Low‐level circulation and precipitation simulated by CMIP5 GCMS over southeastern South America

Barros, Vicente; Doyle, Moira Evelina

doi:10.1002/joc.5740

Cited by 19 publications

(20 citation statements)

References 64 publications

(104 reference statements)

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“…This study proposes that a thorough understanding of the SALLJ should be studied considering the variability of the lowlevel jet along the entire eastern Andes. In general, global climate models have difficulty in simulating the low-level flow on the eastern Andes, 31 and, consequently, realistically representing water vapor transport in South America. To increase the confidence in climate projections, global climate models need to be able to represent the variability of the SALLJ as shown in this study based on ERA-I reanalysis.…”

Section: Discussionmentioning

confidence: 99%

Recent changes in the South America low-level jet

Jones

2019

npj Clim Atmos Sci

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level Jet (SALLJ) is a climatological feature with a critical role in the spatiotemporal distribution of precipitation in South America. While previous studies have focused on the mechanisms and variability of the SALLJ in the central Andes (i.e., southeast Peru, Bolivia, and Paraguay), the occurrence of the low-level jet in the eastern slopes of the northern Andes (i.e., northeast Peru, Colombia, and Venezuela) and its linkages to the central region have not been previously explored. This study shows that the SALLJ in the northern branch exceeds 10 m s −1 during September-February and the frequency can be as high as in the central region. Moreover, the SALLJ can occur simultaneously or separately in both regions. When the SALLJ is active only in the northern branch, wind speeds are very low from Bolivia towards southeast South America (SESA) and precipitation is significantly reduced (1-4 mm day −1) from climatology. In contrast, precipitation increases over eastern Bolivia by 2-4 mm day −1. Composites suggest that the SALLJ northern branch is forced by a large-scale circulation pattern with the enhancement of the North Atlantic Subtropical High driving northeasterly winds over the northern Andes. Further analysis shows that the frequency and intensity of the SALLJ in the northern Andes has substantially increased in the last 39 years.

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Section: Discussionmentioning

confidence: 99%

Recent changes in the South America low-level jet

Jones

2019

npj Clim Atmos Sci

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“…Studies by different authors have concluded that, compared to observations, GCMs produce higher total precipitation amounts and a greater precipitation frequency, thus leading to a more active water cycle than the observed (Stephens et al ., ; Tian et al ., ; Demory et al ., , among others). In southern South America, though in general models have an adequate representation of the low‐level circulation (Barros and Doyle, ), the moisture transport from the Amazon region necessary for the warm season precipitation is not captured adequately, hence underestimating the annual precipitation and the annual cycle. The different ways in which the Andes Mountains are represented within GCMs in conjunction with the horizontal resolution used by the model, are also factors which determine moisture fluxes and precipitation in Argentina (Saurral et al ., ).…”

Section: Discussionmentioning

confidence: 99%

“…Projection experiments are conducted with a same set of prescribed greenhouse gases (GHG) emission scenarios (Taylor et al ., ). Monthly data of simulations from 18 GCM experiments were selected for the present study based on a previous study for the region (Gulizia and Camilloni, ; Barros and Doyle, ) and the availability of model outputs. Table shows a short description of the CMIP5 models analysed, indicating horizontal resolution, the institution and country where they were run.…”

Section: Methodsmentioning

confidence: 99%

“…To understand the reliability of such simulations in future scenarios, the quantification of biases and uncertainties in precipitation resulting from climate simulations is fundamental. Many studies have analysed the ability of models to represent monthly, seasonal, or annual totals (Gulizia and Camilloni, ; Vera and Diaz, ; Barros and Doyle, , among others) in southern South America; however, a study about the changes in precipitation seasonality and how models capture this characteristic in the region is lacking. Through a series of metrics, this paper will characterize seasonality of precipitation in southern South America and its changes during the past decades and asses the capability of CMIP5 GCMs to reproduce it.…”

