scholarly journals On the Rainfall and Temperature Forecast Skill for a Tropical Andean Mountain Area in Northern South America Using Different Operational Weather Forecast Strategies: Role of the Diurnal Cycle of Rainfall on the Success of Data Assimilation

2020 ◽  
Author(s):  
Gisel Guzmán ◽  
Lina Isabel Ceballos ◽  
Juan Camilo Hernández ◽  
Mauricio Zapata Henao ◽  
Manuela Guarin Vargas ◽  
...  
Keyword(s):  
Data Assimilation ◽  
South America ◽  
Diurnal Cycle ◽  
Weather Forecast ◽  
Forecast Skill ◽  
Mountain Area ◽  
Temperature Forecast ◽  
Northern 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.

scholarly journals Andean uplift, drainage basin formation, and the evolution of riverweeds (Marathrum, Podostemaceae) in northern South America

2020 ◽  
Author(s):  
Ana M. Bedoya ◽  
Adam D. Leaché ◽  
Richard G. Olmstead
Keyword(s):  
South America ◽  
Landscape Change ◽  
Drainage Basin ◽  
Parental Line ◽  
List Type ◽  
Basin Formation ◽  
Northern South America ◽  
The Impact ◽  
River Drainages

SummaryNorthern South America is a geologically dynamic and species-rich region. While fossil and stratigraphic data show that reconfiguration of river drainages resulted from mountain uplift in the tropical Andes, investigations of the impact of landscape change on the evolution of the flora in the region have been restricted to terrestrial taxa.We explore the role of landscape change on the evolution of plants living strictly in rivers across drainage basins in northern South America by conducting population structure, phylogenomic, phylogenetic networks, and divergence-dating analyses for populations of riverweeds (Marathrum, Podostemaceae).We show that mountain uplift and drainage basin formation isolated populations of Marathrum and created barriers to gene flow across rivers drainages. Sympatric species hybridize and the hybrids show the phenotype of one parental line. We propose that the pattern of divergence of populations reflect the formation of river drainages, which was not complete until <4 MaOur study provides a clear picture of the role of landscape change in shaping the evolution of riverweeds in northern South America, advances our understanding of the reproductive biology of this remarkable group of plants, and spotlights the impact of hybridization in phylogenetic inference.

scholarly journals Assimilation of satellite NO<sub>2</sub> observations at high spatial resolution using OSSEs

2017 ◽  
Vol 17 (11) ◽  
pp. 7067-7081 ◽  
Author(s):  
Xueling Liu ◽  
Arthur P. Mizzi ◽  
Jeffrey L. Anderson ◽  
Inez Y. Fung ◽  
Ronald C. Cohen
Keyword(s):  
Data Assimilation ◽  
Transport Model ◽  
Weather Forecast ◽  
Forecast Errors ◽  
Nox Emissions ◽  
Chemical Transport Model ◽  
Model Framework ◽  
Simulation Experiments ◽  
High Space

Abstract. Observations of trace gases from space-based instruments offer the opportunity to constrain chemical and weather forecast and reanalysis models using the tools of data assimilation. In this study, observing system simulation experiments (OSSEs) are performed to investigate the potential of high space- and time-resolution column measurements as constraints on urban NOx emissions. The regional chemistry–meteorology assimilation system where meteorology and chemical variables are simultaneously assimilated is comprised of a chemical transport model, WRF-Chem, the Data Assimilation Research Testbed, and a geostationary observation simulator. We design OSSEs to investigate the sensitivity of emission inversions to the accuracy and uncertainty of the wind analyses and the emission updating scheme. We describe the overall model framework and some initial experiments that point out the first steps toward an optimal configuration for improving our understanding of NOx emissions by combining space-based measurements and data assimilation. Among the findings we describe is the dependence of errors in the estimated NOx emissions on the wind forecast errors, showing that wind vectors with a RMSE below 1 m s−1 allow inference of NOx emissions with a RMSE of less than 30 mol/(km2  ×  h) at the 3 km scale of the model we use. We demonstrate that our inference of emissions is more accurate when we simultaneously update both NOx emissions and NOx concentrations instead of solely updating emissions. Furthermore, based on our analyses, we recommend carrying out meteorology assimilations to stabilize NO2 transport from the initial wind errors before starting the emission assimilation. We show that wind uncertainties (calculated as a spread around a mean wind) are not important for estimating NOx emissions when the wind uncertainties are reduced below 1.5 m s−1. Finally, we present results assessing the role of separate vs. simultaneous chemical and meteorological assimilation in a model framework without covariance between the meteorology and chemistry.

