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Niño Southern Oscillation (nino + southern_oscillation)
Kinds of Niño Southern Oscillation Selected AbstractsDynamics of the SAR11 bacterioplankton lineage in relation to environmental conditions in the oligotrophic North Pacific subtropical gyreENVIRONMENTAL MICROBIOLOGY, Issue 9 2009Alexander Eiler Summary A quantitative PCR assay for the SAR11 clade of marine Alphaproteobacteria was applied to nucleic acids extracted from monthly depth profiles sampled over a 3-year period (2004,2007) at the open-ocean Station ALOHA (A Long-term Oligotrophic Habitat Assessment; 22°45,N, 158°00,W) in the oligotrophic North Pacific Ocean. This analysis revealed a high contribution (averaging 36% of 16S rRNA gene copies) of SAR11 to the total detected 16S rRNA gene copies over depths ranging from the surface layer to 4000 m, and revealed consistent spatial and temporal variation in the relative abundance of SAR11 16S rRNA gene copies. On average, a higher proportion of SAR11 rRNA gene copies were detected in the photic zone (< 175 m depth; mean = 38%) compared with aphotic (> 175 m depth; mean = 30%), and in the winter months compared with the summer (mean = 44% versus 33%, integrated over 175 m depth). Partial least square to latent structure projections identified environmental variables that correlate with variation in the absolute abundance of SAR11, and provided tools for developing a predictive model to explain time and depth-dependent variations in SAR11. Moreover, this information was used to hindcast temporal dynamics of the SAR11 clade between 1997 and 2006 using the existing HOT data set, which suggested that interannual variations in upper ocean SAR11 abundances were related to ocean-climate variability such as the El Niño Southern Oscillation. [source] Time series analyses reveal transient relationships between abundance of larval anchovy and environmental variables in the coastal waters southwest of TaiwanFISHERIES OCEANOGRAPHY, Issue 2 2009CHIH-HAO HSIEH Abstract We investigated environmental effects on larval anchovy fluctuations (based on CPUE from 1980 to 2000) in the waters off southwestern Taiwan using advanced time series analyses, including the state-space approach to remove seasonality, wavelet analysis to investigate transient relationships, and stationary bootstrap to test correlation between time series. For large-scale environmental effects, we used the Southern Oscillation Index (SOI) to represent the El Niño Southern Oscillation (ENSO); for local hydrographic conditions, we used sea surface temperature (SST), river runoff, and mixing conditions. Whereas the anchovy catch consisted of a northern species (Engraulis japonicus) and two southern species (Encrasicholina heteroloba and Encrasicholina punctifer), the magnitude of the anchovy catch appeared to be mainly determined by the strength of Eng. japonicus (Japanese anchovy). The main factor that caused the interannual variation of anchovy CPUE might change through time. The CPUE showed a negative correlation with combination of water temperature and river runoff before 1987 and a positive correlation with river runoff after 1988. Whereas a significant negative correlation between CPUE and ENSOs existed, this correlation was driven completely by the low-frequency ENSO events and explained only 10% of the variance. Several previous studies on this population emphasized that the fluctuations of larval anchovy abundance were determined by local SST. Our analyses indicated that such a correlation was transient and simply reflected ENSO signals. Recent advances in physical oceanography around Taiwan showed that the ENSOs reduced the strength of the Asian monsoon and thus weakened the China Coastal Current toward Taiwan. The decline of larval anchovy during ENSO may be due to reduced China Coastal Current, which is important in facilitating the spawning migration of the Japanese anchovy. [source] Short-term climatic trends affect the temporal variability of macroinvertebrates in California ,Mediterranean' streamsFRESHWATER BIOLOGY, Issue 12 2007LEAH A. BÊCHE Summary 1. Long-term studies in ecology are essential for understanding natural variability and in interpreting responses to disturbances and human perturbations. We assessed the long-term variability, stability and persistence of macroinvertebrate communities by analysing data from three regions in northern California with a mediterranean-climate. During the study period, precipitation either increased or decreased, and extreme drought events occurred in each region. 2. Temporal trends in precipitation resulted in shifts from ,dry-year' communities, dominated by taxa adapted to no or low flow, to ,wet-year' communities dominated by taxa adapted to high flows. The abundance of chironomid larvae was an important driver of community change. Directional change in community composition occurred at all sites and was correlated with precipitation patterns, with more dramatic change occurring in smaller streams. 3. All communities exhibited high to moderate persistence (defined by the presence/absence of a species) and moderate to low stability (defined by changes in abundance) over the study period. Stability and persistence were correlated with climatic variation (precipitation and El Niño Southern Oscillation) and stream size. Stability and persistence increased as a result of drought in small streams (first-order) but decreased in larger streams (second- and third-order). Communities from the dry season were less stable than those from the wet-season. 