Sea Surface Temperature Anomaly Characteristics Affecting Rainfall in Western Java, Indonesia

Western Java is densely populated with high socio-economic activity. Climate-related disasters can be mitigated with the support of an understanding of systems that produce reliable climate predictions. One of the climate variables included in hydrometeorological disasters is rainfall. The characteristics of rainfall in Western Java cannot be separated from the sea surface temperature (SST) around the area. This study compares the relationship between SST and rainfall with singular value decomposition (SVD) and compares it with Pearson's correlation. SVD Model performance was evaluated using square covariance fraction (SCF) and Pearson correlation. The results showed that rainfall has a higher correlation with SST Anomaly (SSTA) by using SVD, with a correlation of about 0.63 in 6 to 9 months without lag time. Rainfall in western Java was closely related to the positive SSTA anomaly in southern Indonesia, especially the waters south of Java Island, and negative anomalies in other areas. Furthermore, atmospheric dynamic analysis showed that the positive coefficient expansion is followed by warmer SST, lower surface air pressure, higher water vapor, and higher rainfall, all were respective to their normal conditions around western Java. This study concludes that warmer SSTA around Western Java causes increased rainfall in western Java than normal and potentially impacts the hydrological disaster in West Java

Perubahan Temperature Humidity Index (THI) di Pulau Jawa sejak 1981 hingga 2019

Abstrak Pulau Jawa mengalami peningkatan jumlah penduduk dari waktu ke waktu. Peningkatan ini berdampak pada tingginya aktivitas antropogenik yang menghasilkan emisi yang diantaranya dapat menyebabkan perubahan suhu udara. Suhu udara sangat berkaitan dengan thermal stress yang mempengaruhi kenyamanan bahkan kesehatan manusia. Thermal stress dapat diukur dengan Temperature Humidity Index (THI) dengan suhu udara rata-rata permukaan dan Relative Humidity (RH) sebagai variabel bebas. Penelitian ini menganalisis sejauh mana perubahan suhu udara permukaan, RH dan THI terhadap waktu. Kemudian daerah dengan perubahan THI yang paling besar akan dianalisis keterkaitannya jumlah penduduk menggunakan korelasi Pearson. Berdasarkan hasil penelitian diketahui terjadi perubahan suhu udara udara permukaan sebesar -0.27 hingga 1.17⁰C diikuti perubahan RH sebesar -2.21% hingga 0.77% dan terjadi perubahan THI hingga 0,72⁰C sejak 1981 hingga 2019 terutama di pesisir utara bagian barat Pulau Jawa. Selain itu, THI di sekitar DKI Jakarta juga memiliki nilai korelasi simultan yang tinggi dengan jumlah penduduk sebesar 0,81, korelasi lag 1 tahun sebesar 0,69, sementara korelasi lag 2 tahun sebesar 0,67. Temuan ini mengindikasikan peningkatan jumlah penduduk berdampak terhadap peningkatan THI pada DKI Jakarta. Abstract Java has experienced an increase in population from time to time. This increase has an impact on high anthropogenic activity which results in emissions, which can cause changes in air temperature. Air temperature is closely related to thermal stress which affects comfort and even human health. Thermal stress can be measured by the Temperature Humidity Index (THI) with the average surface air temperature and Relative Humidity (RH) as the independent variable. This study analyzes the extent of changes in surface air temperature, RH and THI with time. Then the areas with the greatest THI changes will be analyzed for their correlation using the Pearson correlation. Based on the research results, it is found that there has been a change in surface air temperature of -0.27 to 1.17⁰C followed by changes in RH from -2.21% to 0.77% and there has been a change in THI to 0.72⁰C from 1981 to 2019, especially on the north coast of the western part of Java. In addition, THI around DKI Jakarta also has a high simultaneous correlation value with a population of 0.81, a 1-year lag correlation of 0.69, while a 2-year lag correlation of 0.67. These findings indicate an increase in population has an impact on increasing THI in DKI Jakarta.