scholarly journals Air quality variations in Northern South America during the COVID-19 lockdown

2020 ◽  
Vol 749 ◽  
pp. 141621 ◽  
Author(s):  
Juan F. Mendez-Espinosa ◽  
Nestor Y. Rojas ◽  
Jorge Vargas ◽  
Jorge E. Pachón ◽  
Luis C. Belalcazar ◽  
...  
Keyword(s):  
Air Quality ◽  
South America ◽  
Northern South America

Ground-motion model for subduction earthquakes in northern South America

2021 ◽  
pp. 875529302110275
Author(s):  
Carlos A Arteta ◽  
Cesar A Pajaro ◽  
Vicente Mercado ◽  
Julián Montejo ◽  
Mónica Arcila ◽  
...  
Keyword(s):  
South America ◽  
Ground Motion ◽  
Ground Motions ◽  
Strong Motion ◽  
Motion Prediction ◽  
Depth Range ◽  
Ground Motion Prediction ◽  
Natural Period ◽  
Nazca Plate ◽  
Northern South America

Subduction ground motions in northern South America are about a factor of 2 smaller than the ground motions for similar events in other regions. Nevertheless, historical and recent large-interface and intermediate-depth slab earthquakes of moment magnitudes Mw = 7.8 (Ecuador, 2016) and 7.2 (Colombia, 2012) evidenced the vast potential damage that vulnerable populations close to earthquake epicenters could experience. This article proposes a new empirical ground-motion prediction model for subduction events in northern South America, a regionalization of the global AG2020 ground-motion prediction equations. An updated ground-motion database curated by the Colombian Geological Survey is employed. It comprises recordings from earthquakes associated with the subduction of the Nazca plate gathered by the National Strong Motion Network in Colombia and by the Institute of Geophysics at Escuela Politécnica Nacional in Ecuador. The regional terms of our model are estimated with 539 records from 60 subduction events in Colombia and Ecuador with epicenters in the range of −0.6° to 7.6°N and 75.5° to 79.6°W, with Mw≥4.5, hypocentral depth range of 4 ≤  Zhypo ≤ 210 km, for distances up to 350 km. The model includes forearc and backarc terms to account for larger attenuation at backarc sites for slab events and site categorization based on natural period. The proposed model corrects the median AG2020 global model to better account for the larger attenuation of local ground motions and includes a partially non-ergodic variance model.

scholarly journals Co-occurrences of tropical trees in eastern South America: disentangling abiotic and biotic forces

Plant Ecology ◽  
2021 ◽  
Author(s):  
Emma-Liina Marjakangas ◽  
Otso Ovaskainen ◽  
Nerea Abrego ◽  
Vidar Grøtan ◽  
Alexandre A. de Oliveira ◽  
...  
Keyword(s):  
South America ◽  
Tree Species ◽  
Large Scale ◽  
Environmental Filtering ◽  
Limiting Similarity ◽  
Phylogenetic Relatedness ◽  
Biogeographical Regions ◽  
Dependent Processes ◽  
Occurrence Of Species

