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Bergmann's rule generally predicts larger animal body sizes with colder climates. We tested whether Bergmann's rule at the interspecific level applies to moths (Lepidoptera: Geometridae) along an extended elevational gradient in the Ecuadorian Andes. Moths were sampled at 22 sites in the province Zamora-Chinchipe in southern Ecuador in forest habitats ranging from 1040 m to 2677 m above sea level. Wingspans of 2282 male geometrid moths representing 953 species were measured and analysed at the level of the family Geometridae, as well as for the subfamily Ennominae with the tribes Boarmiini and Ourapterygini, and the subfamily Larentiinae with the genera Eois, Eupithecia and Psaliodes. Bergmann's rule was not supported since the average wingspan of geometrid moths was negatively correlated with altitude ( r = −0.59, P < 0.005). The relationship between body size and altitude in Geometridae appears to be spurious because species of the subfamily Larentiinae are significantly smaller than species of the subfamily Ennominae and simultaneously increase in their proportion along the gradient. A significant decrease of wingspan was also found in the ennomine tribe Ourapterygini, but no consistent body size patterns were found in the other six taxa studied. In most taxa, body size variation increases with altitude, suggesting that factors acting to constrain body size might be weaker at high elevations. The results are in accordance with previous studies that could not detect consistent body size patterns in insects at the interspecific level along climatic gradients. [ABSTRACT FROM AUTHOR]

Drylines have been identified as relevant synoptic-scale phenomena that frequently occur in several regions around the world. Despite previous works and the experience of local forecasters that recognizes the occurrence of drylines in Argentina and suggests its possible association with convection initiation, knowledge about the mechanisms leading to the genesis of these features is poor. This paper presents the first synoptic climatology of these drylines as well as a first approach to the understanding of the processes leading to their formation. The climatology is based on an automated algorithm for dryline identification applied to reanalysis data. We found that drylines are more frequent between the northern Patagonia plateau and the central Argentinean plains. A composite analysis is performed to analyze the processes leading to the formation of synoptic-scale drylines within this region. It was found that these drylines form in the confluence between a warm and moist air mass driven by a northwesterly flow and drier air flowing east over the northern Patagonia plateau. The dry air originates on top of the Pacific maritime boundary layer and experiences lee subsidence after crossing the Andes range creating an area of dry and warm air that is advected to the east by the westerly synoptic-scale flow, and transported downward during the day due to strong boundary layer turbulence. At the same time, surface heating over the plateau leads to substantial warming of the originally colder dry air behind the dryline, thus reversing the horizontal temperature gradient across the dryline. [ABSTRACT FROM AUTHOR]

Background: Climate change is arguably a major threat to biodiversity conservation and there are several methods to assess its impacts on species potential distribution. Yet the extent to which different approaches on species distribution modeling affect species richness patterns at biogeographical scale is however unaddressed in literature. In this paper, we verified if the expected responses to climate change in biogeographical scale—patterns of species richness and species vulnerability to climate change—are affected by the inputs used to model and project species distribution. Methods: We modeled the distribution of 288 vertebrate species (amphibians, birds and mammals), all endemic to the Amazon basin, using different combinations of the following inputs known to affect the outcome of species distribution models (SDMs): 1) biological data type, 2) modeling methods, 3) greenhouse gas emission scenarios and 4) climate forecasts. We calculated uncertainty with a hierarchical ANOVA in which those different inputs were considered factors. Results: The greatest source of variation was the modeling method. Model performance interacted with data type and modeling method. Absolute values of variation on suitable climate area were not equal among predictions, but some biological patterns were still consistent. All models predicted losses on the area that is climatically suitable for species, especially for amphibians and primates. All models also indicated a current East-western gradient on endemic species richness, from the Andes foot downstream the Amazon river. Again, all models predicted future movements of species upwards the Andes mountains and overall species richness losses. Conclusions: From a methodological perspective, our work highlights that SDMs are a useful tool for assessing impacts of climate change on biodiversity. Uncertainty exists but biological patterns are still evident at large spatial scales. As modeling methods are the greatest source of variation, choosing the appropriate statistics according to the study objective is also essential for estimating the impacts of climate change on species distribution. Yet from a conservation perspective, we show that Amazon endemic fauna is potentially vulnerable to climate change, due to expected reductions on suitable climate area. Climate-driven faunal movements are predicted towards the Andes mountains, which might work as climate refugia for migrating species. [ABSTRACT FROM AUTHOR]

Purpose – This paper aims to explore how Andean knowledge and culture have shaped mountain ecosystems by building cultural landscapes where agrobiodiversity is created and recreated, water is domesticated (seeded and harvested), and where a harmonious relationship with the Earth and the Universe is kept. Design/methodology/approach – Through the use of primary and secondary sources, the information is then organized detailing a synthesis of thoughts and joint research studies conducted by various authors regarding the valuable contributions made by the Andean culture. Findings – This paper finds that strategies for facing the ecological crisis affecting planet Earth are being developed: the Pleiades and the Andean Cross continue to be observed in order to predict the weather and climate and make decisions related to traditional agricultural systems; cultural landscapes are being created and maintained; and water continues to be domesticated. Originality/value – The tropical Andes of Peru would be in the third country most affected by global climate change worldwide. The severe impacts of the global phenomenon on mountain ecosystems and cultural landscapes are many, all of which are affecting food security of large human groups and traditional lifestyles of communities and farmers. [ABSTRACT FROM AUTHOR]

One of the main problems in climate reconstruction from documentary sources is the evaluation of the quality of non instrumental meteorological records in absence of instrumental observations to perform a calibration. In these cases it is mandatory to envision different approaches to assess the climatic signal in a reconstruction. This work is aimed to test the consistency of a snow frequency reconstruction in the central Argentinean Andes by studying the synoptic patterns related to the occurrence of precipitation in this area. While the original reconstruction covers the period between 1885 and 1996, the insufficiency of overlapping instrumental data limited the calibration to a short 15-year interval. In this paper we evaluate the performance of the reconstructed series for the entire 45-year period between 1958 and 1996 by analyzing the displacement in the jet stream and the patterns of geopotential height related to anomalies in the reconstructed snow frequency series. Previous works have linked the precipitation in the central Andes to the ENSO through the Pacific South American mode. We also have found this connection between ENSO and the reconstructed precipitation. Finally, it is shown that the ENSO relationship is the cause of a significant link between the precipitation anomalies in the central Argentinean Andes and the ice extent around the Antarctic Peninsula. [ABSTRACT FROM AUTHOR]

