Widada Sultstya, Agus Hartoko and Budi Prayilno

THE CHARACTERISTICS AND VARIABILITY OF SURFACE TEMPERATURE IN SEA

WIDADA SULISTYA1, AGUS HARTOKO1, AND S. BUDI PRAYITN,„Oz

Abstract The phenomena of marine climate can be identified by the sea surface temperature, as lllahude (1999) reported that one of the parameters of oceanography which characterized of sea water mass is sea surface temperature (SST). The distribution of sea surface temperature can be used as an indicator of fishing ground. However, as understanding of marine climate variability it does not well enough (Hartoko, 2000). The characteristic and variability of SST in are not sufficiently enough understood. In order to better understand, we need the Spatial-Temporal Analysis of SST. The Spectral Analysis Method is used to study the characteristic and seasonal variation of SST, while GIS Analysis is used to study SST spatial distribution pattern. Temporally, the highest temperature at Java Sea occurs in April - May and November, whereas the lowest temperature in February and August. The SST fluctuation of Java Sea ranges from 27.48 C to 29.66° C and its periodic cycle generally occurs for 6 months, 1 year and 8 years.

Key Word: SST. Variability, Spatio-Temporal Analysis

I. Introduction Handoko (2000) reported the fact that characteristic and variability of SST of The climate and weather change in the Java Sea is not yet understood well, and is related closely with fishery activity (J. Le Blanc el. al., 1999). The Spatio-Temporal SST is very useful to influence of climate and weather change understand SST of Java Sea. Based on the depends on scale of space and time. It study of Widyaprasetya (2000). spatial occurs from local scale (as thunderstorm), analysis of SST using Geographic regional scale (as monsoon) to global scale Information System (GIS) which is (as El Nino). Those phenomena used to processed with satellite images can be have a great influence on migration, applied to indicator of fishing ground. reproduction and fish catchments. Marine This idea also was supported by Aryana climate can be identified by Sea Surface (2005) resulting that small pelagic fish are Temperature (SST) monitoring, as Ilahude more comfortable stay at the top of the (1999) reported that SST is one of the layers of warm waters. Until present time, oceanographic parameter which Java Sea is good fishery area where small pelagic is caught for more than 8 million characterized water mass. ton and fishermen time is depend on their The understanding of marine climate life from the production abundance of variability is not sufficient well until now. fishes in Java Sea.

Meteorological and Geophysical Agency, Doctoral Program of Coastal Resources Management, Undip -

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According to influence of marine period are evaluated by the monthly mean climate on fisheries, the understanding of of SST. Meanwhile, the SST spatial SST variability in waters can help distribution is known by spatial analysis understanding of fluctuation of fishes using GIS. Based on monthly spatial stock. Based on above description, the analysis, we can also know the monthly study of SST variability in Java Sea is spatial distribution of SST. This analysis important. can also describe the dynamic pattern of ocean (Hartoko, 2000), while Spectral Analysis Method is applied to 30 years II. Material and Method data series to study the SST seasonal In order to study of SST variability the variation. data of SST in Java Sea for within 30 years is used, insitu data has range from 2° III. Result S - 9° S and 105° E - 120° E. The coordinate of west part is (108° E; -4° S), a. SST Monthly Mean in Java Sea the coordinate of central area is (116° E; - In order to study the characteristic of 6° S) and coordinate of east area is (116° SST distribution of Java Sea, three areas E; -6° S). The results of reanalysis from representing west part, central part and satellite images producing from NCEP east part of Java are taken. West part of Data Centre are used for west, central and Java Sea has temperature variation range east areas. from 28.25° C - 29.66° C with the highest The SST monthly mean fits with the temperature in May and the lowest standard of WMO (World Meteorological temperature in August. The temperature of Organization) are used as series data for SST in east part of Java Sea varied from 30 years (1971-2000). The SST variability 27.48° C - 29.36° C. and the highest characteristic of Java Sea is analyzed by temperature is in April and the lowest Descriptive Statistic Analysis Method. temperature is in August (see Figure 1). The variability and the anomaly in certain

Grafik Rata - rata SPL di Laut Jawa (1971-2000)