4. This study demonstrates the importance of long-term studies in capturing the effects of and recovery from rare events, such as the prolonged and extreme droughts considered here. [source] Regeneration patterns and persistence of the fog-dependent Fray Jorge forest in semiarid Chile during the past two centuriesGLOBAL CHANGE BIOLOGY, Issue 1 2008ALVARO G. GUTIÉRREZ Abstract The persistence of rainforest patches at Fray Jorge National Park (FJNP) in semiarid Chile (30°40,S), a region receiving approximately 147 mm of annual rainfall, has been a source of concern among forest managers. These forests are likely dependent on water inputs from oceanic fog and their persistence seems uncertain in the face of climate change. Here, we assessed tree radial growth and establishment during the last two centuries and their relation to trends in climate and canopy disturbance. Such evaluation is critical to understanding the dynamics of these semiarid ecosystems in response to climate change. We analyzed forest structure of six forest patches (0.2,22 ha) in FJNP based on sampling within 0.1 ha permanent plots. For the main canopy species, the endemic Aextoxicon punctatum (Aextoxicaceae), we used tree-ring analysis to assess establishment periods, tree ages, growing trends and their relation to El Niño Southern Oscillation (ENSO), rainfall, and disturbance. The population dynamics of A. punctatum can be described by a continuous regeneration mode. Regeneration of A. punctatum was sensitive to different canopy structures. Growth release patterns suggest the absence of large scale human impact. Radial growth and establishment of A. punctatum were weakly correlated with rainfall and ENSO. If water limits forests patch persistence, patches are likely dependent on the combination of fog and rain water inputs. Forest patches have regenerated continuously for at least 250 years, despite large fluctuations in rainfall driven by ENSO and a regional decline in rainfall during the last century. Because of the positive influence on fog interception, forest structure should be preserved under any future climate scenario. Future research in FJNP should prioritize quantifying the long-term trends of fog water deposition on forests patches. Fog modeling is crucial for understanding the interplay among physical drivers of water inputs under climate change. [source] Herbivory and plant growth rate determine the success of El Niño Southern Oscillation-driven tree establishment in semiarid South AmericaGLOBAL CHANGE BIOLOGY, Issue 12 2006MILENA HOLMGREN Abstract While climatic extremes are predicted to increase with global warming, we know little about the effect of climatic variability on biome distribution. Here, we show that rainy El Niño Southern Oscillation (ENSO) events can enhance tree recruitment in the arid and semiarid ecosystems of north-central Chile and northwest Peru. Tree-ring studies in natural populations revealed that rainy El Niño episodes have triggered forest regeneration in Peru. Field experiments indicate that tree seedling recruitment in Chile is much less successful than in Peru due mostly to larger mortality caused by herbivores. The dramatic impact of herbivores in Chile was derived from the combined result of slower plant growth and the presence of exotic herbivores (European rabbits and hares). The interplay of herbivory and climatic effects we demonstrated implies that rainy ENSO events may represent ,windows of opportunity' for forest recovery if herbivore pressure is minimized at the right moment. [source] Amazon drought and its implications for forest flammability and tree growth: a basin-wide analysisGLOBAL CHANGE BIOLOGY, Issue 5 2004Daniel Nepstad Abstract Severe drought in moist tropical forests provokes large carbon emissions by increasing forest flammability and tree mortality, and by suppressing tree growth. The frequency and severity of drought in the tropics may increase through stronger El Niño Southern Oscillation (ENSO) episodes, global warming, and rainfall inhibition by land use change. However, little is known about the spatial and temporal patterns of drought in moist tropical forests, and the complex relationships between patterns of drought and forest fire regimes, tree mortality, and productivity. We present a simple geographic information system soil water balance model, called RisQue (Risco de Queimada , Fire Risk) for the Amazon basin that we use to conduct an analysis of these patterns for 1996,2001. RisQue features a map of maximum plant-available soil water (PAWmax) developed using 1565 soil texture profiles and empirical relationships between soil texture and critical soil water parameters. PAW is depleted by monthly evapotranspiration (ET) fields estimated using the Penman,Monteith equation and satellite-derived radiation inputs and recharged by monthly rain fields estimated from 266 meteorological stations. Modeled PAW to 10 m depth (PAW10 m) was similar to field measurements made in two Amazon forests. During the severe drought of 2001, PAW10 m fell to below 25% of PAWmax in 31% of the region's forests and fell below 50% PAWmax in half of the forests. Field measurements and experimental forest fires indicate that soil moisture depletion below 25% PAWmax corresponds to a reduction in leaf area index of approximately 25%, increasing forest flammability. Hence, approximately one-third of Amazon forests became susceptible to fire during the 2001 ENSO period. Field measurements also suggest that the ENSO drought of 2001 reduced carbon storage by approximately 0.2 Pg relative to years without severe soil moisture deficits. RisQue is sensitive to spin-up time, rooting depth, and errors in ET estimates. Improvements in our ability to accurately model soil moisture content of