Winter orographic precipitation over the Andes between 30° and 37°S is examined using precipitation gauges in the mountains and adjacent lowlands. Because of the limited number of precipitation gauges, this paper focuses on the large-scale variation in cross-barrier precipitation and does not take into account the fine ridge-valley scale. The maximum amount of precipitation was observed on the windward slope of the mountain range below the crest, which was twice that observed on the low-windward side between 32.5° and 34°S. Toward the east of the crest, precipitation amounts drop sharply, generating a strong cross-barrier gradient. The rain shadow effect is greater in the north (32°-34.5°S) than in the south (35°-36.5°S) of the low-lee side, which is probably due to more baroclinic activity in southernmost latitudes and a southward decrease in the height of the Andes enabling more spillover precipitation. The effect of the Andes on winter precipitation is so marked that it modifies the precipitation regimes in the adjacent windward and leeward lowlands north of 35°S. Based on the fact that ~75%% of the wintertime precipitation accumulated in the fourth quartile, through four or five heavy events on average, the synoptic-scale patterns of the heavy (into fourth quartile) orographic precipitation events were identified. Heavy events are strongly related to strong water vapor transport from the Pacific Ocean in the pre-cold-front environment of extratropical cyclones, which would have the form of atmospheric rivers as depicted in the reanalysis and rawinsonde data. The composite fields revealed a marked difference between two subgroups of heavy precipitation events. The extreme (100th-95th percentiles) events are associated with deeper cyclones than those for intense (95th-75th percentiles) events. These deeper cyclones lead to much stronger plumes of water vapor content and cross-barrier moisture flux against the high Andes, resulting in heavier orographic precipitation for extreme events. In addition, regional airflow characteristics suggest that the low-level flow is typically blocked and diverted poleward in the form of an along-barrier jet. On the lee side, downslope flow dominates during heavy events, producing prominent rain shadow effects as denoted by the domain of downslope winds extending to low-leeward side (i.e., zonda wind). [ABSTRACT FROM AUTHOR]

The Andes as mountain regions worldwide, provide fundamental resources, not only for the local population. Due to the topographic characteristics, the potential for natural hazards is higher than elsewhere. In these areas, assessments of climate change impacts and the development of adequate adaptation strategies therefore become particular important. The data basis, however, is often scarce. Moreover, perceptions of changes and needs are often divergent between national and local levels, which make the implementation of adaptation measures a challenge. Taking the Peruvian Andes as an example, this paper aims at initiating a discussion about scientific baseline and integrative concepts needed to deal with the adverse effects of climate change in mountain regions. [ABSTRACT FROM AUTHOR]

In this study, we assess the performance of the Regional Climate Model version 4 (RegCM4) in simulating the climatology of the cyclones near the west coast of South America. The synoptic evolution and seasonality of these systems are thoroughly investigated. The analyses are based on four simulations from the CORDEX-CORE Southern America (SA) domain, at 0.25° of horizontal resolution: one driven by ERA-Interim and three driven by different GCMs. The reference dataset is represented by ERA5. Cyclones were detected by an objective scheme in the period 1995–2005 and classified in three different classes: (i) Coastal Lows (CLs) and cyclones affecting the coast (CAC) (ii) crossing and (iii) not crossing the Andes. In general, RegCM4 is able to reproduce the climatology of cyclones affecting the western coast of SA. In particular: (i) CLs are shown to be more frequent in austral summer although their frequency is underestimated by the simulations in this season; (ii) CAC not crossing the Andes represent 76% of all CAC and are more frequent in winter, with simulation underestimating their frequency by ~ 22% due to the differences in the simulated upper-level jets, which tend to get weaker (by ~ 5–10 m s− 1) northwards of 30°S; (iii) the frequency of CAC crossing the Andes tends to be overestimated mainly in winter, which is associated with the combination of the stronger upper-level jets and weaker SLP in the simulations, especially southwards of 40°S. [ABSTRACT FROM AUTHOR]

Climate patterns are natural processes that drive climate variability in the short, medium, and long term. Characterizing the patterns behind climate variability is essential to understand the functioning of the regional atmospheric system. Since investigations typically reveal only the link and extent of the influence of climate patterns in specific regions, the magnitude of that influence in meteorological records usually remains unclear. The central Peruvian Andes are affected by most of the common climate patterns of tropical areas, such as Intertropical Convergence Zone (ITCZ), Sea Surface Temperature (SST), solar irradiance, Madden Julian Oscillation (MJO), Pacific Decadal Oscillation (PDO), and El Niño Southern Oscillation (ENSO). They are also affected by regional processes that are exclusive from South America, such as the South American Low-Level Jet (SALLJ), South American Monsoon System (SAMS), Bolivian High (BH), and Humboldt Current. The aim of this research is to study the climate variability of precipitation, maximum and minimum temperature records over Cordillera Blanca (Peru), and its relationship with the intensity and periodicity of the common climate patterns that affect this region. To achieve this aim, a spectral analysis based on Lomb's Periodogram was performed over meteorological records (1986–2019) and over different climate pattern indexes. Results show a coincidence in periodicity between MJO and SALLJ, with monthly cycles for precipitation and temperature (27-day, 56-day, and 90-day cycles). Moreover, the most intense periodicities, such as annual (365 days) and biannual (182 and 122 days) cycles in meteorological variables, possibly would be led by ITCZ and ENSO together, as well as a combination of the Humboldt Current and SALLJ. Additionally, interannual periodicities (3-year, 4.5-year, 5.6–7-year and 11-year cycles) would have coincidence with the ENSO–solar combination, while the longest cycles (16 years) could match PDO variability. [ABSTRACT FROM AUTHOR]

