Central-eastern Pacific Research Articles

Impacts of Interannual Variations of Chlorophyll on Seasonal Predictions of the Tropical Pacific

In this study, we explored impacts of interannual variations of chlorophyll on seasonal predictions of the tropical Pacific by the SINTEX-F2 dynamical climate prediction system, which is highly skillful at predicting El Niño/Southern Oscillation (ENSO) and other tropical climate phenomena. We conducted twin re-forecast experiments; one system used the observed climatology of chlorophyll to compute the shortwave absorption in the upper ocean, while the other used the observed chlorophyll with year-to-year variations. Although the chlorophyll impacts on predictions of the Niño 3.4 index were limited, improvements are noticed in the predictions of sea surface temperature over the eastern edge of the Western Pacific Warm Pool. This region corresponds to the separation between warm, low-salinity waters of the warm Pool and cold, high-salinity upwelled waters of the Pacific cold tongue in the central-eastern equatorial Pacific. The improvement was very striking in the 2015 case, when a super El Nino occurred.

Last Millennium ENSO Diversity and North American Teleconnections: New Insights From Paleoclimate Data Assimilation

AbstractEl Niño‐Southern Oscillation (ENSO) variability affects year‐to‐year changes in North American hydroclimate. Extra‐tropical teleconnections are not always consistent between El Niño events due to stochastic atmospheric variability and diverse sea surface temperature anomalies, making it difficult to quantify teleconnections using only instrumentally‐based records. Here we use two paleoclimate data assimilation (DA) products spanning the Last Millennium (LM) to compare changes in amplitudes and frequencies of diverse El Niño events during the pre‐industrial period and 20th century, and to assess the stationarity of their North American hydroclimate impacts on multi‐decadal to centennial timescales. Using several definitions for Central Pacific (CP) and Eastern Pacific (EP) El Niño, we find a marked increase in 20th century EP El Niño intensity, but no significant changes in CP or EP El Niño frequencies in response to anthropogenic forcing. The associated hydroclimate anomalies indicate (a) dry conditions across the eastern‐central and northwestern U.S. during CP El Niño and wetter conditions in the same regions during EP El Niño; (b) wet conditions over the southwestern U.S. for both El Niño types. The magnitude of regional hydroclimate teleconnections also shows large natural variability on multi‐decadal to centennial timescales. However, when the entire LM is considered, mean hydroclimate anomalies in North America during CP or EP El Niño are consistent in terms of sign (wet vs. dry). Results are sensitive to proxy data and model priors used in DA products. Inconsistencies between El Niño classification methods underscore the need for improved ENSO diversity classification when assessing precipitation teleconnections.

Improving the Predictability of Two Types of ENSO by the Characteristics of Extratropical Precursors

AbstractThe Central Pacific (CP) and Eastern Pacific (EP) types of El Niño‐Southern Oscillation events are distinctly different in terms of their forming locations and mechanisms. Using an updated physical‐base statistical forecast model, the forecast of CP indices has overall higher skills than that of EP indices due to the higher persistent forecast skill. At lead time beyond 6‐month, the predictability of CP indices can be greatly enhanced by including the extratropical precursor from the North Pacific, confirming the ocean‐atmosphere interaction associated with North Pacific Oscillation (NPO)/Victoria Mode (VM) evolution. The predictability of EP indices can be moderately enhanced by including the extratropical precursor from the south, resulting from the charging of the equatorial Pacific. We also find that the predictability of CP indices does not significantly decrease after 2000 while the predictability of EP indices drops dramatically, suggesting the strengthening impacts of NPO/VM on the CP‐ENSO in the recent two decades.

