Microfísica Atmosférica y Radiación
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Item Restricted Revisiting wintertime cold air intrusions at the east of the Andes: propagating features from subtropical Argentina to Peruvian Amazon and relationship with large-scale circulation patterns(Springer, 2013) Espinoza, Jhan Carlo; Ronchail, Josyane; Lengaigne, Matthieu; Quispe, Nelson; Silva Vidal, Yamina; Bettolli, María Laura; Avalos, Grinia; Llacza, AlanThis study investigates the spatial and temporal characteristics of cold surges that propagates northward along the eastern flank of the Andes from subtropical to tropical South America analysing wintertime in situ daily minimum temperature observations from Argentina, Bolivia and Peru and ERA-40 reanalysis over the 1975–2001 period. Cold surges usually last 2 or 3 days but are generally less persistent in the southern La Plata basin compared to tropical regions. On average, three to four cold surges are reported each year. Our analysis reveals that 52 % of cold episodes registered in the south of La Plata basin propagate northward to the northern Peruvian Amazon at a speed of around 20 m s⁻¹. In comparison to cold surges that do not reach the tropical region, we demonstrate that these cold surges are characterized, before they reach the tropical region, by a higher occurrence of a specific circulation pattern associated to southern low-level winds progression toward low latitudes combined with subsidence and dry condition in the middle and low troposphere that reinforce the cold episode through a radiative effect. Finally, the relationship between cold surges and atmosphere dynamics is illustrated for the two most severe cold intrusions that reached the Peruvian and Bolivian Amazon in the last 20 years.Item Restricted A framework for the science contribution in climate adaptation: experiences from science-policy processes in the Andes(Elsevier, 2015-03) Huggel, Christian; Scheel, Marlene; Albrecht, Franziska; Andres, Norina; Calanca, Pierluigi; Jurt, Christine; Khabarov, Nikolay; Mira-Salama, Daniel; Rohrer, Mario; Salzmann, Nadine; Silva Vidal, Yamina; Silvestre, Elizabeth; Vicuña, Luis; Zappa, MassimilianoAs significant impacts of climate change are increasingly considered unavoidable, adaptation has become a policy priority. It is generally agreed that science is important for the adaptation process but specific guidance on how and to what degree science should contribute and be embedded in this process is still limited which is at odds with the high demand for science contributions to climate adaptation by international organizations, national governments and others. Here we present and analyze experiences from the tropical Andes based on a recent science-policy process on the national and supra-national government level. During this process a framework for the science contribution in climate adaptation has been developed; it consists of three stages, including (1) the framing and problem definition, (2) the scientific assessment of climate, impacts, vulnerabilities and risks, and (3) the evaluation of adaptation options and their implementation. A large amount of methods has been analyzed for stage (2), and a number of major climate adaptation projects in the region assessed for (3). Our study underlines the importance of joint problem framing among various scientific and non-scientific actors, definition of socio-environmental systems, time frames, and a more intense interaction of social and physical climate and impact sciences. Scientifically, the scarcity of environmental, social and economic data in regions like the Andes continue to represent a limitation to adaptation, and further investments into coordinated socio-environmental monitoring, data availability and sharing are essential.Item Restricted Spatial analysis and temporal trends of daily precipitation concentration in the Mantaro River basin: central Andes of Peru(Springer, 2017-08) Zubieta Barragán, Ricardo; Saavedra Huanca, Miguel; Silva Vidal, Yamina; Giráldez, LucyThe analysis of annual or seasonal data can lead to misinterpretation of spatio-temporal rainfall distribution. A high percentage of total annual precipitation can fall in just a few days, causing floods or landslides. Large economic losses from these events are particularly common in Peru, where the daily precipitation has been poorly investigated. This study presents a spatio-temporal analysis of concentration index over the Mantaro River basin in the central Peruvian Andes. Daily rainfall data recorded at 46 rainfall stations between 1974 and 2004 were selected in this study. In terms of average values, the analysis of daily rainfall indicates that low-intensity events account for 38 % of rainy days but only approximately 9 % of the total rain amount. In contrast, high- and very high-intensity events account for 35 % of rainy days and approximately 71 % of the total rain amount. The results also indicate higher concentration and lower intensity over the Northern and Central regions, compared to Southern region of the basin. Rainfall concentration gives evidence of why some of these places are more likely to be affected by extreme weather events; spatial distribution of event intensity can be partly explained by daily rainfall heterogeneity and orography. Moreover, Mann–Kendall test mostly shows a significant change toward a weaker seasonality of daily precipitation distribution over high-mountain regions.Item Open Access Teleconnections between the Peruvian central Andes and northeast Brazil during extreme rainfall events in austral summer(American Meteorological Society, 2016-02) Sulca Jota, Juan Carlos; Vuille, Mathias; Silva Vidal, Yamina; Takahashi, KenExtreme precipitation events in the Peruvian Andes have significant socioeconomic impacts, yet their atmospheric dynamics are poorly understood. Here austral summer (December–March) wet and dry spells and their continental- and large-scale teleconnections are analyzed using reanalysis, gridded, and in situ precipitation data. Dry and wet spells in the Peruvian Andes show a pervasive dipole pattern with precipitation anomalies of the opposite sign over northeastern Brazil. Composite anomalies of various atmospheric fields during extreme precipitation events indicate that this dipole is related to large-scale adjustments in the upper-tropospheric Bolivian high–Nordeste low system, which in turn are modulated by northward-propagating extratropical Rossby wave trains. At upper- and midtropospheric levels, westerly wind anomalies over the Peruvian Andes suppress moisture flux from the Amazon during dry events, while wet events are characterized by opposite conditions. Yet, while easterly wind anomalies appear to be a prerequisite for heavy precipitation events in the region, they are not a sufficient forcing, as dry days can still occur during such periods. Dry spells in the Peruvian Andes appear to be linked to weakened convective activity over the western tropical Pacific, consistent with the previously documented El Niño influence over the region. Extreme dry and wet spells in northeastern Brazil only show a weak link to precipitation anomalies of the opposite sign over Peru but are strongly coupled with changes in the position and strength of the Nordeste low and the South Atlantic convergence zone.