote forcing of typhoon is involved as a reason for taking suchcourse. In order to achieve this research purpose, we investigated the influence of typhoon
intensity using a numerical weather forecast model and verified the influence of the Kuroshio
Extension flow using data assimilation.

5

2. Data and Methods
2.1 Model configuration
We conducted a numerical experiment by using the Weather Research and Forecasting (WRF)
Model Version 3.4.1 (Michalakes et al. 2001). Calculating area is shown in Fig.1. The outermost
domain (d01) had horizontal resolution of 30km. The second outside domain (d02) had
horizontal resolution of 6km. All domains included 50 vertical layers. Using parameters is shown
table 1.
The initial and lateral boundary conditions of the atmosphere used the European Centre for
Medium-Range Weather Forecasting (ECMWF) ERA-interim data(Simmons et al, 2007) withhorizontal resolution 1.5° × 1.5°. The initial and lateral boundary conditions of sea surface
temperature (SST) used daily National Oceanic and Atmospheric Administration (NOAA)
optimum interpolation sea surface temperature (OISST,Reynolds et al. 2002) data withhorizontal resolution 0.25° × 0.25°. Calculation period was 5 day, from 0000 UTC 18 July 2011
to 0000 UTC 23 July 2011.
Calculation results using the above data is referred to as control run (CTL). Calculation results
to weakened the strength of the typhoon is referred to as weak run(Weak). In Weak,remove thetyphoon from the initial value, inserted a weaker vortex than the actual typhoon. The actual

6

typhoon went south while weakening. In the computation result of CTL, weakening of the actual

typhoon was not expressed.
We verified by comparing the both of calculation results that difference between strength of
typhoon influences course.

7

2.2 Data assimilation
2.2.1 Radiosonde Observations form a ship
This study uses GPS radiosondes data taken research vessel Wakatakamaru. In 2011
observation, GPS radiosondes were launched over the Sanriku conducted every other hour off
from 1600 UTC 19 Jul 2011 to 0900 UTC 19 July 2011. The observation point is shown in Fig.2.
2.2.2 Ensemble Reanalysis
An observing system experiment was performed by comparing two analyses produced using
ALEDAS2 (AFES–LETKF ensemble data assimilation system 2) with and without the additional
radiosonde observations(hereafter referred to as CTL and OSE, respectively). ALEDAS2 is anatmospheric ensemble reanalysis data assimilation system composed of the Atmospheric General
Circulation Model (AGCM) for the Earth Simulator (AFES; Ofuchi et al. 2004; Enomoto et al.
2008) and the Local Ensemble Transform Kalman Filter (LETKF; Hunt et al. 2007; Miyoshi andYamane 2007).
ALERA2 is an experimental ensemble reanalysis produced using ALEDAS2 and includes theanalysis ensemble mean and analysis ensemble spreads for wind, temperature, humidity andgeopotential height for 63 ensemble members at 48 levels with a horizontal resolution 1.25° ×1.25°.

8By comparing the two reanalysis data, it becomes possible to evaluate the influence of a small
scale disturbance captured by observation.

93. Result
3.1 Simulated results of the numerical model
Figure 3 shows the typhoon of CTL_RUN headed east, no movement toward the south east likethe actual typhoon was seen, and the traveling speed was also faster than the reality (red line inFig. 3). The track of the Weak_RUN’s typhoon resulted in a rough reproduction of the path likethe actual U-turn of the typhoon (white line in Fig.3). Weak_RUN reproduces to some extent thereason why the typhoon made its way to the south.
Figure 4 shows the geopotential height at 500 hPa (Z500) in (a) CTL_Run and (b) Weak_Run
at 0000 UTC 20 July 2011. The typhoon started to go southward in this time. These can be due tothe synoptic-scale atmospheric pressure pattern where the north wind dominates.
Figure 5 shows the difference between CTL_RUN and Weak_RUN of sea level pressure(SLP) at 0000 UTC 20 July 2011. In order to eliminate the difference due to the strength of thetyphoon, we masked out the area around the typhoon. Focusing on the typhoon surroundings, theanticyclone anomaly distributed the eastern side of the typhoon. This high pressure anomaly
continued to the upper level. suggesting that the typhoon was strongly driven by the north wind
to the upper level at the front of the typhoon at Weak_RUN.
Also, in the range of 30-40°N and 140-160°E where the high pressure anomaly appears on the10eastern side of the typhoon, each term of the vorticity equation (1) below is area averaged. Thiscalculation was done to investigate the origin of high pressure anomaly.The term enclosed in red
is the horizontal divergence term, the term enclosed in blue is the beta term, and the term
enclosed in yellow is the advection term. Horizontal divergence term 6.5 × 10 -10 / s, beta term
5.6 × 10 -12 / s. The advection term was -1.8 × 10 -10 / s, indicating that the high pressure anomaly𝝏𝜻𝝏𝒕= −𝒖