The Intraseasonal Variations of the Leading Mode of Summer Precipitation Anomalies in Meiyu Area of East Asia

The intraseasonal variations of summer precipitation anomalies in the Meiyu area of East Asia are analyzed by applying a combined empirical orthogonal function (CEOF) of the latest meteorological reanalysis data ERA5 of European Center for Medium-Range Weather Forecasts for the period from 1991 to 2020, and the circulation structures and sources of variability of CEOF are also investigated. The first mode of the intraseasonal variations shows an in-phase pattern over the Meiyu area in June, July, and August, accounting for 22.2% of the total variance in the intraseasonal variations of summer precipitation anomalies. The positive (negative) CEOF1 is accompanied by the negative (positive) East Asia/Pacific pattern, including strong westerly wind anomalies in the upper troposphere and southwest monsoon in the lower troposphere, and the Western Pacific Subtropical High extending westward and its ridge line slightly south. The positive CEOF1 is preceded by decay of El Niño episodes, including the abnormal warm sea surface temperature anomalies (SSTAs) in the equatorial Central-Eastern Pacific in spring and warm SSTAs in the equatorial Indian Ocean in summer. The second mode shows an opposite precipitation anomaly in June and July, and the distribution in August is not significant. The corresponding geopotential height circulation of positive CEOF2 shows the large negative anomaly in the region north of 40° N and a positive anomaly over Japan in June, whereas the pattern reverses in July. At the same time, there is a radical reversion from abnormal eastly to westly wind in the upper troposphere. The structure of CEOF2 is somewhat induced by local SSTAs over the Northern Indian Ocean and South China Sea.

Dynamic Causes of ENSO Decay and Its Asymmetry

AbstractEl Niño and La Niña exhibit asymmetric evolution characteristics during their decay phases. The decay speed of El Niño is significantly greater than that of La Niña. This study systematically and quantitatively investigates the relative contributions of the equatorial western Pacific (WP) and central-eastern Pacific (CEP) wind stress anomalies to ENSO decay and its asymmetry through data analysis, numerical experiments, and dynamic and thermodynamic diagnoses. It is demonstrated that the sea surface temperature anomalies (SSTAs) forced by the wind stress anomalies in the equatorial CEP play a dominant role in ENSO decay and contribute to ENSO decay asymmetry, while the forcing by the equatorial WP wind stress anomalies has a small contribution. Diagnoses of the oceanic mixed layer heat budget indicate that anomalous zonal advection term and vertical advection term forced by the wind stress anomalies in the equatorial CEP are the most important dynamic terms contributed to ENSO decay. Both terms in El Niño decay phase are much larger than in La Niña decay phase, resulting in a larger decay speed in El Niño than in La Niña. The contributions of these two terms do not depend on the equatorial WP wind field, confirming that the equatorial WP wind stress anomalies do not act as a pivotal part in ENSO asymmetric decay. Moreover, it is demonstrated that within the equatorial CEP, dominant contribution comes from the wind stress anomalies in the equatorial central Pacific, in which those in the equatorial southern central Pacific play a major role.Significance StatementPrevious studies proposed why wind fields in the equatorial western Pacific (WP) or central-eastern Pacific (CEP) are asymmetric and how the asymmetric wind fields affect ENSO decay and decay asymmetry. By using an oceanic general circulation model, we quantitatively estimate the relative contributions of the wind stress anomalies over the equatorial WP and CEP. It is demonstrated that the wind stress anomalies over the equatorial CEP and the associated ocean response play a dominant role in the asymmetric decay. Additionally, it is further illustrated the predominant role comes from the wind stress anomalies in the equatorial southern central Pacific within the equatorial CEP. Our study provides a physical explanation on the ENSO decay and its asymmetry.

Increased summer electric power demand in Beijing driven by preceding spring tropical North Atlantic warming

