Negative El Nino Southern Oscillation Research Articles

Controls of Spring Persistence Barrier Strength in Different ENSO Regimes and Implications for 21st Century Changes

AbstractThis paper investigates potential factors that control the El Niño–Southern Oscillation (ENSO) Spring Persistence Barrier (SPB) strength in two different ENSO regimes and apply it to explain the ENSO SPB strength modulation after the 21st century. In a damped, noise‐driven model, the theoretical solution of SPB strength illustrates that a weaker ENSO growth rate strengthens SPB. In the self‐sustained regime, as in the Cane‐Zebiak model (chaotic system), the strengthened thermodynamic damping and weakened thermocline positive feedback lead to a more negative ENSO growth rate and, in turn, a stronger SPB. Therefore, in both ENSO regimes, a weaker ENSO growth rate intensifies the SPB. The application of the theory to the real world suggests that a more negative ENSO growth rate, corresponding to a more damped feedback system, is responsible for the stronger SPB in recent decades than in 1980–2000.

Human Disturbances of Shoreline Morphodynamics and Dune Ecosystem at the Puerto Velero Spit (Colombian Caribbean)

Villate D. A.; Portz L.; Manzolli, R.P., and Alcantara-Carrio J., 2020. Human disturbances of shoreline morphodynamics and dune ecosystem at the Puerto Velero spit (Colombian Caribbean), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No.95, pp. 711-716. Coconut Creek (Florida), ISSN 0749-0208.Evolution of present coastal environments is controlled by both natural processes and anthropogenic activities, last one causing global, regional and local disturbances. This study analyze the effects of shortage of sediments from Magdalena River and tourism development in the recent shoreline morphodynamics and dune vegetation structure of the Puerto Velero spit, in the northern Colombian Caribbean coast. Shoreline position, dune vegetation and human occupation were taken from the interpretation of satellite images, aerial photographs and field trips. Three methods were applied to analyze shoreline migration. It allowed to deduce trends of very high erosion for the outer neck and moderate to high erosion for the inner neck, while the northern border and the point of the spit present an erosional trend in the outer and inner. Therefore, the outer neck and iner neck show predominance of an erosional trend, more intense for the outer one, while the northern border and particularly the point of the spit present trends of high and very high accretion. It implicates a present progradation of the spit, but a narrowing of its neck. The shortage of coastal sand due to the construction of a jettie at Magdalena River favored the formation of the spit by the erosion of the extinct Isla Verde barrier island, but currently cause erosion of the neck. Erosion of the outer and inner neck is also due to the impact of local disturbances on the backshore and dune system, mainly a rapid increase of occupation and a large circulation of people and vehicles. Dune vegetation distribution is affected by these disturbance, including the presence of invasive aloctonous Calotropis procera over a large area of the dune field. The natural climatic oscillations, particularly the negative El Nino Southern Oscillation (ENSO) events, also favor the progradation of the spit. The analysis of these disturbances on the present geomorphological and ecological evolution on the spit constitutes an important instrument for coastal management.

Effects of the El Niño Southern Oscillation phenomenon and sowing dates on soybean yield and on the occurrence of extreme weather events in southern Brazil

ABSTRACT Brazil accounts for 32% of world soybean production and potential yield losses related to climate variability in the country can have an adverse effect on global supply. Recent soybean production declines in Brazil (e.g. The 15.6% soybean yield drop occurred during the 2011/12 growing season) were a consequence of extreme weather events caused by the effects of the El Nino Southern Oscillation (ENSO) phenomenon. ENSO is one of the most important atmospheric-oceanic phenomena responsible for climate and crop yield variability in several agricultural producing regions of Brazil. The greatest challenge related to adapting to ENSO climate cycles is to understand how to minimize the negative impacts and take advantage of favorable conditions to improve yields. Thus, the aim of this study was to determine the spatial and temporal impacts of sowing dates and ENSO phases on soybean yield and the frequency of extreme weather events (high, low temperature and dry period) during the vegetative and reproductive soybean phenological phases in southern Brazil. For that, soybean yields for 16 different sowing dates (from September to February) were simulated using a well-calibrated crop growth and development model (CROPGRO-Soybean) for 12 locations across southern Brazil and considering historical weather series of 56 years (1961-2016). Homogeneous regions related to ENSO impacts were defined by cluster analysis to facilitate the understanding and use of the information produced. Alternative ENSO phases were found to affect the frequency of extreme weather events and soybean yields across the region studied. Potential negative ENSO effects could be minimized by adjusting the sowing windows according to the expected climate cycle. Our results revealed that ENSO impacts on soybean yields in southern Brazil vary according to the location and can be categorized into three main groups: Group I, where the impacts of the El Nino phase on soybean yield tend to be positive, and its positive impact did not vary with the different sowing dates; Group II, where the negative soybean yield anomalies were more frequent in Neutral years; and Group III, where the positive and negative impacts of ENSO phases varied with sowing dates.

