Impact of global warming on ENSO phase change

We compare the physical mechanisms involved in the generation and decay of ENSO events in a control (present day conditions) and Scenario (Is92a, IPCC 1996) simulations performed with the coupled ocean-atmosphere GCM ECHAM4-OPYC3. A clustering technique which objectively discriminates common features in the evolution of the Tropical Pacific Heat Content anomalies leading to the peak of ENSO events allows us to group into a few classes the ENSO events occurring in 240 years of data in the control and scenario runs. In both simulations, the composites of the groups show differences in the generation and development of ENSO. We present the changes in the statistics of the groups and explore the possible mechanisms involved

On the impact of atmospheric vs oceanic resolutions on the representation of the sea surface temperature in the South Eastern Tropical Atlantic

Despite the efforts of the modelling community to improve the representation of the sea surface temperature (SST) over the South Eastern Tropical Atlantic, warm biases still persist. In this work we use four different configurations of the fully-coupled AWI Climate Model (AWI-CM) which allow us to gain physics-based insight into the role of the oceanic and atmospheric resolutions of the model in the regional distribution of the SST. Our results show that a sole refinement of the oceanic resolution reduces warm biases further than a single increase of the atmospheric component. An increased oceanic resolution is required (i) to simulate properly the Agulhas Current and its associated rings; (ii) to reinforce the northward-flowing Benguela Current and (iii) to intensify coastal upwelling. The best results are obtained when both resolutions are refined. However, even in that case, warm biases persist, reflecting that some processes and feedbacks are still not optimally resolved. Our results indicate that overheating is not due to insufficient upwelling, but rather due to upwelling of waters which are warmer than observations as a result of an erroneous representation of the vertical distribution of temperature. Errors in the representation of the vertical temperature profile are the consequence of a warm bias in the simulated climate state

Impact of ocean-atmosphere coupling on regional climate: the Iberian Peninsula case

Regional models used for downscaling the European climate usually include a relatively small area of the Atlantic Ocean and are uncoupled, with the SST used as lower boundary conditions much coarser than the mesh of the regional atmospheric model. Concerns thus arise about the proper representation of the oceanic influence and the role of air-sea coupling in such experiments. A complex orography and the exposure to different air and ocean masses make the Iberian Peninsula (IP) an ideal test case for exploring the impact of including explicitly the North Atlantic in the regional domain and the added value that coupling brings to regional climate modeling. To this end, the regionally-coupled model ROM and its atmospheric component, the regional atmospheric model REMO are used in a set of coupled and uncoupled experiments forced by the ERA-Interim reanalysis and by the global climate model MPI-ESM. The atmospheric domain is the same in all simulations and includes the North Atlantic and the ocean component is global and eddy permitting. Results show that the impact of air-sea coupling on the IP winter biases can be traced back to the features of the simulated North Atlantic Ocean circulation. In summer, it is the air-sea interactions in the Mediterranean that exert the largest influence on the regional biases. Despite improvements introduced by the eddy-permitting ocean, it is suggested that a higher resolution could be needed for a correct simulation of the features of the large-scale atmospheric circulation that impact the climate of the IP

Future projections of Mediterranean cyclone characteristics using the Med-CORDEX ensemble of coupled regional climate system models

