Revisiting the CMIP5 Thermocline in the Equatorial Pacific and Atlantic Oceans

The thermocline is defined as the ocean layer for which the vertical thermal gradient is maximum. In the equatorial ocean, observations led to the use of the 20 °C isotherm depth (z20) as an estimate of the thermocline. This study compares z20 against the physical thermocline in the equatorial Atlantic and Pacific Oceans, using Simple Ocean Data Assimilation reanalysis and fifth phase of the Coupled Model Intercomparison Project preindustrial control simulations. Our results show that z20 is systematically deeper and flatter than the thermocline and does not respond correctly to surface wind stress variations. It is also shown that the annual cycle of z20 is much weaker than that of the physical thermocline. This happens in both equatorial basins and indicates that z20 does not react to the same mechanisms as the thermocline. This could have important consequences in the assessment of air-sea coupling in current general circulation models and bias reduction strategies

Changes in interannual tropical Atlantic-Pacific basin interactions modulated by a South Atlantic cooling

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. Wecontrast 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 altered Walker circulations, stronger interannual variability over the tropical oceans, a westward extension of the Atlantic Ni˜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–Pacificbasin 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˜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

A Review of ENSO Influence on the North Atlantic. A Non-Stationary Signal

The atmospheric seasonal cycle of the North Atlantic region is dominated by meridional movements of the circulation systems: from the tropics, where the West African Monsoon and extreme tropical weather events take place, to the extratropics, where the circulation is dominated by seasonal changes in the jetstream and extratropical cyclones. Climate variability over the North Atlantic is controlled by various mechanisms. Atmospheric internal variability plays a crucial role in the mid-latitudes. However, El Niño-Southern Oscillation (ENSO) is still the main source of predictability in this region situated far away from the Pacific. Although the ENSO influence over tropical and extra-tropical areas is related to different physical mechanisms, in both regions this teleconnection seems to be non-stationary in time and modulated by multidecadal changes of the mean flow. Nowadays, long observational records (greater than 100 years) and modeling projects (e.g., CMIP) permit detecting non-stationarities in the influence of ENSO over the Atlantic basin, and further analyzing its potential mechanisms. The present article reviews the ENSO influence over the Atlantic region, paying special attention to the stability of this teleconnection over time and the possible modulators. Evidence is given that the ENSO–Atlantic teleconnection is weak over the North Atlantic. In this regard, the multidecadal ocean variability seems to modulate the presence of teleconnections, which can lead to important impacts of ENSO and to open windows of opportunity for seasonal predictability

Can reducing the incoming energy flux over the Southern Ocean in a CGCM improve its simulation of tropical climate?

Atmosphere-ocean general circulation models (CGCMs) show important systematic errors. Simulated precipitation in the tropics is generally overestimated over the oceans south of the equator, and stratocumulus (SCu) clouds are underestimated above too warm sea surface temperatures (SSTs). In the extratropics, SSTs are also too warm over the Southern Ocean. We argue that ameliorating these extratropical errors in a CGCM can result in an improved model's performance in the tropics depending upon the success in simulating the sensitivity of SCu to underlying SST. Our arguments are supported by the very different response obtained with two CGCMs to an idealized reduction of solar radiation flux incident at the top of the atmosphere over the Southern Ocean. It is shown that local perturbation impacts are very similar in the two models but that SST reductions in the SCu regions of the southern subtropics are stronger in the model with the stronger SCu-SST feedbacks.NOAA's Climate Program Office, Climate Variability and Predictability Program Award. Grant Number: NA14OAR4310278. European Union Seventh Framework Programme. Grant Numbers: FP7/2007–2013, 60352Peer reviewe

Coastal sea level monitoring in the Mediterranean and Black seas

Employed for over a century, the traditional way of monitoring sea level variability by tide gauges – in combination with modern observational techniques like satellite altimetry – is an inevitable ingredient in sea level studies over the climate scales and in coastal seas. The development of the instrumentation, remote data acquisition, processing, and archiving in the last decades has allowed the extension of the applications to a variety of users and coastal hazard managers. The Mediterranean and Black seas are examples of such a transition – while having a long tradition of sea level observations with several records spanning over a century, the number of modern tide gauge stations is growing rapidly, with data available both in real time and as a research product at different time resolutions. As no comprehensive survey of the tide gauge networks has been carried out recently in these basins, the aim of this paper is to map the existing coastal sea level monitoring infrastructures and the respective data availability. The survey encompasses a description of major monitoring networks in the Mediterranean and Black seas and their characteristics, including the type of sea level sensors, measuring resolutions, data availability, and existence of ancillary measurements, altogether collecting information about 240 presently operational tide gauge stations. The availability of the Mediterranean and Black seas sea level data in the global and European sea level repositories has been also screened and classified following their sampling interval and level of quality check, pointing to the necessity of harmonization of the data available with different metadata and series in different repositories. Finally, an assessment of the networks' capabilities for their use in different sea level applications has been done, with recommendations that might mitigate the bottlenecks and ensure further development of the networks in a coordinated way, a critical need in the era of human-induced climate changes and sea level rise.En prens