Unraveling the relationship between humidity, wind, and rainfall is vitally important to understand the dynamics of water vapor transport. In recent years, the use of causal networks to identify causal flows has gained much ground in the field of climatology to provide new insights about physical processes and hypothesize previously unknown ones. In this paper, the concept of a virtual control volume is proposed, which resembles the Eulerian description of a vector field, but is based on causal flows instead. A virtual control surface is used to identify the influence of surrounding climatic processes on the control volume (i.e., the study region). Such an influence is characterized by using a causal inference method that gives information about its direction and strength. The proposed approach was evaluated by inferring and spatially delineating areas of influence of humidity and wind on the rainfall of Ecuador. It was possible to confirm known patterns of influence, such as the influence of the Pacific Ocean on the coast and the influence of the Atlantic Ocean on the Amazon. Moreover, the approach was able to identify plausible new hypotheses, such as the influence of humidity on rainfall in the northern part of the boundary between the Andes and the Amazon, as well as the origin (the Amazon or the tropical Atlantic) and the altitude at which surrounding humidity and wind influence rainfall within the control volume. These hypotheses highlight the ability of the approach to exploit a large amount of scalar data and identify pathways of influence between climatic variables. [ABSTRACT FROM AUTHOR]

[Display omitted] • The meteorological variables are correlated with altitude, latitude and longitude. • Temperature, altitude, latitude and longitude control the δ18O of precipitation. • Unrecorded rainfall in sampling points is obtained by means of correlation models. • These models are useful if the available data are scarce and discontinuous in time. • Aquifer recharge zones are identified by estimating δ18O values with these models. A knowledge of the evolution of isotopic composition of air masses humidity and precipitation in the Western Cordilleras of the Central Andes is still incomplete. This study contributes to a better understanding of the factors that control the δ18O and δ2H contents in precipitation water in the north of Chile, above 2000 m a.s.l.. This paper deals with: (1) the relevant effects and processes that control the spatial (longitude, latitude and altitude) distribution of stable isotope contents of precipitation events in northern Chile, (2) the influence of local meteorological variables: temperature, precipitation and relative humidity on the δ18O and δ2H of precipitation, and (3) the estimation of these meteorological and isotopic variables at specific sites. To achieve these objectives, the relationships between geospatial and meteorological values are identified and analysed, followed by the estimation with empirical models. These estimation models (linear and non-linear) are obtained after examining, validating and calibrating techniques to find the best fit. This results in models for temperature, relative humidity and precipitation for each month of the year. In the same way, three isotopic models are derived from the spatial and meteorological variables (summer, winter and annual). Temperature has been shown to be controlled to a greater extent by altitude and latitude, while relative humidity is by latitude and precipitation in summer is by altitude and latitude. Monthly meteorological variables have been estimated throughout the study area. Precipitation δ18O and δ2H are controlled mainly by temperature and altitude and to a lesser extent by latitude, longitude and precipitation. In the same way, three isotopic models are derived from the spatial and meteorological variables: summer, winter and annual. This opens a new perspective of precipitation and its isotopic contents, but also allows the calculation of runoff and aquifer recharge and the path for linking future precipitation and aquifer recharge through their isotopic composition. [ABSTRACT FROM AUTHOR]

Summary: This paper presents an analysis on the hydrological regimes from several rivers flowing from the western slope of the Andes Cordillera. We compiled a database of 40 unimpaired average monthly streamflow records located in central and southern Chile, spanning the region between latitudes 30°S and 40°S and the period between years 1961 and 2006. River categories encompass snowmelt, mixed and rainfall dominated watersheds. The water year hydrograph center of timing (CT) is used as an indicator of flow regime and as a proxy for streamflow distribution throughout the year. The CT for each river is correlated to local climatic variables such as seasonal temperature and precipitation, and to large-scale circulation indexes. We assess CT trends using the Mann–Kendall test for varying time windows within the study period. Overall results for the 1961–2006 period show a significant (95% confidence level) negative trend (CT date shifting towards earlier in the year) for 23 out of the 40 analyzed series. However, when studying time windows within the entire period there seems to be a break in the trend during the late 1970s, with positive or null changes for the latter half of the study period for most of the stations analyzed. We found that even though the CT is significantly correlated (r >0.5) to temperature indexes in the snowfed watersheds, there has been no significant change in CT timing for most of these watersheds despite documented warming on the region. CT for all types of watersheds present clear correlation to precipitation indexes (r >0.8), and we observed high and significant correlation between CT and ONI, SOI and MEI indexes for all the study region: higher (lower) precipitation amounts during El Niño (La Niña), rather than temperature variations, seem to be the most important factor controlling CT timing during these episodes. In order of importance, the CT showed higher correlation with annual precipitation amounts and timing, MEI, ONI and SOI, mean winter and spring temperature, and finally PDO. The detected trends are consistent only with trends in precipitation, as rivers that showed high correlation to temperature do not show any trend. These conclusions suggest that rivers on the region show a different response to temperature changes when compared to rivers of similar regime in the northern hemisphere, and that precipitation amount and timing are the source of most of the variability in streamflow timing for both snowmelt and rainfall dominated watersheds. Temperature induced variability in streamflow timing should be studied with more precise hydrological models, as the CT has a complex behavior due to multiple climatical dependencies. Studying such behavior using only historical data might be insufficient for drawing more precise conclusions. [Copyright &y& Elsevier]