Amazon forests will depend upon better understanding of forest rooting depths, which can extend to beyond 15 m. RisQue provides a tool for early detection of forest fire risk. [source] Sub-saharan desertification and productivity are linked to hemispheric climate variabilityGLOBAL CHANGE BIOLOGY, Issue 3 2001Gufu Oba Summary Vegetation productivity and desertification in sub-Saharan Africa may be influenced by global climate variability attributable to the North Atlantic Oscillation (NAO) and El Niño Southern Oscillation (ENSO). Combined and individual effects of the NAO and ENSO indices revealed that 75% of the interannual variation in the area of Sahara Desert was accounted for by the combined effects, with most variance attributable to the NAO. Effects were shown in the latitudinal variation on the 200 mm isocline, which was influenced mostly by the NAO. The combined indices explained much of the interannual variability in vegetation productivity in the Sahelian zone and southern Africa, implying that both the NAO and ENSO may be useful for monitoring effects of global climate change in sub-Saharan Africa. [source] El Niño Southern Oscillation link to the Blue Nile River Basin hydrologyHYDROLOGICAL PROCESSES, Issue 26 2009Wossenu Abtew Abstract The objective of this study is to evaluate the relationships of El Niño Southern Oscillation (ENSO) indices and the Blue Nile River Basin hydrology using a new approach that tracks cumulative ENSO indices. The results of this study can be applied for water resources management decision making to mitigate drought or flood impacts with a lead time of at least few months. ENSO tracking and forecasting is relatively easier than predicting hydrology. ENSO teleconnections to the Blue Nile River Basin hydrology were evaluated using spatial average basin rainfall and Blue Nile flows at Bahir Dar, Ethiopia. The ENSO indices were sea surface temperature (SST) anomalies in region Niño 3·4 and the Southern Oscillation Index (SOI). The analysis indicates that the Upper Blue Nile Basin rainfall and flows are teleconnected to the ENSO indices. Based on event correspondence and correlation analysis, high rainfall and high flows are likely to occur during La Niña years and dry years are likely to occur during El Niño years at a confidence level of 90%. Extreme dry and wet years are very likely to correspond with ENSO events as given above. The great Ethiopian famine of 1888,1892 corresponds to one of the strongest El Niño years, 1888. The recent drought years in Ethiopia correspond to strong El Niño years and wet years correspond to La Niña years. In this paper, a new approach is proposed on how to classify the strength of ENSO events by tracking consecutive monthly events through a year. A cumulative SST index value of ,5 and cumulative SOI value of , ,7 indicate strong El Niño. A cumulative SST index value of ,,5 and cumulative SOI index of ,7 indicate strong La Niña. Copyright © 2009 John Wiley & Sons, Ltd. [source] Long-term trends and cycles in the hydrometeorology of the Amazon basin since the late 1920sHYDROLOGICAL PROCESSES, Issue 22 2009José A. Marengo Abstract Rainfall and river indices for both the northern and southern Amazon were used to identify and explore long-term climate variability on the region. From a statistical analysis of the hydrometeorological series, it is concluded that no systematic unidirectional long-term trends towards drier or wetter conditions have been identified since the 1920s. The rainfall and river series showing variability at inter-annual scales linked to El Niño Southern Oscillation was detected in rainfall in the northern Amazon. It has a low-frequency variability with a peak at , 30 years identified in both rainfall and river series in the Amazon. The presence of cycles rather than a trend is characteristic of rainfall in the Amazon. These cycles are real indicators of decadal and multi-decadal variations in hydrology for both sides of the basin. Sea-level pressure (SLP) gradients between tropics and sub topics were explored in order to explain variability in the hydrometeorology of the basin. Sea surface temperature (SST) gradients inside the tropical Atlantic and between the tropical Atlantic and the sub-tropical Atlantic have been assessed in the context of changes in rainfall in the Amazon, as compared to northern Argentina. Trends in SSTs in the subtropical Atlantic are linked to changes in rainfall and circulation in northern Argentina, and they seem to be related to multi-decadal variations of rainfall in the Amazon. Copyright © 2009 John Wiley & Sons, Ltd. [source] On the interannual wintertime rainfall variability in the Southern AndesINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 5 2010M. H. González Abstract The paper concentrates on the analysis of the interannual variability of wintertime rainfall in the Southern Andes. Besides the socio-economic relevance of the region, mainly associated with hydroelectric energy production, the study of the climate variability in that area has not received as much attention as others along the Andes. The results show that winter rainfall explains the largest percentage of regional total annuals. A principal component analysis (PCA) of the winter rainfall anomalies showed that the regional year-to-year variability is mostly explained by three leading patterns. While one of them is significantly associated with both the El Niño Southern Oscillation (ENSO), and the Southern Annular Mode (SAM), the other two patterns are significantly related to interannual changes of the sea surface temperature (SST) anomalies in the tropical Indian Ocean. Specifically, changes in the ocean surface