Sub-monthly variability of the South American summer precipitation under El Niño and La Niña backgrounds during the 1998-2012 period

Climatic anomalies have changed the ocean circulation pattern and thus the demographic connectivity. However, in many geographical regions there is insufficient evidence of this change. Therefore, comparisons were made between neutral years and years of El Niño and La Niña with moderate intensity, for the North Equatorial Counter Current (NECC), the South Equatorial Current (SEC), the Coastal Current (CoaC) and the main anticyclonic eddy in the Panama Bight. Daily dynamics topography data of the Maps of Absolute Dynamic Topography (MADT) provided by AVISO and daily wind stress data provide by the European Centre for Medium Range Weather (ECMWF) were used to calculate the speed of surface currents (multi-year, quarterly average), during months with the highest number of eggs and larvae released by the species with a pelagic phase (Sept-Nov). It was found that the speed magnitude for the three oceanic currents was statistically different among the compared events, except for the anticyclonic eddy; obtaining higher values of speed for neutral years in relation to years with El Niño or La Niña for the NECC, for the SEC higher values for La Niña years, followed by neutral years and a moderate El Niño years; for the CoaC higher velocity for neutral and La Niña years but the lowest for El Niño years; and a tendency of higher values in La Niña years for the anticyclonic eddy. Additionally, the number of eddies increased in moderate El Niño years. The results suggest that the decreased velocity of the NECC and the potential barriers created by the cyclonic eddies and the anticyclonic eddy near the South American coast could diminish the passive dispersal of larvae and the potential functional connectivity between the Western, Central and Eastern Tropical Pacific. Therefore, there are implications at the evolutionary, biogeographic, and ecologic levels (dispersion rates and population rescue effect). In contrast, during La Niña the SEC could favor teleplanktonic larval transport to the Central Pacific, material which is exported from the South American coast by CoaC, aided by the anticyclonic eddy. In conclusion, anomalous climatic events alter the velocity of oceanic currents in the Panama Bight; consequently these could change the functional potential connectivity from September to November.

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Can small pelagic fish landings be used as predictors of high-frequency oceanographic fluctuations in the 1–2 El Niño region?

Advances in Geosciences ◽

10.5194/adgeo-42-61-2016 ◽

2016 ◽

Vol 42 ◽

pp. 61-72 ◽

Cited By ~ 4

Author(s):

Franklin Isaac Ormaza-González ◽

Alejandra Mora-Cervetto ◽

Raquel María Bermúdez-Martínez ◽

Mario Armando Hurtado-Domínguez ◽

Manuel Raúl Peralta-Bravo ◽

...

Keyword(s):

Linear Correlation ◽

El Niño ◽

El Nino ◽

Pelagic Fish ◽

La Niña ◽

Negative Slope ◽

South American ◽

Small Pelagic Fish ◽

La Nina

Abstract. A group of small pelagic fish captured between 1981 and 2012 within El Niño area 1–2 by the Ecuadorian fleet was correlated with the oceanographic Multivariate ENSO Index (MEI), and the Oceanographic El Niño Index (ONI) referred to El Niño region 3–4. For the period 1981–2012, total landings correlated poorly with the indexes, but during 2000–2012 (cold PDO) they proved to have a 14–29 % association with both indexes; the negative slope of the curves suggested higher landing during cold events (La Niña) and also indicated a tendency to decrease at extreme values ( >  0.5 and < −1.0). Round herring (Etrumeus teres) fourth-quarter (Q4) landings were related to the MEI in a nonlinear analysis by up to 80 %. During moderate or strong La Niña events landings noticeably increased. Bullet tuna (Auxis spp.) catches showed a negative gradient from cold to warm episodes with an R2 of 0.149. For Chilean jack mackerel (Trachurus murphyi) irregular landings between 2003 and 2007 were observed and were poorly correlated (R2 < 0.1) with ONI or MEI. Anchovy (Engraulis ringens) captured in Ecuadorian waters since 2000 had an R2 of 0.302 and 0.156 for MEI and ONI, respectively, but showed a higher correlation with the cold Pacific Decadal Oscillation (PDO). South American pilchard (Sardinops sagax) was higher than −0.5 for the ONI and MEI, and landings dramatically decreased; however, Q4 landings correlated with ONI and MEI, with R2 of 0.109 and 0.225, respectively (n = 3). Linear correlation of Q4 indexes against the following year's Q1 landings had a linkage of up to 22 %; this species could therefore be considered a predictor of El Niño. Chub mackerel (Scomber japonicus) landings did not have a significant linear correlation with the indexes for 1981–2012 and therefore could not be considered a valid predictor. Chuhueco (Cetengraulis mysticetus) is a local species with high landings during El Niño years and, conversely, remarkably low landings during La Niña years. Additionally, chuhueco availability and landings were negatively affected by cold PDOs. Pacific thread herring (Opisthonema spp.) showed a 24 and 36 % relationship between landings (Q1) and the MEI and ONI (Q4). Therefore, results suggest that the South American pilchard and Pacific thread herring could be considered good species to use as predictors of El Niño in region 1–2 (Ecuador), especially when average Q4 MEI ∕ ONI is used against the next trimester Q1 landing. All species were prone to lower landings and/or fishing availability during strong–extreme events (ONI/MEI, >  1.0 and <  −1.0), and were also shown to be affected by the PDO. In the long term, landings decreased under warm PDO and vice versa, and therefore PDO fluctuations could be used to help manage these fisheries and to help the industry in long-term planning.

