Capturing the influence of ENSO on land surface variables for Tropical South America

2020 ◽  
Author(s):  
Lina M. Estupinan-Suarez ◽  
Alexander Brenning ◽  
Fabian Gans ◽  
Guido Kraemer ◽  
Carlos A. Sierra ◽  
...  
Keyword(s):  
South America ◽  
Land Surface ◽  
Southern Oscillation ◽  
Northern Region ◽  
Climatic Conditions ◽  
Caribbean Region ◽  
Climate Data ◽  
Local Conditions ◽  
Non Linear ◽  
Tropical South America

<p>The response of tropical vegetation to El Niño Southern Oscillation (ENSO) is considered a main driver of global annual atmospheric CO2 concentrations at inter-annual time scales. ENSO warm and cold phases, El Niño and La Niña respectively, cause contrasting climatic conditions along tropical South America. While some regions experience wetter conditions during El Niño, such as  the Pacific coast, others regions such as the Amazon are exposed to warmer and drier climates. Besides this spatial variation, the biospheric response also differs between ENSO type and intensity, overruling of local conditions and ecosystems types. Due to this complexity, there is a lack of understanding on what ecosystems and regions are systematically affected by ENSO and how biospheric variables respond. Here, we analysed the Northern region of tropical South America covering tropical savannas, forests, and mountainous ecosystems in several countries. To do this, we assessed different land surface (e.g. GPP, NDVI,  FPAR, LST) and climate data streams compiled in the regional Earth System Data Lab (ESDL, https://www.earthsystemdatalab.net/) at 1 km and 10 km pixel size from 2001 to 2015. We applied Isomap, a non-linear dimensionality reduction method in the time domain for high dimensional dynamical systems. Our analysis was constrained to the fourth order continental basins and dominant land cover types. Land use change pixels were disregarded. Further, a comparison of ENSO indexes was conducted among basins. We found that isomap components  are able to capture the biosphere variability related to ENSO in basins that have been historically affected such as Magdalena-Cauca valleys and the Caribbean region. Implementation of non-linear methods increases our understanding of ENSO impacts spatially in regions where events intensity and frequency is increasing, and effective ecosystems management is urgent.</p>

scholarly journals New Insights on Land Surface-Atmosphere Feedbacks over Tropical South America at Interannual Timescales

Water ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 1095 ◽  
Author(s):  
Juan Bedoya-Soto ◽  
Germán Poveda ◽  
David Sauchyn
Keyword(s):  
South America ◽  
River Basin ◽  
Land Surface ◽  
Lower Troposphere ◽  
Surface Air Temperature ◽  
Specific Humidity ◽  
Volumetric Soil Water Content ◽  
Maximum Covariance Analysis ◽  
Non Linear ◽  
Tropical South America

We present a simplified overview of land-atmosphere feedbacks at interannual timescales over tropical South America as structural sets of linkages among surface air temperature (T), specific humidity at 925 hPa (q925), volumetric soil water content (Θ), precipitation (P), and evaporation (E), at monthly scale during 1979–2010. Applying a Maximum Covariance Analysis (MCA), we identify the modes of greatest interannual covariability in the datasets. Time series extracted from the MCAs were used to quantify linear and non-linear metrics at up to six-month lags to establish connections among variables. All sets of metrics were summarized as graphs (Graph Theory) grouped according to their highest ENSO-degree association. The core of ENSO-activated interactions is located in the Amazon River basin and in the Magdalena-Cauca River basin in Colombia. Within the identified multivariate structure, Θ enhances the interannual connectivity since it often exhibits two-way feedbacks with the whole set of variables. That is, Θ is a key variable in defining the spatiotemporal patterns of P and E at interannual time-scales. For both the simultaneous and lagged analysis, T activates non-linear associations with q925 and Θ. Under the ENSO influence, T is a key variable to diagnose the dynamics of interannual feedbacks of the lower troposphere and soil interfaces over tropical South America. ENSO increases the interannual connectivity and memory of the feedback mechanisms.