conditions at both tropical basins induce in the atmospheric circulation the generation of Rossby wave trains that extend along the South Pacific towards South America, and alter the circulation at the region under study. The relationship between variability in the Indian Ocean and the Andes climate variability has not been previously addressed. Therefore, this result makes a significant contribution to the identification of the sources of predictability in South America with relevant consequences for future applications in seasonal predictions. Copyright © 2009 Royal Meteorological Society [source] Variability in the characteristics of cut-off low pressure systems over subtropical southern AfricaINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 3 2007A. T. Singleton Variability in the characteristics of cut-off low pressure systems over subtropical southern Africa is examined for the 1973,2002 period. These characteristics include their seasonality, frequency, duration, location and size. It is found that on average 11 cut-off lows occur over southern Africa south of 20°S per year and are most common in the March-May season. Potential relationships between the number of cut-off lows over southern Africa with the El Niño Southern Oscillation (ENSO), the Pacific South America pattern, the wave number 3 pattern and the semi-annual oscillation (SAO) are discussed. La Niña years appear to be associated with above average annual frequencies of cut-off lows but the reverse is generally not true for El Niño years. There was a shift in the preferred season for cut-off lows from March,May to June,August in the 1980s, which coincided with a weakening of the SAO and a shift in zonal wave number 3. This period also showed a change in the preferred location of these systems from southwestern subtropical southern Africa to the northeast of the region. The results suggest that there may be a relationship between cut-off lows over subtropical southern Africa, the wave number 3 pattern in the Southern Hemisphere and the SAO. Copyright © 2006 Royal Meteorological Society. [source] Post-dispersal fate of seeds in the Monte desert of Argentina: patterns of germination in successive wet and dry yearsJOURNAL OF ECOLOGY, Issue 6 2000Luis Marone Summary 1,Patterns of seed germination of grass and forb species were studied in open Prosopis woodland of the central Monte desert (Argentina) during several years, to test the hypotheses that (i) seed germination is positively affected by both rainfall and protection afforded by vegetation cover (a facilitative effect), (ii) the number of surviving plants is positively influenced by rainfall but negatively affected by established vegetation (a competitive effect), and (iii) seed loss from soil banks owing to germination is lower than that caused by granivorous animals. 2,Forb species germinated during restricted periods, either in early autumn or in spring. Grasses, however, germinated throughout the growing season, but because seedlings could not be identified to species level, it was impossible to discern whether different species germinated in particular seasons, or if all grasses germinated in all seasons. Grass and forb germination were generally of similar magnitude, but grass germination increased by an order of magnitude during a summer of unusually abundant rainfall related to an El Niño Southern Oscillation (ENSO) event. 3,Overall, the spatial distribution of neither germinating seeds nor surviving plants could be explained by interactions with established vegetation (facilitation and competition effects, respectively). An alternative explanation may be provided by the distribution of forb and grass seeds in the soil. 4,Seed loss owing to germination was low in both dry and rainy years. For forbs, such loss totalled <,1% of soil-seed reserves, and no forb species suffered losses >,4%. Total grass-seed loss to germination was usually <,0.5%, and the 5% reached in 1997,98 corresponded to an interruption of a prolonged drought by unusually abundant rainfall associated with a reduced seed bank. 5,Grass-seed loss caused by germination was one to two orders of magnitude lower than that reported due to autumn-winter granivory in the central Monte desert. [source] CLIMATE FORECASTS IN FLOOD PLANNING: PROMISE AND AMBIGUITY,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2002Kris Wernstedt ABSTRACT: Recent technical and scientific advances have increased the potential use of long term, seasonal climate forecasts for improving water resource management. This paper examines the role that forecasts, in particular those based on the El Niño Southern Oscillation (ENSO) cycle, can play in flood planning in the Pacific Northwest. While strong evidence exists of an association between ENSO signals and flooding in the region, this association is open to more than one interpretation depending on: (a) the metric used to test the strength of the association; (b) the definition of critical flood events; (c) site specific features of watersheds; and (d) the decision environment of flood management institutions. A better understanding and appreciation of such ambiguities, both social and statistical, will help facilitate the use of climate forecast information for flood planning and response. [source] Response of the Asian summer monsoon to changes in El Niño propertiesTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 607 2005H. Annamalai Abstract Diagnostics from observed precipitation and National Centers for Environmental Prediction,National Center for Atmospheric Research re-analysis products reveal that after the 1976,77 climate shift in the Pacific there was a dramatic change in