Subseasonal prediction performance for South American land–atmosphere coupling in extended austral summer

Abstract Amazonian deforestation has accelerated during the last decade, threatening an ecosystem where almost one third of the regional rainfall is transpired by the local rainforest. Due to the precipitation recycling, the southwestern Amazon, including the Amazon-Andes transition region, is particularly sensitive to forest loss. This study evaluates the impacts of Amazonian deforestation in the hydro-climatic connectivity between the Amazon and the eastern tropical Andes during the austral summer (December-January-February) in terms of hydrological and energetic balances. Using 10-year high-resolution simulations (2001–2011) with the Weather Research and Forecasting Model, we analyze control and deforestation scenario simulations. Regionally, deforestation leads to a reduction in the surface net radiation, evaporation, moisture convergence and precipitation (~ 20%) over the entire Amazon basin. In addition, during this season, deforestation increases the atmospheric subsidence over the southern Amazon and weakens the regional Hadley cell. Atmospheric stability increases over the western Amazon and the tropical Andes inhibiting convection in these areas. Consequently, major deforestation impacts are observed over the hydro-climate of the Amazon-Andes transition region. At local scale, nighttime precipitation decreases in Bolivian valleys (~ 20–30%) due to a strong reduction in the humidity transport from the Amazon plains toward Andes linked to the South American low-level jet. Over these valleys, a weakening of the daytime upslope winds is caused by local deforestation, which reduces the turbulent fluxes at lowlands. These alterations in rainfall and atmospheric circulation could impact the rich Andean ecosystems and its tropical glaciers.

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Centennial-scale precipitation anomalies in the southern Altiplano (18° S) suggest an extratropical driver for the South American summer monsoon during the late Holocene

Climate of the Past ◽

10.5194/cp-15-1845-2019 ◽

2019 ◽

Vol 15 (5) ◽

pp. 1845-1859 ◽

Cited By ~ 2

Author(s):

Ignacio A. Jara ◽

Antonio Maldonado ◽

Leticia González ◽

Armand Hernández ◽

Alberto Sáez ◽

...

Keyword(s):

Summer Monsoon ◽

Large Scale ◽

Southern Oscillation ◽

Atlantic Coast ◽

Austral Summer ◽

High Elevation ◽

South American ◽

Tropical Andes ◽

The South ◽

Precipitation Anomalies

Abstract. Modern precipitation anomalies in the Altiplano, South America, are closely linked to the strength of the South American summer monsoon (SASM), which is influenced by large-scale climate features sourced in the tropics such as the Intertropical Convergence Zone (ITCZ) and El Niño–Southern Oscillation (ENSO). However, the timing, direction, and spatial extent of precipitation changes prior to the instrumental period are still largely unknown, preventing a better understanding of the long-term drivers of the SASM and their effects over the Altiplano. Here we present a detailed pollen reconstruction from a sedimentary sequence covering the period between 4500 and 1000 cal yr BP in Lago Chungará (18∘ S; 4570 m a.s.l.), a high-elevation lake on the southwestern margin of the Altiplano where precipitation is delivered almost exclusively during the mature phase of the SASM over the austral summer. We distinguish three well-defined centennial-scale anomalies, with dry conditions between 4100–3300 and 1600–1000 cal yr BP and a conspicuous humid interval between 2400 and 1600 cal yr BP, which resulted from the weakening and strengthening of the SASM, respectively. Comparisons with other climate reconstructions from the Altiplano, the Atacama Desert, the tropical Andes, and the southwestern Atlantic coast reveal that – unlike modern climatological controls – past precipitation anomalies at Lago Chungará were largely decoupled from north–south shifts in the ITCZ and ENSO. A regionally coherent pattern of centennial-scale SASM variations and a significant latitudinal gradient in precipitation responses suggest the contribution of an extratropical moisture source for the SASM, with significant effects on precipitation variability in the southern Altiplano.