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Tropical cyclone genesis in the Southern Hemisphere and its relationship with the ENSO

Annales Geophysicae ◽

10.5194/angeo-27-2523-2009 ◽

2009 ◽

Vol 27 (6) ◽

pp. 2523-2538 ◽

Cited By ~ 37

Author(s):

Y. Kuleshov ◽

F. Chane Ming ◽

L. Qi ◽

I. Chouaibou ◽

C. Hoareau ◽

...

Keyword(s):

Relative Humidity ◽

Geographical Distribution ◽

El Niño ◽

Large Scale ◽

El Nino ◽

Vertical Wind Shear ◽

La Niña ◽

The South ◽

La Nina ◽

South Indian

Abstract. Tropical cyclogenesis climatology over the South Indian and South Pacific Oceans has been developed using a new tropical cyclone (TC) archive for the Southern Hemisphere, and changes in geographical distribution of areas favourable for TC genesis related to changes in the El Niño-Southern Oscillation (ENSO) phases have been investigated. To explain these changes, large-scale environmental variables which influence TC genesis and development such as sea surface temperatures (SSTs), relative humidity in mid-troposphere, vertical wind shear and lower tropospheric vorticity have been examined. In the South Indian Ocean, reduction of TC genesis in the western part of the basin and its increase in the eastern part as well as displacement of the area favourable for TC genesis further away from the equator during La Niña events compared to El Niño events can be explained by changes in geographical distribution of relative humidity and vorticity across the basin as primary contributors; positive anomalies of SSTs observed during La Niña seasons in the eastern part of the basin additionally contribute to enhanced cyclogenesis near the Western Australia. In the South Pacific Ocean, changes in geographical distribution of relative humidity and vorticity appear to be the key large-scale environmental factors responsible for enhanced TC genesis in the eastern (western) part of the basin as well as for the northeast (southwest) shift of points of cyclogenesis during El Niño (La Niña) events, with vertical wind shear and SSTs as additional contributing large-scale environmental variables.

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Trends in Twentieth-Century U.S. Extreme Snowfall Seasons

Journal of Climate ◽

10.1175/2009jcli2631.1 ◽

2009 ◽

Vol 22 (23) ◽

pp. 6204-6216 ◽

Cited By ~ 38

Author(s):

Kenneth E. Kunkel ◽

Michael A. Palecki ◽

Leslie Ensor ◽

David Easterling ◽

Kenneth G. Hubbard ◽

...

