Tropical and South Atlantic marine ecosystems support fisheries that have vital environmental and socioeconomic importance. In this Review, we outline how the El Niño–Southern Oscillation — a Pacific mode of sea surface temperature variability — influences Atlantic fisheries via teleconnections and cascading linkages between physical, biogeochemical and ecological systems. Connections are driven by tropical pathways (involving changes in atmospheric stability associated with the Walker circulation and tropospheric warming) and extratropical pathways (involving the Pacific–South American and Pacific–North American teleconnection patterns). Depending on the location, these pathways modify rainfall and river discharge, winds and upwelling, or a combination of both, impacting salinity, nutrient availability, primary production and, thus, fish recruitment, biomass and catch. Fishery responses are strongly species dependent, reflecting variations in behaviour between species to environmental factors (such as temperature, oxygen, salinity, habitat and food availability). This regional variability and species dependency, coupled with strong non-stationarity, highlights the complexity of El Niño–Southern Oscillation impacts on Atlantic marine ecosystems. This historical signal is projected to weaken in the future. Enhanced observational systems and refined ecosystem models are urgently needed to enhance predictive capabilities, reduce societal impacts and improve sustainable management in these regions. The influence of the El Niño–Southern Oscillation on Atlantic marine systems and fisheries is complex. This Review outlines the mechanisms by which El Niño–Southern Oscillation impacts the tropical and South Atlantic, connecting physical climate perturbations to biogeochemical and ecological responses.

We apply a novel approach to studying eddy mixing and transport in the northern middle atmosphere during winter (December-January-February), based on the concept of Lagrangian diffusivity – a measure of how quickly air parcels mix together. Unlike traditional diagnostics that rely on longitudinal or contour-based averages, Lagrangian diffusivity provides a detailed three-dimensional view of the mixing process. Our formulation of Lagrangian diffusivity requires the calculation of parcel trajectories, performed on isentropic surfaces using ERA5 reanalysis data. Additionally, we have applied several diagnostic techniques to contextualize our results on Lagrangian diffusivity within the broader framework of the stratospheric polar vortex and quasi-geostrophic wave properties. Specifically, we investigate the influence of quasi-geostrophic motions on the stratospheric polar vortex using wave activity flux and local wave activity. Furthermore, we employ a Lagrangian descriptor, a tool based on parcel trajectory length, to locate the boundary of the stratospheric polar vortex (SPV).The results reveal pronounced zonal asymmetries in Lagrangian diffusivity and wave activity flux. Mixing is highest at mid-latitudes around the prime meridian and at locations within the SPV. Local wave activity is elevated at high latitudes and upstream of the climatological vortex boundary opening, highlighting the role of quasi-geostrophic waves in the southward displacement of mid-latitude westerlies.