Here, we analyze future projections of cyclone activity in the Mediterranean region at the end of the twenty-first century based on an ensemble of state-of-the-art fully-coupled Regional Climate System Models (RCSMs) from the Med-CORDEX initiative under the Representative Concentration Pathway (RCP) 8.5. Despite some noticeable biases, all the RCSMs capture spatial patterns and cyclone activity key characteristics in the region and thus all of them can be considered as plausible representations of the future evolution of Mediterranean cyclones. In general, the RCSMs show at the end of the twenty-first century a decrease in the number and an overall weakening of cyclones moving across the Mediterranean. Five out of seven RCSMs simulate also a decrease of the mean size of the systems. Moreover, in agreement with what already observed in CMIP5 projections for the area, the models suggest an increase in the Central part of the Mediterranean region and a decrease in the South-eastern part of the region in the cyclone-related wind speed and precipitation rate. These rather two opposite tendencies observed in the precipitation should compensate and amplify, respectively, the effect of the overall reduction of the frequency of cyclones on the water budget over the Central and South-eastern part of the region. A pronounced inter-model spread among the RCSMs emerges for the projected changes in the cyclone adjusted deepening rate, seasonal cycle occurrence and associated precipitation and wind patterns over some areas of the basin such as Ionian Sea and Iberian Peninsula. The differences observed appear to be determined by the driving Global Circulation Model (GCM) and influenced by the RCSM physics and internal variability. These results point to the importance of (1) better characterizing the range of plausible futures by relying on ensembles of models that explore well the existing diversity of GCMs and RCSMs as well as the climate natural variability and (2) better understanding the driving mechanisms of the future evolution of Mediterranean cyclones properties

On the Non‐Linear Nature of Long‐Term Sea Surface Temperature Global Trends

Abstract The year‐to‐year rate and acceleration of the changes in global sea surface temperatures (SSTs) for 1870–2022 are determined using non‐linear techniques. Our methodology identifies the non‐linear, long‐term tendencies of the warming, revealing subtle but essential features of the SST changes that are impossible to identify by linear techniques. Our analysis identifies inhomogeneous patterns of SST evolution. For instance, in most equatorial regions, including the western Pacific, the acceleration of the warming is positive, and sustained warming replaces the cooling at the beginning of the records. On the contrary, the warming acceleration in the central and eastern equatorial Pacific is negative, indicating a sustained warming at the beginning of the record that weakens over the years, resulting in a stagnated warming or even a cooling in recent years. We identify a strong warming with a negative acceleration for the North Atlantic. We hypothesize that this warming is part of the multidecadal variability of SST rather than a long‐term trend

Climate change impact on the Northwestern African offshore wind energy resources

Offshore wind is one of the most important sources of renewable energy. Therefore, it is crucial to assess how this resource will evolve within the 21st century, in the context of a changing climate. The North African Coastal Low-Level Jet (CLLJ) region, which encompasses offshore areas from Northwest Morocco to Senegal, has an enormous wind harvesting potential, as it provides a strong, persistent alongshore flow. In the current study, the present climate wind energy potential is featured for two heights (100 and 250m). More importantly, the climate change impact on the wind energy density in the region is also depicted. For that purpose, the newest and highest resolution regional climate simulations available are used, which include two ROM simulations (uncoupled and coupled) at 25km resolution, and 19 CORDEX-Africa runs at 50km resolution. Historical and future (under the RCP4.5 and RCP8.5 scenarios) simulations are used, for the periods 1976-2005 and 2070-2099, respectively. Overall, the results show that the annual wind energy density is projected to increase slightly in the northern offshore areas (< +10%) and decrease in the southern ones (> -10%). In close connection to the projected changes for the seasonal changes of the CLLJ system, in the further north regions (downwind Cap Ghir), the spring season shows the largest increases of wind energy, up to +20%, while in the offshore western Sahara it is projected an increase of wind energy in all seasons. For the southern areas, it is expected a decrease of wind energy

Future evolution of Marine Heatwaves in the Mediterranean Sea

International audienceExtreme ocean warming events, known as marine heatwaves (MHWs), have been observed to perturb significantly marine ecosystems and fisheries around the world. Here, we propose a detection method for long-lasting and large-scale summer MHWs, using a local, climatological 99th percentile threshold, based on present-climate (1976-2005) daily SST. To assess their future evolution in the Mediterranean Sea we use, for the first time, a dedicated ensemble of fully-coupled Regional Climate System Models from the Med-CORDEX initiative and a multi-scenario approach. The models appear to simulate well MHW properties during historical period, despite biases in mean and extreme SST. In response to increasing greenhouse gas forcing, the events become stronger and more intense under RCP4.5 and RCP8.5 than RCP2.6. By 2100 and under RCP8.5, simulations project at least one long-lasting MHW every year, up to three months longer, about 4 times more intense and 42 times more severe than present-day events. They are expected to occur from June-October and to affect at peak the entire basin. Their evolution is found to occur mainly due to an increase in the mean SST, but increased daily SST variability also plays a noticeable role. Until the mid-21st century, MHW characteristics rise independently of the choice of the emission scenario, the influence of which becomes more evident by the end of the period. Further analysis reveals different climate change responses in certain configurations, more likely linked to their driving global climate model rather than to the individual model biases