By using electric power data, observational station temperature data in Beijing, CN05.1 temperature data, ERA5 atmospheric reanalysis data, and ERSST.v3b sea surface temperature (SST) data, it is found that summer (July–August) electric power demand in Beijing is remarkably positively correlated with the previous spring (March–April) tropical North Atlantic (TNA) SST anomaly (SSTA). The possible physical mechanism of the TNA SSTA affecting summer electric power in Beijing is also revealed. When a positive SSTA occurs in the TNA during spring, anomalous easterlies prevail over the tropical central Pacific, which can persist to the following summer. Trade winds are thus enhanced over the northern Pacific, which favors a strengthening of upwelling cold water in the tropical central-eastern Pacific. As a result, a negative SSTA appears in the central-eastern Pacific in summer, which means a La Niña event is triggered by the previous TNA SSTA through the Bjerknes feedback. During the La Niña event, an anomalous anticyclonic circulation occupies the northwestern Pacific. The southerly anomalies at the western edge of this anomalous anticyclone strengthen the transportation of warm and humid airflow from the low latitudes to North China, where Beijing is located, causing higher summer temperatures and increased electricity usage for air conditioning, and vice versa. The results of this study might provide a new scientific basis and clues for the seasonal prediction of summer electric power demand in Beijing.摘要本文利用北京市电力负荷资料, 北京市站点观测温度资料, CN05.1温度资料, ERA5大气再分析资料及ERSST v3b海表温度资料, 发现3–4月副热带北大西洋海温异常和北京市夏季电力呈很好的正相关关系, 并揭示了副热带北大西洋海温异常影响北京市夏季电力的可能物理机制. 春季副热带北大西洋海温异常偏暖, 热带中太平洋出现东风异常并持续至夏季, 太平洋信风增强, 热带中东太平洋冷水上翻增强, 通过Bjerkness正反馈机制激发了La Niña事件. La Niña事件时, 西北太平洋反气旋环流异常, 将低纬度暖湿气流输送至北京地区, 引起北京市夏季温度增高, 电力负荷需求增加. 反之亦然. 研究结果可为北京市夏季电力负荷需求的季节预测提供新的科学依据和线索.

Genome Survey Sequencing of an Iconic 'Trophy' Sportfish, the Roosterfish Nematistius pectoralis: Genome Size, Repetitive Elements, Nuclear RNA Gene Operon, and Microsatellite Discovery.

The ‘Pez Gallo’ or the Roosterfish, Nematistius pectoralis, is an ecologically relevant species in the shallow water soft-bottom environments and a target of a most lucrative recreational sport fishery in the Central Eastern Pacific Ocean. According to the International Union for Conservation of Nature, N. pectoralis is assessed globally as Data Deficient. Using low-coverage short Illumina 300 bp pair-end reads sequencing, this study reports, for the first time, the genome size, single/low-copy genome content, and nuclear repetitive elements, including the 45S rRNA DNA operon and microsatellites, in N. pectoralis. The haploid genome size estimated using a k-mer approach was 816.04 Mbp, which is within the range previously reported for other representatives of the Carangiformes order. Single/low-copy genome content (63%) was relatively high. A large portion of repetitive sequences could not be assigned to the known repeat element families. Considering only annotated repetitive elements, the most common were classified as Satellite DNA which were considerably more abundant than Class I-Long Interspersed Nuclear Elements and Class I-LTR Retroviral elements. The nuclear ribosomal operon in N. pectoralis consists of, in the following order: a 5′ ETS (length = 948 bp), ssrDNA (1835 bp), ITS1 (724 bp), a 5.8S rDNA (158 bp), ITS2 (508 bp), lsrDNA (3924 bp), and a 3′ ETS (32 bp). A total of 44 SSRs were identified. These newly developed genomic resources are most relevant for improving the understanding of biology, developing conservation plans, and managing the fishery of the iconic N. pectoralis.

Mercury and Cadmium Concentrations in Muscle Tissue of the Blue Shark (Prionace glauca) in the Central Eastern Pacific Ocean.