Strengthened Relationships of Northwest China Wintertime Precipitation with ENSO and Midlatitude North Atlantic SST since the Mid-1990s

AbstractThe present study investigates the interdecadal changes in the relationship between El Niño–Southern Oscillation (ENSO) and midlatitude North Atlantic (MNA) sea surface temperature (SST) with northwest China (NWC) winter precipitation (WP) variability and the plausible causes. Results show that ENSO and MNA SST have weak correlations with NWC WP before the mid-1990s, whereas the connections are enhanced sharply afterward, with above (below) normal precipitation occuring when there are positive (negative) ENSO SST and negative (positive) MNA SST anomalies (SSTA). Remarkable differences are found in the atmospheric circulations. After the mid-1990s, there is a pronounced Pacific–North American–Eurasian (PNA-EU)-like pattern in the Northern Hemisphere, whereas an Arctic Oscillation–like pattern is found before the mid-1990s. The change in the relationships between NWC WP and SSTs is likely attributable to the enhanced connection between ENSO and MNA SST after the mid-1990s. It is found that ENSO and MNA SSTA can cause NWC WP variation independently through atmospheric teleconnections. In addition, significant precipitation anomalies also occur when concurrent but oppositely signed SSTs anomalies in the two regions are observed. The reinforced negative correlations between ENSO and MNA SST after the mid-1990s act in concert on NWC WP by exciting a PNA-EU-like pattern. This information would help us to better understand the physical processes of the teleconnections between NWC WP variability and the ENSO/MNA SST, in which the strength of the correlation between ENSO and MNA SST should be taken into account.

Quantifying spatiotemporal influences of climate index on seasonal extreme precipitation based on hierarchical Bayesian method

AbstractQuantifying spatiotemporal influence of climate index on extreme precipitation will help to better understand the variability of extreme precipitation. The extreme precipitation is usually influenced by different climate indices, and mutual offset is unavoidable to occur, thus the rotated empirical orthogonal function was used to identify the different influences of climate indices on extreme precipitation in space and time. The variation of extreme precipitation in data‐scarce region is also concerned, hence, an improved spatiotemporal regional frequency analysis model was further developed, therein the identified spatiotemporal influences of climate indices on extreme precipitation were quantified using Bayesian hierarchical method. In this study, the in situ seasonal maximum one‐day precipitation amount (Rx1day) was used to represent seasonal precipitation extremes from 1957 to 2010 in the Poyang Lake basin, and spatiotemporal influences of El Niño‐Southern Oscillation (ENSO), North Atlantic oscillation (NAO) and Indian Ocean Dipole (IOD) on seasonal Rx1day were quantified. Results indicated that the seasonal Rx1day was influenced by different climate indices in the Poyang Lake basin, ENSO tends to affect spring and autumn Rx1day, IOD tends to affect summer Rx1day, and NAO tends to affect spring and winter Rx1day. The response of extreme precipitation on climate index is varied in different regions, and this was well distinguished and verified, such as negative ENSO (in the same year) events tends to cause spring Rx1day slight decrease in the southern part of the basin while increase about 15% in the northern part with center around the Poyang lake.