the response of the Indian summer monsoon (ISM) to El Niño, particularly during the months of July and August. Based on 1950,75 (PRE76) and 1977,2001 (POST76) El Niño composites: the western North Pacific monsoon (WNPM) was stronger than normal in both periods; the ISM was weaker than normal during the entire monsoon season in PRE76, but in POST76 was weaker only during the onset and withdrawal phases. In terms of observed sea surface temperature (SST) during July,August, the major differences between the two periods are the presence of cold SST anomalies over the Indo,Pacific warm pool and the intensity of warm SST anomalies in the central Pacific in POST76. The effect of these differences on the ISM is investigated in a suite of experiments with an Atmospheric General Circulation Model (AGCM) that has a realistic monsoon precipitation climatology. Separate ten-member ensemble simulations with the AGCM were conducted for PRE76 and POST76 El Niño events with SST anomalies inserted as follows: (i) tropical Indo,Pacific (TIP), (ii) tropical Pacific only (TPO), and (iii) tropical Indian Ocean only (TIO). Qualitatively, TPO solutions reproduce the observed differences in the monsoon response in both periods. Specifically, during July,August of POST76 the cold SST anomalies in conjunction with remote subsidence suppress precipitation (3,5 mm day,1) over the maritime continent and equatorial central Indian Ocean. Inclusion of Indian Ocean SST anomalies in the TIP runs further suppresses precipitation over the entire equatorial Indian Ocean. The low-level anticyclonic circulation anomalies that develop as a Rossby-wave response to these convective anomalies increase the south-westerlies over the northern Indian Ocean, and favour a stronger ISM and WNPM. During PRE76 the non-occurrence of cold SST anomalies over the Indo,Pacific warm pool reinforces El Niño's suppression on the ISM. In contrast, TIO solutions show a reduced ISM during July,August of POST76; the solutions, however, show a significant effect on the WNPM during both PRE76 and POST76 periods. It is argued that SSTs over the entire tropical Indo,Pacific region need to be considered to understand the El Niño Southern Oscillation,monsoon linkage, and to make predictions of rainfall over India and the western North Pacific. Copyright © 2005 Royal Meteorological Society [source] A probability and decision-model analysis of PROVOST seasonal multi-model ensemble integrationsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 567 2000T. N. Palmer Abstract A probabilistic analysis is made of seasonal ensemble integrations from the PROVOST project (PRediction Of climate Variations On Seasonal to interannual Time-scales), with emphasis on the Brier score and related Murphy decomposition, and the relative operating characteristic. To illustrate the significance of these results to potential users, results from the analysis of the relative operating characteristic are input to a simple decision model. The decision-model analysis is used to define a user-specific objective measure of the economic value of seasonal forecasts. The analysis is made for two simple meteorological forecast conditions or ,events', E, based on 850 hPa temperature. The ensemble integrations result from integrating four different models over the period 1979,93. For each model a set of 9-member ensembles is generated by running from consecutive analyses. Results from the Brier skill score analysis taken over all northern hemisphere grid points indicate that, whilst the skill of individual-model ensembles is only marginally higher than a probabilistic forecast of climatological frequencies, the multi-model ensemble is substantially more skilful than climatology. Both reliability and resolution are better for the multi-model ensemble than for the individual-model ensembles. This improvement arises both from the use of different models in the ensemble, and from the enhanced ensemble size obtained by combining individual-model ensembles; the latter reason was found to be the more important. Brier skill scores are higher for years in which there were moderate or strong El Niño Southern Oscillation (ENSO) events. Over Europe, only the multi-model ensembles showed skill over climatology. Similar conclusions are reached from an analysis of the relative operating characteristic. Results from the decision-model analysis show that the economic value of seasonal forecasts is strongly dependent on the cost, C, to the user of taking precautionary action against E, in relation to the potential loss, L, if precautionary action is not taken and E occurs. However, based on the multi-model ensemble data, the economic value can be as much as 50% of the value of a hypothetical perfect deterministic forecast. For the hemisphere as a whole, value is enhanced by restriction to ENSO years. It is shown that there is potential economic value in seasonal forecasts for European users. However, the impact of ENSO on economic value over Europe is mixed; value is enhanced by El Niño only for some potential users with specific C/L. The techniques developed are applicable to complex E for arbitrary regions. Hence these techniques are proposed as the basis of an objective probabilistic and decision-model evaluation of operational seasonal ensemble forecasts. [source] Boreal winter predictions with the GEOS-2 GCM: The role of boundary forcing and initial conditionsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 567 2000Yehui Chang Abstract Ensembles of atmospheric General Circulation Model (GCM) seasonal forecasts and long-term simulations are analysed to assess the controlling influences of boundary forcing and memory