Blue sharks (Prionace glauca) are an important resource in Ecuador's fisheries; however, biological and ecological information of this species in the area is scarce. The goal of this study was to determine Hg and Cd concentration levels in muscle tissue, as well as its relationship with size, sex, and sexual maturity stages. A total of 80 specimens (34 females and 46 males) collected from the Ecuadorian longline fishing fleet between June and December 2012 were examined. Sizes for females ranged from 97 to 280cm total length, with values of Hg between 0.20 to 2.38mgkg-1 wet weight (x̄ = 0.71, ± 0.61) and values of Cd between 0.01 and 0.12mgkg-1 (x̄ = 0.04, ± 0.02). Sizes for males ranged from 137 to 290cm TL with values of Hg between 0.17 and 2.94mgkg-1 (x̄ = 0.81, ± 0.68) and Cd concentrations between 0.01 and 0.12mgkg-1 (x̄ = 0.04, ± 0.03). A Spearman's rank correlation showed a medium positive association between TL and Hg concentrations (ρ = 0.66; p < 0.05), but there was no correlation between TL and Cd concentrations (ρ = 0.00, p < 0.05). Of the analyzed sharks, 46% and 20% had Hg and Cd concentrations, respectively, greater than the limit established by authorities for fishes consumed by humans.

Mechanisms linking multi-year La Ni\xf1a with preceding strong El Ni\xf1o

El Niño-Southern Oscillation (ENSO), characterized by anomalous sea surface temperature in the central-eastern equatorial Pacific, is a dominant interannual variability, impacting worldwide weather and socioeconomics. The ENSO cycle contains irregularity, in which La Niña often persists for more than two years, called “multi-year La Niña”. Observational records show that multi-year La Niña tends to accompany strong El Niño in the preceding year, but their physical linkage remains unclear. Here we show using reanalysis data that a strong El Niño excites atmospheric conditions that favor the generation of multi-year La Niña in subsequent years. Easterly wind anomalies along the northern off-equatorial Pacific during the decay phase of the strong El Niño are found crucial as they act to discharge ocean heat content (OHC) via an anomalous northward Ekman transport. The negative OHC anomaly is large enough to be restored by a single La Niña and, therefore, causes another La Niña to occur in the second year. Furthermore, analyses of the Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models support the abovementioned mechanisms and indicate that the occurrence frequencies of multi-year La Niña and strong El Niño are highly correlated.

The role of background SST changes in the ENSO-driven rainfall variability revealed from the atmospheric model experiments in CMIP5/6

The tropical Pacific rainfall variability driven by El Niño–Southern Oscillation (ENSO rainfall) is the crucial bridge across which ENSO exerts its influence on global climate. Previous modeling studies have documented a robust intensification and eastward shift of ENSO-driven rainfall under global warming despite large inter-model biases in ENSO-related sea surface temperature variability (ENSO SST), but the formation mechanisms of the robust ENSO rainfall changes are not well clarified. Here, we utilized a set of atmospheric model experiments—namely, “amip”, forced by observed SST; “amip-p4K”, forced by observed SST plus uniform 4-K warming, and “amip-future4K”, forced by observed SST plus spatially patterned SST warming, in CMIP5/CMIP6—to disentangle the role of the changes in mean-state SST (uniform and spatially patterned SST warming) with an unchanged ENSO SST. Relative to the weak ENSO rainfall changes in amip-p4K, those in amip-future4K forced by an El Niño-like SST warming pattern show an increase and eastward shift over the equatorial central–eastern Pacific. The results in amip-future4K without ENSO SST changes coincide well with previous results of the coupled models in CMIP5/3, suggesting a dominant role played by the mean-state SST warming pattern in ENSO rainfall changes. By diagnosing the moisture budget decomposition and moist static energy transport, we revealed that the structural and amplitude changes in ENSO rainfall are mainly controlled by the dynamic and thermodynamic components, respectively. In addition, the El Niño-like SST warming pattern in amip-future4K can increase low-level specific humidity with a remarkable spatial gradient, particularly in the equatorial central–eastern Pacific. As a result, the low-level specific humidity dominates the pattern of changes in the vertical transport of moist static energy, and subsequently the ENSO rainfall changes, in amip-future4K. This study further verified the importance of background SST changes to ENSO rainfall under global warming.

