Southern Hemisphere Summer Mesopause Responses to El Niño-Southern Oscillation

In the Southern Hemisphere (SH) polar region, satellite observations reveal a significant upper-mesosphere cooling and a lower-thermosphere warming during warm ENSO events in December. An opposite pattern is observed in the tropical mesopause region. The observed upper-mesosphere cooling agrees with a climate model simulation. Analysis of the simulation suggests that enhanced planetary wave (PW) dissipation in the Northern Hemisphere (NH) high-latitude stratosphere during El Nino strengthens the Brewer-Dobson circulation and cools the equatorial stratosphere. This increases the magnitude of the SH stratosphere meridional temperature gradient and thus causes the anomalous stratospheric easterly zonal wind and early breakdown of the SH stratospheric polar vortex. The resulting perturbation to gravity wave (GW) filtering causes anomalous SH mesospheric eastward GW forcing and polar upwelling and cooling. In addition, constructive inference of ENSO and quasi-biennial oscillation (QBO) could lead to stronger stratospheric easterly zonal wind anomalies at the SH high latitudes in November and December and early breakdown of the SH stratospheric polar vortex during warm ENSO events in the easterly QBO phase (defined by the equatorial zonal wind at similar to 25 hPa). This would in turn cause much more SH mesospheric eastward GW forcing and much colder polar temperatures, and hence it would induce an early onset time of SH summer polar mesospheric clouds (PMCs). The opposite mechanism occurs during cold ENSO events in the westerly QBO phase. This implies that ENSO together with QBO could significantly modulate the breakdown time of SH stratospheric polar vortex and the onset time of SH PMC.

Variability of the ocean heat content during the last millennium - an assessment with the ECHO-g Model

Studies addressing climate variability during the last millennium generally focus on variables with a direct influence on climate variability, like the fast thermal response to varying radiative forcing, or the large-scale changes in atmospheric dynamics (e. g. North Atlantic Oscillation). The ocean responds to these variations by slowly integrating in depth the upper heat flux changes, thus producing a delayed influence on ocean heat content (OHC) that can later impact low frequency SST (sea surface temperature) variability through reemergence processes. In this study, both the externally and internally driven variations of the OHC during the last millennium are investigated using a set of fully coupled simulations with the ECHO-G (coupled climate model ECHAMA4 and ocean model HOPE-G) atmosphere-ocean general circulation model (AOGCM). When compared to observations for the last 55 yr, the model tends to overestimate the global trends and underestimate the decadal OHC variability. Extending the analysis back to the last one thousand years, the main impact of the radiative forcing is an OHC increase at high latitudes, explained to some extent by a reduction in cloud cover and the subsequent increase of short-wave radiation at the surface. This OHC response is dominated by the effect of volcanism in the preindustrial era, and by the fast increase of GHGs during the last 150 yr. Likewise, salient impacts from internal climate variability are observed at regional scales. For instance, upper temperature in the equatorial Pacific is controlled by ENSO (El Nino Southern Oscillation) variability from interannual to multidecadal timescales. Also, both the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO) modulate intermittently the interdecadal OHC variability in the North Pacific and Mid Atlantic, respectively. The NAO, through its influence on North Atlantic surface heat fluxes and convection, also plays an important role on the OHC at multiple timescales, leading first to a cooling in the Labrador and Irminger seas, and later on to a North Atlantic warming, associated with a delayed impact on the AMO.

Climate simulation for 125 kyr BP with a coupled ocean-atmosphere general circulation model

The ECHAM-1 T21/LSG coupled ocean-atmosphere general circulation model (GCM) is used to simulate climatic conditions at the last interglacial maximum (Eemian. 125 kyr BP). The results reflect thc expected surface temperature changes (with respect to the control run) due to the amplification (reduction) of the seasonal cycle of insolation in the Northern (Southern) Hemisphere. A number of simulated features agree with previous results from atmospheric GCM simulations e.g. intensified summer southwest monsoons) except in the Northern Hemisphere poleward of 30 degrees N. where dynamical feedback, in the North Atlantic and North Pacific increase zonal temperatures about 1 degrees C above what would be predicted from simple energy balance considerations. As this is the same area where most of the terrestrial geological data originate, this result suggests that previous estimates of Eemian global average temperature might have been biased by sample distribution. This conclusion is supported by the fact that the estimated global temperature increase of only 0.3 degrees C greater than the control run ha, been previously shown to be consistent a with CLIMAP sea surface temperature estimates. Although the Northern Hemisphere summer monsoon is intensified. globally averaged precipitation over land is within about 1% of the present, contravening some geological inferences bur not the deep-sea delta(13)C estimates of terrestrial carbon storage changes. Winter circulation changes in the northern Arabian Sea. driven by strong cooling on land, are as large as summer circulation changes that are the usual focus of interest, suggesting that interpreting variations in the Arabian Sea. sedimentary record solely in terms of the summer monsoon response could sometimes lead to errors. A small monsoonal response over northern South America suggests that interglacial paleotrends in this region were not just due to El Nino variations.

La cooperación sur-sur como nueva dimensión de la política exterior brasileña en el gobierno de Lula: una aproximación constructiva

Over the last decade, we have witnessed a growing number of academic researches that have Brazil and its position in the international system as an object of study, which debate is open, because there is no consensus of its role and intentions: if it is to promote the development and cooperation, or, after all, if it also has international political interests, like greater weight in the international system, greater decision capability, and others typically economics like how to gain market for its companies. Because of its geographical size, its growing economic importance, its visibility for the Brazil 2014 World Cup and the Rio 2016 Olympics, and the political demonstrations in the streets, it is hard to deny the attraction that Brazil is gaining every day. This work was created with several objectives that are tried to be answered along the writing of this thesis: a general objective that generates secondary ones and, at the same time, subsequent collateral objectives. Among the general objectives, we have the purpose of understanding and analyzing how the South-South Cooperation (SSC) is in the wider debate of the International Cooperation for Development (ICD). In this sense, it is necessary to point out the difficulty to trace clear lines of differentiation between the traditional North-South Cooperation (NSC) and the latest SSC. This is because, among other questions, there is not a definition until this moment shared by all the countries participating in it, as well as the lack of database that indicates precisely which are all the 'development partners' emerging. This thesis introduces the debate about international cooperation analyzing the challenges that it faces, the global changes that have come to transform the 'new architecture to development' and to analyze the gaps that Brazil can take with other emerging powers to improve the current and weakened assistance system...