Abstract: The South American Low-Level Jet Experiment (SALLJEX) provided a unique dataset to investigate the existence of a mesoscale low-level circulation and of a diurnal cycle in its related convergence pattern over the Southeastern South American region east of the Andes, as well as its relationship with deep convection during the warm season. The present paper builds upon high-resolution analyses produced, assimilating the data collected during the SALLJEX field campaign using BRAMS, and explores their capability to reproduce mesoscale circulations not resolved by the low density observational network available in this region. Results of the analyses show a diurnal oscillation signal in the mean boundary layer convergence pattern over the plains with a nocturnal (daytime) convergence (divergence) maximum. These results are coherent with previous findings of a nocturnal phase in the mature stage of organized deep convection and related precipitation in subtropical latitudes east of the Andes during the warm season. The diurnal cycle of convergence/divergence in the boundary layer is described over a 15-day period, during which different synoptic conditions occurred. During weakly forced environments a regime characterized by nocturnal eastward anomaly flow and convergence and daytime westward anomaly flow and divergence related to a mesoscale northwestern mountain–central plain flow regime dominates over the plains between the Andes Mountains, the Parana River Valley, and the southern Brazil mountain range. In contrast, during synoptic conditions dominated by the presence of a deep thermal low over northwestern Argentina and a related low-level jet, convergence at night is mainly accomplished by the predominantly meridional low-level jet, which exhibits an anomalous weak wind speed diurnal cycle with respect to its summer climatological mean. On the other hand daytime divergence is completely produced by the zonal wind component as in the previous synoptic situation. Mesoscale circulations are altered (still effecting mean divergence in the domain, which exhibits a diurnal oscillation) upon the initiation of deep convective circulations in the evening in an increasingly convectively unstable atmosphere driven by a persistent horizontal advection of heat and moisture at low levels and forced by convergence generated by the low-level jet and the presence of a frontal zone. Convection intensifies at night when its related convergence over the plains comes in phase with the convergence related to the nocturnal maximum in the low-level jet. [Copyright &y& Elsevier]

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The article presents a study on the light reaching the ground vegetation in the high forest phase and its relation on the differences in forest structure of two selected sites, where one is on the slopes of Mount Andes and the other is at the extreme western edge of the Amazon basin. The authors state that their observations and analysis have enabled them to associated some of the differences between the two forests with differences in light climate. They mention that the interactions between light and other factors, specially root competition, may be very important. They believe that future studies on light as an ecological factor in tropical forests will most productively be aimed to the reaction of individual species to light at various stages of growth.

This study presents an assessment of the ability of the Hadley Centre Global Environment Model version 2—Earth system configuration (HadGEM2-ES)—in simulating the mid-latitude storm tracks over the Southern Hemisphere (SH). The storm tracks are primarily assessed using cyclone tracking using data from a 4 member ensemble of 27-year simulations of HadGEM2-ES over the historical period, and the European Centre for Medium-Range Weather Forecasts Interim Reanalysis. Both winter and summer periods are considered and contrasted. Results show that the storm track (ST) climatology of HadGEM2-ES presents similar patterns to those of the reanalysis. However, the model tends to represent the austral winter ST position with an equatorward bias and a zonal bias in the spiral towards the pole. The main differences were found during the austral winter, with large track density biases over the Indian Ocean indicating a poor representation of the ST in this specific region. This was found to be related to two factors. First, the large negative genesis biases over South America, Antarctic Peninsula and the Antarctic coast. Second, the model resolution and the representation of the Andes Mountains in South America. The link between STs and the large-scale circulation is examined and shows at upper levels an equatorward jet position bias of the subtropical jet and a negative bias in the eddy-driven, associated with a large cold bias over the extratropical and polar regions. The analysis of the large-scale circulation shows that the split jet during winter has problems in the model linked to these biases, including geopotential anomaly and sea surface temperature biases. Consequently, in general the track densities over the Southern oceans are underestimated in the austral winter. During summer, the results show the STs move poleward and there is a single eddy-driven jet, which is represented relatively well compared with the winter situation. These factors tend to reduce the differences seen in the cyclone track distribution biases. Although the model has biases in the ST behaviour in the SH it is still considered that these do not preclude this model being used for perturbation and future projection studies. [ABSTRACT FROM AUTHOR]

The purpose of this study is to assess the ability of a set of large ensembles (LE) of Global Climate Model (GCM) simulations from the Multi‐Model Large Ensemble Archive, Coupled Model Intercomparison Project Phase 6 (CMIP6) and database for Policy Decision making for Future climate change in reproducing the variability and change of the austral summer precipitation observed in South America along the second part of the 20th century and beginning of the 21st. LE show similar biases in the mean austral summer rainfall and interannual variability than those detected in previous model sets, such as the Coupled Model Intercomparison Project Phase 5 (CMIP5). The positive trends in south‐eastern South America (SESA) and negative ones in the southern Andes (SAn), that are the most significant observed regional features, are identified to some extent in LE simulations. The negative trend in SAn is a feature consistently shown among different models. For all models, mean trend is negative in that particular region and larger than the inter‐member dispersion for each large ensemble. Trend magnitudes in the SESA region show a larger dispersion between models than the SAn region. While the mean trend among models is consistent with the observations, models underestimate the observed trend. The multi‐model ensemble of selected models that best reproduce both mean and interannual variability features of rainfall in South America shows an 18% larger positive mean trend in SESA rainfall than those that have the worst performance. However, internal variability uncertainty is still higher than the mean trend for both sets of multi‐model ensembles [5% (18%) for selected (non‐selected) models]. Improvements in the representation of the main features of mean rainfall and variability are needed in order to better describe and reduce the uncertainties associated with the main climate change related signals in the continent. [ABSTRACT FROM AUTHOR]

The Atacama Desert in northern Chile is the driest place on Earth. In this region, climate models are subject to large biases, especially precipitation is significantly overestimated. Meteorological observations in the region are sparse and limited to inhabited places at the coast or the foothills of the Andes. To fill this gap, a new network of 15 automatic weather stations has been established beginning April 2017. These stations do not only record standard meteorological parameters such as temperature, humidity and wind, but also soil temperatures and humidity, additionally a wetness sensor gives information about the occurrence of fog. Data from the first year(s) of this network show a very regular wind pattern with easterly winds during night and morning and westerly winds from noon to evening. This wind transports moisture from the Pacific Ocean into the desert which forms fog during the night which may account for a moisture supply on the order of the rare precipitation events in the region. A few precipitation events have been observed during the first years. The recorded data allows to distinguish between different sources: convective precipitation above the Altiplano, which in some cases extended to the western slope of the Andes, and troughs extending from mid latitudes to the region, directing moist air from the pacific into the region. Both of these mechanisms brought only some tenths of mm precipitation. In one case the accidental combination of flow over the Andes and a weak cut-off low above the Pacific led to moisture convergence off the coast of northern Chile and initiated a convective system moving south-east ward which brought for the region extreme precipitation of 3-10 mm. • We present a new network of climate stations in the Atacama Desert • 15 Stations have been installed between the coast and 2500m AMSL and between 20°S and 25°S. • Wind measurements of the stations support the existence of the Rutlland circulation cell driven by the Andes. • Fog is a regular occurring phenomenon mainly during night with frequency and duration depending on location. • Precipitation occured on some occasions and is driven by certain synoptic situtations described in the paper. [ABSTRACT FROM AUTHOR]