The source of uncertainty in projecting the anomalous western North Pacific anticyclone during El Niño–decaying summers

AbstractThe western North Pacific anomalous anticyclone (WNPAC) is a key bridge that links El Niño and East Asian climate variability. Future projections of ENSO-related WNPAC changes under global warming are highly uncertain across climate models. Based on a 40-member ensemble from the Community Earth System Model Large Ensemble (CESM-LE) project, we investigate the effects of internal variability on the El Niño-related WNPAC projection. Here, we first develop a decomposition method to separate the contributions of El Niño amplitude change and non-amplitude change from the leading uncertainty in the El Niño-related WNPAC projection. Based on the decomposition, approximately 23% of the uncertainty in the El Niño-related WNPAC projection is attributed to the El Niño amplitude change, while the remaining 77% is from the non-amplitude change, which is mainly related to the change in the El Niño decaying pace. A larger (smaller) El Niño amplitude can enhance (weaken) the WNPAC through a stronger (weaker) tropical Indian Ocean (TIO) capacitor effect. For non-amplitude change, a faster (slower) El Niño decaying pace can also enhance (weaken) the WNPAC through descending Rossby waves in response to cold sea surface temperature anomalies (SSTA) over the tropical central-eastern Pacific. The decomposition method can be generalized to investigate the sources of uncertainty related to El Niño properties in climate projections and to help improve the understanding of changes in the interannual variability of East Asian-western Pacific climate under global warming.

The Dynamic of Convergence Zone Displacement in Western Pacific Ocean on 2015 Super El Niňo Event

Warm pool and the existence of equatorial processes in the Pacific Ocean have an important role on El-Nino Southern Oscillation (ENSO). The eastward advection of warm and less saline water from the western Pacific together with the westward advection of cold and more saline water from the central-eastern Pacific induces a convergence of water masses at the eastern edge of the warm pool. The aim of this study is to determine convergence zone displacement in Western Pacific Ocean based on oceanography parameters such as temperature, salinity and surface current from insitu Argo Float, satellite and model data. The convergence zone displacement was characterized by proxies variable of isotherm 28,5 °C and isohaline 34,6 psu. The convergence zone is zonally displaced in association with EI Niño-La Niña and wind-driven surface current variations. The displacement of the convergence zone moved as far east as 136 °W in the eastern Pacific during the 2015 Super El Niňo. Otherwise, convergence zone moved westward near 154 °E in the western Pacific, during La Niňa periods. During Super El Niňo, the stronger-than-normal speed of the North Equatorial Counter Current (NECC) was increased by 0,8 m/s and appears to have been a major factor in convergence zone reaching the far eastern Pacific. A strong significant positive correlation (R= 0.88, 0.82 and 0.84) between SST and skipjack tuna catch on Super El Niňo, La Niňa and Normal respectively suggested that changes in skipjack CPUE occurred in phase with movement of convergence zone.

Time-Spatial Features of Mix El Niño

The diversity of El Niño is a critical field of the climate research. The eastern Pacific (EP) and central Pacific (CP) types of El Niño have been identified in the previous studies. However, the extreme El Niño event that occurred in 2015–2016 is quite different from both the EP and CP El Niño events. The sea surface temperatures anomalies (SSTA) for this event widely spread in both the central and eastern Pacific and have a small zonal gradient in the central-eastern Pacific. Many researchers regarded this event as a mixed type of El Niño. Using the regression-EOF method, the Mix El Niño pattern is extracted from the tropical Pacific SSTA field during the period from 1900 to 2019. Here, we reveal that the Mix El Niño is a very usual rather than a new type of El Niño, it is just that the EP and CP El Niño events are more frequent since the 1980s, while the Mix El Niño events frequently appear before the 1980s. The time-spatial features of the Mix El Niño are further investigated. The results demonstrate a unique westward propagation of the maximum SSTA for the Mix El Niño from the far eastern Pacific to the central Pacific. In contrast, the SSTA center is locked in the far eastern Pacific region for the EP El Niño and the central Pacific region for the CP El Niño. The evolutions of subsurface ocean temperature anomalies and sea surface height anomalies are also examined to support this. The ocean–atmosphere interaction plays an important role in the evolution of the Mix El Niño. The anomalous atmospheric Walker circulation for the Mix El Niño is mainly in the western and central Pacific as well as very weak in the eastern Pacific. In contrast, there are significant westerlies/easterlies in the eastern Pacific for the EP/CP El Niño. The small gradient of SSTA in the central-eastern Pacific for the Mix El Niño leads to weak zonal wind anomalies, which further weaken the zonal gradient of SSTA. All this suggests that the Mix El Niño is not unusual and fundamentally different from the EP and CP El Niño with important implications for global climate effects.

