Climatic Teleconnection of Indian and Pacific Ocean Over the Korean Region By Using Satellite Data.
Sobhan Kumar Sahu1, Hong-Joo Yoon1, Dae Hyun Kim2
1Dept. of Geoinformatic Engineering, College of Environmental and Marine Science & Technology, Pukyong National University, Korea
2Korean Inter-University Institute of Ocean Science, Pukyong National University, Korea Email:ٻ [email protected]
Abstract
The teleconnection of Pacific and Indian Ocean climatic events on Sea Surface Height Anomaly (SSHA) over the Korean Region (Lat. 115o~150oE, Lon. 20o~45oN) which includes the Yellow Sea, the East Sea and the East China Sea were studied from 1993 to 2006 by AVISO (Sea Surface Height Deviation) data. To show the teleconnection between the Eastern Indian Ocean (IO) and the Pacific Ocean (PO), we have studied the Empirical Orthogonal Function (EOF) of Sea Surface Temperature anomaly (SSTA) of above mentioned regions. SST is the major influencing factor in the ocean, and we studied EOF of other oceanic parameters such as Sea Surface Height Anomaly(SSHA), Wind-stress Curl Anomaly(WC) and Mean, Level Pressure Anomaly(MSLPA) and Ekman’s Surface Current which influences the SSH over the study region. The major event happen in the Pacific Ocean is El-Nino, which appears between December and February and in the Indian Ocean, Indian Ocean Dipole (IOD) generally appears in between September and November. Here we have studied two seasons from Sep. to Nov. (SON) and from Dec. to Feb(DJF). Correlation between the Pacific Ocean and the Korean Region of the same parameter we are getting a Positive correlation of MSLPA and SSHA but SSTA shows negative correlation and WCA shows negative correlation in the Yellow sea, the East Sea and East-coast of Japan in DJF. This indicates teleconnection between PO and Korean Region during El-Nino condition. Here we are finding the influence of IOD on SSH over Yellow Sea and East Sea region is more influential in 1994 and 2006 (Oceanic Nino Index was ūR&) but less in 1997 and 2002(Oceanic Nino Index was ŬR&) but just reverse in North-West region of Pacific-Ocean ( Near Japan) in the same condition.
Introduction
Any change in Earth's atmosphere or an ocean that disrupts typical weather patterns near the disruption and far from it. Here we have studied two different weather events—IOD and El-Nino for teleconnection over the Korean Region. Fourteen years atmospheric and oceanic data were analyzed for sea surface height fluctuation over the Korean Region. The fluctuation of SSH over the Korean Region is teleconnected by the equatorial Indian Ocean(IO) and Pacific Ocean(PO) Bin et al., (2000), Guan(2003). Earlier studies by Liu et al., (2002) found that there is a Kuroshio Current affects more than 30% variation of SSH in the North-South China Sea. Many studies on the Dipole phenomenon
using observational data, ocean general circulation models have demonstrated that IOD is an ocean atmospheric coupled phenomenon (Vinaychandran et al., 1999; Webster et al., 1999; Rao et al., 2002; Yamagata et al., 2003). The East Asian summer monsoon interacts with the Indian summer monsoon via the tropospheric jet, Tibetan high pressure and the westerly jet stream at about 40oN in the upper troposphere(Lu et al., 2002:
Enomoto et al., 2003). Isoguchi et al., (1997) showed that the variation of the first EOF of the Sea Level Anomaly (SLA) relative to the mean SLA north of 20o in the Pacific agreed well with those of the dominant EOFs of ECMWF based wind stress curl and Sverdrup
transport near 40oN by using 2 years TOPEX/POSEIDON altimeter data. The climate in the southwestern China and Korea is warmer and wetter than normal during ENSO winter and the ensuing spring(Tao and Zhang, 1998; Kang and Jeong, 1996). The thermodynamic coupling between atmospheric Rossby waves and ocean mixed layer temperature variation depends on the boreal winter mean surface winds, the development and maintenance of the western Pacific wind and SST anomalies are favored in the boreal cold season from late fall to spring in response to ENSO warming (Bin et al., 2000). We are finding positive correlation with SSHA over the Yellow sea and Eastern region of China Sea; it is due to the shifting of circulation pattern. Park and Schubert, (1997) suggested that the local high SSTA around Japan might have feedback to the circulation changes during the summer of 1994. In this paper we have studied elaborately the impact of IOD and ENSO on SSH over the Korean Region by using other atmospheric and oceanic parameter such as Wind-stress Curl, Mean Sea Level Pressure, Ekman’ Surface Current and SST.