Fig. 1. Monthly SST Pattern of Java Sea

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In general, the variation of SST average. After 1980, the SST anomaly is distribution in Java Sea shows that the above averaged temperature or warmer lowest averaged SST occurs in the eastern than the average. In the period of 1971- part of the sea while the highest SST is in 1980, the highest anomaly is 0.72 °C and it the western part. The variation of SST at occurred in August 1973, and the lowest eastern part of Java Sea is relatively bigger anomaly is -1.47 °C and it occurred in than both of central and western parts. The January 1976. While in the period of whole part of Java Sea has cycle of the 1981-1990, the highest anomaly is 1.39 °C highest SST and the lowest SST for two in March 1983 and the lowest anomaly is - times in a year. The first highest SST is in 1.02 °C in November 1982. In the period April to May, and the second one occurs in of 1990-2000, the highest anomaly is 1.82 November. The first lowest SST occurs in °C in July 1998 and the lowest anomaly is February and the second one is in August. -1.0 °C in June 1994. b. Anomaly of SST in Java Sea c. Spatial Distribution of SST It is also necessary to consider the SST Based on the analyses above, it shows anomaly for each month in 30 years to that the highest monthly SST occurs in study of the characteristics of SST of Java April and November, and the lowest Sea. For this purpose, we chose the monthly SST occurs in February and coordinate in 110° E -6° S located in the August. According to this description, SST middle of Java Sea (see Figure 2). As monthly mean of February, April, August general tendency, in the period before and November are chosen as the samples 1980 SST anomaly distribution is below of spatial distribution for discussion. averaged temperature or colder than the

RRMOTF. SENSING AND EARTH SCIENCES September 2007 Volume 4 87 The Characteristics and Variability of Sea Surface Temperature in Java Sea c.l. SST distribution of February between 28.6 °C to 29.8 UC. Water mass is relatively cold (28.6 °C) in the eastern and The first lowest temperature of SST mainly in the south part, while water mass temporal distribution appears in February, is hot (29.8 °C) in west and north part (see while the SST spatial distribution of Java Figure 4). sea spreads evenly with the temperature range from 28.2 °C to 28.8 °C. Water mass is relatively cold (28.2 °C) and distributed c.3. SST distribution of August in the western part of Java Sea, where Temporal distribution of SST pattern mainly at the north part is closed to South in Java Sea gets the second lowest China Ocean. The water mass is warm temperature in August, and its SST spatial (28.8 °C) and concentrated in the middle distribution also spreads evenly around and western parts (see Figure 3). range from 26.4 °C - 28.6 °C. Water mass is relatively cold (26.4 °C) distributed in c.2. SST distribution of May eastern of Java Sea mainly, while the The first highest temperature of water mass is relatively warm (28.6 °C) temporal distribution of SST pattern concentrated in the west part (see Figure appears in May, and SST spatial 5). distribution of Java Sea spreads evenly

Fig. 3. SST Distribution of February

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c.4. SST distribution of November mass is relatively cold (28.8 °C), spreading in western of Java Sea and mainly in the The second highest temperature of south part, while water mass is relatively SST temporal distribution appears in warm (29.6 °C) concentrated in the eastern November, whereas SST spatial sea, and mainly in the north part (see distribution of Java Sea spreads evenly Figure 6). with ranges from 28.8 °C - 29 °C. Water

Fig. 5. SST Distribution of August

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d. Spectrum Analysis happens for 1 year cycle period (see Figure 7a). The highest spectrum appears According to the result of spectrum for annual period at the middle and the analysis, it shows that the fluctuations of western sea, whereas the lowest signal SST in Java Sea have a cycle of period for occurs in 0.5 and 8 years cycle period (see half year, 1 year (annual), and 8 years picture 7b and 7c). Generally Java Sea has (interannual). In the western sea, the seasonal, annual and interannual strong signal happens for 8 and 0.5 years variations. cycle period, while the weak signal

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IV. Discussion minimum SST occurs after sun arrives in furthest position. T he duration of time Based on the description above, the between those cycles is approximately for SST monthly variation in certain area of 6 months. Java Sea gets the highest temperature in April to May and November and the The SST variability in Java Sea is also lowest temperature in February and influenced by the seasonal variability as a August. Both of the highest and the consequence of monsoon. The Asian lowest temperature occurred for two times. Monsoon has a dominant influence to the The SST cycle in Java Sea shows that the variation of Indonesian sea SST (Qu et ah, warm water mass oscillation depends on 2005). The maritime of the position in the sun relative to the is situated in a monsoon regime, equator. with a major shift in wind direction between seasons, namely South East In March and September the position Monsoon and North West Monsoon. The of sun is on above equator. T he furthest South East Monsoon takes places from position in the comes April to October, the wind blows from on January, and in the northern continent and brings fresh water hemisphere comes on July. When sun mass from the east. On the contrary, the leaves the equator, maximum SST North West Monsoon occurs in October to happened in the next month, whereas the April (Susanto et ah, 2005). In this period