AbstractSpecies co-occurrences in local communities can arise independent or dependent on species’ niches. However, the role of niche-dependent processes has not been thoroughly deciphered when generalized to biogeographical scales, probably due to combined shortcomings of data and methodology. Here, we explored the influence of environmental filtering and limiting similarity, as well as biogeographical processes that relate to the assembly of species’ communities and co-occurrences. We modelled jointly the occurrences and co-occurrences of 1016 tropical tree species with abundance data from inventories of 574 localities in eastern South America. We estimated species co-occurrences as raw and residual associations with models that excluded and included the environmental effects on the species’ co-occurrences, respectively. Raw associations indicate co-occurrence of species, whereas residual associations indicate co-occurrence of species after accounting for shared responses to environment. Generally, the influence of environmental filtering exceeded that of limiting similarity in shaping species’ co-occurrences. The number of raw associations was generally higher than that of the residual associations due to the shared responses of tree species to the environmental covariates. Contrary to what was expected from assuming limiting similarity, phylogenetic relatedness or functional similarity did not limit tree co-occurrences. The proportions of positive and negative residual associations varied greatly across the study area, and we found a significant tendency of some biogeographical regions having higher proportions of negative associations between them, suggesting that large-scale biogeographical processes limit the establishment of trees and consequently their co-occurrences.

scholarly journals Beyond feasibility—the role of motivation to implement measures to enhance resilience

2021 ◽  
Vol 26 (5) ◽  
Author(s):  
Luzian Messmer ◽  
Braida Thom ◽  
Pius Kruetli ◽  
Evans Dawoe ◽  
Kebebew Assefa ◽  
...  
Keyword(s):  
Food Security ◽  
Conceptual Framework ◽  
General Framework ◽  
Rural Livelihoods ◽  
Weather Forecast ◽  
Reduced Tillage ◽  
Shade Trees ◽  
The World ◽  
Cocoa Farmers

AbstractMany regions around the world are experiencing an increase in climate-related shocks, such as drought. This poses serious threats to farming activities and has major implications for sustaining rural livelihoods and food security. Farmers’ ability to respond to and withstand the increasing incidence of drought events needs to be strengthened and their resilience enhanced. Implementation of measures to enhance resilience is determined by decisions of farmers and it is important to understand the reasons behind their behavior. We assessed the viability of measures to enhance resilience of farmers to drought, by developing a general framework that covers economic-technical and psychological-cognitive aspects, here summarized under the terms (1) motivation and (2) feasibility. The conceptual framework was applied to cocoa farmers in Ghana and tef farmers in Ethiopia by using questionnaire-based surveys. A portfolio of five specific measures to build resilience (i.e., irrigation, shade trees, fire belts, bookkeeping, mulching, early mature varieties, weather forecast, reduced tillage, improved harvesting) in each country was evaluated with a closed-ended questionnaire that covered the various aspects of motivation and feasibility whereby farmers were asked to (dis)agree on a 5-point Likert scale. The results show that if the motivation mean score is increased by 0.1 units, the probability of implementation increases by 16.9% in Ghana and by 7.7% in Ethiopia. If the feasibility mean score is increased by 0.1 units, the probability of implementation increases by 24.9% in Ghana and by 11.9% in Ethiopia. We can conclude that motivation and feasibility matter, and we improve our understanding of measure implementation if we include both feasibility and motivation into viability assessments.

STUDIES ON STRONGYLOIDES AGOUTII SP. NOV. FROM THE AGOUTI (DASYPROCTA AGOUTI)

1940 ◽  
Vol 18d (5) ◽  
pp. 173-190 ◽  
Author(s):  
Henry J. Griffiths
Keyword(s):  
Seasonal Variation ◽  
South America ◽  
Biological Study ◽  
Free Living ◽  
Classical Studies ◽  
Group A ◽  
Northern South America

A morphological and biological study is presented of a hitherto unrecorded member of the genus Strongyloides from the golden-rumped agouti (Dasyprocta agouti), a rodent native to Trinidad, B.W.I., and northern South America. The name Strongyloides agoutii sp. nov. is proposed for this species.Observations on the free-living development over a period of three years showed the indirect type to prevail; no seasonal variation was observed. Continuous propagation of the free-living generation of this species was not observed in faecal cultures or on artificial media.A brief résumé of the classical studies on species of the genus Strongyloides is included, together with a summary of existing hypotheses and theories on the biology of this group. A list of species and hosts for this genus is given.

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