Optimally growing initial errors of El Ni\xf1o events in the CESM

The optimally growing initial errors (OGEs) of El Niño events are found in the Community Earth System Model (CESM) by the conditional nonlinear optimal perturbation (CNOP) method. Based on the characteristics of low-dimensional attractors for ENSO (El Niño Southern Oscillation) systems, we apply singular vector decomposition (SVD) to reduce the dimensions of optimization problems and calculate the CNOP in a truncated phase space by the differential evolution (DE) algorithm. In the CESM, we obtain three types of OGEs of El Niño events with different intensities and diversities and call them type-1, type-2 and type-3 initial errors. Among them, the type-1 initial error is characterized by negative SSTA errors in the equatorial Pacific accompanied by a negative west–east slope of subsurface temperature from the subsurface to the surface in the equatorial central-eastern Pacific. The type-2 initial error is similar to the type-1 initial error but with the opposite sign. The type-3 initial error behaves as a basin-wide dipolar pattern of tropical sea temperature errors from the sea surface to the subsurface, with positive errors in the upper layers of the equatorial eastern Pacific and negative errors in the lower layers of the equatorial western Pacific. For the type-1 (type-2) initial error, the negative (positive) temperature errors in the eastern equatorial Pacific develop locally into a mature La Niña (El Niño)-like mode. For the type-3 initial error, the negative errors in the lower layers of the western equatorial Pacific propagate eastward with Kelvin waves and are intensified in the eastern equatorial Pacific. Although the type-1 and type-3 initial errors have different spatial patterns and dynamic growing mechanisms, both cause El Niño events to be underpredicted as neutral states or La Niña events. However, the type-2 initial error makes a moderate El Niño event to be predicted as an extremely strong event.

Modulation of Madden-Julian Oscillation Activity by the Tropical Pacific-Indian Ocean Associated Mode

In this study, the impacts of the tropical Pacific-Indian Ocean associated mode (PIOAM) on Madden-Julian Oscillation (MJO) activity were investigated using reanalysis data. In the positive (negative) phase of the PIOAM, the amplitudes of MJO zonal wind and outgoing longwave radiation are significantly weakened (enhanced) over the Indian Ocean, while they are enhanced (weakened) over the central and eastern Pacific. The eastward propagation of the MJO can extend to the central Pacific in the positive phase of the PIOAM, whereas it is mainly confined to west of 160°E in the negative phase. The PIOAM impacts MJO activity by modifying the atmospheric circulation and moisture budget. Anomalous ascending (descending) motion and positive (negative) moisture anomalies occur over the western Indian Ocean and central-eastern Pacific (Maritime Continent and western Pacific) during the positive phase of the PIOAM. The anomalous circulation is almost the opposite in the negative phases of the PIOAM. This anomalous circulation and moisture can modulate the activity of the MJO. The stronger moistening over the Indian Ocean induced by zonal and vertical moisture advection leads to the stronger MJO activity over the Indian Ocean in the negative phase of the PIOAM. During the positive phase of the PIOAM, the MJO propagates farther east over the central Pacific owing to the stronger moistening there, which is mainly attributable to the meridional and vertical moisture advection, especially low-frequency background state moisture advection by the MJO’s meridional and vertical velocities.