Possible combined effect of El Niño–Southern Oscillation and Pacific Decadal Oscillation on Korea affecting tropical cyclone passage frequency

AbstractThis study found that the passage frequency of tropical cyclones (TCs) affecting Korea has had negative correlations with the Pacific Decadal Oscillation (PDO) and the El Niño–Southern Oscillation (ENSO) since the early 1980s. To examine the actual combined effects of PDO and ENSO on the passage frequency of TCs affecting Korea, the positive PDO and ENSO years for 9 years and the negative PDO and ENSO years for 9 years were selected during the periods of 1951–1981 (pre‐1981) and 1982–2012 (post‐1981), and then the average difference between these two phases was analyzed. An analysis of anomalous stream flows at 500 hPa showed the formation of anomalous cyclonic circulations in an east‐to‐west direction from East Asia to the North Pacific both in the pre‐1981 and post‐1981 periods in the positive PDO and ENSO years. However, the anomalous cyclones in East Asia were stronger in the pre‐1981 period, whereas the anomalous cyclones in the North Pacific were stronger in the post‐1981 period. Consequently, China, Korea and the west of Japan were affected by strong anomalous northerlies in the pre‐1981 period, and the TC passage frequency was lower in these regions as a result. In the post‐1981 period, these countries were affected by anomalous northwesterlies or anomalous westerlies.

Extreme precipitation events over Saudi Arabia during the wet season and their associated teleconnections

An assessment of the Extreme Precipitation Events (EPEs) is important because of their potential impacts on the local livelihood, ecosystem, and water resource management. In the present study, the EPEs are defined by applying a non-parametric (95th percentile) approach over different climatic regions of Saudi Arabia using observed daily precipitation data for the period 1984–2016 obtained from 27 meteorological stations. The frequency, composite and correlation analyses are performed to evaluate the statistics of EPEs and their teleconnections. During the wet season (Nov-Apr), the frequency of the EPEs (≥25 mm/day) are higher over northeastern, central and southwestern coastal parts of Saudi Arabia. The composites and correlation analyses show that the EPEs over Saudi Arabia are associated with mid-latitude circumglobal wave train (CGT), which evolves a few days before the onset of EPEs and decays afterwards. The CGT modulates the upper-level trough over the Arabian Peninsula (AP) along with the surface anomalous low-pressure system that enhances moisture convergence, favoring the occurrence of EPEs over the region. The EPEs over Saudi Arabia are also associated with El Niño Southern Oscillation (ENSO), which shows that during the positive (negative) ENSO phase the frequency of EPEs increases (decreases) over the country. Moreover, the El Niño (with positive CGT) enhances the EPEs frequency over Saudi Arabia while vice-versa happens for La Niña (with negative CGT) phase.

The Cape Point wave record, extreme events and the role of large-scale modes of climate variability

Situated on the southwestern coast of South Africa, Cape Point is directly impacted by ocean surface waves generated by midlatitude cyclones in the westerly wind belt. Severe swell events have a huge impact on coastal communities, infrastructure and maritime operations. We use the long term Council for Industrial and Scientific Research (CSIR) Cape Point Waverider buoy data and WaveWatch III model data together with atmospheric reanalysis data to investigate the role of the El Niño Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) and their associated adjustments of cyclone tracks and intensities on the variability and extreme events of the Cape Point wave record. During austral summer (DJF), when the waves are generally smaller and more southerly, SAM and ENSO tend to result in robust responses: a negative (positive) SAM tends to result in bigger (smaller) more westerly (southerly) waves, while a positive (negative) ENSO results in bigger (smaller) waves from a more westerly (southerly direction). The mean austral (JJA) winter waves do not respond coherently to either SAM or ENSO. A shift in the wave characteristics between periods 1980–1992 and 1994–2006 is clear. The waves become smaller and more southerly during the latter period. This shift is associated with the shift to a more coherently out of phase relationship between SAM and ENSO, dominated by a positive SAM and negative ENSO, that amplifies the wave response, giving rise to smaller waves from a more southerly direction. During summer months there is a significant reduction in not only the mean wave heights, but also the extreme wave heights between the two periods, while during winter months there is only a significant change in the mean wave direction that becomes more southerly during the latter period. During a positive ENSO and negative SAM combination, the summer extreme wave heights tend to be more westerly while the inverse combination does not produce a robust result. Finally, we show that during summer months a positive (negative) ENSO leads to more frequent extreme wave events. On the other hand, a positive (negative) SAM leads to less (more) frequent extreme wave events during winter months.

ENSO and NAO affect long-term leaf litter dynamics and stoichiometry of Scots pine and European beech mixedwoods.