Global warming can jeopardize important ecosystem functions and services in sensitive Neotropical mountain areas. However, untangling the relative roles of natural climate variability pattern from current global warming trends still represent a major challenge. Here, we propose a novel analytical approach based on Structural Equation Models to evaluate the relative roles of different sources of climate variability on tree growth. Specifically, we investigate direct and indirect linkages between Basal Area Increments (BAI) and a set of different climatic sources of variability, such as: (i) large-scale atmospheric oscillation patterns (i.e., the El Niño Southern Oscillation, ENSO and the Pacific Decadal Oscillation, PDO); and (ii) local meteorology in terms of temperature and precipitation. Additionally, we included in the SEM framework other important variables such as: (iii) calendar year (representative of temporal linear trends); and (iv) tree size (representative of main biological trends). Results indicate that the ENSO and PDO modulate minimum temperatures (Tmin) in the study area. These indices describe the oscillating behavior of the climatic modes (i.e., South Oscillation Index and PDO index) and are negatively correlated with Tmin. As such, they also influence tree growth (represented here by BAI) indirectly. Furthermore, through its direct impact on Tmin increase, ongoing climate warming has an indirect negative effect on BAI, thereby implying that the ongoing temperature rise could exert control on productivity in high mountain forests of the Andes, and that this influence could become more important with continued temperature increase. [ABSTRACT FROM AUTHOR]

Detecting and understanding historical changes in the frequency of geo-climatic hazards (G-CHs) is crucial for the quantification of current hazards and project them into the future. Here we focus in the eastern subtropical Andes (32–33 ∘ S), using meteorological data and a century-long inventory of 553 G-CHs triggered by rainfall or snowfall. We first analyse their spatio-temporal distributions and the role of climate variability in the year-to-year changes in the number of days per season with G-CHs. Precipitation is positively correlated with the number of G-CHs across the region and year-round; mean temperature is negatively correlated with snowfall-driven hazards in the western (higher) half of the study region during winter and with rainfall-driven hazards in the eastern zone during summer. The trends of the G-CH frequency since the mid-20th century were calculated, paying attention to their non-systematic monitoring. The G-CH series for the different triggers, zones and seasons were generally stationary. Nonetheless, there is a small positive trend in rainfall-driven G-CHs in the eastern zone during summer, congruent with a rainfall increase there. We also found a decrease in snowfall-driven G-CHs in the western zone from the late 1990s onwards, most likely due to a reduction in winter precipitation rather than to an increase in temperature. [ABSTRACT FROM AUTHOR]

A new gridded rainfall dataset available for Peru is introduced, called PISCOp V2.1 (Peruvian Interpolated data of SENAMHI's Climatological and Hydrological Observations). PISCOp has been developed for the period 1981 to the present, with an average latency of eight weeks at 0.1° spatial resolution. The merging algorithm is based on geostatistical and deterministic interpolation methods including three different rainfall sources: (i) the national quality-controlled and infilled raingauge dataset, (ii) radar-gauge merged precipitation climatologies and (iii) the Climate Hazards Group Infrared Precipitation (CHIRP) estimates. The validation results suggest that precipitation estimates are acceptable showing the highest performance for the Pacific coast and the western flank of the Andes. Furthermore, a meticulous quality-control and gap-infilling procedure allowed us to reduce the formation of inhomogeneities (non-climatic breaks). The dataset is publicly available at and is intended to support hydrological studies and water management practices. [ABSTRACT FROM AUTHOR]

Adaptive capacity and transformation to climate variability not only depend on the environmental conditions of a farm, but on the way in which farmers are able to face and change factors related to structural political, economic, and cultural dynamics. The objective of this research is to analyse how perceptions and traditional knowledge influence the resilience of farmers in the Colombian Andes, in the face of climate variability, through a set of qualitative methods. The main identified perceived causes of climate variability were deforestation and pollution, while greater solar radiation intensity was the most mentioned effect, linked to crops and biodiversity loss. The most extended adaptation strategies consisted of on-farm, short-term agricultural measures, which favour a certain degree of adaptation but are limited in their potential to build up resilience. This research provides insights on the feedback between the perceptions and traditional ecological knowledge of peasant communities and the social-ecological factors that enhance or hamper their resilience towards climate variability. It is argued that successful strategies must respond not only to climatic conditions, but to the transformation of unequal economic and political factors that hinder resilience. Including these factors in research and policy-making is fundamental if resilience is to be achieved. [ABSTRACT FROM AUTHOR]

The Cenozoic climate of tropical South America was fundamental to the development of its biota, the most biodiverse on Earth. No previous studies have explicitly addressed how the very different atmospheric composition and Atlantic geometry during the early Eocene (approximately 55 million years ago) may have affected South American climate. At that time, the Atlantic Ocean was approximately half of its current width and the CO2 concentration of Earth's atmosphere ranged from ~550 to ~1500 ppm or even higher. Climate model simulations were performed to examine the effects of these major state changes on the climate of tropical South America. Reducing the width of the Atlantic by approximately half produces significant drying relative to modern climate. Drying is only partly offset by an enhancement of precipitation due to the higher CO2 of the early Eocene. The main mechanism for drier conditions is simple. Low-level air crosses the tropical Atlantic from North Africa in much less time for a narrower Atlantic (2 days) than for the modern Atlantic (~6 days); as a result, much less water is evaporated into the air and thus there is far lower moisture imported to the continent in the Eocene simulation than in the modern control. The progressive wetting (during the mid- to late Cenozoic) of the Amazon due to the widening Atlantic and the rising Andes, only partly offset by decreasing CO2 values, may have been partly responsible for the accumulating biodiversity of this region. [ABSTRACT FROM AUTHOR]