Coastal Sea Level Monitoring in the Mediterranean and Black Seas

Spanning over a century, a traditional way to monitor sea level variability by tide gauges is – in combination with modern observational techniques like satellite altimetry – an inevitable ingredient in sea level studies over the climate scales and in coastal seas. The development of the instrumentation, remote data acquisition, processing and archiving in last decades allowed for extending the applications towards a variety of users and coastal hazard managers. The Mediterranean and Black50 seas are an example for such a transition – while having a long tradition for sea level observations with several records spanning over a century, the number of modern tide gauge stations are growing rapidly, with data available both in real-time and as a research product at different time resolutions. As no comprehensive survey of the tide gauge networks has been carried out recently in these basins, the aim of this paper is to map the existing coastal sea level monitoring infrastructures and the respective data availability. The survey encompasses description of major monitoring networks in the Mediterranean and Black55 seas and their characteristics, including the type of sea level sensors, measuring resolutions, data availability and existence of ancillary measurements, altogether collecting information about 236 presently operational tide gauge stations. The availability of the Mediterranean and Black seas sea level data in the global and European sea level repositories has been also screened and classified following their sampling interval and level of quality-check, pointing to the necessity of harmonization of the data available with different metadata and series at different repositories. Finally, an assessment of the networks’ capabilities60 for their usage in different sea level applications has been done, with recommendations that might mitigate the bottlenecks and assure further development of the networks in a coordinated way, being that more necessary in the era of the human-induced climate changes and the sea level ris

Interacciones tropicales océano-atmósfera en modelos acolpados.El caso de la termoclina ecuatorial y el afloramiento del noroeste de África

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física de la Tierra y Astrofísica, leída el 30-10-2019The tropics show great climate variability at different timescales. Part of this variability is related to the processes that couple the ocean and the atmosphere. Surface winds drive ocean currents, while the combination of wind stress and solar heating leads to the development of the mixed layer, the topmost layer of the ocean, which is the most affected by the ocean-atmosphere coupling. This layer rests on the thermocline, an oceanic region in which the vertical temperature gradient is maximum, forming a physical barrier between the colder water of the deep ocean and the mixed layer. Understanding the dynamics of that layer and in particular its relation to wind forcings is fundamental for studying coupled atmosphere-ocean phenomena...Los trópicos muestran una gran variabilidad climática en diferentes escalas de tiempo. Parte de esta variabilidad está relacionada con los procesos de acomplamiento entre el océano y la atmósfera. Los vientos superficiales impulsan las corrientes oceánicas, mientras que la combinación de la cizalla del viento y el calentamiento solar conduce al desarrollo de la capa de mezcla,la más somera del océano, que es la más afectada por el acoplamiento océano-atmósfera. Esta capa descansa sobre la termoclina, una región en la que el gradiente vertical de temperatura es máximo, formando una barrera física entre el agua más fría del océano profundo y la capa de mezcla. Comprender la dinámica de esa capa y en particular su relación con los forzamientos del viento es fundamental para estudiar los fenómenos acoplados atmósfera-océano...Depto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEunpu

Revisiting the CMIP5 Thermocline in the Equatorial Pacific and Atlantic Oceans

The thermocline is defined as the ocean layer for which the vertical thermal gradient is maximum. In the equatorial ocean, observations led to the use of the 20 °C isotherm depth (z20) as an estimate of the thermocline. This study compares z20 against the physical thermocline in the equatorial Atlantic and Pacific Oceans, using Simple Ocean Data Assimilation reanalysis and fifth phase of the Coupled Model Intercomparison Project preindustrial control simulations. Our results show that z20 is systematically deeper and flatter than the thermocline and does not respond correctly to surface wind stress variations. It is also shown that the annual cycle of z20 is much weaker than that of the physical thermocline. This happens in both equatorial basins and indicates that z20 does not react to the same mechanisms as the thermocline. This could have important consequences in the assessment of air‐sea coupling in current general circulation models and bias reduction strategies.The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement 603521 (PREFACE project) and from the Spanish Ministry of Science (Project PRE4CAST, CGL2017‐86415‐R).Peer reviewe

Las bibliotecas de instituto : una fuente histórica : segunda parte

Continuar con el registro, sellado, catalogación y clasificación de los fondos existentes en los Institutos Bárbara de Branganza y Castelar hasta 1900. En primer lugar se registraron los libros manualmente, pasándolos después a la base de datos creada a tal efecto y asignando a cada volumen un número de la CDU (versión reducida) para clasificar temáticamente las obras. Se han catalogado 490 registros en el Instituto Bárbara de Branganza y 369 en el Instituto Castelar en este último y debido a la falta de tiempo no se han podido catalogar los fondos antiguos tarea que se realizará próximamente.ExtremaduraES