Rainfall In Indonesia Research Articles

Relationships between Sea Surface Temperature (SST) and rainfall distribution pattern in South-Central Java, Indonesia

Although there has been a high relationship between global climate and rainfall in Indonesia, little evidence is available for relationship between Sea Surface Temperature (SST) and rainfall pattern in highland of country. This study evaluates the relationships between Sea Surface Temperature (SST) and rainfall distribution pattern in Gunungkidul district, highland of South-Central Java, Indonesia. Principal Component Analysis (PCA) approach was used to summarize the average of SSTs during rainy season (October to March) for the El Niño monitoring regions: IOBW (Indian Ocean Basin-Wide), Niño.West and Niño.3. Monthly rainfall data was collected from Agricultural Government of Gunungkidul district. In this area, rainfall was highest in the southern and western mountainous areas, especially near the coast, and SSTs values were highly correlated with rainfall in those areas. Almost all sub districts in Gunungkidul district has significant correlations between PC1 SSTs and rainfall during October-November-December (OND).

Observation of spatial patterns on the rainfall response to ENSO and IOD over Indonesia using TRMM Multisatellite Precipitation Analysis (TMPA)

Remote sensing data of Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis for 13 years have been used to observe the spatial patterns relationship of rainfall with El Ni˜ no-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) over Indonesia. Linear correlation was measured to determine the relationship level by the restriction analysis of seasonal and monthly relationship, while the partial correlation technique was utilized to distinguish the impact of one phenomenon from that of the other. Application of remote sensing data can reveal an interaction of spatial-temporal relationship of rainfall with ENSO and IOD between land and sea. In general, the temporal patterns relationship of rainfall with ENSO confirmed fairly similar temporal patterns between rainfall with IOD, which is high response during JJA (June-July-August) and SON (September-October-November) and unclear response during DJF (December-January-February) and MAM (March-April-May). Spatial patterns relationship of both phenomena with rainfall is high in the southeastern part of Sumatra Island and Java Island during JJA and SON. During the SON season, IOD has a higher relationship level than ENSO in this part. In the spatial-temporal pattern seen, a dynamic movement of the relationship between IOD and ENSO with rainfall in Indonesia is indicated, where the influence of ENSO and IOD started during JJA especially in July in the southwest of Indonesia and ended in the DJF period especially in January in the northeast of Indonesia.

Multiple tree-ring chronologies (ring width, δ13C and δ18O) reveal dry and rainy season signals of rainfall in Indonesia

Climatic hazards, such as severe droughts and floods, affect extensive areas across monsoon Asia and can have profound impacts on the populations of that region. The area surrounding Indonesia, including large portions of the eastern Indian Ocean and Java Sea, plays a key role in the global climate system because of the enormous heat and moisture exchange that occurs between the ocean and atmosphere there. Here, we evaluate the influence of rainfall variability on multiple tree-ring parameters of teak (Tectona grandis) trees growing in a lowland rain forest in Central Java (Indonesia). We assess the potential of, annually resolved, tree-ring width, stable carbon (δ13C) and oxygen (δ18O) isotope records to improve our understanding of the Asian monsoon variability. Climate response analysis with regional, monthly rainfall data reveals that all three tree-ring parameters are significantly correlated to rainfall, albeit during different monsoon seasons. Precipitation in the beginning of the rainy season (Sep–Nov) is important for tree-ring width, confirming previous studies. Compared to ring width, the stable isotope records possess a higher degree of common signal, especially during portions of the peak rainy season (δ13C: Dec–May; δ18O: Nov–Feb) and are negatively correlated to rainfall. In addition, tree-ring δ18O also responds positively to peak dry season rainfall, although the δ18O rainy season signal is stronger and more time-stable. The correlations of opposite sign reflect the distinct seasonal contrast of the δ18O signatures in rainfall (18OPre) during the dry (18O-enriched rain) and rainy (18O-depleted rain) seasons. This difference in 18OPre signal reflects the combination of two signals in the annual tree-ring δ18O record. Highly resolved intra-annual δ18O isotope analyses suggest that the signals of dry and rainy season can be distinguished clearly. Thereby reconstructions can improve our understanding of variations and trends of the hydrological cycle over the Indonesian archipelago.