The uncertainty of the precipitation parameter in the ECMWF twentieth-century (ERA-20C) centennial reanalysis is assessed by means of a comparison with the GPCC in situ product Full Data Monthly Version 7 (FDM-V7). For the spatial and temporal validation of ERA-20C, global temporal scores were calculated on monthly, seasonal, and annual time scales. These include contingency table scores, correlations, and differences in the trend, along with time series analyses. Not surprisingly, the regions with the strongest deviations correspond to regions with data scarcity, such as mountainous regions with their upwind and downwind effects, and monsoon regions. They all show a strong systematic bias (ERA-20C minus FDM-V7) and significant breaks in the time series. The mean annual global bias is about 37 mm, and the median is about 8 mm yr−1. Among the largest mean annual biases are, for example, 3361 mm in the southern Andes, 2603 mm in the Western Ghats, and 2682 mm in Papua New Guinea. However, if there is high station density, the precipitation distribution is correctly reproduced, even in orographically demanding regions such as the Alps. [ABSTRACT FROM AUTHOR]

Mesoscale convective systems (MCSs) climatology, the thermodynamic and dynamical variables, and teleconnections influencing MCSs development are assessed for the Paute basin (PB) in the Ecuadorian Andes from 2000 to 2009. The seasonality of MCSs occurrence shows a bimodal pattern, with higher occurrence during March-April (MA) and October-November (ON), analogous to the regional rainfall seasonality. The diurnal cycle of MCSs shows a clear nocturnal occurrence, especially during the MA and ON periods. Interestingly, despite the higher occurrence of MCSs during the rainy seasons, the monthly size relative frequency remains fairly constant throughout the year. On the east of the PB, the persistent high convective available potential and low convective inhibition values from midday to nighttime are likely related to the nocturnal development of the MCSs. A significant positive correlation between the MCSs occurrence to the west of the PB and the Trans-Niño index was found, suggesting that ENSO is an important source of interannual variability of MCSs frequency with increasing development of MCSs during warm ENSO phases. On the east of the PB, the variability of MCSs is positively correlated to the tropical Atlantic sea surface temperature anomalies south of the equator, due to the variability of the Atlantic subtropical anticyclone, showing main departures from this relation when anomalous conditions occur in the tropical Pacific due to ENSO. [ABSTRACT FROM AUTHOR]

We evaluated if two sigmodontine rodent taxa (Abrothrix olivacea and Phyllotis darwini) from the Andes and Coastal mountaintops of central Chile, experienced distributional shifts due to altitudinal movements of habitat and climate change during and after the Last Glacial Maximum (LGM). We tested the hypothesis that during LGM populations of both species experienced altitudinal shifts from the Andes to the lowlands and the coastal Cordillera, and then range retractions during interglacial towards higher elevations in the Andes. These distributional shifts may have left remnants populations on the mountaintops. We evaluated the occurrence of intraspecific lineages for each species, to construct distribution models at LGM and at present, as extreme climatic conditions for each lineage. Differences in distribution between extreme climatic conditions were interpreted as post-glacial distributional shifts. Abrothrix olivacea displayed a lineage with shared sequences between both mountain systems, whereas a second lineage was restricted to the Andes. A similar scenario of panmictic unit in the past was recovered for A. olivacea in the Andes, along with an additional unit that included localities from the rest of its distribution. For P. darwini, both lineages recovered were distributed in coastal and Andean mountain ranges at present as well, and structuring analyses for this species recovered coastal and Andean localities as panmictic units in the past. Niche modeling depicted differential postglacial expansions in the recovered lineages. Results suggest that historical events such as LGM triggered the descending of populations to Andean refuge areas (one of the A. olivacea’s lineages), to the lowlands, and to the coastal Cordillera. Backward movements of populations after glacial retreats may have left isolates on mountaintops of the coastal Cordillera, suggesting that current species distribution would be the outcome of climate change and habitat reconfiguration after LGM. [ABSTRACT FROM AUTHOR]

ABSTRACT This study develops a method for characterizing snow climatology in the Andes Mountains using the 8-day maximum binary snow cover product from the Moderate Resolution Imaging Spectroradiometer sensor. The objectives are to: (1) identify regions with similar snow patterns and (2) identify snow persistence zones within these regions. Within a study area between 8° and 39°S, snow regions are defined using the (1) minimum elevation of snow cover, (2) rate of change of snow persistence with elevation, and (3) timing of the minimum elevation snow cover. In tropical latitudes (8°-23°S), snow cover is constrained to high elevations (>5000 m), and these areas have steep changes in snow persistence with elevation. Minimal differences in the elevation of snow on the east and west sides of the range suggest that temperature is a primary control on snow presence. Snow cover has minimal seasonal variability in the Tropics between 8° and 14°S, but it peaks in austral fall (March) after the wet season from 14° to 23°S. In mid-latitudes (south of 23°S) snowline decreases in elevation with increasing latitude, and snow persistence changes with elevation are more gradual than in tropical regions. Snow cover peaks in the austral winter throughout the mid-latitudes. Differences in elevations of snow accumulation between the east and west sides of the Andes are greatest between 28° and 37°S, where high mountain peaks produce a strong orographic effect and precipitation shadow. Within the snow regions, four snow zones are defined based on the average fraction of the year that snow persists: (1) little or no snow, (2) intermittent, (3) seasonal, and (4) permanent snow zones. Tropical latitudes have snow cover only on the highest peaks. Areas of seasonal and permanent snow zones are greatest between latitudes 28° and 37°S as a result of higher precipitation than mountains further north and higher elevations than mountains further south. [ABSTRACT FROM AUTHOR]