Data and Method
Here we have studied five different parameters such as Sea Surface Height (SSH), Sea Surface Temperature (SST), Wind-stress Curl (WC), Mean Sea Level Pressure (MSLP) and Ekman’s Surface Current.
SSH data downloaded from AVISO (Sea Surface Height Deviation) SST from NOAA (OISST), WC and MSLP from CDC-NOAA. All datasets made in equal grid size 2o×2o. To verify the IOD and El-Nino years SST we have followed the web sites of FRCGC (fc. Jamstec) and NOAA.(cf. CPC). For our study purpose we have selected the three different regions such as Equatorial Indian Ocean (50o ~ 70oE; 10oS ~ 10oN), Equatorial Pacific Ocean (170oW ~ 110oW; 10oS ~ 10oN) and
Korean Region (115o ~ 150oE; 20o ~ 45oN) which united with Yellow Sea, East Sea and East China Sea. We studied the two different seasons such as September to November (SON) for Indian Ocean and December to February (DJF) for Pacific Ocean because in SON Indian Ocean Dipole occurs in Equatorial Indian Ocean and in DJF El-Nino condition found in Equatorial Pacific Ocean. Anomaly and Empirical Orthogonal Function of each variable were studied for analysis of 14 years of data i.e. from 1993 to 2006. Afterwards we did the correlation between the KR and EIO for SON and KR and EPO for DJF for individual parameter. For Korean Region we have studied correlation between SSH with SST, WC and MSLP separately Finally we have studied about the Ekman’s Surface Current over the Korean Region for IOD years only.
Results and Discussion
Here we have studied about the Indian Ocean Dipole (IOD) and its impact over the Korean Region.
The IOD events occurred in the month of SON and the study period are 1994, 1997, 2002 and 2006. During these periods SSH raises over the western equatorial Indian Ocean (Fig.1a) with variance 22% and simultaneously we found the rise of SST also occurs in same region (Fig.2a) but we got the reverse result of Wind-stress Curl and MSLP.
(a)
(b)
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3
1993 1998 2003
(c)
(d)
-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2
1993 1998 2003
Fig.1. (a) EOF Mode-2(SON of IO) SSH with Variance-27%,
(b) 2nd Principal Component of Fig.1.b (c) EOF Mode-2(SON of PO) SSH with
Variance-19%
(d) 2nd Principal Component of fig.1.d
(a)
(b)
-3 -2 -1 0 1 2 3
1993 1998 2003
(c)
(d)
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5
1993 1998 2003
Fig.2. (a) EOF Mode-2(SON of IO) SST with Variance-22%,
(b) 2nd Principal Component of Fig.2.b (c) EOF Mode-2(SON of PO) SST Variance-
16%
(d) 2nd Principal Component of fig.2.d
Simultaneously if we will compare to Korean Region then we are finding a positive SSTA over the region 28o
~ 34oN and 135o ~ 150oE with variance of 13% in EOF mode-2 (Fig.4a) and corresponding PC shows a normal SSTA during IOD event except 2006. Similarly SSHA shows high in the same time (Fig.3b). Here we are finding that all the IOD years are conjugate period of El- Nino years except 2006 IOD event. It indicates that El- Nino condition decreases the temperature over the Korean Region simultaneously it surpasses the effect of IOD event but its influence is more during IOD year without El-Nino condition. During El-Nino condition Eastern equatorial Pacific Ocean temperature raises
shown in EOF mode-2 with variance 16% and positive SSHA shows with variance 19% in EOF mode-2. Over the Korean Region we are finding less SSTA and SSHA with variance 27% and 25% in EOF mode-2 (Fig.4c and 3c).
(a)
(b)
(c)
(d)
Fig.3. (a) EOF Mode-2(SON of KR) SSH with Variance- 13%,
(b) 2nd Principal Component of Fig.3.b (c) EOF Mode-2(DJF of KR) SSH with
Variance-25%
(d) 2nd Principal Component of fig.3.d
(a)
(b) K_SST_SON
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2
1993 1998 2003
(c)
(d)
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5
1993 1998 2003
Fig.4. (a) )EOF Mode-2(SON of KR) SST with Variance-13%,
(b) 2nd Principal Component of Fig.4.b (c) EOF Mode-2(DJF of KR) SST with
Variance-27%
(d) 2nd Principal Component of fig.4.d
Afterwards we have correlated all the variables of Korean Region with Indian Ocean for the period of SON
and Pacific Ocean for the month of DJF. First of all we have studied the SSTA correlation and we found a positive correlation in East China Sea and the Northern coast of Japan in IOD event but we are finding all over the Korean Region negative except east cost of Japan during El-Nino condition. For SSH study during IOD event we found the negative correlation over the yellow sea (Fig.5a). It is due to the high wind stress curl (Fig.7c) in the northern side but east sea shows slight positive correlation due to high temperature and less Wind-stress Curl (Fig.7a and b). During DJF (El-Nino event) a slight positive correlation of SSH over the south of Korea and Japan (Fig.6a) but Wind-stress Curl shows a positive correlation in East Sea (Fig.6d) and a negative correlation of MSLP over the same region and south part of the East China Sea.