Litterfall dynamics (production, seasonality and nutrient composition) are key factors influencing nutrient cycling. Leaf litter characteristics are modified by species composition, site conditions and water availability. However, significant evidence on how large-scale, global circulation patterns affect ecophysiological processes at tree and ecosystem level remains scarce due to the difficulty in separating the combined influence of different factors on local climate and tree phenology. To fill this gap, we studied links between leaf litter dynamics with climate and other forest processes, such as tree-ring width (TRW) and intrinsic water-use efficiency (iWUE) in two mixtures of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) in the south-western Pyrenees. Temporal series (18years) of litterfall production and elemental chemical composition were decomposed following the ensemble empirical mode decomposition method and relationships with local climate, large-scale climatic indices, TRW and Scots pine's iWUE were assessed. Temporal trends in N:P ratios indicated increasing P limitation of soil microbes, thus affecting nutrient availability, as the ecological succession from a pine-dominated to a beech-dominated forest took place. A significant influence of large-scale patterns on tree-level ecophysiology was explained through the impact of the North Atlantic Oscillation (NAO) and El Niño-Southern Oscillation (ENSO) on water availability. Positive NAO and negative ENSO were related to dry conditions and, consequently, to early needle shedding and increased N:P ratio of both species. Autumn storm activity appears to be related to premature leaf abscission of European beech. Significant cascading effects from large-scale patterns on local weather influenced pine TRW and iWUE. These variables also responded to leaf stoichiometry fallen 3years prior to tree-ring formation. Our results provide evidence of the cascading effect that variability in global climate circulation patterns can have on ecophysiological processes and stand dynamics in mixed forests.

Variability of Summer Precipitation Events Associated with Tropical Cyclones over Mid-Lower Reaches of Yangtze River Basin: Role of the El Niño–Southern Oscillation

Based on tropical cyclone (TC) track data and gridded observational rainfall data of CN05.1 during the period of 1961 to 2014, we examine the contribution of TCs on three metrics of summertime rainfall regimes and identify the connection between TC-induced precipitation events and El Niño–Southern Oscillation (ENSO) in middle–lower reaches of Yangtze River Basin (MLYRB). At the regional scale, TCs are responsible for approximately 14.4%, 12.5%, and 6.9% of rainfall events for normal, 75th, and 95th percentile precipitation cases, respectively. There is no evidence of significant long-term trends of the three type events linked with TCs, while their interdecadal variability is remarkable. Fractionally, larger proportions of TC-induced events occur along southeast coastal regions of MLYRB for normal rainfall events, and they are recorded over southwest and central-east MLYRB for 95th percentile cases. Moreover, a larger contribution of 95th percentile precipitation events to summer total rainfall is found than that for 75th percentile cases, suggesting that TCs may exert stronger impacts on the upper tail of summertime precipitation distribution across MLYRB. The TC-induced normal rainfall events tend to occur more frequency over central-west MLYRB during negative phase of ENSO in summer. However, the higher likelihood of TC-induced rainfall for three defined metrics are found over the majority of areas over MLYRB during negative ENSO phase in spring. In preceding winter, La Niña episode plays a crucial role in controlling the frequency of both normal and 75th percentile precipitation events.

Seasonal and interannual changes in planktic foraminiferal fluxes and species composition in Guaymas Basin, Gulf of California

Abstract Paleoclimate records based on planktic foraminifera shells are reliant upon an understanding of how populations respond to annual and interannual changes in surface hydrography. In particular, annual and interannual flux variability would be expected to impact the interpretation of geochemical proxies from foraminifera shells. A seven-year time series from Guaymas Basin, Gulf of California reveals a seasonal progression of foraminiferal species flux, with faunal assemblages characteristic of winter, summer, and fall conditions. Observations of flux along with remotely sensed sea surface temperatures and previously published oxygen isotope data are used here to assess the range of environmental conditions each species would be expected to represent in the fossil record. We find that both species abundances and phenology are altered during negative El Nino Southern Oscillation (ENSO) phases, as occurred over the course of the study period. This observation is used in conjunction with published δ18O data to subsample fluxes in simulation of assemblages collected and analyzed by standard paleontological methods. This approach indicates that during periods more influenced by El Nino conditions, Globigerina bulloides would record warmer conditions, while Neogloboquadrina dutertrei would reflect cooler conditions.

