THE ROLE OF SEA SURFACE TEMPERATURE IN THE RAINFALL REGIME IN SUB-SAHARAN AFRICA

This study sought to understand the role of the surface temperatures of the ocean and continent in the variability of rains in sub-Saharan Africa, contributing to the improvement of weather forecasting and prevention of extreme events in the region.Through perturbation experiments using a climate model of intermediate complexity,we seek to understand the roles of sea surface temperature (SST) of ocean basins around the sub-Saharan Africa and the surface temperature in Southern Africa, in defining the spatial distribution of Spatial distribution of rainfall in the region of action of Intertropical Convergence Zone (ITCZ) which assumes an approximate shape of an "inverted S" during the quarter December-January-February in this continent, due to connections with other systems of the same scale. By comparing the regional perturbation experiments of SST and the continental surface temperaturewith respect to the climatology we came to the conclusion that the SST in the Atlantic and Indian Oceans have major contribution in the formation of "inverted S" of precipitation than the continent's surface temperature. Comparing these two ocean basins, the Indian SST has predominant role in the climate variability in sub-Saharan Africa, modulating the position and intensity of the ITCZ and therefore the formation of their spatial distribution across the continent.  

A Influência da Circulação de Revolvimento Meridional do Atlântico na Definição da Posição Média da ZCIT ao Norte do Equador. Uma Revisão

Resumo A Zona de Convergência Intertropical (ZCIT) é considerada o sistema atmosférico mais importante na geração de precipitação nos trópicos. Embora no clima presente a insolação média anual seja simétrica em torno do equador, a ZCIT se posiciona ao norte do equador apresentando ali também o máximo de precipitação. Neste artigo de revisão descrevemos a visão desenvolvida em trabalhos recentes sobre a influência da Circulação de Revolvimento Meridional do Atlântico sobre a Célula de Hadley na determinação da assimetria de posição da ZCIT. Indicamos a importância de se aprofundar este tópico de pesquisa em face a possíveis futuros deslocamentos da ZCIT com o aquecimento global e as consequentes mudanças no regime de chuvas nos trópicos

The Influence of the Atlantic Meridional Overturning Circulation in the Definition of the Mean Position of the ITCZ North of the Equator. A Review Luis Aimola1

The Intertropical Convergence Zone (ITCZ) is considered the most important atmospheric system in the generation of precipitation in the tropics. Although in the present climate the annual average insolation is symmetrical around the equator, the ITCZ is positioned north of the equator, also having the maximum of precipitation there. In this review article we describe the vision developed in recent studies of the influence of the Atlantic Meridional Overturning Circulation on the Hadley cell in determining of the ZCIT's position asymmetry. We indicate the importance of strengthening this research topic in face of possible future displacements of the ITCZ with global warming and the consequent tropical rain regime changes.A Zona de Convergência Intertropical (ZCIT) é considerada o sistema atmosférico mais importante na geração de precipitação nos trópicos. Embora no clima presente a insolação média anual seja simétrica em torno do equador, a ZCIT se posiciona ao norte do equador apresentando ali também o máximo de precipitação. Neste artigo de revisão descrevemos a visão desenvolvida em trabalhos recentes sobre a influência da Circulação de Revolvimento Meridional do Atlântico sobre a Célula de Hadley na determinação da assimetria de posição da ZCIT. Indicamos a importância de se aprofundar este tópico de pesquisa em face a possíveis futuros deslocamentos da ZCIT com o aquecimento global e as consequentes mudanças no regime de chuvas nos trópicos

The impacts of the Indonesian Throughflow on the inter‐basin seesaw mechanism, in idealized experiments