(a)
(b)
(c)
(d)
Fig.5. Correlation between Korean Region Versus Equatorial Indian Ocean During SON (a) SSH, (b) SST, (c) MSLP, (d) WC
(a)
(b)
(c)
(d)
Fig.6. Correlation between Korean Region Versus Equatorial Pacific Ocean During DJF.
(a)SSH, (b) SST, (c) MSLP, (d) WC
If we will compare IOD event and El-Nino effect over Korean Region we found a positive correlation of MSLP over (Fig.5c and 6c) the Northern region of Japan but just reverse during El-Nino. In case of Wind-stress Curl (Fig.5d and 6d) we are finding Eastern region of East China Sea and East coast of Japan shows a positive correlation in IOD event but just reverse during El-Nino effect.
(a)
(b)
(c)
Fig.7. Correlation of SSH Vs SST, SSH Vs MSLP and SSH Vs WC over the Korean Region during SON.
(a) SSH Vs SST, (b) SSH Vs WC, (c) SSH Vs MSLP
(a)
(b)
(c)
Fig.8. Correlation of SSH Vs SST, SSH Vs MSLP and SSH Vs WC over the Korean Region during DJF.
(a) SSH Vs SST, (b) SSH Vs WC, (c) SSH Vs MSLP
Now we will discuss about the correlation of SST, WC and MSLP with SSH over Korean Region in two different events. During IOD event shows a positive correlation of SSHA with SSTA over the East Sea region (Fig.7a) and SSHA with WCA shows a positive correlation towards the Eastern region of East Sea and Yellow Sea. The El-Nino event shows a negative correlation of SST with SSH and few regions show slightly positive correlation with WCA. Slightly negative correlation of MSLP with SSH shows towards eastern region of East China Sea and Yellow Sea (Fig.8c).
(a)
G (b)
G (c)
G (d)
G
Fig.9. Average Ekman’ Surface Current over the Korean Region for the period of SON in four different IOD years (a) 1994 (b) 1997 (c) 2002 (d) 2006
Finally we have shown in Fig.9 the Ekman’s Surface
Current over the Korean Region during IOD years is less over Yellow Sea and East Sea during 1994 and 2006(Fig.9a and d). Other two IOD events i.e. in 1997 and 2002 indicates more in the same region but it shows just reverse in North-West region of Pacific-Ocean ( Near Japan) (Fig.9b and c). All the IOD years are conjugate to El-Nino years and the intensity of El-Nino was more in 1997 and 2002. Oceanic Nino Index was ŬR& in 1997 and 2002 but in 1994 and 2006 it was ūR&
Conclusions
Teleconnection due to IOD event of Equatorial Indian Ocean and El-Nino effect of Equatorial Pacific Ocean over the Korean Region shows a positive correlation of SSH in the East Sea during IOD, Yellow Sea and Southern coast of Japan shows positive correlation during El-Nino condition. The EOF of SSH and its corresponding Principal Component shows the more variation of SSHA during IOD as compared to El- Nino effect. During the study period we have found all IOD years are conjugate El-Nino events except 2006 and showing in corresponding PC of EOF Mode-2 in SON is the highest SSH compared to other IOD period. Here we are finding a reverse correlation of MSLP during El- Nino and IOD event over the northern region of Japan.
Overall study implies that the influence of IOD on SSH over Yellow Sea and East Sea region is more influential in 1994 and 2006 (Oceanic Nino Index was ūR&) but less in 1997 and 2002(Oceanic Nino Index was ŬR&).
but it shows just reverse in North-West region of Pacific-Ocean ( Near Japan).
Acknowledgement
This study was supported by the Geostationary Ocean Color Image Research Program of the Korean Ocean Research and Development Institute and the Brain Korea 21 Project.
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