of the initial conditions. Both the forecasts and simulations are carried out with version 2 of the Goddard Earth Observing System (GEOS-2) GCM forced with observed sea surface temperatures (SSTs). While much of the focus is on the seasonal time-scale (January-March; 1981,95) and the Pacific North American (PNA) region, we also present results for other regions, shorter time-scales, and other known modes of variability in the northern hemisphere extratropics. Forecasts of indices of some of the key large-scale modes of variability show that there is considerable variability in skill between different regions of the northern hemisphere. The eastern North Atlantic region has the poorest long-lead forecast skill, showing no skill beyond about 10 days. Skilful seasonal forecasts are primarily confined to the wave-like El Niño Southern Oscillation (ENSO) response emanating from the tropical Pacific. In the northern hemisphere, this is similar to the well-known PNA pattern. Memory of the initial conditions is the major factor leading to skilful extratropical forecasts of lead time less than one month, while boundary forcing is the dominant factor at the seasonal time-scale. Boundary forcing contributes to skilful forecasts at sub-seasonal time-scales only over the PNA region. The GEOS-2 GCM produces average signal-to-noise ratios which are less than 1.0 everywhere in the extra-tropics, except for the subtropical Pacific where they approach 1.5. An assessment of the sampling distribution of the forecasts suggests the model's ENSO response is very likely too weak. These results show some sensitivity to the uncertainties in the estimates of the SST forcing fields. In the North Pacific region, the sensitivity to SST forcing manifests itself primarily as changes in the variability of the PNA response, underscoring the need for an ensemble approach to the seasonal-prediction problem. [source] Effects of ENSO-induced forest fires and habitat disturbance on the abundance and spatial distribution of an endangered riverine bird in BorneoANIMAL CONSERVATION, Issue 1 2005Resit Sözer Droughts induced by the 1997,1998 El Niño Southern Oscillation (ENSO) event sparked large-scale forest fires affecting millions of hectares on Borneo. We studied the effects of ENSO-induced disturbances on a riverine bird, the critically endangered white-shouldered ibis, Pseudibis davisoni, along the Mahakam River in East Kalimantan, Indonesian Borneo. Island-wide fire hotspots were more likely to occur near rivers and part of our study area was indeed affected by fire. Based on 25 boat surveys (2590 km) that yielded 91 records, we recorded significant changes in abundance and spatial distribution of this bird in our study area. Encounter rates were higher during the pre-ENSO (1992,1996) periods than the post-ENSO (1997,2000) ones and differed between seasons. No ibises were seen post-ENSO along river sections that were affected by the fires, whereas pre-ENSO encounter rates were 2.4 birds/102 km. Encounter rates along those sections that were not affected by the forest fires more than doubled from 2.0 birds/102 km pre-ENSO to 5.6 birds/102 km post-ENSO. This was most probably due to enhancement of displaced birds. In view of the permanent character of the change in spatial distribution, active protection of the remaining stretches of riverine forest is of the utmost importance for the survival of white-shouldered ibis. [source] Short-term propagation of rainfall perturbations on terrestrial ecosystems in central CaliforniaAPPLIED VEGETATION SCIENCE, Issue 2 2010Mónica García Abstract Question: Does vegetation buffer or amplify rainfall perturbations, and is it possible to forecast rainfall using mesoscale climatic signals? Location: Central California (USA). Methods: The risk of dry or wet rainfall events was evaluated using conditional probabilities of rainfall depending on El Niño Southern Oscillation (ENSO) events. The propagation of rainfall perturbations on vegetation was calculated using cross-correlations between monthly seasonally adjusted (SA) normalized difference vegetation index (NDVI) from the Advanced Very High Resolution Radiometer (AVHRR), and SA antecedent rainfall at different time-scales. Results: In this region, El Niño events are associated with higher than normal winter precipitation (probability of 73%). Opposite but more predictable effects are found for La Niña events (89% probability of dry events). Chaparral and evergreen forests showed the longest persistence of rainfall effects (0-8 months). Grasslands and wetlands showed low persistence (0-2 months), with wetlands dominated by non-stationary patterns. Within the region, the NDVI spatial patterns associated with higher (lower) rainfall are homogeneous (heterogeneous), with the exception of evergreen forests. Conclusions: Knowledge of the time-scale of lagged effects of the non-seasonal component of rainfall on vegetation greenness, and the risk of winter rainfall anomalies lays the foundation for developing a forecasting model for vegetation greenness. Our results also suggest greater competitive advantage for perennial vegetation in response to potential rainfall increases in the region associated with climate change predictions, provided that the soil allows storing extra rainfall. [source] Changes in northern Tanzania coral reefs during a period of increased fisheries management and climatic disturbanceAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 7 2009Tim R. McClanahan Abstract 1.Surveys of coral reefs in northern Tanzania were conducted in 2004/5 with the aim of comparing them over an,8-year period during a time of increased efforts at fisheries management and the 1998 El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) coral mortality event that caused 45% mortality in northern Tanzania and much of the Indian Ocean. 