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The Southern Indonesian (SI) region is known for its high-intensity coastal upwelling caused by monsoonal wind. Interannual phenomena such as El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) also influence upwelling activity in this region. This study analyzed the relationship between upwelling intensity (UI sst) and those variables and their impact on oceanographic features such as Sea Surface Temperature (SST) and chlorophyll-a concentration. We used satellite imagery data, including SST from the National Oceanic and Atmospheric Administration (NOAA) and chlorophyll-a from MODIS, to analyze the aforementioned issue. To identify the impact of wind patterns on coastal upwelling, we analyzed using zonal wind stress from ERA-5 Data. Quantification of UI sst is defined as the SST gradient between the coastal and open ocean waters. Linear and partial correlation analysis between UI sst with the Ocean Niño Index (ONI) and Dipole Mode Index (DMI) were conducted to see the influence of ENSO and IOD phenomena. Anomaly analysis was also conducted on SST, chlorophyll-a concentration, zonal windstress and UI sst to see how large the values were during the years of the ENSO and IOD events. Upwelling in the SI region typically occurs during southeast monsoon (SEM) periods, starting earlier in the East side (Nusa Tenggara Islands) and moving towards the West side (South Coast of Java). The correlation analysis (both linear and partial) indicates that the IOD has a stronger influence on UI sst in the SI region compared to ENSO, especially during June to October (SEM periods). This finding is confirmed by anomaly analysis, which reveals significant changes in SST, chlorophyll-a concentration, zonal windstress, and UI sst during ENSO and IOD events. The magnitude of the anomalies is generally stronger during IOD events than those observed under ENSO conditions. • Remote sensing satellite data can identify the variability of upwelling phenomena in the Southern Indonesian (SI) seas. • The strength of upwelling intensity in SI is strongly influenced by Interannual phenomena such as the ENSO and IOD. • Sea Surface Temperature and Chlorophyll-a anomalies confirm the influence of changes in upwelling intensity by ENSO and IOD. • IOD has a stronger influence than ENSO on Upwelling intensity in the SI Region. [ABSTRACT FROM AUTHOR]

Water availability and food security are tightly coupled on a global scale. The occurrence of drought puts this balance at risk due to reductions in dryland farming production and water allocations to irrigated agriculture. Improved understanding of drought initiation and cessation would therefore be beneficial for drought planning and management. The study objective was to determine factors affecting drought initiation and cessation over the past century in two climatologically similar regions that represent net agricultural exporters; south central U.S. (Texas) and southeast Australia (Murray Darling Basin, MDB). Drought indices included the Standardized Precipitation Index (SPI, 1900–2014) for meteorological drought, the Normalized Difference Vegetation Index (NDVI, 1981–2014) for agricultural drought, and the Streamflow Drought Index (SDI, 1930–2014) for hydrological drought. Results show that meteorological drought tends to develop gradually over a period of up to six months, with agricultural drought developing shortly thereafter (within one month) in both regions. Evidence of hydrological drought was observed within one month (Texas) and within four months (MDB) on average after meteorological drought was established. Further, droughts appear to cease more quickly than they initiate over Texas, whereas rates of drought initiation and cessation are similar over the MDB. Drought breaking rainfall in Texas is generally a result of a southward shift in the Polar Jet Stream or a low-pressure trough over central North America, whereas drought cessation in the MDB is typically associated with a monsoon trough or low-pressure system in the Tasman Sea/Great Australian Bight. Improved knowledge of the climate mechanisms controlling the onset and termination of drought periods should enhance drought forecasts and improve drought management practices, particularly in regions where water security is a primary objective. [ABSTRACT FROM AUTHOR]

The relationship between the number of lightning flashes (NLF) and the cosmic ray flux (CRF) during the period of ENSO (El Niño/La Niña Southern Oscillations) with and without IOD (Indian Ocean Dipole) has been studied for the first time in the region of South/Southeast Asia (8°N–35°N and 60°E–120°E) to the authors' knowledge. Our analysis shows that the relationship is governed by regional meteorology and not by direct solar influence. Unlike on global scale, the data during ENSO are important for this relationship on regional scale. CRF and NLF are in statistically significant relationship only when CRF is significantly correlated with the meteorological parameters. CRF and NLF are significantly correlated during the period of ENSO with IOD (ENSO–IOD) but not during the period of ENSO without IOD (ENSO). The Aerosol Optical Depth (AOD), the positive temperature anomaly (TA) and an increase in TA may be responsible for this relationship during the ENSO–IOD period. On the shorter temporal/spatial scale, meso-scale meteorological parameters are responsible for the negative correlation between the CRF and the NLF. On the other hand, on the longer scale, an amount of Low Level Cloud Fraction (LLCF) is responsible for the positive correlation between the CRF and the NLF. Our partial correlation analysis shows that controlling for the AOD weakens the correlation between the CRF and the NLF but does not affect that between the 12month running means of the same. Thus, aerosols are responsible during the total study period and during the IOD period for enhancing the significant CRF–NLF relationship. Solar radio flux F10.7 cm (SRF10.7) seems to be the main controlling parameter for the stronger relationship. We find that there is a distinct difference in the average magnitude of different solar and meteorological parameters between that during the ENSO period and the ENSO–IOD period which may be attributed to the difference in cloud types and aerosol properties between the two periods. The results of our analysis may be confirmed with longer data sets and more number of IOD events in the future. [ABSTRACT FROM AUTHOR]