Modulation of wet‐season rainfall over Iran by the Madden–Julian Oscillation, Indian Ocean Dipole and El Niño–Southern Oscillation

The intra‐seasonal variation of precipitation over Iran is examined in terms of the combined effects of the Madden–Julian Oscillation (MJO), Indian Ocean Dipole (IOD) and El Niño–Southern Oscillation (ENSO), using daily observations during the wet season (October–May) from 1961 to 2015. We have examined how the probability of daily rainfall above the upper tercile varies across MJO phases during positive and negative IOD and ENSO states. The results indicate that the response of Iran's wet‐season rainfall to the MJO is affected more by large‐scale atmospheric variations associated with the IOD than by ENSO. The negative (positive) IOD strengthens (suppresses) the MJO–rainfall relationship in the wet and dry MJO phases. The variation in the atmospheric variables (relative humidity and vertical velocity) indicates more (less) humidity and upwards (downwards) motion which increases (decreases) precipitation in wet (dry) MJO phases during the negative IOD. The rainfall relationship with the MJO during the negative IOD is statistically significant, while the relationship during the positive IOD is weak; and no significant relationship is found during either phase of ENSO.

The Changing Influences of ENSO and the Pacific Meridional Mode on Mesoscale Eddies in the South China Sea

This study finds that the correlation between El Niño–Southern Oscillation (ENSO) and the activity of mesoscale oceanic eddies in the South China Sea (SCS) changed around 2004. The mesoscale eddy number determined from satellite altimetry observations using a geometry of the velocity vector method was significantly and negatively correlated with the Niño-3.4 index before 2004, but the correlation weakened and became insignificant afterward. Further analyses reveal that the ENSO–eddy relation is controlled by two major wind stress forcing mechanisms: one directly related to ENSO and the other indirectly related to ENSO through its subtropical precursor—the Pacific meridional modes (PMMs). Both mechanisms induce wind stress curl variations over the SCS that link ENSO to SCS eddy activities. While the direct ENSO mechanism always induces a negative ENSO–eddy correlation through the Walker circulation, the indirect mechanism is dominated by the northern PMM (nPMM), resulting in a negative ENSO–eddy correlation before 2004, and by the southern PMM (sPMM) after 2004, resulting in a positive ENSO–eddy correlation. As a result, the direct and indirect mechanisms enhance each other to produce a significant ENSO–eddy relation before 2004, but they cancel each other out, resulting in a weak ENSO–eddy relation afterward. The relative strengths of the northern and southern PMMs are the key to determining the ENSO–eddy relation and may be related to a phase change of the interdecadal Pacific oscillation.

A Nonstationary ENSO–NAO Relationship Due to AMO Modulation

Abstract Many previous studies have demonstrated a high uncertainty in the relationship between El Niño–Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). In the present work, decadal modulation by the Atlantic multidecadal oscillation (AMO) is investigated as a possible cause of the nonstationary ENSO–NAO relationship based on observed and reanalysis data. It is found that the negative ENSO–NAO correlation in late winter is significant only when ENSO and the AMO are in phase (AMO+/El Niño and AMO−/La Niña). However, no significant ENSO-driven atmospheric anomalies can be observed over the North Atlantic when ENSO and the AMO are out of phase (AMO−/El Niño and AMO+/La Niña). Further analysis indicates that the sea surface temperature anomaly (SSTA) in the tropical North Atlantic (TNA) plays an essential role in this modulating effect. Because of broadly analogous TNA SSTA responses to both ENSO and the AMO during late winter, a warm SSTA in the TNA is evident when El Niño occurs during a positive AMO phase, resulting in a significantly weakened NAO, and vice versa when La Niña occurs during a negative AMO phase. In contrast, neither the TNA SSTA nor the NAO shows a prominent change under out-of-phase combinations of ENSO and AMO. The AMO modulation and the associated effect of the TNA SSTA are shown to be well reproduced by historical simulations of the HadCM3 coupled model and further verified by forced experiments using an atmospheric circulation model. These offer hope that similar models will be able to make predictions for the NAO when appropriately initialized.