Pathways and modification of the upper and intermediate waters of the Arctic Ocean,

The purpose of this study is to investigate the pathways and the ventilation of source water masses of the upper and intermediate waters of the Arctic Ocean. For the Arctic and subarctic domain, a coupled ice-ocean general circulation model is set up to be integrated for several decades. It is driven by a climatological seasonal cycle of monthly mean atmospheric data from 1980-89 and by restored sea surface salinities. Passive tracers are used to visualise and interpret the modelled flow and to compare it with observations.The model is able to reproduce known features of the Arctic Ocean circulation like the inflow of two branches of Atlantic origin via the Fram Strait and the Barents Sea and their subsequent passage at mid depths in several cyclonic circulation cells. The fate of these Atlantic source water masses, river water and Bering Strait inflow water in the model are studied. The branch crossing the Barents Sea is subject to an intense heat loss and ice formation. As a result water of this branch leaves the shelf towards the central part of the Arctic Ocean not only at the surface but also in denser varieties which finally feed the central Arctic at halocline and mid depths. The lightest part turns northward and finally westward joining the Transpolar Drift, the densest part (200-1000 m depth) move eastward along the continental slope. A similar path is taken by the Atlantic water branch from the Fram Strait. The inflowing branch over the Barents Sea turns out to be the dominant source for the lower Atlantic Water layer in the Arctic Ocean in this investigation.Atlantic tracers starting in Fram Strait need 6 years to reach the northern Laptev Sea slope. Travel times to return to Fram Strait are 15 - 20 years along the Lomonossov Ridge and about 30 years along the continental slope of the Canadian Basin. Tracers which mark the Pacific Water or the Mackenzie river water flow eastward and leave the Arctic mainly via the Canadian Archipelago. The Siberian river water tracers at the surface penetrate far into the Canadian Basin before they join the Transpolar Drift. The travel times of the river water from the river mouths are 2-3 years to the shelf edge and 12-14 years to Fram Strait

La utilización del Portafolio discente interdisciplinar como metodología en la evaluación de la asignatura de Meterología, Climatología y Contaminación Atmosférica de Grado en Ciencias Ambientales

El portafolio discente interdisciplinar se ha empleado como metodología de evaluación formativa y sumativa en la asignatura Meteorología, Climatología y Contaminación atmosférica de tercer curso del Grado de Ciencias Ambientales de la Universidad de Alcalá.El conjunto de evidencias que proporciona esta metodología de trabajo, aparte de su significado básico (aportaciones de muy distinta índole que permiten al alumno y a los demás ver y valorar el esfuerzo, los logros, las dificultades), requiere y estimula de una manera peculiar la coordinación y planificación docente que permite intercambios y enriquecimiento didáctico en términos de estrategias docentes, flexibilidad y toma de decisiones de cada uno de los docentes implicados, proporcionando una visión integradora, plural, implicada, responsable, autodisciplinada y cooperativa del aprendizaje en Ciencias Ambientales.The interdisciplinary learner portfolio methodology has been used as formative and summative assessment in Meteorology, Climatology and Air Pollution third year course of the Bachelor of Environmental Science at University of Alcalá. The collection of various forms of evidence of achievement of learning outcomes provides apart from its basic meaning (learning outcomes that allow students and others to assess the efforts, achievements, difficulties,strengths and weaknesses) requires and strongly encourages the coordination and planning of teaching that allows exchanges and educational enrichment in terms of strategies, flexibility, assessment decision of each of the teachers involved, thus providing a comprehensive, plural, involved, responsible, selfdisciplined and cooperative learning view in Environmental Science