GCM sensitivity experiments with locally modified land surface properties over tropical South America

2006 ◽  
Vol 26 (7-8) ◽  
pp. 729-749 ◽  
Author(s):  
Čedo Branković ◽  
Franco Molteni ◽  
Pedro Viterbo
Keyword(s):  
South America ◽  
Surface Properties ◽  
Land Surface ◽  
Sensitivity Experiments ◽  
Tropical South America

The Amplification of the ENSO Forcing over Equatorial Amazon

2009 ◽  
Vol 10 (6) ◽  
pp. 1561-1568 ◽  
Author(s):  
Vasubandhu Misra
Keyword(s):  
South America ◽  
Diurnal Cycle ◽  
Land Surface ◽  
Large Scale ◽  
French Guiana ◽  
Southern Oscillation ◽  
Moisture Flux ◽  
Precipitation Anomalies ◽  
Upper Level

Abstract The remote influence of the El Niño–Southern Oscillation (ENSO) strongly manifests over the equatorial Amazon (EA)—including parts of southern Venezuela, Guyana, French Guiana, and Suriname—when there is a large-scale anomalous upper-level divergence over continental tropical South America. Modeling studies conducted in this paper suggest that it is because of the modulation of the local diurnal cycle of the moisture flux convergence, which results in the local amplification of the ENSO signal over the EA. Further, it is shown that the local land surface feedback plays a relatively passive but important role of maintaining these interannual precipitation anomalies over the EA region.

Atmospheric Circulation and Climatic Variability

2007 ◽  
Author(s):  
René D. Garreaud ◽  
Patricio Aceituno
Keyword(s):  
South America ◽  
Atmospheric Circulation ◽  
Amazon Basin ◽  
Southern Oscillation ◽  
Climatic Variability ◽  
Climatic Conditions ◽  
The West ◽  
The Andes ◽  
Weather And Climate ◽  
Atmospheric Phenomena

Regional variations in South America’s weather and climate reflect the atmospheric circulation over the continent and adjacent oceans, involving mean climatic conditions and regular cycles, as well as their variability on timescales ranging from less than a few months to longer than a year. Rather than surveying mean climatic conditions and variability over different parts of South America, as provided by Schwerdtfeger and Landsberg (1976) and Hobbs et al. (1998), this chapter presents a physical understanding of the atmospheric phenomena and precipitation patterns that explain the continent’s weather and climate. These atmospheric phenomena are strongly affected by the topographic features and vegetation patterns over the continent, as well as by the slowly varying boundary conditions provided by the adjacent oceans. The diverse patterns of weather, climate, and climatic variability over South America, including tropical, subtropical, and midlatitude features, arise from the long meridional span of the continent, from north of the equator south to 55°S. The Andes cordillera, running continuously along the west coast of the continent, reaches elevations in excess of 4 km from the equator to about 40°S and, therefore, represents a formidable obstacle for tropospheric flow. As shown later, the Andes not only acts as a “climatic wall” with dry conditions to the west and moist conditions to the east in the subtropics (the pattern is reversed in midlatitudes), but it also fosters tropical-extratropical interactions, especially along its eastern side. The Brazilian plateau also tends to block the low-level circulation over subtropical South America. Another important feature is the large area of continental landmass at low latitudes (10°N–20°S), conducive to the development of intense convective activity that supports the world’s largest rain forest in the Amazon basin. The El Niño–Southern Oscillation phenomenon, rooted in the ocean-atmosphere system of the tropical Pacific, has a direct strong influence over most of tropical and subtropical South America. Similarly, sea surface temperature anomalies over the Atlantic Ocean have a profound impact on the climate and weather along the eastern coast of the continent. In this section we describe the long-term annual and monthly mean fields of several meteorological variables.

scholarly journals Shifts in the Statistics of Daily Rainfall in South America Conditional on ENSO Phase

