Spatiotemporal Analysis on the Teleconnection of ENSO and IOD to the Stream Flow Regimes in Java, Indonesia

While many studies on the relationship between climate modes and rainfall in Indonesia already exist, studies targeting climate modes’ relationship to streamflow remain rare. This study applied multiple regression (MR) models with polynomial functions to show the teleconnection from the two prominent climate modes—El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD)—to streamflow regimes in eight rivers in Java, Indonesia. Our MR models using data from 1970 to 2018 successfully show that the September–November (SON) season provides the best predictability of the streamflow regimes. It is also found that the predictability in 1970–1989 was better than that in 1999–2018. This suggests that the relationships between the climate modes and streamflow in Java were changed over periods, which is suspected due to the river basin development. Hence, we found no clear spatial distribution patterns of the predictability, suggesting that the effect of ENSO and IOD are similar for the eight rivers. Additionally, the predictability of the high flow index has been found higher than the low flow index. Having elucidated the flow regimes’ predictability by spatiotemporal analysis, this study gives new insight into the teleconnection of ENSO and IOD to the Indonesian streamflow.

Likelihood of unprecedented drought and fire weather during Australia’s 2019 megafires

Between June 2019 and March 2020, thousands of wildfires spread devastation across Australia at the tragic cost of many lives, vast areas of burnt forest, and estimated economic losses upward of AU$100 billion. Exceptionally hot and dry weather conditions, and preceding years of severe drought across Australia, contributed to the severity of the wildfires. Here we present analysis of a very large ensemble of initialized climate simulations to assess the likelihood of the concurrent drought and fire-weather conditions experienced at that time. We focus on a large region in southeast Australia where these fires were most widespread and define two indices to quantify the susceptibility to fire from drought and fire weather. Both indices were unprecedented in the observed record in 2019. We find that the likelihood of experiencing such extreme susceptibility to fire in the current climate was 0.5%, equivalent to a 200 year return period. The conditional probability is many times higher than this when we account for the states of key climate modes that impact Australian weather and climate. Drought and fire-weather conditions more extreme than those experienced in 2019 are also possible in the current climate.

El Nino/La Nina and IOD impact on Kharif Season Crops Over Western Agro-Climatic Zones of India

Climate modes like ENSO (El Nino Southern Oscillation) and IOD (Indian Ocean Dipole) produce an impact on the monsoon rainfall over India. Monsoon rainfall is extremely important for the agriculture of our country. The impact of these climate modes on monsoon rainfall thus in turn affects the rain-fed crops (Kharif). In this study, four Kharif season crops namely Rice (Oryzasativa), Maize (Zea mays), pulses and sugarcane (Saccharum officinarum) are chosen over four arid/semi-arid agro-climatic zones of western India to study the effect of the climate modes on selected crops. The detailed analysis has been carried out to show the impact of El Nino/La Nina (phases of ENSO) and IOD years on the crop productions over the mentioned zones viz. (Central plateau & hills region; Western plateau & hills region; Gujarat hills and plains region; Western Dry region) from 1966-2011. Rice production has been largely affected during drought years associated with El-Nino. The production of Pulses shows marginal improvement during the neutral years or non-El Nino/non-La Nina. The Maize production seems to be better in La Nina years as compared to neutral years and worst in the El Nino years. El Nino years provides a minor impact on Sugarcane productions in different zones. La Nina years are well suited for sugarcane production in any zones of our study. Positive IOD years are associated with poor crop productions as compared to negative IOD years mostly in all zones due to the co-occurrence of positive IOD years with El Nino. The correlations between positive IOD and rainfall are much weaker as compared to the correlations between the El Nino and rainfall in the years of co-occurrences over the zones making El Nino much more influential than positive IOD events.