A three-dimensional winter (DJF) climatology of Lagrangian diffusivity characterizing eddy mixing and transport in the northern middle atmosphere is presented. To emphasize aspects other than zonal averages, we use the theory of Lagrangian diffusivity (kappa yy) hitherto not applied in stratospheric contexts to our knowledge. Our formulation of Lagrangian diffusivity requires the calculation of parcel trajectories, which is made on isentropic surfaces. A Lagrangian descriptor is used to estimate the boundary of the stratospheric polar vortex (SPV). To characterize quasi-geostrophic motions and their influence on the SPV we apply the wave activity flux (W) and Local Wave Activity (A) $(\mathcal{A})$. Our data set is the ERA5 reanalysis for the period 1979-2013. Results for kappa yy show important zonal asymmetries. In the lower and middle stratosphere, kappa yy is highest at midlatitudes, particularly around the prime meridian. This location is surrounded by manifolds associated with hyperbolic trajectories emanating from the outer SPV boundary. kappa yy is also high within the SPV, and near the locations where the SPV boundary is open. Zonal asymmetries are also clear in W at midlatitudes. The larger values of A $\mathcal{A}$ are at high latitudes and upstream of the opening of the vortex boundary. The role of quasi-geostrophic waves on the south-north shift of the midlatitude westerlies is highlighted. In particular, the waves contribute to open the SPV boundary at around 90W. The interannual variability of kappa yy is explored by contrasting winters with positive-negative Northern Annular Mode index, and Sudden Stratospheric Warmings of displacement-split type. This paper applies a novel approach to studying eddy mixing and transport in the northern middle atmosphere during winter (December-January-February). The approach is based on the concept of Lagrangian diffusivity, a measure of how quickly air parcels mix together. Unlike traditional diagnostics that rely on longitudinal or contour-based averages, Lagrangian diffusivity provides a detailed three-dimensional view of the mixing. This approach, hitherto restricted to oceanographic applications, is a significant contribution of the present work. We employ a Lagrangian descriptor, a tool based on parcel trajectory length, to locate the stratospheric polar vortex SPV boundary. Also, we investigate the influence of quasi-geostrophic motions on the SPV using wave activity flux and local wave activity (LWA). The data set is the ERA5 reanalysis from 1979 to 2013. The results reveal pronounced zonal asymmetries in Lagrangian diffusivity and wave activity flux. Mixing is highest at midlatitudes around the prime meridian and at locations within the SPV. LWA is elevated at high latitudes and upstream of the climatological vortex boundary opening, highlighting the role of quasi-geostrophic waves in the southward displacement of midlatitude westerlies. Comparisons are made of diffusivity during weak and strong vortex winters, as well as of during winters with and without Sudden Stratospheric Warmings. Locally, the largest values of Lagrangian diffusivity around the vortex are along the prime meridian at all levels in the stratosphere The location of maximum diffusivity is bounded by the edge of the climatological displaced vortex and a manifold emanating from the vortex edge When the Northern Annular Mode is positive, the vortex boundary closes and diffusivity is much lower inside

Subseasonal to seasonal (S2S) prediction of droughts and floods is one of the major challenges of weather and climate prediction. Recent studies suggest that the springtime land surface temperature/subsurface temperature (LST/SUBT) over the Tibetan Plateau (TP) can be a new source of S2S predictability. The project “Impact of Initialized Land Surface Temperature and Snowpack on Subseasonal to Seasonal Prediction (LS4P)” was initiated to study the impact of springtime LST/SUBT anomalies over high mountain areas on summertime precipitation predictions. The present work explores the simulated global scale response of the atmospheric circulation to the springtime TP land surface cooling by 16 current state-of-the-art Earth System Models (ESMs) participating in the LS4P Phase I (LS4P-I) experiment. The LS4P-I results show, for the first time, that springtime TP surface anomalies can modulate a persistent quasi-barotropic Tibetan Plateau-Rocky Mountain Circumglobal (TRC) wave train from the TP via the northeast Asia and Bering Strait to the western part of the North America, along with the springtime westerly jet from TP across the whole North Pacific basin. The TRC wave train modulated by the TP thermal anomaly play a critical role on the early summer surface air temperature and precipitation anomalies in the regions along the wave train, especially over the northwest North America and the southern Great Plains. The participant models that fail in capturing the TRC wave train greatly under-predict climate anomalies in reference to observations and the successful models. These results suggest that the TP LST/SUBT anomaly via the TRC wave train is the first order source of the S2S variability in the regions mentioned. Furthermore, the TP surface temperature anomaly can influence the Southern Hemispheric circulation by generating cross-equator wave trains. However, the simulated propagation pathways from the TP into the Southern Hemisphere show large inter-model differences. More dynamical understanding of the TRC wave train as well as its cross-equator propagation into the Southern Hemisphere will be explored in the newly launched LS4P phase II experiment.