2.Changes associated with both management, its absence, and the ENSO were found but changes were generally small and ecological measures indicated stability or improvements over this period, particularly when compared with reports from much of the northern Indian Ocean. 3.Fisheries management in two areas increased the biomass of fish and benthic communities. A small fisheries closure (0.3,km2) displayed little change in the coral community but ecological conditions declined as measured by sea urchins and fish abundances. This change may be associated with its small size because similar changes were not measured in the large closure (28,km2). 4.The few sites without any increased management were still degraded and one site had experienced a population explosion of a pest sea urchin, Echinometra mathaei. 5.The lack of significant changes across this disturbance indicates that these reefs are moderately resilient to climate change and, therefore, a high priority for future conservation actions. Copyright © 2009 John Wiley & Sons, Ltd. [source] Retracted: ENSO-related modulation of coastal upwelling along the central east coast of IndiaATMOSPHERIC SCIENCE LETTERS, Issue 1 2009K. Muni Krishna Abstract An index of El Niño Southern Oscillation (ENSO) in the Pacific during February through April is shown to account for a significant part of the variability of coastal sea surface temperature (SST) anomalies measured a few months later within the central east coast of India (CEI). This ENSO-related modulation of coastal upwelling appears to contribute to the connection observed at the basin-scale between ENSO and SST in the Bay of Bengal. The ability to use this teleconnection to give warning of large changes in the CEI a few months in advance is exemplified using data 1998,1999 ENSO events. Copyright © 2008 Royal Meteorological Society [source] Are local patterns of anthropoid primate diversity related to patterns of diversity at a larger scale?JOURNAL OF BIOGEOGRAPHY, Issue 6 2000M. J. Lawes Abstract Aims, (1) To determine the relationship between local and regional anthropoid primate species richness. (2) To establish the spatial and temporal scale at which the ultimate processes influencing patterns of primate species coexistence operate. Location Continental landmasses of Africa, South America and Asia (India to China, and all islands as far south as New Guinea). Methods, The local,regional species richness relationship for anthropoid primates is estimated by regressing local richness against regional richness (independent variable). Local richness is estimated in small, replicate local assemblages sampled in regions that vary in total species richness. A strong linear relationship is taken as evidence that local assemblages are unsaturated and local richness results from proportional sampling of the regional pool. An asymptotic curvilinear relationship is interpreted to reflect saturated communities, where strong biotic interactions limit local richness and local processes structure the species assemblage. As a further test of the assumption of local assemblage saturation, we looked for density compensation in high-density local primate assemblages. Results, The local,regional species richness relationship was linear for Africa and South America, and the slope of the relationship did not differ between the two continents. For Asia, curvilinearity best described the relationship between local and regional richness. Asian primate assemblages appear to be saturated and this is confirmed by density compensation among Asian primates. However, density compensation was also observed among African primates. The apparent assemblage saturation in Asia is not a species,area phenomenon related to the small size of the isolated islands and their forest blocks, since similar low local species richness occurs in large forests on mainland and/or peninsular Asia. Main conclusions In Africa and South America local primate assemblage composition appears to reflect the influence of biogeographic processes operating on regional spatial scales and historical time scales. In Asia the composition of primate assemblages are by-and-large subject to ecological constraint operating over a relatively small spatial and temporal scale. The possible local influence of the El Niño Southern Oscillations on the evolution and selection of life-history characteristics among Asian primates, and in determining local patterns of primate species coexistence, warrants closer inspection. [source] Climatic signals in growth and its relation to ENSO events of two Prosopis species following a latitudinal gradient in South AmericaGLOBAL CHANGE BIOLOGY, Issue 5 2006BERNAT C. LÓPEZ Abstract Semiarid environments throughout the world have lost a major part of their woody vegetation and biodiversity due to the effects of wood cutting, cattle grazing and subsistence agriculture. The resulting state is typically used for cattle production, but the productivity of these systems is often very low, and erosion of the unprotected soil is a common problem. Such dry-land degradation is of great international concern, not only because the resulting state is hardly productive but also because it paves the way to desertification. The natural distribution of the genus Prosopis includes arid and semiarid zones of the Americas, Africa and Asia, but the majority of the Prosopis species are, however, native to the Americas. In order to assess a likely gradient in the response of tree species to