Section: Introductionmentioning

confidence: 99%

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Observed and simulated changes in precipitation seasonality in Argentina

Doyle

2019

Intl Journal of Climatology

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Seasonality in Argentina is examined using precipitation observations from 56 weather stations north of 42°S and CRU gridded precipitation. The Walsh and Lawler Seasonality Index (SI) and Precipitation Concentration Index (PCI) are calculated to determine the different seasonality regimes. The main characteristic is an eastwest gradient, where precipitation tends to be more evenly distributed throughout the different months of the year in the east while rainfall in the west is concentrated in 3 months or less. High replicability values indicate that the wettest month generally occurs during a same period of months in central and northern Argentina. Several stations in eastern humid Argentina have significant positive changes in the mean of seasonality indices between 1961 and 1985 and 1986 and 2010, and increasing trend. In most cases this leads to a change in the regime from rather seasonal with a short dry season to a seasonal regime. Through a PAM Clustering technique a new regionalization of precipitation seasonality is obtained. The mean series in each cluster show a tendency towards more seasonal and highly seasonal regimes in all regions. The SI and PCI indices were calculated using the precipitation outputs of 18 global climate models (GCMs) from the Coupled Model Inter‐comparison Project Phase 5 (CMIP5) to examine the ability of these models to represent seasonality spatial distribution and changes in Argentina. To some extent the spatial distribution of seasonality is captured by models; however, there are considerable discrepancies in the location and extension of the eastwest gradient. The sign and location of trends and changes in the mean SI and PCI are adequately reproduced in only a few models. The low ability of GCMs to represent seasonality and its changes is a consequence of the difficulties GCMs have simulating precipitation characteristics in Argentina reported by different authors.

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“…From reanalysis data, the SALLJ intensity, frequency (Jones, 2019), and moisture flux (Montini et al, 2019) have shown an increase in the last decades in most of the seasons, affecting precipitation in the eastern Andes. Further studies are needed to understand how these changes will be projected in a warmer climate, which will require improvements in global models to better representing the low-level circulation in the region (Barros and Doyle, 2018). In addition, interactions between large-scale atmospheric features (Intertropical Convergence Zone (ITCZ), SAMS, Bolivian High, Hadley, and Walker cell, etc.…”

Section: Summary and Open Research Questionsmentioning

confidence: 99%

Hydroclimate of the Andes Part I: Main Climatic Features

et al. 2020

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The Andes is the longest cordillera in the world and extends from northern South America to the southern extreme of the continent (from 11 • N to 53 • S). The Andes runs through seven countries and is characterized by a wide variety of ecosystems strongly related to the contrasting climate over its eastern and western sides, as well as along its latitudinal extension. This region faces very high potential impacts of climate change, which could affect food and water security for about 90 million people. In addition, climate change represents an important threat on biodiversity, particularly in the tropical Andes, which is the most biodiverse region on Earth. From a scientific and societal view, the Andes exhibits specific challenges because of its unique landscape and the fragile equilibrium between the growing population and its environment. In this manuscript, we provide an updated review of the most relevant scientific literature regarding the hydroclimate of the Andes with an integrated view of the entire Andes range. This review paper is presented in two parts. Part I is dedicated to summarize the scientific knowledge about the main climatic features of the Andes, with emphasis on mean large-scale atmospheric circulation, the Andes-Amazon hydroclimate interconnections and the most distinctive diurnal and annual cycles of precipitation. Part II, which is also included in the research topic "Connecting Mountain Hydroclimate Through the American Cordilleras," focuses on the hydroclimate variability of the Andes at the sub-continental scale, including the effects of El Niño-Southern Oscillation.

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Low‐level circulation and precipitation simulated by CMIP5 GCMS over southeastern South America

Cited by 19 publications

References 64 publications

Recent changes in the South America low-level jet

Recent changes in the South America low-level jet

Observed and simulated changes in precipitation seasonality in Argentina

Hydroclimate of the Andes Part I: Main Climatic Features

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