EDITORIAL article Front. Clim., 24 January 2023Sec. Predictions and Projections Volume 5 - 2023 | https://doi.org/10.3389/fclim.2023.1138642

Introduction Observational and modeling studies have examined the interactions between El Niño-Southern Oscillation (ENSO) and the equatorial Atlantic variability as incorporated into the classical charge-recharge oscillator model of ENSO. These studies included the role of the Atlantic in the predictability of ENSO but assumed stationarity in the relationships, i.e., that models’ coefficients do not change over time. A recent work by the authors has challenged the stationarity assumption in the ENSO framework but without considering the equatorial Atlantic influence on ENSO. Methods The present paper addresses the changing relationship between ENSO and the Atlantic El Niño using an extended version of the recharge oscillator model. The classical two-variable model of ENSO is extended by adding a linear coupling on the SST anomalies in the equatorial Atlantic. The model’s coefficients are computed for different periods. This calculation is done using two methods to fit the model to the data: (1) the traditional method (ReOsc), and (2) a novel method (ReOsc+) based on fitting the Fisher’s Z transform of the auto and cross-correlation functions. Results We show that, during the 20th century, the characteristic damping rate of the SST and thermocline depth anomalies in the Pacific have decreased in time by a factor of 2 and 3, respectively. Moreover, the damping time of the ENSO fluctuations has doubled from 10 to 20 months, and the oscillation period of ENSO has decreased from 60-70 months before the 1960s to 50 months afterward. These two changes have contributed to enhancing ENSO amplitude. The results also show that correlations between ENSO and the Atlantic SST strengthened after the 70s and the way in which the impact of the equatorial Atlantic is added to the internal ENSO variability. Conclusions The remote effects of the equatorial Atlantic on ENSO must be considered in studies of ENSO dynamics and predictability during specific time-periods. Our results provide further insight into the evolution of the ENSO dynamics and its coupling to the equatorial Atlantic, as well as an improved tool to study the coupling of climatic and ecological variables.

The prediction skill for precipitation anomalies in late spring and summer months—a significant component of extreme climate events—has remained stubbornly low for years. This paper presents a new idea that utilizes information on boreal spring land surface temperature/subsurface temperature (LST/SUBT) anomalies over the Tibetan Plateau (TP) to improve prediction of subsequent summer droughts/floods over several regions over the world, East Asia and North America in particular. The work was performed in the framework of the GEWEX/LS4P Phase I (LS4P-I) experiment, which focused on whether the TP LST/SUBT provides an additional source for subseasonal-to-seasonal (S2S) predictability. The summer 2003, when there were severe drought/flood over the southern/northern part of the Yangtze River basin, respectively, has been selected as the focus case. With the newly developed LST/SUBT initialization method, the observed surface temperature anomaly over the TP has been partially produced by the LS4P-I model ensemble mean, and 8 hotspot regions in the world were identified where June precipitation is significantly associated with anomalies of May TP land temperature. Consideration of the TP LST/SUBT effect has produced about 25–50% of observed precipitation anomalies in most hotspot regions. The multiple models have shown more consistency in the hotspot regions along the Tibetan Plateau-Rocky Mountain Circumglobal (TRC) wave train. The mechanisms for the LST/SUBT effect on the 2003 drought over the southern part of the Yangtze River Basin are discussed. For comparison, the global SST effect has also been tested and 6 regions with significant SST effects were identified in the 2003 case, explaining about 25–50% of precipitation anomalies over most of these regions. This study suggests that the TP LST/SUBT effect is a first-order source of S2S precipitation predictability, and hence it is comparable to that of the SST effect. With the completion of the LS4P-I, the LS4P-II has been launched and the LS4P-II protocol is briefly presented.