Australasian monsoon response to Dansgaard–Oeschger event 21 and teleconnections to higher latitudes

Dansgaard–Oeschger (D–O) cycles were the most prominent, abrupt climate events of the last glacial period whose impact was most strongly felt in the high latitudes of the North Atlantic region. The climate links between the North Atlantic, the Asian and American tropics, and Antarctica during these cycles are well documented. However, the potential role of the Indo-Pacific Warm Pool and Australasian monsoon system in propagating climate impacts across the hemispheres is still unclear. Here, we use tandem measurements of oxygen isotopes in calcite and fluid inclusions, as well as carbon-isotope ratios, from multiple stalagmites from Liang Luar Cave, Flores (southern Indonesia) to examine the monsoon response to D–O event number 21 (~87,000–84,000 years ago), the longest and warmest event recorded in Greenland ice cores. The record shows that there was a rapid decline in monsoon rainfall in Indonesia during D–O21 warming in Greenland and cooling in Antarctica. At around the same time, the East Asian monsoon was intensified, indicating that the intertropical convergence zone (ITCZ) shifted abruptly to the north during this event. Our record also shows that there was a 2–3°C increase in local air temperature, which would have acted to increase primary productivity and promote the generation of soil carbon for methanogenesis. Therefore, our findings indicate that ITCZ positioning in tropical Australasia—through its influence on large-scale oceanic–atmospheric circulation—played a key role in transmitting the abrupt climate signal between the hemispheres, thereby facilitating the rapid rise of atmospheric CO2 and CH4 concentrations during D–O21 that ultimately led to global warming and the demise of the MIS5b stadial.

KESESUAIAN METODE FUZZY AUTO-REGRESSIVE UNTUK MODEL CURAH HUJAN DI INDONESIA

Rain is one of the attenuation factors in very high frequency radio wave. Attenuation caused by rainfall gives a big impact in communication systems, especially wireless communication systems at millimeter-wave. This paper seeks to apply the fuzzy auto-regressive model (fuzzy AR) for rainfall in Indonesia. In this study, firstly the rainfall is measured, followed by getting the fuzzy variables for each event of rainfall measurements. Thirdly, the fuzzy variables based on the timing of the rain to get a fuzzy time series is set, and fourth step is the fuzzy time series modeling as a fuzzy AR(2) process. The fifth is estimating the matrix of model parameter, and the last step is simulating the generation of rainfall using fuzzy AR(2) model. The results obtained from the generation of simulated rainfall with Fuzzy AR(2) shows a good agreement with the actual measurement results.

Leaching of heavy metals in acid mine drainage

Acid mine drainage is one of the most serious environmental problems that the coal and metal mining industry is currently facing. The generation of low pH drainage enhances the dissolution of heavy metals in water. The samples used in this research originated from three pits at mine dumps. In a study reported in this paper, three types of tests; namely static test, kinetic test and column test were conducted to estimate acid generation and acid neutralization reaction rates, and to predict the solubility of metals and their release rates. Static test showed that all samples had a pH of net acid generation (NAG pH) <4, a net acid producing potential (NAPP) >10 kg H2SO4tonne(-1), and a S-content >3%, which can be classified as a high acid-forming capacity. Simulated runoff in the column tests was equivalent to 5-year average rainfall in Indonesia, the resultant leachates showed acidic behaviour (pH < 3.5). Based on the results, it was found that high mobilization of heavy metals (Cr, Cu, Zn, Cd and Pb) takes place under strong acidic conditions (pH approximately equal 2).

&lt;strong&gt;PREDIKSI CURAH HUJAN BULANAN BERDASARKAN SUHU PERMUKAAN LAUT NINO 3.4 : SUATU PENDEKATAN DENGAN METODE FILTER KALMAN&lt;/strong&gt;&lt;br&gt;(MONTHLY RAINFALL PREDICTION BASED ON SEA SURFACE TEMPERATURE NINO 3.4 : THE APPROACH WITH KALMAN FILTERING)

Many approaches have been applied to forecast climate using statistical and deterministic models using independent and dependent variables empirically. It is more practical to analyze the parameters, but it needs validation anytime and anywhere. Kalman filtering unites physical and statistical model approaches to stochastic model renewable anytime for objective of on line forecasting. Based on research, sea surface temperature Nino 3.4 have high correlation with rainfall in Indonesia, so it is used to forecast rainfall in Cirebon as area study. Rainfall clustering in Cirebon results 6 groups with rainfall average 1400-1500 mm/year for dry area and 3000-3200 mm/year for wet area. Validation have correlation coefficient validation value more than 94%, correlation coefficient model value more than 78% and fit model value more than 38%. The result of regression gives R2 value of more than 0,8. It implies that predicting model using Kalman Filter is feasible to forecast montly rainfall based on sea surface temperature Nino 3.4. The result of rainfall prediction in Cirebon show increasing in rainfall until February 2005, with correlation coeficient value of model more than 90% and fit model more than 40%.