𝝏𝜻
𝝏𝒙−𝒗

𝝏𝜻
𝝏𝒚−𝒗

𝝏𝒇
𝝏𝒚− (𝜻 + 𝒇) (𝝏𝒖𝝏𝒙+𝝏𝒗𝝏𝒚) (1)was caused by divergence.
Figure 6 shows the precipitation at (a) CTL_RUN (b) Weak_RUN at 1200 UTC 19 July 2011.
The precipitation of CTL_RUN is heavier on the east side of the typhoon itself and the upward
flow accompanying the typhoon is stronger on the east side of the typhoon itself (figure notshown).

113.2 Analysis results of data assimilation
Figure 7 shows the difference between OSE and REF of (a) SLP and (b) Z500 at 0600 UTC 20July 2011. High pressure anomaly distributed near the observation point. There are two low
pressure anomalies in the east and west of the high pressure. The result of OSE reflects thedevelopment of the small-scale disturbance captured by Radiosonde observations, which is notseen in REF. Furthermore, it is suggested that the disturbance may affect the large-scale lowpressure of the upper layer.
Figure 8 shows the SLP and SST at (a) REF (b) OSE at 1200 UTC 20 July 2011. In OSE,
compared to REF, the low pressure section extends from the typhoon to the east along theKuroshio Extension basin.
Figure 9 shows the difference between the OSE and the REF of the wind direction and windspeed, and absolute wind speed averaged from 925 hPa to 600 hPa at 1800 UTC 20 July 2011. In
OSE, rotation of low pressure is distributed. The result of OSE is a north wind on the northeast
side of the typhoon, and the typhoon becomes a peripheral field which makes it easy to gosouthward.

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4. Discussion and conclusion
Typhoon Ma-on landed of Tokushima prefecture on 20 July 2011, then moved southward
until July 22. Focusing on the characteristic course of this typhoon.
In order to verify the relationship between course and strength, we verified by numericalmodel.From the results of numerical model experiments, the typhoon of CTL_RUN did not go
southward and that of Weak_RUN went go southward (Fig.3).The difference between theCTL_RUN and the Weak_RUN suggests that there is a high pressure anomaly in the front (east)of the typhoon from the lower level to the upper level and in the Weak_RUN it is a north wind at
the front of the typhoon southward(Fig.5).Since the difference between the CTL_RUN and theWeak_RUN is only the initial typhoon intensity, we suggest that this anticyclone anomaly wasexcited by the difference in typhoon intensity.
The reason for the high pressure anomaly on the east side of the typhoon is believed to berelated to the strong rainfall on the east side of the typhoon itself by CTL_RUN(Fig.6). In theCTL_RUN, the upward flow is strong on the east side of the typhoon itself, and there was adownward flow at the front(east) of the typhoon as a supplementary flow.
This is a result suggesting that a strong intensity typhoon may affect the course. Thismechanism has been clarified in this research.

13

From the results of data assimilation, the developing of disturbance and the strengthening oftrough were seen on the Kuroshio Extension.(Fig.7). In Ose, low pressure anomaly was observedon the Kuroshio Extension compared to REF. It is thought that the disturbance captured by theobservation developed on the Kuroshio Extension.

From the results of the two analyzes, the remote influence of the typhoon and thedevelopment of the disturbance occurred on the Kuroshio Extension, which supported thesouthward movement of the typhoon.

14

Acknowledgements
I extend grateful thanks for Prof. Yoshihiro Tachibana who is my supervisor. Prof. Tachibanataught me the amusingness to research for meteorology or climate and he gave me a chance toinnovative research, irreplaceable meteorological knowledge and technics for analysis.
I extend special thanks to Dr. Kunihiko Kodera and Dr. Koji Yamazaki for their very helpful
discussions. Members of Weather and Climate Dynamics Division provided some advices for myresearch. I would like to thank for them.