Although tropical interbasin interactions at interannual time scales are presently receiving much attention, their controlling factors and variations on longer time scales are under debate. Tropical convection plays a crucial role in the occurrence and nonstationarity of them. In this paper, we investigate the dependence of interannual tropical AtlanticPacific basin interactions on convection-related features of the tropical oceans' climatology, especially the ITCZ position. We contrast a CGCM control simulation with an experiment in which tropical convection is modified by an artificial perturbation outside the tropics that reduces the incident shortwave radiation in a region of the South Atlantic. Based on previous work, this modification is expected to shift in latitude the climatological position of the simulated ITCZ. The experiment shows alteredWalker circulations, stronger interannual variability over the tropical oceans, a westward extension of the Atlantic Ni (n) over tilde no pattern and of convection, and shallower thermocline in the Pacific, making the basin more sensitive to both local and remote perturbations. As a consequence, the experiment shows enhanced interannual Atlantic-Pacific basin interactions at the equator, and weaker teleconnections between the north tropical Atlantic and the equatorial Pacific. The latter seems to occur because the impact of the warm Atlantic SST anomalies is offset by the presence of warm SST anomalies in El Ni (n) over tilde no region. Despite the uncertainties raised because the simulations are relatively short, we conclude that this work presents a potential explanation for the long-term changes in the tropical basin interactions and offers a novel and useful methodology for their analysis.

Observational studies have reported that tropical Atlantic interannual variability impacts on ENSO in different seasons and periods: Atlantic Ni ̃nos (AN) in boreal summer during negative phases of the Atlantic Multidecadal Variability (AMV); and tropical north Atlantic (TNA) in boreal spring during positive AMV. Nevertheless, this relation is not clear for the whole observational record. This paper is an step forward towards understanding of tropical Atlantic impacts on ENSO: how and when do they occur? Using observations and a pool of preindustrial control simulations from the CMIP5 initiative we investigate the background ocean and atmospheric conditions promoting these tropical interbasin connections.Periods with a negative AN-ENSO connection appear characterized by a shallower thermocline over the western Pacific and deeper in the east, together with an increase in interannual SST variability over the tropics. Periods with a negative TNA-ENSO connection appear characterized by a steeper thermocline in the Pacific and positive interhemispheric SST gradient in the the Atlantic. A decrease in tropical Pacific atmospheric and ocean variability characterizes these periods.

Tropical interbasin teleconnections at inter-annual time scales are receiving much attention in the last years. However, their controlling factors and long-term changes are still under debate. In this work, we investigate whether selected features in the climatology, the position of the ITCZ and strong tropical convection, can influence the teleconnections between the tropical Atlantic and Pacific basins at inter-annual timescales. For investigation, we contrast a CGCM control simulation with an experiment in which the climatological position of the ITCZ is shifted in latitude by artificially reducing the shortwave radiation incident in a region of the south Atlantic sector. The perturbation magnitude and sign are such that the local model’s biases in Atlantic SST are reduced. The experiment shows stronger interannual variability over the tropical Atlantic and Pacific oceans, a westward extension of the Atlantic Niño pattern, and enhanced interannual teleconnections between equatorial Atlantic and Pacific. We examine the mechanisms at work for these changes. We find several factors as major contributors to enhance the tropical interbasin teleconnections. One is the modified Walker circulation resulting from the westward extension of SST anomalies during the Atlantic Niño and concurrent westward displacement of convection. The other factors are the enhancement of the precipitation at the equator and the shallowing of thermocline in the Pacific, which make the latter basin more sensitive to both local and remote perturbations. On the contrary, the North Tropical Atlantic – equatorial Pacific teleconnection is weakened in the experiment, despite the strongest impact of the NTA anomalies in the north tropical Pacific winds. due to the opposite effect on divergence exerted by the off equatorial winds related to NTA and the equatorial winds related to the concomitant warming in the eastern and central equatorial Pacific.

The present paper examines the northern stratosphere during April 2020, when the polar vortex split into two cyclonic vortices after a winter with the strongest ozone depletion on record. We examin...

Abstract The present study examines the northern stratosphere during April 2020, when the polar vortex split into two cyclonic vortices during a winter‐early spring period with the strongest ozone depletion on record. We investigate the dynamical evolution leading to the split at middle stratospheric levels, including the fate of fluid parcels on the vortex boundary during its rupture and the distribution of ozone between the vortices resulting from the split. We also illustrate the vertical structure of the vortices after the split. The findings obtained with Lagrangian methods confirm the key role for the split played by a flow with a special configuration of barriers to the motion of parcels. A trajectory analysis clarifies how the ozone distribution between vortices was such that ozone poorest air remained in the main vortex. The offspring vortex had a deep structure from the troposphere and later decayed to vanish by the end of April.