A laser-optical disdrometer served as reference to assess the absolute percent bias of calculated rainfall intensity using the data of different-resolution tipping-bucket rain gauges classically applied by climatologists and hydrologists in the Andean region. Additionally, the impact of the calculation method (tip counting versus cubic spline interpolation) was examined. The combined effect was assessed for different rainfall intensity classes (0-0.99, 1-1.99, 2-4.99, and 5-10 mm.h-1) and timescales (5, 10, 30, and 60 min). Additionally, the variation in percent absolute bias of the Davis rain gauge, the collector most widely used in the study region, was defined with respect to the Texas rain gauge along an elevation gradient between 3300 and 4000 m a.s.l. Results reveal that the value of the percent absolute bias is largest for small rainfall intensities (≼2 mm.h-1) and short timescales (≼10 min), and decreases when the cubic spline interpolation is used. No relation was found between the error, the elevation, and rainfall depth along the gradient. Based on the research findings, it is recommended to measure precipitation in the high Andean mountain region with a high-resolution sensor and to consider cubic spline for the computation of intensities. [ABSTRACT FROM AUTHOR]

The Andes/Amazon transition is among the rainiest regions of the world and the interactions between large-scale circulation and the topography that determine its complex rainfall distribution remain poorly known. This work provides an in-depth analysis of the spatial distribution, variability, and intensity of rainfall in the southern Andes/Amazon transition, at seasonal and intraseasonal time scales. The analysis is based on comprehensive daily rainfall data sets from meteorological stations in Peru and Bolivia. We compare our results with high-resolution rainfall TRMM-PR 2A25 estimations. Hotspot regions are identified at low elevations in the Andean foothills (400-700 masl) and in windward conditions at Quincemil and Chipiriri, where more than 4000 mm rainfall per year are recorded. Orographic effects and exposure to easterly winds produce a strong annual rainfall gradient between the lowlands and the Andes that can reach 190 mm/km. Although TRMM-PR reproduces the spatial distribution satisfactorily, it underestimates rainfall by 35% in the hotspot regions. In the Peruvian hotspot, exceptional rainfall occurs during the austral dry season (around 1000 mm in June-July-August; JJA), but not in the Bolivian hotspot. The direction of the low-level winds over the Andean foothills partly explains this difference in the seasonal rainfall cycle. At intraseasonal scales in JJA, we found that, during northerly wind regimes, positive rainfall anomalies predominate over the lowland and the eastern flank of the Andes, whereas less rain falls at higher altitudes. On the other hand, during southerly regimes, rainfall anomalies are negative in the hotspot regions. The influence of cross-equatorial winds is particularly clear below 2000 masl. [ABSTRACT FROM AUTHOR]

Summertime [December-February (DJF)] precipitation over the western slopes of the subtropical Andes (32°-36°S) accounts for less than 10% of the annual accumulation, but it mostly occurs as rain and may trigger landslides leading to serious damages. Based on 13 year of reanalysis, in situ observations, and satellite imagery, a synoptic climatology and physical diagnosis reveal two main weather types lead to distinct precipitation systems. The most frequent type (~80% of the cases) occurs when a short-wave midlevel trough with weak winds and thermally driven mountain winds favor the development of convective precipitation during the daytime. The trough progresses northwest of a long-lasting warm ridge, which produces low-level easterly airflow that enhances its buoyancy as it moves over the arid land of western Argentina toward the Andes. The weak winds aloft facilitate the penetration of the moist easterly flow into the Andes. Midlevel flow coming from the west side of the Andes is decoupled from the low-level maritime air by a temperature inversion, and thus provides little moisture to support precipitation. The less frequent type (~20% of the cases) occurs when a deep midlevel trough and strong westerly flow produces stratiform precipitation. This type has a baroclinic nature akin to winter storms, except that they are rare in summer and there is no evidence of a frontal passage at low levels. The lifting and cooling ahead of the trough erode the typical temperature inversion over the Pacific coast, and thus allows upslope transport of low-level marine air by the strong westerlies forming a precipitating cloud cap on the western slope of the Andes. [ABSTRACT FROM AUTHOR]

In the Southern Hemisphere, a relatively well-known preferential pathway along which cold air surges equatorward is situated to the east of the Andes Mountains. In this study, a second preferred pathway is identified to the east of the African Highlands, with additional minor pathways identified east of the Brazilian Highlands and Madagascar. The primary objective of this study is to compare climatological and synoptic characteristics of extreme cold events (ECEs) along the Andes and African Highlands pathways. ECEs are defined as the top 1% coldest 925-hPa temperatures within the Andes and the African Highlands pathways using the 1977-2001 subset of the 2.5° × 2.5° 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40). ECEs within the Andes and African Highlands pathways are associated with dynamically forced anticyclogenesis and have low-level characteristics that vary substantially. Along the Andes pathway, ECEs feature 925-hPa temperatures as much as 17°C below normal, with 925-hPa southerly winds ranging from 0 to 10 m s−1 and 925-700-hPa lapse rates as low as −3°C km−1. In contrast, ECEs along the African Highlands pathway feature 925-hPa temperatures up to 10°C below normal, with 925-hPa southerly winds ranging from 5 to 15 m s−1, and 925-700-hPa lapse rates generally between 2° and 5°C km−1. Composite analyses reveal that despite stronger southerly winds, ECEs along the African Highlands pathway are typically not as cold or stable as those along the Andes pathway because cold air from Antarctica must traverse a longer distance over water to reach Africa. [ABSTRACT FROM AUTHOR]