15References
Chan, J. C. L., and R. T. Williams, 1987: Analytical and numerical studies of the beta-effect intropical cyclone motion. Part I: Zero mean flow. J. Atmos. Sci., 44, 1257–1265.
Kawamura,R., and T. Ogasawara, 2006: On the Role of Typhoons in Generating PJ
Teleconnection Patterns over the Western North Pacific in Late Summer. SOLA., 2, 37‒40.
K. Yamada and R. Kawamura, 2007: Dynamical Link between Typhoon Activity and the PJ
Teleconnection Pattern from Early Summer to Autumn as Revealed by the JRA-25
Reanalysis. SOLA., 3, 65‒68
Katsube, K., and M. Inatsu, 2016: Response of tropical cyclone tracks to sea surface temperaturein the Western North Pacific. J. Climate, 29, 1955-1975.
Michalakes, J.,and S. Chen, and J. Dudhia, and L. Hart, and J. Klemp, and J. Middlecoff, and W.
Skamarock, 2001: Development of a next generation regional weather research and forecastmodel. Developmentsin Teracomputing: Proceedings of the Ninth ECMWF Workshop on theUse of High Performance Computing in Meteorology, W. Zwieflhofer and N. Kreitz, Eds.,
World Scientific, 269–276.

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Simmons, A., and S. Uppala, D. Dee, and S. Kobayashi, 2007: ERA-Interim: New ECMWF reanalysis products from 1989 onwards. ECMWF Newsletter, 110, 25–35, ECMWF, Reading,United Kingdom.
Reynolds, R. W., 1988: A real-time global sea surface temperature analysis. J. Climate, 1, 75–76.

17

List of Table
1. Using parameters of regional meteorological model.

Figure Captions
1.

Domains of regional meteorological model.

2.

The map of Sanriku.Red point shows observation point. Observations were made from 16

UTC on July 19, 2011 to 09 UTC on 20 July 2011, St.1 to St.18 at one hour intervals.
3.

Course in each of the calculation results.CTL_RUN：red line，Weak_RUN：white line,

Besttrack:blue line.
4.

Z500 on 0000UTC 20 July 2011.(a)CTL_RUN, (b)Weak_run

5. The SLP differences between CTL_RUN and Weak_RUN at 0000 july 20. Green line:SLP ofCTL_RUN，black line SLP of Weak_RUN.
6. The precipitation and SLP at 0000UTC 20 July 2011. Color:precipitation(mm/hr) line:SLP.
(a)CTL_RUN, (b)Weak_run.
7. The difference between OSE and REF of (a)SLP (b)Z500 at 0600 UTC 20 July 2011.
Black line:SST.
8. The SLP and SST at (a)REF (b) OSE at 1200 UTC 20 July 2011.
9. The difference between the OSE and the REF of the average wind direction wind speed and18

absolute wind speed at 925 hPa to 600 hPa at 1800 UTC 20 July 2011.

19

Figure 1. Domains of regional meteorological model.

20

Figure 2. The map of the positions of radiosonde observation. Red point shows observation point.
Observations were made from 16 UTC on July 19, 2011 to 09 UTC on 20 July 2011, St.1 to St.18
at one hour intervals.

21

Figure 3. Course in each of the calculation results.CTL_RUN：red line，Weak_RUN：whiteline, Besttrack:blue line.

22

（a）

（b）Figure 4. Z500 on 0000UTC 20 July 2011.(a)CTL_RUN, (b)Weak_run.

23

Figure 5. The SLP differences between CTL_RUN and Weak_RUN at 0000 july 20. Greenline:SLP of CTL_RUN，black line SLP of Weak_RUN.

24

（a）

（b）

Figure 6. The precipitation and SLP at 0000UTC 20 July 2011. Color:precipitation(mm/hr)
line:SLP. (a)CTL_RUN, (b)Weak_run.

25

（a）

（b）

Figure 7. The difference between OSE and REF of (a)SLP (b)Z500 at 0600 UTC 20 July 2011.
Black line:SST.

26

（a）

（b）

Figure 8. The SLP and SST at (a)REF (b) OSE at 1200 UTC 20 July 2011.

27

Figure 9. The difference between the OSE and the REF of the average wind direction wind speed
and absolute wind speed at 925 hPa to 600 hPa at 1800 UTC 20 July 2011.

28

Table 1 Using parameters of regional meteorological model

CTL_Run,Weak_Run
Domain2

Horizontal
Resolution

30km,6km

Vertical Layers

50Layers

Nesting1way

The initial andlateral boundary
conditions

ERA-Interim
OISST

2011/07/18

Initial time

00:00

Microphysics

WDM6Cumulus
Parameterization

Kain-Fritsch

Planetary Boundary
Layer

MYNN２29