Highlights: [•] We modelled rainfall using multiple regression and Artificial Neural Networks for Victoria, Australia. [•] We examined combined lagged months of ENSO and IOD as potential predictors of spring rainfall. [•] Spring rainfall was predicted three years in advance with the developed models using ENSO–IOD lagged months. [•] ANN models proved to be more accurate than multiple regression models in terms of long term predictions. [ABSTRACT FROM AUTHOR]

Abstract: Trace element and stable isotope ratios from an active stalagmite (LR06-B1) recovered from Liang Luar Cave on the island of Flores (eastern Indonesia) are used to reconstruct the position of the austral summer inter-tropical convergence zone and Australian-Indonesian summer monsoon variability during the Holocene. Uranium-series dating of the stalagmite shows that it commenced growth 12,640years ago, with hiatuses spanning 8,560 to 6,420 and 3,670 to 2,780years ago. Stalagmite Mg/Ca and Sr/Ca ratios correlate significantly with one another, and with δ 18O and δ 13C, throughout the record. This suggests that the Mg/Ca and Sr/Ca ratios are dominated by prior calcite precipitation, a process whereby degassing in the vadose zone during periods of low recharge causes deposition of calcite and disproportionate loss of Ca2+ ions (relative to Mg2+ and Sr2+) ‘upstream’ of the stalagmite. The degree of initial 234U/238U disequilibrium also appears to have been controlled by recharge to the overlying aquifer. Together with the Mg/Ca, Sr/Ca, and δ 18O values, the initial uranium isotope activity ratios ([234U/238U]I) imply a generally drier early Holocene, coincident with a lower sea level and lower Southern Hemisphere summer insolation. Comparison of speleothem δ 18O time-series from Flores and Borneo shows that they vary in unison for much of the Holocene. However, there is a significant decrease in the Borneo δ18O record ~6,000 to 4,000 years ago that does not occur in the Flores record. This anomaly may be related to a change in the Australian-Indonesian summer monsoon circulation in response to a protracted positive phase of the Indian Ocean Dipole. Under this scenario, stronger upwelling off of western Indonesia would, based on present-day effects, result in reduced summer convective activity over Flores and a subsequent northward shift of the intertropical convergence zone. [Copyright &y& Elsevier]

The Indian Ocean Dipole (IOD) has major climate impacts worldwide, and most profoundly for nations around the Indian Ocean basin. It has been 20 years since the IOD was first formally defined and research since that time has focused primarily on examining IOD dynamics, trends and impacts in observational records and in model simulations. However, considerable uncertainty exists due to the brevity of reliable instrumental data for the Indian Ocean basin and also due to known biases in model representations of tropical Indian Ocean climate. Consequently, the recent Intergovernmental Panel on Climate Change (IPCC) report on the Ocean and Cryosphere in a Changing Climate (SROCC) concluded that there was only low confidence in projections of a future increase in the strength and frequency of positive IOD events. This review examines the additional perspectives that palaeoclimate evidence provides on IOD trends, variability, interactions with the El Niño–Southern Oscillation (ENSO), and impacts. Palaeoclimate data show that recent trends towards more frequent and intense positive IOD events have been accompanied by a mean shift toward a more positive IOD-like mean zonal SST gradient across the equatorial Indian Ocean (due to enhanced warming in the west relative to the east). The increasing frequency of positive IOD events will imminently move outside of the range of natural variability in the last millennium if projected trends continue. Across a range of past climate states, periods of a mean positive IOD-like state in the Indian Ocean have been accompanied by elevated IOD variability. This includes events that exceed the magnitude of even the strongest measured historical events, demonstrating that the Indian Ocean can harbour even stronger variability than what has been observed to date. During the last millennium there has been a tight coupling between the magnitude of interannual IOD and ENSO variability, although positive IOD events have frequently occurred without any indication of a co-occurring El Niño event. This IOD–ENSO coupling may not have persisted across past climates that were very different from the present, raising questions of whether their interaction will change in a rapidly warming future. Palaeoclimate evidence for hydroclimate changes during the last millennium further points to the importance of interannual IOD and ENSO variability in providing the rainfall that breaks droughts in regions that are impacted by these modes of variability. Overall, this review highlights the rich insights into the IOD that can be gained from palaeoclimate evidence. Palaeoclimate data helps to overcome known limitations in observations and model simulations of the IOD, and demonstrates that strong conclusions about the IOD and its impacts can be reached when the evidence for past, present and future behaviour of the IOD are assessed together. • Rich insights into the Indian Ocean Dipole can be gained from palaeoclimate evidence. • Rising frequency of positive IOD events will imminently move outside natural range. • Indian Ocean can harbour even stronger variability than observed in recent decades. • Indo-Pacific covariance is strong today, but not always in the past. • Strong Indo-Pacific variability was important in breaking droughts in last 1000 years. [ABSTRACT FROM AUTHOR]