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The influence of ENSO on South American precipitation during austral summer and autumn in observations and models

International Journal of Climatology ◽

10.1002/joc.4371 ◽

2015 ◽

Vol 36 (2) ◽

pp. 618-635 ◽

Cited By ~ 29

Author(s):

Renata G. Tedeschi ◽

Matthew Collins

Keyword(s):

Austral Summer ◽

South American

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A mid-Holocene climate reconstruction for eastern South America

Climate of the Past ◽

10.5194/cp-9-2117-2013 ◽

2013 ◽

Vol 9 (5) ◽

pp. 2117-2133 ◽

Cited By ~ 46

Author(s):

L. F. Prado ◽

I. Wainer ◽

C. M. Chiessi ◽

M.-P. Ledru ◽

B. Turcq

Keyword(s):

South America ◽

Late Holocene ◽

Austral Summer ◽

South Atlantic Convergence Zone ◽

Northeastern Brazil ◽

South American ◽

The South ◽

Holocene Climate ◽

Sea Temperature ◽

Summer Insolation

Abstract. The mid-Holocene (6000 calibrated years before present) is a key period in palaeoclimatology because incoming summer insolation was lower than during the late Holocene in the Southern Hemisphere, whereas the opposite happened in the Northern Hemisphere. However, the effects of the decreased austral summer insolation over South American climate have been poorly discussed by palaeodata syntheses. In addition, only a few of the regional studies have characterised the mid-Holocene climate in South America through a multiproxy approach. Here, we present a multiproxy compilation of mid-Holocene palaeoclimate data for eastern South America. We compiled 120 palaeoclimatological datasets, which were published in 84 different papers. The palaeodata analysed here suggest a water deficit scenario in the majority of eastern South America during the mid-Holocene if compared to the late Holocene, with the exception of northeastern Brazil. Low mid-Holocene austral summer insolation caused a reduced land–sea temperature contrast and hence a weakened South American monsoon system circulation. This scenario is represented by a decrease in precipitation over the South Atlantic Convergence Zone area, saltier conditions along the South American continental margin, and lower lake levels.

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Precipitation Characteristics of the South American Monsoon System Derived from Multiple Datasets

Journal of Climate ◽

10.1175/jcli-d-11-00335.1 ◽

2012 ◽

Vol 25 (13) ◽

pp. 4600-4620 ◽

Cited By ~ 33

Author(s):

Leila M. V. Carvalho ◽

Charles Jones ◽

Adolfo N. D. Posadas ◽

Roberto Quiroz ◽

Bodo Bookhagen ◽

...

Keyword(s):

South America ◽

Large Scale ◽

Austral Summer ◽

Global Precipitation Climatology Project ◽

South American ◽

The South ◽

Frequency Distributions ◽

South American Monsoon ◽

Monsoon System ◽

South American Monsoon System

Abstract The South American monsoon system (SAMS) is the most important climatic feature in South America and is characterized by pronounced seasonality in precipitation during the austral summer. This study compares several statistical properties of daily gridded precipitation from different data (1998–2008): 1) Physical Sciences Division (PSD), Earth System Research Laboratory [1.0° and 2.5° latitude (lat)/longitude (lon)]; 2) Global Precipitation Climatology Project (GPCP; 1° lat/lon); 3) Climate Prediction Center (CPC) unified gauge (CPC-uni) (0.5° lat/lon); 4) NCEP Climate Forecast System Reanalysis (CFSR) (0.5° lat/lon); 5) NASA Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis (0.5° lat/0.3° lon); and 6) Tropical Rainfall Measuring Mission (TRMM) 3B42 V6 data (0.25° lat/lon). The same statistical analyses are applied to data in 1) a common 2.5° lat/lon grid and 2) in the original resolutions of the datasets. All datasets consistently represent the large-scale patterns of the SAMS. The onset, demise, and duration of SAMS are consistent among PSD, GPCP, CPC-uni, and TRMM datasets, whereas CFSR and MERRA seem to have problems in capturing the correct timing of SAMS. Spectral analyses show that intraseasonal variance is somewhat similar in the six datasets. Moreover, differences in spatial patterns of mean precipitation are small among PSD, GPCP, CPC-uni, and TRMM data, while some discrepancies are found in CFSR and MERRA relative to the other datasets. Fitting of gamma frequency distributions to daily precipitation shows differences in the parameters that characterize the shape, scale, and tails of the frequency distributions. This suggests that significant uncertainties exist in the characterization of extreme precipitation, an issue that is highly important in the context of climate variability and change in South America.