Estimating the direct radiative forcing due to haze from the 1997 forest fires in Indonesia

The El Niño event of 1997–1998 caused a severe reduction of rainfall in Indonesia that promoted the spread of forest fires, leading to a pervasive haze in the region. Here we use fire coverage data from the 1997 World Fire Atlas with a review of other available data and literature to estimate the distribution of particulate emissions from August to November 1997 and the particle size and radiative properties. Our preferred estimate of the total particulate emissions is approximately 41 Tg. The emissions have been used to drive an atmospheric model to simulate the distribution of the haze and its direct radiative effect, with and without allowing for the effects of the smoke on the atmospheric evolution. Model diagnostics of the aerosol and its radiative impact are compared with measurements and output from other models. Large decreases in the incident solar flux at the surface are obtained in the region. The simulated global mean shortwave radiative forcing at the top of the atmosphere, averaged over the 4 months, is −0.32 Wm−2. The accuracy of this calculation is discussed, and the importance of the Indonesian fires in particular and of biomass burning in general is assessed.

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Dansgaard–Oeschger (D–O) cycles were the most prominent, abrupt climate events of the last glacial period whose impact was most strongly felt in the high latitudes of the North Atlantic region. The climate links between the North Atlantic, the Asian and American tropics, and Antarctica during these cycles are well documented. However, the potential role of the Indo-Pacific Warm Pool and Australasian monsoon system in propagating climate impacts across the hemispheres is still unclear. Here, we use tandem measurements of oxygen isotopes in calcite and fluid inclusions, as well as carbon-isotope ratios, from multiple stalagmites from Liang Luar Cave, Flores (southern Indonesia) to examine the monsoon response to D–O event number 21 (~87,000–84,000 years ago), the longest and warmest event recorded in Greenland ice cores. The record shows that there was a rapid decline in monsoon rainfall in Indonesia during D–O21 warming in Greenland and cooling in Antarctica. At around the same time, the East Asian monsoon was intensified, indicating that the intertropical convergence zone (ITCZ) shifted abruptly to the north during this event. Our record also shows that there was a 2–3 °C increase in local air temperature, which would have acted to increase primary productivity and promote the generation of soil carbon for methanogenesis. Therefore, our findings indicate that ITCZ positioning in tropical Australasia—through its influence on large-scale oceanic–atmospheric circulation—played a key role in transmitting the abrupt climate signal between the hemispheres, thereby facilitating the rapid rise of atmospheric CO2 and CH4 concentrations during D–O21 that ultimately led to global warming and the demise of the MIS5b stadial.

Spatial Coherence and Predictability of Indonesian Wet Season Rainfall

Rainfall from 63 stations across Indonesia is examined for the period 1950–98 to determine the spatial coherence of wet season anomalies. An example of almost unrelated anomalies at two neighboring stations is presented. Principal component analysis is used to quantify the spatial coherence across the entire region. The significant components show high loadings over only a small region, suggesting that rainfall in only this small region varies coherently on an interannual timescale. Correlation with the Southern Oscillation index (SOI) shows that rainfall over only this same region is being largely governed by the El Niño–Southern Oscillation (ENSO) phenomenon. In contrast, a similar analysis for the transition season (Sep–Nov) rainfall shows coherence across almost the entire region and a similarly large area of high correlation with the SOI. Results for all seasons are summarized with the use of an all-Indonesian rainfall index constructed from an averaged percentile ranking of seasonal rainfall from each station across the region. At the times of the year when a large (small) percentage of the variance of rainfall is described by the lowest-order principal components, there is a large (small) correlation between the SOI and the all-Indonesian rainfall index. The implication is that wet season rainfall in Indonesia is inherently unpredictable.