2008 ◽  
Vol 21 (5) ◽  
pp. 849-865 ◽  
Author(s):  
C. F. Ropelewski ◽  
M. A. Bell
Keyword(s):  
South America ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Daily Rainfall ◽  
Detailed Comparison ◽  
Gridded Data ◽  
Climate Data ◽  
Station Data ◽  
Geographical Regions

Abstract There are several well-documented studies showing the shifts in seasonal mean rainfall and temperature conditional on El Niño–Southern Oscillation (ENSO) phase. Here the shifts in the seasonal histograms of daily rainfall over South America conditional on ENSO phase are examined. The authors are motivated to analyze daily rainfall statistics over seasons by the demands for information on the shorter temporal scales voiced by users of climate data. In the first stage of the analysis the Kolmogorov–Smirnov (K-S) test is used, comparing El Niño to La Niña histograms of daily station data, to identify regions where there are significant shifts in the histograms. The K-S statistic analyses of daily station data are then compared to the same analyses performed on existing publicly available gridded station datasets. The degree to which the station and gridded data agree in showing geographical regions of significance provides evidence that the gridded fields might provide guidance on the nature of the ENSO signal where station data are not available. Further, the analysis of the gridded datasets can be used to motivate and guide efforts to obtain more complete daily data where the gridded datasets suggest an ENSO signal. As an example a detailed comparison of one station in southern Brazil and its nearest neighbors in the gridded data are presented, suggesting that, despite biases, the gridded fields are generally consistent with the station data where both are available. For many regions of the world neither daily station data nor daily gridded datasets are available for analysis. Thus despite documented and well-known regional biases in the precipitation fields available in the NCEP–NCAR reanalysis the extent to which shifts in the daily statistics of the NCEP–NCAR reanalysis precipitation are consistent with station and gridded station analyses is also examined. The preliminary work described here suggests that while the reanalysis does not ideally replicate the gridded station results the reanalysis may be useful as a tool for indicating candidate regions for further analysis with station or gridded data.

scholarly journals High-resolution hydraulic parameter maps for surface soils in tropical South America

2013 ◽  
Vol 6 (4) ◽  
pp. 6741-6774 ◽  
Author(s):  
T. R. Marthews ◽  
C. A. Quesada ◽  
D. R. Galbraith ◽  
Y. Malhi ◽  
C. E. Mullins ◽  
...  
Keyword(s):  
High Resolution ◽  
South America ◽  
Soil Profile ◽  
Land Surface ◽  
Water Movement ◽  
Land Surface Models ◽  
Hydraulic Parameter ◽  
Surface Models ◽  
Soil Hydraulic ◽  
Tropical South America

Abstract. Modern land surface model simulations capture soil profile water movement through the use of soil hydraulics sub-models, but good hydraulic parameterisations are often lacking, especially in the tropics. We present much-improved gridded datasets of hydraulic parameters for surface soil for the critical area of tropical South America, describing soil profile water movement across the region to 30 cm depth. Optimal hydraulic parameter values are given for the Brooks and Corey, Campbell, van Genuchten–Mualem and van Genuchten–Burdine soil hydraulic models, which are widely-used hydraulic sub-models in Land Surface Models. This has been possible through interpolating soil measurements from several sources through the SOTERLAC soil and terrain database and using the most recent pedotransfer functions (PTFs) derived for South American soils. All soil parameter data layers are provided at 15 arcsec resolution and available for download, this being 20 × higher resolution than the best comparable parameter maps available to date. Specific examples are given of the use of PTFs and the importance highlighted of using PTFs that have been locally-parameterised and that are not just based on soil texture. Details are provided specifically on how to assemble the ancillary data files required for grid-based vegetation simulation using the Joint UK Land Environment Simulator (JULES). We discuss current developments in soil hydraulic modelling and how high-resolution parameter maps such as these can improve the simulation of vegetation development and productivity in land surface models.

scholarly journals High-resolution hydraulic parameter maps for surface soils in tropical South America