This study presents results from an assessment of climate change projections over South America using fifth phase of the Coupled Model Intercomparison Project models. Change in near‐surface temperature, precipitation, evapotranspiration, integrated water vapour transport (IVT), sea level pressure (SLP), and wind at three pressure levels is quantified across the multi‐model suite. Additionally, model agreement for the sign and significance of projected change is assessed within the ensemble. Models are in strong agreement that the highest magnitude of projected warming will be over tropical regions. The CMIP5 models project a decrease in precipitation for all seasons over southern South America, especially along the northern portions of the present‐day mid‐latitude storm track. This is consistent with a robustly projected poleward shift of the Pacific extratropical high‐pressure system and mid‐latitude storm track indicated by a systematic increase in SLP and decrease in westerly wind magnitude over the region. Decreased precipitation for the months of September, October, and November is also projected, with strong model agreement, over portions of northern and northeastern Brazil, coincident with decreases in SLP and increases in evapotranspiration. IVT is broadly projected to decrease over southern South America, coincident with the projected poleward shift of the mid‐latitude storm track, with increases projected in the vicinity of the South Atlantic Convergence Zone in spring and summer. Results provide a comprehensive picture of climate change across South America and highlight where model consensus on change is most robust.

Convective transition statistics, which describe the relation between column-integrated water vapor (CWV) and precipitation, are compiled over tropical oceans using satellite and ARM site measurements to quantify the temperature and resolution dependence of the precipitation–CWV relation at fast time scales relevant to convection. At these time scales, and for precipitation especially, uncertainties associated with observational systems must be addressed by examining features with a variety of instrumentation and identifying robust behaviors versus instrument sensitivity at high rain rates. Here the sharp pickup in precipitation as CWV exceeds a certain critical threshold is found to be insensitive to spatial resolution, with convective onset occurring at higher CWV but at lower column relative humidity as bulk tropospheric temperature increases. Mean tropospheric temperature profiles conditioned on precipitation show vertically coherent structure across a wide range of temperature, reaffirming the use of a bulk temperature measure in defining the convective transition statistics. The joint probability distribution of CWV and precipitation develops a peak probability at low precipitation for CWV above critical, with rapidly decreasing probability of high precipitation below and near critical, and exhibits systematic changes under spatial averaging. The precipitation pickup with CWV is reasonably insensitive to time averaging up to several hours but is smoothed at daily time scales. This work demonstrates that CWV relative to critical serves as an effective predictor of precipitation with only minor geographic variations in the tropics, quantifies precipitation-related statistics subject to different spatial–temporal resolution, and provides a baseline for model comparison to apply these statistics as observational constraints on precipitation processes.

Observational studies have reported that interannual variability of sea surface temperature in two tropical Atlantic regions can act as ENSO predictors in different seasons and periods: boreal summer Atlantic Nino (AN) in negative phases of the Atlantic Multidecadal Variabil- ˜ ity (AMV); and boreal spring tropical north Atlantic (TNA) in positive AMV. The robustness of the AMV role in the interbasin connection remains an open question due to the short observational record. Using observations and pre-industrial climate model simulations, we demonstrate for the first time that latitudinal displacements of the Atlantic ITCZ act as a switch for the type of inter-basin teleconnection. During periods in which the Atlantic ITCZ is further equatorward (northward) AN (TNA) impacts ENSO. This ITCZ location can be 1 affected by several factors, including the inter-hemispheric SST gradients associated with AMV.Coupled models success in capturing the AN-ENSO connection. Nevertheless, they have difficulties in reproducing the TNA-ENSO connection because they overestimate rainfall in the southern tropical Atlantic. The TNA-ENSO connection occurs sporadically during periods when the ITCZ is shifted further northward in association with strong heat transports by the AMOC. Weaker AMOC periods in coupled models don't present the TNA-ENSO connection. State-of-the-art models still need to improve for correctly representing tropical Atlantic impact on ENSO.