Interannual Salinity Variability Associated With the Central Pacific and Eastern Pacific El Niños in the Tropical Pacific

AbstractOcean reanalysis products and observations are used to analyze the differences between the two types of El Niño in terms of interannual salinity variability in the tropical Pacific; a budget analysis for mixed layer (ML) salinity (MLS) is performed in the region. The center of negative MLS anomalies associated with the central Pacific (CP) El Niño tends to move further westward in winter along the equator, as compared with the eastern Pacific (EP) El Niño. The oscillation period with the EP El Niño is found to be approximately 10 years, longer than that with the CP El Niño (approximately 6–8 years). Our budget analyses further reveal that surface advection, surface forcing, and subsurface effect are the three main contributors to ML tendency of interannual salinity anomalies, which are regionally dependent. In the eastern edge of the warm pool (WP), surface advection makes a larger contribution (about 40–60%) to the MLS budget, and subsurface effect (about 20%) and surface forcing (about 20–40%) are relatively smaller. The subsurface effects on the MLS tendency tend to compensate for the imbalance induced by the surface forcing and advection: A weakened MLS tendency occurs with the CP El Niño, whereas an enhanced MLS tendency occurs with the EP El Niño, respectively. The MLS tendency leads the Niño3.4 SST by 8–10 months for the EP El Niño, whereas there is no such apparent lead/lag relationship for the CP El Niño. It is demonstrated that the relationships between the interannual sea surface temperature (SST) variability and MLS budget terms can be a clear indicator to distinguish the two types of El Niño.

Interdecadal enhancement in the interannual variability of the summer monsoon meridional circulation over the South China Sea around the early 1990s

The interdecadal enhancement in the interannual variability of summer monsoon meridional circulation (SMMC) over the South China Sea around the early 1990s is investigated. Results show the change in the SMMC variability may arise from the interdecadal shift in the leading modes of low-level geopotential height over East Asia–Australia and Indo–Pacific sea surface temperature anomalies (SSTAs) in boreal summer. Before the early 1990s, the leading mode of Indo–Pacific SSTAs shows a zonal tripole pattern, with abnormally warm eastern Pacific and northern Indian Ocean and cold western Pacific. At the lower level, the western North Pacific cooling and northern Indian Ocean warming generate an anticyclonic anomaly over western North Pacific, while the cooling over the Maritime Continent and east of Australia favors an abnormal anticyclone over Australia. Hence region-wide positive geopotential height anomalies cover East Asia–Australia, which resemble the major mode of geopotential height and generate weak south–north pressure gradient and SMMC variability. After the early 1990s, the leading SSTAs mode shifts to a zonal dipole with abnormally cold western Pacific and warm equatorial central–eastern Pacific. The central Pacific warming induces an anomalous low-level cyclone over Philippines and it is further maintained by the Maritime Continent cooling. Meanwhile, the cooling over the east of Australia and Maritime Continent favors an abnormal Australian anticyclone. The low-level geopotential height thus shows south–north dipole anomalies over East Asia–Australia, resembling its major mode and generating obvious meridional pressure gradient and SMMC variability. The atmospheric responses to different SSTAs modes are confirmed by CAM4 experiments.

Reliable drug war data: The Consolidated Counterdrug Database and cocaine interdiction in the “Transit Zone”