Keyword(s):

United States ◽

El Niño ◽

El Nino ◽

The United States ◽

La Niña ◽

The South ◽

North Central ◽

La Nina ◽

Central United States ◽

Highly Correlated

Abstract Temporal variability in the occurrence of the most extreme snowfall years, both those with abundant snowfall amounts and those lacking snowfall, was examined using a set of 440 quality-controlled, homogenous U.S. snowfall records. The frequencies with which winter-centered annual snowfall totals exceeded the 90th and 10th percentile thresholds at individual stations were calculated from 1900–01 to 2006–07 for the conterminous United States, and for 9 standard climate regions. The area-weighted conterminous U.S. results do not show a statistically significant trend in the occurrence of either high or low snowfall years for the 107-yr period, but there are regional trends. Large decreases in the frequency of low-extreme snowfall years in the west north-central and east north-central United States are balanced by large increases in the frequency of low-extreme snowfall years in the Northeast, Southeast, and Northwest. During the latter portion of the period, from 1950–51 to 2006–07, trends are much more consistent, with the United States as a whole and the central and northwest U.S. regions in particular showing significant declines in high-extreme snowfall years, and four regions showing significant increases in the frequency of low-extreme snowfall years (i.e., Northeast, Southeast, south, and Northwest). In almost all regions of the United States, temperature during November–March is more highly correlated than precipitation to the occurrence of extreme snowfall years. El Niño events are strongly associated with an increase in low-extreme snowfall years over the United States as a whole, and in the northwest, northeast, and central regions. A reduction in low-extreme snowfall years in the Southwest is also associated with El Niño. The impacts of La Niña events are strongest in the south and Southeast, favoring fewer high-extreme snowfall years, and, in the case of the south, more low-extreme snowfall years occur. The Northwest also has a significant reduction in the chance of a low-extreme snowfall year during La Niña. A combination of trends in temperature in the United States and changes in the frequency of ENSO modes influences the frequency of extreme snowfall years in the United States.

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Diversity of Marine Heatwaves in the South China Sea regulated by the ENSO phase

Journal of Climate ◽

10.1175/jcli-d-21-0309.1 ◽

2021 ◽

pp. 1-51

Author(s):

Kai Liu ◽

Kang Xu ◽

Congwen Zhu ◽

Boqi Liu

Keyword(s):

South China Sea ◽

Latent Heat ◽

South China ◽

El Niño ◽

El Nino ◽

The South China Sea ◽

La Niña ◽

The South ◽

China Sea ◽

La Nina

Abstract Marine heatwaves (MHWs) in the South China Sea (SCS) have dramatic impacts on local ecosystems, fisheries, and aquacultures. Our results show that SCS MHWs were strongly regulated by El Niño-Southern Oscillation (ENSO) with a distinct life cycle during 1982–2018. Based on the ENSO-associated sea surface temperature anomaly (SSTA) warming peaks in the SCS, we can classify SCS MHWs into three categories, namely, El Niño-P1 during the first warming peak of El Niño from September to the following February, El Niño-P2 during the second warming peak of El Niño from the following June to September, and La Niña-P1 during the single warming peak of La Niña from the following February to May. The three types of SCS MHWs are all affected by the lower-level enhanced anticyclone over the western North Pacific (WNP), but their physical mechanisms are quite different. In El Niño-P1, SCS MHWs are mostly induced by enhanced net downward shortwave radiation and reduced latent heat flux loss over the southwestern and northern SCS, respectively. In El Niño-P2, SCS MHWs are primarily attributed to weaker entrainment cooling caused by a local enhanced anticyclone and stronger Ekman downwelling in the central-northern SCS. However, in La Niña-P1, SCS MHWs are mainly contributed by the reduced latent heat loss due to the weaker WNP anticyclone centered east of the Philippines on the pentad timescale. The distinct spatial distributions of MHWs show phase locking with ENSO-associated SCS SSTA warming, which provides a potential seasonal forecast of SCS MHWs according to the ENSO phase.

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Asymmetric Relationship between Indian Ocean SST and the Western North Pacific Summer Monsoon

Journal of Climate ◽

10.1175/jcli-d-14-00289.1 ◽

2015 ◽

Vol 28 (4) ◽

pp. 1383-1395 ◽

Cited By ~ 13

Author(s):

Riyu Lu ◽

Shu Lu

Keyword(s):