Eastward Shift of Interannual Climate Variability in the South Indian Ocean since 1950

The subtropical Indian Ocean Dipole (SIOD) and Ningaloo Niño are the two dominant modes of interannual climate variability in the subtropical South Indian Ocean. Observations show that the SIOD has been weakening in the recent decades, while Ningaloo Niño has been strengthening. In this study, we investigate the causes for such changes by analyzing climate model experiments using the NCAR Community Earth System Model version 1 (CESM1). Ensemble-mean results from CESM1 large-ensemble (CESM1-LE) suggest that the external forcing causes negligible changes in the amplitudes of the SIOD and Ningaloo Niño, suggesting a dominant role of internal climate variability. Meanwhile, results from CESM1 pacemaker experiments reveal that the observed changes in the two climate modes cannot be attributed to the effect of sea surface temperature anomalies (SSTA) in either the tropical Pacific or tropical Indian Oceans. By further comparing different ensemble members from the CESM1-LE, we find that a Warm Pool Dipole mode of decadal variability, with opposite SSTA in the southeast Indian Ocean and the western-central tropical Pacific Ocean plays an important role in driving the observed changes in the SIOD and Ningaloo Niño. These changes in the two climate modes have considerable impacts on precipitation and sea level variabilities in the South Indian Ocean region.

Modes of climate variability bridge proximate and evolutionary mechanisms of masting

There is evidence that variable and synchronous reproduction in seed plants (masting) correlates to modes of climate variability, e.g. El Niño Southern Oscillation and North Atlantic Oscillation. In this perspective, we explore the breadth of knowledge on how climate modes control reproduction in major masting species throughout Earth's biomes. We posit that intrinsic properties of climate modes (periodicity, persistence and trends) drive interannual and decadal variability of plant reproduction, as well as the spatial extent of its synchrony, aligning multiple proximate causes of masting through space and time. Moreover, climate modes force lagged but in-phase ecological processes that interact synergistically with multiple stages of plant reproductive cycles. This sets up adaptive benefits by increasing offspring fitness through either economies of scale or environmental prediction. Community-wide links between climate modes and masting across plant taxa suggest an evolutionary role of climate variability. We argue that climate modes may ‘bridge’ proximate and ultimate causes of masting selecting for variable and synchronous reproduction. The future of such interaction is uncertain: processes that improve reproductive fitness may remain coupled with climate modes even under changing climates, but chances are that abrupt global warming will affect Earth's climate modes so rapidly as to alter ecological and evolutionary links. This article is part of the theme issue ‘The ecology and evolution of synchronized seed production in plants’.

Analysis of the interannual variability in satellite gravity solutions: detection of climate modes fingerprints in water mass displacements across continents and oceans

This study analyzes the interannual variability of the water mass transport measured by satellite gravity missions in regard to eight major climate modes known to influence the Earth’s climate from regional to global scales. Using sparsity promoting techniques (i.e., LASSO), we automatically select the most relevant predictors of the climate variability among the eight candidates considered. The El Niño–Southern Oscillation, Southern Annular Mode and Arctic Oscillation are shown to account for a large part the interannual variability of the water mass transport observed in extratropical ocean basins (up to 40%) and shallow seas (up to 70%). A combination of three Pacific and one Atlantic modes is needed to account for most (up to 60%) of the interannual variability of the terrestrial water storage observed in the North Amazon, Parana and Zambezi basins. With our technique, the impact of climate modes on water mass changes can be tracked across distinct water reservoirs (oceans, continents and ice-covered regions) and we show that a combination of climate modes is necessary to explain at best the natural variability in water mass transport. The climate modes predictions based on LASSO inversions can be used to reduce the inter-annual variability in satellite gravity measurements and detect processes unrelated with the natural variability of climate but with similar spatio-temporal signatures. However, significant residuals in the satellite gravity measurements remain unexplained at inter-annual time scales and more complex models solving the water mass balance should be employed to better predict the variability of water mass distributions.

Is the Red Sea Sea-Level Rising at a Faster Rate than the Global Average? An Analysis Based on Satellite Altimetry Data

Satellite altimetry sea-level data was taken for nearly three decades (1993–2020) and is used to understand the variability and associated dynamics in the Red Sea sea-level. Seasonally, the sea-level is higher during December–January and lower during August, with a consistent pattern from south to north. The interannual fluctuations in sea-level have a close agreement with the variability in the global climate modes, i.e., El-Nino Southern Oscillation events, East Atlantic-West Russian oscillation, and the Indian Ocean Dipole. The impact of the El-Nino Southern Oscillation mode on sea-level is higher than other climate modes. The Red Sea sea-level was seen to rise at a rate of 3.88 mm/year from 1993–present, which was consistent with the global rate of 3.3 ± 0.5 mm/year. However, a noticeably faster rate of 6.40 mm/year was observed in the Red Sea sea-level from 2000-present.