13 pages, 10 figures, 2 tables, supporting information https://doi.org/10.1002/joc.5424The role that the Indonesian Throughflow plays on climate is investigated in an alternative scenario, expected during glacial ages. The equatorwards shift of the Southern Hemisphere westerlies found in glacial ages acts to decrease the Agulhas Leakage (AL) and the thermohaline circulation (THC) in the Atlantic. Recent results suggest that these changes are followed by an increased THC in the Pacific, through an inter-basin seesaw mechanism. The enhanced circulation in the Pacific demands thermocline water to cross the equator towards northern latitudes, which shifts the water source of the throughflow from the low-salinity North Pacific to the relative saltier South Pacific. It is shown that in this equilibrium, the salinity anomalies of the throughflow impact the inter-basin seesaw towards the restoration of the modern climate, enhancing the North Atlantic Deep Water (NADW) formation and decreasing the THC in the Pacific. These results are consistent with paleo-observations and provide new insights to interpreting the climate changes in glacial periods.We are very grateful to the Brazilian National Council of Scientific and Technologic Development (CNPq) for the fellowship (140821/2013‐9) and we want specially to acknowledge to the Vale Institute of Technology (ITV) for the financial and academic support to this project. The numerical experiments were also a contribution to Projects SAMOC (grant 2011/5055‐4) and SANSAO (grant 2008/58101‐9), funded by the São Paulo State Foundation for Research Support (FAPESP). Furthermore, the co‐authors acknowledges the Brazilian National Council for Scientific and Technological Development (CNPq) for a Research Fellowship (grant 302018/2014‐0), and the support of the Spanish government, through project VA‐DE‐RETRO (CTM2014‐56987‐P)Peer Reviewe

The impacts of the atmospheric annular mode on the AMOC and its feedback in an idealized experiment

12 pages, 11 figures, supplementary data https://doi.org/10.1016/j.dynatmoce.2017.11.004The interdecadal variability of the atmospheric and oceanic meridional overturning circulation is studied, using a coupled model with two narrow meridional barriers representing the land and a flat bottomed Aquaplanet. Empirical orthogonal function (EOF) analysis are used in the atmospheric and oceanic meridional overturning cells, revealing the atmospheric interdecadal variability is dominated by an annular mode, in both hemispheres, which introduces in the ocean a set of patterns of variability. The most energetic EOFs in the ocean are the barotropic responses from the annular mode. The interaction between the heat anomalies, due to the barotropic response, and the thermohaline circulation of each basin leads to a resonance mechanism that feeds back to the atmospheric forcing, modulating the annular mode spectrum. Besides the barotropic response, the annular mode introduces anomalies of salinity and temperature in the subtropical Atlantic that affects its upper buoyancy. These anomalies are incorporated within the ocean circulation and advected until the areas of deep sinking in the northern Atlantic, impacting on its overturning circulation as wellWe are very grateful to the Brazilian National Council of Scientific and Technologic Development (CNPq) for the fellowship (140821/2013-9) and we want specially to acknowledge to the Vale Institute of Technology (ITV) for the financial and academic support to this project. The numerical experiments were conducted at the IO-USP Ocean Modeling Laboratory (LABMON) using computer resources funded by the São Paulo State Foundation for Research Support (FAPESP, Grants 2010/01943-8, and 2011/50552-4). Furthermore, the co-authors acknowledges the Brazilian National Council for Scientific and Technological Development (CNPq) for a Research Fellowship (Grant 302018/2014-0), and the support of the Spanish government, through project VA-DE-RETRO (CTM2014-56987-P)Peer Reviewe

Expanding the scope of Actualistic Taphonomy in Archaeological Research

This chapter presents the application of actualistic taphonomy to the study of one of the inorganic remains produced by hominins since 3 million year BP up to historical times: lithic artifacts. As rocks are among the most durable raw materials employed by modern humans and their ancestors, differential preservation has conferred a leading role in archaeological research upon lithic artifacts. Indeed, lithics -flaked artifacts in particular- are the proxy for culture or anthropic presence most commonly used by scholars all over the world. This artifact-human relationship promoted actualistic research on flintknapping in archaeology but no similar effort was devoted to assessing alternative non-cultural (i.e. taphonomic) sources for flaked stone objects. Even though actualistic studies have already shown that taphonomic processes may produce lithic pseudomorphs, this fact is only rarely considered in archaeological practice and research design. Furthermore, it is commonly assumed that human products are different enough from any natural specimen to be detected by lithic analysts. However, the current lack of knowledge on non-cultural flaking processes and their byproducts prevents their identification in the archaeological record, thus undermining the accuracy and reliability of archaeological interpretations. This paper illustrates the contribution of actualistic taphonomy to study the inorganic remains of the archaeological record and its critical role in assessing the cultural vs natural origin of lithic specimens in Fuego-Patagonia (South America). Naturalistic and experimental research on rockfall and trampling presented here suggests that the effects of these taphonomic processes result in pseudoartifacts that progressively incorporate to the regional archaeological record.Fil: Borrazzo, Karen Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Multidisciplinario de Historia y Ciencias Humanas; Argentin