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Fishers' perception of the interaction between the South American sea lions and the Chinook salmon fishery in southern Chile

Scientific Reports ◽

10.1038/s41598-021-93675-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

M. Sanguinetti ◽

B. Cid-Aguayo ◽

A. Guerrero ◽

M. Durán ◽

D. Gomez-Uchida ◽

...

Keyword(s):

Chinook Salmon ◽

Native Species ◽

Formal Education ◽

Austral Summer ◽

Economic Losses ◽

Attack Behavior ◽

South American ◽

The South ◽

Sea Lions ◽

The Relationship

AbstractWe studied how the South American sea lion (SASL, Otaria flavescens) interacts with the operation of an artisanal fishery of Chinook salmon, a non-native species in Chile, using a combination of biological and social approaches, including a valuation by fishers about this interaction. During austral summer of 2019, an observer onboard artisanal fishing boats characterized the attack behavior of SASLs to gillnet-captured Chinook salmon during 33 hauls and analyzed which factors may affect the intensity of attacks. To analyze the relationship between fishers and SASLs, a Likert scale about the perception and views about nature was applied. A total of 23 interviews—including 35 open and 16 closed questions—with fishers were conducted to describe how they perceived the interactions with SASLs. Interactions with SASLs were recorded in 35% of the fishing events and varied depending on both operational factors, such as the number of boats, as well as environmental factors, such as moon’s luminosity. Even though SASL interactions resulted in seven fish (~ 70 kg) damaged of a total catch of 2815 kg (2.5%) during the survey, boats with a damaged catch by SASL lost up to 11% of their revenue. This is consistent with 87% of the interviewed fishers who considered that the conflict with the SASL negatively impacts their activity and results in economic losses. A negative perception towards SASLs likely results from personal experience and revenue loss, even though impacts of SASL interactions at the scale of the entire fishery may be less important. While older fishers with less formal education have a productivist and instrumental focus, younger fishers with a more sustainable and conservationist view of fishing offer an opportunity to lead an improved local understanding of the relationship between salmon, SASLs, and humans.

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Inter-El Niño variability and its impact on the South American low-level jet east of the Andes during austral summer − two case studies

Advances in Geosciences ◽

10.5194/adgeo-6-283-2006 ◽

2006 ◽

Vol 6 ◽

pp. 283-287 ◽

Cited By ~ 20

Author(s):

G. A. M. Silva ◽

T. Ambrizzi

Keyword(s):

El Niño ◽

El Nino ◽

Austral Summer ◽

South American ◽

The South ◽

Trade Winds ◽

Low Level ◽

The Andes ◽

Low Level Jet ◽

The Impact

Abstract. The impact of the maximum convection location over eastern and central Equatorial Pacific over the intensity and positioning of the South American Low-Level Jet east of the Andes (SALLJ) during the austral summer was investigated. The Bonner criteria 1 was applied to the NCEP-NCAR circulation fields during the El Niño of 1997/1998 and 2002/2003 to identify the SALLJ episodes. The composites of the atmospheric circulation over the South America during El Niño events showed that the SALLJ can be influenced by small displacements of the quasi-stationary Rossby waves position. During the strong El Niño event of 1997/1998 the SALLJ is maintained by the eastern trade winds. A low-level anomalous anticyclonic circulation over the central part of Brazil enhanced the wind in the nucleus of the jet and displaced its axis to the Northern Argentina and South of Brazil. However, the northern trade winds seem to maintain the SALLJ during the weak El Niño of 2002/2003. The jet was weaker and displaced more southeastward of Brazil than during the strong event.