Indian Ocean ◽

El Niño ◽

North Pacific ◽

Western North Pacific ◽

El Nino ◽

Summer Precipitation ◽

La Niña ◽

La Nina ◽

Precipitation Anomalies ◽

Sst Anomalies

Abstract The summer precipitation anomalies over the tropical western North Pacific (WNP), which greatly affect East Asian climate, are closely related to Indian Ocean (IO) SST anomalies, and this WNP–IO relationship is widely assumed to be linear. This study indicates that the IO SST–WNP precipitation relationship is generally linear only when the IO SST anomalies are positive and not when the IO SST anomalies are negative, that is, a strongly cooler IO, in comparison with a moderately cooler IO, does not correspond to stronger precipitation enhancement over the WNP. Further analysis suggests that the phases of ENSO play a crucial role in modifying the impacts of IO SSTs on WNP anomalies. The reverse IO SST–WNP precipitation relationship, which exists without apparent ENSO development/decay, is intensified by El Niño decay through the enhancement of IO SST anomalies, but weakened by El Niño development and La Niña decay through the concurrence of SST anomalies in the tropical central and eastern Pacific. After removing El Niño developing and La Niña decaying cases, the IO SST and WNP precipitation anomalies show a clear linear relationship. Because of the effects of the phases of ENSO, the years of negative precipitation or anticyclonic anomalies over the WNP are highly concentrated over strongly warmer IO and El Niño decaying years, which is consistent with previous studies. However, the years of positive precipitation anomalies are scattered over cooler IO and moderately warmer IO years, implying a complexity of tropical SST forcing on positive WNP precipitation anomalies.

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Climatological Characteristics and Seasonal Forecasting of Tropical Cyclones Making Landfall along the South China Coast

Monthly Weather Review ◽

10.1175//2554.1 ◽

2003 ◽

Vol 131 (8) ◽

pp. 1650-1662 ◽

Cited By ~ 81

Author(s):

K. S. Liu ◽

Johnny C. L. Chan

Keyword(s):

Tropical Cyclones ◽

South China ◽

El Niño ◽

El Nino ◽

Southern Oscillation ◽

La Niña ◽

The South ◽

La Nina ◽

South China Coast ◽

China Coast

Abstract This paper presents the important climatological features of the tropical cyclones making landfall along the South China coast and proposes a statistical scheme for the prediction of the annual number of such tropical cyclones. This number is found to have a large variation, which is mainly due to the occurrence or nonoccurrence of the El Niño–Southern Oscillation (ENSO) phenomenon. A strong El Niño event is found to reduce the number of landfalling tropical cyclones whereas more tropical cyclones tend to make landfall in years associated with La Niña events. Such variations are more prominent in some seasons. The late season (October–November) activity is generally suppressed (enhanced) in El Niño (La Niña) years whereas the chance of a tropical cyclone striking the South China coast increases (decreases) significantly in the early season (May and June) after the mature phase of a La Niña (El Niño) event. These anomalous activities are apparently linked to the ENSO-induced anomalies in the low- and midlevel large-scale circulation. Based on the ENSO-related indices such as the Niño-3.4 sea surface temperature anomaly and the equatorial Southern Oscillation index, a statistical prediction scheme for the annual number of such landfalling tropical cyclones by 1 April is developed using the projection–pursuit regression technique. This scheme provides a 40% skill improvement in root-mean-square error with respect to climatology. A real-time prediction made in 2001 gave reasonable results.

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Assessing the Skill of Precipitation and Temperature Seasonal Forecasts in Spain: Windows of Opportunity Related to ENSO Events

Journal of Climate ◽

10.1175/2009jcli2824.1 ◽

2010 ◽

Vol 23 (2) ◽

pp. 209-220 ◽

Cited By ~ 38

Author(s):

M. D. Frías ◽

S. Herrera ◽

A. S. Cofiño ◽

J. M. Gutiérrez

Keyword(s):