precipitation, temperature and their connection to El Niño southern oscillation (ENSO) events, two Prosopis species were chosen along a latitudinal gradient in Latin America, from northern Peru to central Chile: Prosopis pallida from a semi-arid land in northern and southern Peru and P. chilensis from a semiarid land in central Chile. Growth rings of each species were crossdated at each sampling site using classical dendrochronological techniques. Chronologies were related with instrumental climatic records in each site, as well as with SOI and N34 series. Cross-correlation, spectral and wavelet analysis techniques were used to assess the relation of growth with precipitation and temperature. Despite the long distance among sites, the two Prosopis species presented similar responses. Thus, the two species' growth is positively correlated to precipitation, while with temperature it is not. In northern Peru, precipitation and growth of P. pallida present a similar cyclic pattern, with a period of around 3 years. On the other hand, P. pallida in southern Peru, and P. chilensis also present this cyclic pattern, but also another one with lower frequency, coinciding with the pattern of precipitation. Both cycles are within the range of the ENSO band. [source] Association of early annual peak influenza activity with El Niño southern oscillation in JapanINFLUENZA AND OTHER RESPIRATORY VIRUSES, Issue 4 2008Hassan Zaraket Background, Seasonality characterizing influenza epidemics suggests susceptibility to climate variation. El Niño southern oscillation (ENSO), which involves two extreme events, El Niño and La Niña, is well-known for its large effects on inter-annual climate variability. The influence of ENSO on several diseases has been described. Objectives, In this study, we attempt to analyze the possible influence of ENSO on the timing of the annual influenza activity peak using influenza-like illness report data in Japan during 1983,2007. Materials, Influenza surveillance data for 25 influenza epidemics, available under the National Epidemiological Surveillance of the Infectious Diseases, was used in this study. ENSO data were obtained from the Japan Meteorological Agency. Results, Influenza-like illness peak week varied largely during the study period, ranging between 4th and 11th weeks (middle of winter to early spring). The average of peak week during ENSO cycles (n = 11, average = 4·5 ± 0·9) was significantly earlier than in non-ENSO years (n = 14, average = 7·6 ± 2·9; P = 0·01), but there was no significant difference in the peak timing between hot (El Niño) and cold (La Niña) phases. Earlier peaks of influenza activity were observed in 16, out of 25, epidemics. These coincided with 10 (90·9%) out of 11 ENSO and 6 (85·7%) out of seven large-scale epidemics. Conclusion, Influenza activity peak occurred earlier in years associated with ENSO and/or large scale epidemics. [source] Trend patterns in global sea surface temperatureINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 14 2009Susana M. Barbosa Abstract Isolating long-term trend in sea surface temperature (SST) from El Niño southern oscillation (ENSO) variability is fundamental for climate studies. In the present study, trend-empirical orthogonal function (EOF) analysis, a robust space-time method for extracting trend patterns, is applied to isolate low-frequency variability from time series of SST anomalies for the 1982,2006 period. The first derived trend pattern reflects a systematic decrease in SST during the 25-year period in the equatorial Pacific and an increase in most of the global ocean. The second trend pattern reflects mainly ENSO variability in the Pacific Ocean. The examination of the contribution of these low-frequency modes to the globally averaged SST fluctuations indicates that they are able to account for most (>90%) of the variability observed in global mean SST. Trend-EOFs perform better than conventional EOFs when the interest is on low-frequency rather than on maximum variance patterns, particularly for short time series such as the ones resulting from satellite retrievals. Copyright © 2009 Royal Meteorological Society [source] Effects of the El Niño southern oscillation on Turbo torquatus (Gastropoda) and their kelp habitatAUSTRAL ECOLOGY, Issue 5 2008PIERS ETTINGER-EPSTEIN Abstract Turbo torquatus (hereafter Turbo) were abundant and patchily distributed, especially in algal dominated habitats in shallow water (less then 10 metres) on rocky reefs in central New South Wales, Australia. Although the assemblage of algae was similar in barrens with and without crevices, Turbo were most abundant in crevices, suggesting that shelter was important. Experimental removal of the kelp canopy resulted in a great decrease in the number of Turbo. This was despite cleared patches containing more filamentous food algae, further highlighting the importance of shelter. The density of Turbo in kelp forests ranged from six to seven per square metre in times of abundance and less then one per square metre at other times over a 12-year period. Variation in the resource base (i.e. food algae and kelp cover) was strongly linked to the abundance of Turbo. Abundance of Turbo was lowest when the density of adult kelp was low (less than 14 plants per square metre). The condition of kelp was severely affected during the 1997,1998 and 2002 El Niño events and was compromised 2,4 years after each event. These pulse events and related loss of shelter probably contributed to a decline in abundance of Turbo. This model was further supported when Turbo abundance increased with a subsequent increase in the density of kelp. [source] | ||||||||||||||||||||||||||||