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Assessment of ECMWF SEAS5 Seasonal Forecast Performance over South America

Weather and Forecasting ◽

10.1175/waf-d-19-0106.1 ◽

2019 ◽

Vol 35 (2) ◽

pp. 561-584 ◽

Cited By ~ 7

Author(s):

S. Gubler ◽

K. Sedlmeier ◽

J. Bhend ◽

G. Avalos ◽

C. A. S. Coelho ◽

...

Keyword(s):

South America ◽

Minimum Temperature ◽

High Performance ◽

Austral Summer ◽

Prediction Performance ◽

Dynamical Model ◽

Maximum Temperature ◽

Forecast Performance ◽

Empirical Prediction ◽

The North

Abstract Seasonal predictions have a great socioeconomic potential if they are reliable and skillful. In this study, we assess the prediction performance of SEAS5, version 5 of the seasonal prediction system of the European Centre for Medium-Range Weather Forecasts (ECMWF), over South America against homogenized station data. For temperature, we find the highest prediction performances in the tropics during austral summer, where the probability that the predictions correctly discriminate different observed outcomes is 70%. In regions lying to the east of the Andes, the predictions of maximum and minimum temperature still exhibit considerable performance, while farther to the south in Chile and Argentina the temperature prediction performance is low. Generally, the prediction performance of minimum temperature is slightly lower than for maximum temperature. The prediction performance of precipitation is generally lower and spatially and temporally more variable than for temperature. The highest prediction performance is observed at the coast and over the highlands of Colombia and Ecuador, over the northeastern part of Brazil, and over an isolated region to the north of Uruguay during DJF. In general, Niño-3.4 has a strong influence on both air temperature and precipitation in the regions where ECMWF SEAS5 shows high performance, in some regions through teleconnections (e.g., to the north of Uruguay). However, we show that SEAS5 outperforms a simple empirical prediction based on Niño-3.4 in most regions where the prediction performance of the dynamical model is high, thereby supporting the potential benefit of using a dynamical model instead of statistical relationships for predictions at the seasonal scale.

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Summertime Moisture Transport to the Southern South American Altiplano: Constraints from In Situ Measurements of Water Vapor Isotopic Composition

Journal of Climate ◽

10.1175/jcli-d-14-00511.1 ◽

2015 ◽

Vol 28 (7) ◽

pp. 2635-2649 ◽

Cited By ~ 16

Author(s):

Joseph Galewsky ◽

Kimberly Samuels-Crow

Keyword(s):

Water Vapor ◽

Isotopic Composition ◽

Austral Summer ◽

Dry Season ◽

In Situ Measurements ◽

South American ◽

Moist Air ◽

Wet Season ◽

Rayleigh Distillation

Abstract Austral summer transport of water vapor to the southern South American Altiplano is investigated using in situ measurements of water vapor isotopic composition collected from 1 November 2012 to 10 February 2013 on the Chajnantor Plateau in the Chilean Andes. Onset of the wet season in December was associated with an increase in mixing ratios from an average of 1500 ppmv during the winter dry season to 5400 ppmv in early December. Water vapor isotopes δD and δ18O increased from dry season averages of −235‰ and −31‰, respectively, to wet season averages of −142‰ and −17‰, reaching as high as −70‰ and −17‰, respectively. The highest water vapor δ values were close to those measured in coastal settings, suggesting little condensation during transport to the site. About 5% of the wet season data have δ values that are lower than expected for Rayleigh distillation and are associated with high relative humidity (>75%), easterly winds, and periods of low outgoing longwave radiation over the Altiplano, consistent with moistening by deep convection. The remainder of the data have δ values that are greater than expected for Rayleigh distillation, up to 250‰ above the Rayleigh curve. These data are consistent with mixing between very dry air and moist air from the boundary layer. The data show intraseasonal variability coherently linked to the position of the Bolivian high, with moist air associated with a southward displacement in the Bolivian high. The humidity over the southern Altiplano during the wet season reflects a balance among advective drying, advective moistening with little condensation, and convective moistening.

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