Widada Sultstya, Agus Hartoko and Budi Prayilno THE CHARACTERISTICS AND VARIABILITY OF SEA SURFACE TEMPERATURE IN JAVA 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 Java Sea 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 ocean 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, Bali Doctoral Program of Coastal Resources Management, Undip - Semarang REMOTE SENSING AND EARTH SCIENCES September 2007 Volume 4 85 The Characteristics and Variability of Sea Surface Temperature in Java Sea 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 86 REMOTE SENSING AND EARTH SCIENCES September 2007 Volume 4 Widada Sulistya, Agus Hartoko and Budi Prayitno 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 88 REMOTE SENSING AND EARTH SCIENCES September 2007 Volume 4 Widada Sulistya, Agus Hartoko and Budi Prayitno 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 REMOTE SENSING AND EARTH SCIENCES September 2007 Volume 4 89 The Characteristics and Variability of Sea Surface Temperature in Java Sea 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).