Evolution of Eastern Equatorial Pacific Seasonal and Interannual Variability in Response to Orbital Forcing During the Holocene and Eemian From Model Simulations

AbstractCharacteristics of the seasonal and interannual sea surface temperature variability in the eastern equatorial Pacific (EEP) over last two interglacials, the Holocene and Eemian, are analyzed using transient climate simulations with the Kiel Climate Model. There is a tendency toward a strengthening of the seasonal as well as the El Niño/Southern Oscillation (ENSO)‐related variability from the early to the late interglacials. The weaker EEP sea surface temperature annual cycle during the early interglacials is mainly a result of insolation‐forced cooling during its warm phase and dynamically induced warming during its cold phase. Enhanced convection over northern South America weakens northeasterlies in the EEP leading to weaker equatorial upwelling, deeper thermocline and subsequent warming in this region. We show that a negative ENSO modulation of the annual cycle operates only on short timescales and does not affect their evolutions on orbital time scales where both ENSO and annual cycle show similar tendencies to increase.

Opportunities for Joint Water–Energy Management: Sensitivity of the 2010 Western U.S. Electricity Grid Operations to Climate Oscillations

Abstract The increasing interconnectedness of energy and water systems makes it important to understand how interannual variations in water availability—and climate oscillations—could potentially impact the electric grid operations. The authors assess the vulnerability of the current western U.S. grid to historical climate variability using multiple energy and water system models. A 55-yr-long natural water availability benchmark is combined with the 2010 level of water demand from an integrated assessment model to drive a large-scale water management model over the western United States. The regulated flow at hydropower and thermoelectric power plants is then translated into boundary conditions for electricity generation in a production cost model. This analysis focuses on assessing regional interdependencies and the impact of interannual changes in water availability on power system operations, including reliability, cost, and carbon emissions. Results for August grid operations—when stress on the grid is often highest—show a range of sensitivity in production cost (–8% to +11%) and carbon emissions (–7% to +11%), as well as a 1-in-10 chance that electricity demand will exceed estimated supply. The authors also show that operating costs are lower under neutral El Niño–Southern Oscillation (ENSO) conditions than under other ENSO phases; carbon emissions are highest under La Niña conditions, especially in California; and the risk of brownouts may be higher under neutral and negative ENSO conditions. These results help characterize the grid’s performance under historical climate variations, are useful for seasonal and multiyear planning of joint water–electricity management, and can be used to support impact, adaptation, and vulnerability analyses.

Storm wave clustering around New Zealand and its connection to climatic patterns

ABSTRACTClusters of storm waves contribute disproportionately to coastal erosion hazards because the coastline has insufficient time to recover between events. Here, the change in occurrence of clustered storms and its association with atmospheric oscillation modes were investigated in New Zealand waters using 44 years (1958–2001) of wave hindcast data. First, long‐term averages of cluster parameters (number of storms within the cluster, potential for coastal erosion, and cluster duration) were assessed. Then, the relationships between clustering and the El Niño‐Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), Zonal Wavenumber‐3 Pattern (ZW3), Pacific Decadal Oscillation (PDO), and Southern Annular Mode (SAM) were explored through correlation analysis over several timescales. Clusters were more frequently observed to the northeast of New Zealand and on the central eastern coast of the South Island. The most vulnerable regions to cluster‐induced coastal erosion were southern New Zealand and the northwestern coast, which resulted from steady southwesterly swells, although clusters with the longest duration occurred on the east coast of the South Island. Trends suggest that clusters have incorporated more storms, have become more hazardous, and have increased in duration, particularly along the South Island coastline. Although these trends may be sensitive to the reanalysed wind fields used to force the wave hindcast, they reflect trends in the ENSO, PDO, and SAM. Stronger southwesterly winds during El Niño (negative ENSO) and El Niño‐like conditions (positive IOD/PDO) generated more clustered storms mainly on the southwestern coast of New Zealand, whereas increases in clustering were observed on the north coast during La Niña and La Niña‐like conditions (stronger northeasterly winds). Higher occurrence of clustering was also evident on the west coast during the strong atmospheric zonal flow associated with negative ZW3. Lastly, strengthened westerlies related to positive SAM led to increased clustering primarily to the south of New Zealand.