REMOTE SENSING AND EARTH SCIENCES September 2007 Volume 4 91 The Characteristics and Variability of Sea Surface Temperature in Java Sea the wind blows from continent, and IV. Conclusion fresh water mass comes from the South a. The characteristic of the SST China sea to the Strait (Qu T. et distribution in the Java Sea is al., 2004 and 2005). identified by the monthly mean As the consequence of fresh water fluctuation range from 27.48 C to supply, the South East Monsoon period is 29.66 °C. The SST variability in Java followed by cold SST that covered Java Sea shows seasonal, annual and Sea. The impact of South East Monsoon interannual variation. is obviously seen on the SST distribution in August. The cold water mass from b. In the North West Monsoon period, Indonesia Sea around Australia comes the cold water mass is concentrated in through the and the Bali the western part and warm water mass Strait and spreads to the . in the eastern part. While in the South East Monsoon period, inversely cold The Java Sea becomes warm in the water mass is concentrated in the transition period that happened in April to eastern and warm water mass in the May. Whereas the warm water is in north western. In the transition period, the part and the cold water is in south part. warm water mass distribution pattern The influence of North West Monsoon to is in the north part and the south part SST distribution shows in February. T he for cold. cold water mass comes from the and spreading up to north of the c. The SST distribution of the Java Sea is Bali Island. However around the Makasar the result of the interaction of a few Strait, there is fresh water mass supply phenomena as seasonal factor coming from the through (monsoon), ARLINDO, EI Nino/La the Makasar Strait that is usually called Nina (come from the Pacific Ocean) ARLINDO (Indonesian Through Flow) and Dipole Mode (come from the (Susanto, 2005). Hindia Ocean). d. Regarding to the regularity of the SST The variability of the marine climate in variability in Java Sea, this study the Java Sea is not just influenced by monsoon, but also the following needs to be continued for further phenomena in the Indian and Pacific understand of the respond of primary Ocean. The waters of eastern of Indian productivity to the SST variability. Ocean (near by Indonesia) is influenced by The result of this study is expected to the Dipole Mode (Saji et al., 1999), help better understand to the Webster et al. (1999), Martugude et al. fluctuation of fish production in the (2000), J.L. Gaol (2004) and the Java Sea. interannual variation of SST in the Java Sea also influenced by ENSO (Susanto, 2006). It can be seen that the SST cycle Acknowledgement periods of the Java Sea are seasonal, annual and also interannual variations (8 This study is written in portion of doctoral years). The interaction between monsoon, program in Coastal Resources the Dipole Mode from and Management UNDIP Semarang. Author ENSO from Pacific Ocean are not still would like to appreciate to the support and understood. encouragement by Professor Lamudin Syahrani, Professor S. Budi Prayitno and Dr Agus Hartoko. I also wish to thank

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BMG for the recommendation, and my Hartoko. A., N.R. Nganro, J. Rais, S. colleagues in BMG that have provided a Mira, and J. Kahar. 2000. Aplikasi great deal of input and much help for this Inderaja Untuk Pemetaan Karakter study. Ekosistem Ikan Pclagis Besar di Utara Irian Jaya/Papua. Konperensi Nasional II Pengclolaan Sumber Daya References Pcsisir danLautan di Indonesia, Mei. Makasar. Aryana, I.N. 2005. The Assessment of Pelagic Fish Slock and Its Ilahude, A. 1999. Pengantar ke Distributions in Indian Ocean By Split Oseanologi Fisika. Puslitbang Beam Acoustic System. International Oseanologi LIPI. . Journal of Remote Sensing and Earth Susanto, D. and J. Marra. 2005. Effect of Sciences, Vol 2, September. Denpasar. the 97/98 El Nino on Chlorophyll a Blanc, J.L.L. and F. Mirsac. 1999. Variability Along the Souther Coast of Climate Information and Prediction Java and . Oceanography, Vol Services for Fishiers. Climar 99, 18, No. 4 Dec. WMO - NOAA - Ecnvironment Susanto, D., I.I. Moore, S. Thomas, and J. Canada. Canada. Marra. 2006. Ocean Color Variability Gaol, J.L., Wudianto, B.P. Pasaribu, D. in the Indonesian during the Manurung, and Endriati. 2004. The SeaWiFS Era. Electronic Journal of Fluctuation of Chlorophyll A Earth Sciences, Vol 7, No. 5, May. Concentration Derived from Satellite Widyaprasetya, G. 2000. Pcnentuan Imagery and Catch of Oily Sardine Daerah Ikan Pelagis Dengan (Sardinella Lemuru) in . Tcknologi Inderaja di Pcrairan Natuna International of Journal Remote Laut Cina Selatan. Remote Sensing Sensing and Earth Sciences, Vol 1, and Geographic Information System, September, IReSES. Denpasar Year Book 2000, BPPT. Jakarta. Gordon, A. 2005. Oceanography of the Qu Tangdong, Du Yan, J. Strachan, G. Indonesian Seas and Its Their Gary and J. Slingo. 2005. Sea Surface Throughflow, Oceanography, Vol 18, Temperature and Its Variability in The No. 4. Dec. Indonesian , Oceanography, Vol 18. No. 4, Dec.

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