BackgroundFor almost three decades, a U.S. government dataset has vetted and recorded all known cocaine trafficking events in the massive Western Hemisphere ‘transit zone’ (including Central America, the Caribbean, eastern Pacific, and Mexico) and tracked all cocaine seizures reported by counternarcotic forces there. This is the “cocaine module” of the Consolidated Counterdrug Database (CCDB), and by U.S. law it is the exclusive source for performance data on key aspects of the drug interdiction mission, one of the foundations of U.S. supply-side drug policy. Nevertheless, the dataset remains poorly known or used among drug policy researchers despite being unclassified. To make the existence and strengths of this dataset better known, this paper describes its provenance, ongoing production, and analytical utility. MethodsThe analysis draws on the archive of reports produced by the Government Accountability Office (GAO), an independent, non-partisan entity that has been tracking U.S. government agencies’ drug war accounting for almost 50 years. The analysis also relies on third-party assessments of interdiction, and on correspondence with staff in the Office of National Drug Control Policy. ResultsThe CCDB emerged in the 1990s following two decades of drug war failures in the transit zone. It is an “all source” product, which curates data from a variety of sources produced by the 26 U.S. agencies and 20 foreign partners involved in transit zone interdiction. There is a high threshold for inclusion of cocaine trafficking events into the CCDB; it therefore offers a highly reliable yet conservative representation of cocaine trafficking and counternarcotic response. Instances of CCDB data in the public record yield several insights: a) the volume of cocaine moving annually through the transit zone has for the past decade well exceeded 1,000 MT/year; b) cocaine seizures in the transit zone are greater than anywhere else, and significantly higher than indicated by the UNODC's World Drug Reports; c) interdiction appears to have little to no effect on cocaine prices in the U.S.; d) interdiction is highly “outcome-ineffective”; in FY2018, for example, the U.S. and partners intercepted only 6% of the cocaine trafficking events known to have occurred in the transit zone that year; e) traffickers respond quickly and constantly to interdiction by shifting their routes and transport strategies. ConclusionThe CCDB deserves greater attention from researchers as a high-quality dataset that: a) challenges the “unknowability” of illicit activities and underscores the need for better sharing of unclassified government data; b) opens up new ways of exploring drug enforcement policies and actions in transit areas; c) contradicts rosy assessments of drug interdiction effectiveness by unequivocally demonstrating interdiction's longstanding and persistent failure and thus the need for fundamentally different approaches.

Diversity and paleoenvironmental implications of an elasmobranch assemblage from the Oligocene-Miocene boundary of Ecuador.

The occurrence and diversity of elasmobranchs from the Oligocene–Miocene boundary from Tropical America is poorly known in comparison with the paleodiversity from younger Neogene intervals of the region. Here we describe a new elasmobranch assemblage from the rich fossil site of Montañita-Olón (Dos Bocas Formation, Santa Elena, Ecuador), where other vertebrates have already been described: for example, sea turtles and cetaceans. We report a total of 27 elasmobranch taxa, 19 of which are new fossil records for Ecuador, 10 new records for the Central Eastern Pacific and four new records for South America. Additionally, in order to reconstruct the environment where these marine remains were deposited, we performed abundance, paleobathymetric and habitat preference analyses, concluding that they were likely deposited in an outer neritic (open shelf) environment. The study of Oligocene and early Miocene marine elasmobranchs faunas in Tropical America is key to addressing the issues in the evolutionary history of this group.

Intra-seasonal differences in the atmospheric systems contributing to interannual variations of autumn haze pollution in the North China Plain

Our understanding of the factors influencing the interannual variation of autumn haze pollution in the North China Plain (NCP) remains quite limited. Here, we investigate interannual variations of atmospheric haze pollution and associated atmospheric anomalies in the NCP during autumn (September, October, and November). Pronounced anticyclonic anomalies tend to be observed around northeastern Asia when more severe haze pollution occurs over the NCP during this season. However, the processes underlying the impact of the atmospheric anomalies on the NCP haze show considerable intra-seasonal differences. In September, anticyclonic anomalies impact the NCP haze via modulating the surface relative humidity (SRH) and boundary layer height (BLH), while changes in surface wind speed (SWS) are not found to be related to the NCP haze. In contrast, the interannual variation of the NCP haze has a close relationship with the changes of SWS, SRH, and BLH in both October and November. The factors responsible for formation of the anticyclonic anomalies around northeastern Asia are found to differ greatly over the 3 months. In September, the formation of anticyclonic anomalies is related to the East Atlantic (EA) pattern, which triggers an eastward propagating atmospheric wave train extending from Europe to northeastern Asia. In October, the Scandinavia teleconnection is crucial for generating anticyclonic anomalies. While in November, the formation of the anticyclonic anomalies is largely due to the joint effect of the Scandinavia and East Atlantic/Western Russian teleconnections, as well as the non-negligible influence caused by sea surface temperature anomalies in the tropical central-eastern Pacific.