El Niño ◽

El Nino ◽

Mediterranean Coast ◽

La Niña ◽

The South ◽

Multimodel Ensemble ◽

Enso Events ◽

La Nina ◽

Downscaling Method ◽

The Mediterranean

Abstract The skill of state-of-the-art operational seasonal forecast models in extratropical latitudes is assessed using a multimodel ensemble from the Development of a European Multimodel Ensemble System for Seasonal-to-Interannual Prediction (DEMETER) project. In particular, probabilistic forecasts of surface precipitation and maximum temperature in Spain are analyzed using a high-resolution observation gridded dataset (Spain02). To this aim, a simple statistical test based on the observed and predicted tercile anomalies is used. First, the whole period 1960–2000 is considered and it is shown that the only significant skill is found for dry events in autumn. Then, the influence of ENSO events as a potential source of conditional predictability is studied and the validation to strong La Niña or El Niño periods is restricted. Skillful seasonal predictions are found in partial agreement with the observed teleconnections derived from the historical records. On the one hand, predictability is found in spring related to El Niño events for dry events over the south and the Mediterranean coast and for hot events in the southeast areas. In contrast, La Niña drives predictability in winter for dry events over the western part and for hot events in summer over the south and the Mediterranean coast. This study considers both the direct model outputs and the postprocessed predictions obtained using a statistical downscaling method based on analogs. In general, the use of the downscaling method outperforms the direct output for precipitation, whereas in the case of the temperature no improvement is obtained.

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The 10–20 d Low-Frequency Oscillation Characteristics of Summer Precipitation in Eastern China in the Decaying Year of CP ENSO

Atmosphere ◽

10.3390/atmos10100616 ◽

2019 ◽

Vol 10 (10) ◽

pp. 616

Author(s):

Cong Cai ◽

Lijuan Wang ◽

Junyu Wang ◽

Zhiqiang Wang

Keyword(s):

El Niño ◽

El Nino ◽

Eastern China ◽

Low Frequency ◽

Summer Precipitation ◽

La Niña ◽

Low Frequency Oscillation ◽

Cp El Niño ◽

La Nina ◽

Oscillation Characteristics

Using National Centers for Atmospheric Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data and observational data, the low-frequency oscillation characteristics of precipitation in eastern China during the decaying summer of central Pacific El Niño–Southern Oscillation (CP ENSO) and the corresponding low-frequency atmospheric oscillation characteristic were investigated. The results showed that summer precipitation in eastern China during the decaying year of CP El Niño (La Niña) was more (less) than the climatological mean and that 10–20 d was its dominant period. Low-frequency oscillations at different tropospheric levels had different effects on low-frequency precipitation. In the upper troposphere, Eastern China was dominated by low-frequency divergence and positive (negative) anomaly of low-frequency height during the decaying year of CP El Niño (La Niña), and there was strong (weak) northwest–southeast wave-active flux transport. In the middle troposphere, the range and intensity of the subtropical western Pacific High (SWPH) of CP El Niño was larger and stronger than that of CP La Niña, which may be related to the low-frequency height fields. Meanwhile, the correspnding low-frequency wind field, water vapor circulation systems and moisture transport channels in the lower troposphere, along with the low-frequency vertical movement were significantly different, causing the low-frequency precipitation of CP El Niño to be stronger than CP La Niña.

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The role of the South Pacific in modulating Tropical Pacific variability

Scientific Reports ◽

10.1038/s41598-019-52805-2 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 2

Author(s):

Christine T. Y. Chung ◽

Scott B. Power ◽

Arnold Sullivan ◽

François Delage

Keyword(s):

El Niño ◽

Decadal Variability ◽

El Nino ◽

South Pacific ◽

Tropical Pacific ◽

Equatorial Pacific ◽

La Niña ◽

The South ◽

La Nina ◽

Sst Anomalies

AbstractTropical Pacific variability (TPV) heavily influences global climate, but much is still unknown about its drivers. We examine the impact of South Pacific variability on the modes of TPV: the El Niño-Southern Oscillation (ENSO) and the Interdecadal Pacific Oscillation (IPO). We conduct idealised coupled experiments in which we suppress temperature and salinity variability at all oceanic levels in the South Pacific. This reduces decadal variability in the equatorial Pacific by ~30% and distorts the spatial pattern of the IPO. There is little change to overall interannual variability, however there is a decrease in the magnitude of the largest 5% of both El Niño and La Niña sea-surface temperature (SST) anomalies. Possible reasons for this include: (i) reduced decadal variability means that interannual SST variability is superposed onto a ‘flatter’ background signal, (ii) suppressing South Pacific variability leads to the alteration of coupled processes linking the South and equatorial Pacific. A small but significant mean state change arising from the imposed suppression may also contribute to the weakened extreme ENSO SST anomalies. The magnitude of both extreme El Niño and La Niña SST anomalies are reduced, and the associated spatial patterns of change of upper ocean heat content and wind stress anomalies are markedly different for both types of events.

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