2014 ◽  
Vol 7 (3) ◽  
pp. 711-723 ◽  
Author(s):  
T. R. Marthews ◽  
C. A. Quesada ◽  
D. R. Galbraith ◽  
Y. Malhi ◽  
C. E. Mullins ◽  
...  
Keyword(s):  
High Resolution ◽  
South America ◽  
Soil Profile ◽  
Land Surface ◽  
Water Movement ◽  
Land Surface Models ◽  
Hydraulic Parameter ◽  
Surface Models ◽  
Soil Hydraulic ◽  
Tropical South America

Abstract. Modern land surface model simulations capture soil profile water movement through the use of soil hydraulics sub-models, but good hydraulic parameterisations are often lacking, especially in the tropics. We present much-improved gridded data sets of hydraulic parameters for surface soil for the critical area of tropical South America, describing soil profile water movement across the region to 30 cm depth. Optimal hydraulic parameter values are given for the Brooks and Corey, Campbell, van Genuchten–Mualem and van Genuchten–Burdine soil hydraulic models, which are widely used hydraulic sub-models in land surface models. This has been possible through interpolating soil measurements from several sources through the SOTERLAC soil and terrain data base and using the most recent pedotransfer functions (PTFs) derived for South American soils. All soil parameter data layers are provided at 15 arcsec resolution and available for download, this being 20x higher resolution than the best comparable parameter maps available to date. Specific examples are given of the use of PTFs and the importance highlighted of using PTFs that have been locally parameterised and that are not just based on soil texture. We discuss current developments in soil hydraulic modelling and how high-resolution parameter maps such as these can improve the simulation of vegetation development and productivity in land surface models.

scholarly journals The influence of volcanic eruptions on the climate of tropical South America during the last millennium in an isotope-enabled general circulation model

2016 ◽  
Vol 12 (4) ◽  
pp. 961-979 ◽  
Author(s):  
Christopher M. Colose ◽  
Allegra N. LeGrande ◽  
Mathias Vuille
Keyword(s):  
South America ◽  
Oxygen Isotope ◽  
Southern Oscillation ◽  
Volcanic Eruptions ◽  
Hydrologic Cycle ◽  
South American ◽  
Last Millennium ◽  
Continental Scale ◽  
The Impact ◽  
Tropical South America

Abstract. Currently, little is known on how volcanic eruptions impact large-scale climate phenomena such as South American paleo-Intertropical Convergence Zone (ITCZ) position and summer monsoon behavior. In this paper, an analysis of observations and model simulations is employed to assess the influence of large volcanic eruptions on the climate of tropical South America. This problem is first considered for historically recent volcanic episodes for which more observations are available but where fewer events exist and the confounding effects of El Niño–Southern Oscillation (ENSO) lead to inconclusive interpretation of the impact of volcanic eruptions at the continental scale. Therefore, we also examine a greater number of reconstructed volcanic events for the period 850 CE to present that are incorporated into the NASA GISS ModelE2-R simulation of the last millennium. An advantage of this model is its ability to explicitly track water isotopologues throughout the hydrologic cycle and simulating the isotopic imprint following a large eruption. This effectively removes a degree of uncertainty associated with error-prone conversion of isotopic signals into climate variables, and allows for a direct comparison between GISS simulations and paleoclimate proxy records. Our analysis reveals that both precipitation and oxygen isotope variability respond with a distinct seasonal and spatial structure across tropical South America following an eruption. During austral winter, the heavy oxygen isotope in precipitation is enriched, likely due to reduced moisture convergence in the ITCZ domain and reduced rainfall over northern South America. During austral summer, however, more negative values of the precipitation isotopic composition are simulated over Amazonia, despite reductions in rainfall, suggesting that the isotopic response is not a simple function of the "amount effect". During the South American monsoon season, the amplitude of the temperature response to volcanic forcing is larger than the rather weak and spatially less coherent precipitation signal, complicating the isotopic response to changes in the hydrologic cycle.

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