The long-tailed pygmy rice rat Oligoryzomys longicaudatus (Sigmodontinae), the major reservoir of Hantavirus in Chile and Patagonian Argentina, is widely distributed in the Mediterranean, Temperate and Patagonian Forests of Chile, as well as in adjacent areas in southern Argentina. We used molecular data to evaluate the effects of the last glacial event on the phylogeographic structure of this species. We examined if historical Pleistocene events had affected genetic variation and spatial distribution of this species along its distributional range. We sampled 223 individuals representing 47 localities along the species range, and sequenced the hypervariable domain I of the mtDNA control region. Aligned sequences were analyzed using haplotype network, Bayesian population structure and demographic analyses. Analysis of population structure and the haplotype network inferred three genetic clusters along the distribution of O. longicaudatus that mostly agreed with the three major ecogeographic regions in Chile: Mediterranean, Temperate Forests and Patagonian Forests. Bayesian Skyline Plots showed constant population sizes through time in all three clusters followed by an increase after and during the Last Glacial Maximum (LGM; between 26,000-13,000 years ago). Neutrality tests and the "g" parameter also suggest that populations of O. longicaudatus experienced demographic expansion across the species entire range. Past climate shifts have influenced population structure and lineage variation of O. longicaudatus. This species remained in refugia areas during Pleistocene times in southern Temperate Forests (and adjacent areas in Patagonia). From these refugia, O. longicaudatus experienced demographic expansions into Patagonian Forests and central Mediterranean Chile using glacial retreats. [ABSTRACT FROM AUTHOR]

Paleoclimate reconstructions reveal that Earth system has experienced sub-millennial scale climate changes over the past two millennia in response to internal/external forcing. Although sub-millennial hydroclimate fluctuations have been detected in the central Andes during this interval, the timing, magnitude, extent and direction of change of these events remain poorly defined. Here, we present a reconstruction of hydroclimate variations on the Pacific slope of the central Andes based on exceptionally wellpreserved plant macrofossils and associated archaeological remains from a hyperarid drainage (Quebrada Maní, ∼21° S, 1000ma.s.l.) in the Atacama Desert. During the late Holocene, riparian ecosystems and farming social groups flourished in the hyperarid Atacama core as surface water availability increased throughout this presently sterile landscape. Twenty-six radiocarbon dates indicate that these events occurred between 1050-680, 1615-1350 and 2500- 2040 cal yr BP. Regional comparisons with rodent middens and other records suggest that these events were synchronous with pluvial stages detected at higher-elevations in the central Andes over the last 2500 yr. These hydroclimate changes also coincide with periods of pronounced SST gradients in the Tropical Pacific (La Niña-like mode), conditions that are conducive to significantly increased rainfall in the central Andean highlands and flood events in the low-elevation watersheds at inter-annual timescales. Our findings indicate that the positive anomalies in the hyperarid Atacama over the past 2500 yr represent a regional response of the central Andean climate system to changes in the global hydrological cycle at centennial timescales. Furthermore, our results provide support for the role of tropical Pacific sea surface temperature gradient changes as the primary mechanism responsible for climate fluctuations in the central Andes. Finally, our results constitute independent evidence for comprehending the major trends in cultural evolution of prehistoric peoples that inhabited the region. [ABSTRACT FROM AUTHOR]

Available proxy records witnessing palaeoclimate of the tropical Andes are comparably scarce. Major implications of palaeoclimate development in the humid and arid parts of the Andes are briefly summarized. The long-term behaviour of ENSO has general significance for the climatic history of the Andes due to its impact on regional circulation patterns and precipitation regimes, therefore ENSO history derived from non-Andean palaeo-records is highlighted. Methodological constraints of the chronological precision and the palaeoclimatic interpretation of records derived from different natural archives, such as glacier sediments and ice cores, lake sediments and palaeo-wetlands, pollen profiles and tree rings are addressed and complementary results concerning former climatic conditions are discussed in terms of possible implications of former atmospheric circulation patterns and main climatic forcing factors. During the last years, increasing tree-ring information is getting available from the tropical Andes, providing high-resolution climate-sensitive records covering the past centuries for the study of climate variability. [ABSTRACT FROM AUTHOR]

The boundary-layer structure of the Elqui Valley is investigated, which is situated in the arid north of Chile and extends from the Pacific Ocean in the west to the Andes in the east. The climate is dominated by the south-eastern Pacific subtropical anticyclone and the cold Humboldt Current. This combination leads to considerable temperature and moisture gradients between the coast and the valley and results in the evolution of sea and valley wind systems. The contribution of these mesoscale wind systems to the heat and moisture budget of the valley atmosphere is estimated, based on radiosoundings performed near the coast and in the valley. Near the coast, a well-mixed cloud-topped boundary layer exists. Both, the temperature and the specific humidity do not change considerably during the day. In the stratus layer the potential temperature increases, while the specific humidity decreases slightly with height. The top of the thin stratus layer, about 300 m in depth, is marked by an inversion. Moderate sea breeze winds of 3–4 m s−1 prevail in the sub-cloud and cloud layer during daytime, but no land breeze develops during the night. The nocturnal valley atmosphere is characterized by a strong and 900 m deep stably stratified boundary layer. During the day, no pronounced well-mixed layer with a capping inversion develops in the valley. Above a super-adiabatic surface layer of about 150 m depth, a stably stratified layer prevails throughout the day. However, heating can be observed within a layer above the surface 800 m deep. Heat and moisture budget estimations show that sensible heat flux convergence exceeds cold air advection in the morning, while both processes compensate each other around noon, such that the temperature evolution stagnates. In the afternoon, cold air advection predominates and leads to net cooling of the boundary layer. Furthermore, the advection of moist air results in the accumulation of moisture during the noon and afternoon period, while latent heat flux convergence is of minor relevance to the moisture budget of the boundary layer. [ABSTRACT FROM AUTHOR]

The quantitative estimation of paleoaltitude has become an increasing focus of Earth scientists because surface elevation provides constraints on the geodynamic mechanisms operating in mountain belts, as well as the influence of mountain belt growth on regional and global climate. The general observation of decreasing δ18O and δ²H values in rainfall as elevation increases has been used in both empirical and theoretical approaches to estimate paleoelevation. These studies rely on the preservation of ancient surface water compositions in authigenic minerals to reconstruct the elevation at the time the minerals were forming. In this review we provide a theory behind the application of stable isotope-based approaches to paleoaltimetry. We apply this theory to test cases using modern precipitation and surface water isotopic compositions to demonstrate that it generally accords well with observations. Examples of the application of paleoaltimetry techniques to Himalaya-Tibet and the Andes are discussed with implications for processes that cause surface uplift. [ABSTRACT FROM AUTHOR]