Environmental Variability and Oceanographic Dynamics of the Central and Southern Coastal Zone of Sonora in the Gulf of California

This study analyzed monthly and inter-annual variability of mesoscale phenomena, including the El Niño Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO) climate indexes and wind intensity considering their influence on sea surface temperature (SST) and chlorophyll a (Chl-a). These analyses were performed to determine the effects, if any, of climate indexes and oceanographic and environmental variability on the central and southern coastal ecosystem of Sonora in the Gulf of California (GC). Monthly satellite images of SST (°C) and Chl-a concentration were used with a 1-km resolution for oceanographic and environmental description, as well as monthly data of the climate indexes and wind intensity from 2002–2015. Significant differences (p > 0.05) were observed while analyzing the monthly variability results of mesoscale phenomena, SST and Chl-a, where the greatest percentage of anti-cyclonic gyres and filaments was correlated with a greater Chl-a concentration in the area of study, low temperatures and, thus, greater productivity. Moreover, the greatest percentage of intrusion was correlated with the increase in temperature and cyclonic gyres and a strong decrease of Chl-a concentration values, causing oligotrophic conditions in the ecosystem and a decrease in upwelling and filament occurrence. As for the analysis of the interannual variability of mesoscales phenomena, SST, Chl-a and winds, the variability between years was not significant (p > 0.05), so no correlation was observed between variabilities or phenomena. The results of the monthly analyses of climate indexes, environmental variables and wind intensity did not show significant differences for the ENSO and PDO indexes (p > 0.05). Nonetheless, an important correlation could be observed between the months of negative anomalies of the ENSO with high Chl-a concentration values and intense winds, as well as with low SST values. The months with positive ENSO anomalies were correlated with high SST values, low Chl-a concentration and moderate winds. Significant inter-annual differences were observed for climate indexes where the years with high SST values were related to the greatest positive anomaly of ENSO, of which 2002 and 2009 stood out, characterized as moderate Niño years, and 2015 as a strong El Niño year. The years with the negative ENSO anomaly were related to the years of lower SST values, of which 2007–2008 and 2010–2011 stood out, characterized as moderate Niñas. Thus, variability associated with mesoscale oceanographic phenomena and seasonal and inter-annual variations of climate indexes had a great influence on the environmental conditions of the coastal ecosystem of Sonora in the Gulf of California.

SynthETC: A Statistical Model for Severe Winter Storm Hazard on Eastern North America.

We develop, evaluate, and apply "SynthETC," a statistical-stochastic model of winter extra-tropical cyclones (ETCs) over eastern North America. SynthETC simulates the life cycle of ETCs from formation to termination, and it can be used to estimate the probability of extreme ETC events beyond the historical record. Two modes of climate variability are used as independent covariates: El Niño/Southern Oscillation (ENSO) Niño3.4 and the monthly North Atlantic Oscillation (NAO). We use SynthETC to estimate the annual occurrence rate over sites in eastern North America of intense ETC passage in different ENSO and NAO states. Positive NAO is associated with increased rates over the North Atlantic, while negative NAO is associated with decreased rates over the North Atlantic and increased rates over northern Quebec. Positive ENSO is associated with decreased rates over the North Atlantic, Ontario, and the Canadian Maritime, while negative ENSO is associated with increased rates over those regions, as well as the Great Lakes region.

Influence of subtropical dipole pattern in Southern Indian Ocean on ENSO event

Subtropical Dipole Pattern (SDP) in southern Indian Ocean is another significant dipolelike sea surface temperature anomalies (SSTA) phenomena besides tropical Indian Ocean dipole (TIOD). It is very clear in interannual and interdecadal variations. But many recent studies have mainly aimed at the SST of equatorial Indian Ocean and less at southern Indian Ocean, especially less at the relationship between SSTA in southern Indian Ocean and El NinoSouthern Oscillation (ENSO). Present works investigated primarily the correlation between the SDP and ENSO. It is found that SDP event act as a crucial linkage between positive and negative ENSO phases. The SSTAs in equatorial eastern Pacific Ocean are completely reversed before and after SDP event. Further, we investigated the possible impact of SDP on ENSO event in interannual scale by researching the anomalous characteristics of sea temperature, wind, convergence and divergence, total cloud amount, radiation and so on. The results showed that the influence of SDP on ENSO involve not only the process of positive and negative air-sea feedback, but also the interaction between atmospheric circulation over tropical and subtropical, specially the eastward propagation of anomalous zonal wind from the equatorial Indian Ocean to the Pacific Ocean. Otherwise, it also relates, to some extent, to the transition of large-scale climatic mean flow over the Indian Ocean and Pacific Ocean.