Western Central Brazil Research Articles

Onset and demise dates of the rainy season in the South American monsoon region: A cluster analysis result

AbstractThis work proposes an adaptation of the method developed in previous papers to determine the onset and demise of the rainy season (ONR and DER) dates in the areas of the South American monsoon system (SAMS) based on the pentad antisymmetric outgoing long‐wave radiation (AOLR). In those papers, the sign change of the mean AOLR in the central Amazon Basin (CAM) and western central Brazil (WCB) from positive to negative defined the ONR, from negative to positive, the DER dates. Since the monsoon convection presents a northwest–southeast oriented progression, the antisymmetric area to the WCB was selected subjectively. Thus, here we propose to use the Ward hierarchical clustering method to select areas in the SAMS and in the northern tropical America (NTA) for the regionalized AOLR calculation. The significant (at the 95% confidence level) negative correlations with the largest magnitude among the clusters in the SAMS and NTA and the outgoing long‐wave radiation (OLR) and precipitation annual cycles in each group define the pairs to calculate the AOLR. Then, the AOLR time series is calculated and subjected to a 5‐pentad running mean filter. This method keeps the climatological features of the convection annual cycle such that the closer (farther) the pair is to the equator the longer (shorter) the rainy season. The ONR and DER dates found with this new method are remarkably close to those found previously. Therefore, the new method proposed here highlights regional aspects of rainy season and can easily be automatized for its routine application at the operational climate monitoring centres, for instance at INPE. This is the most important advantage of the method and might be relevant to the SAMS rainy season monitoring.

Seasonal climate and the onset of the rainy season in western‐central Brazil simulated by Global Eta Framework model

The seasonal cycle of precipitation in tropical South America is determined by the monsoonal system. The transition from dry to wet season occurs in austral spring (September–November, SON) when intense convection from northwestern South America rapidly shifts southwards to the southern Amazon Basin and western‐central Brazil (WCB) in October and further to the southeast of Brazil in November. This study evaluates ability of the global atmospheric model, Global Eta Framework (GEF), at 25‐km horizontal resolution, to simulate the onset of the rainy season in WCB region. The simulations are based on a five‐member ensemble seasonal integrations for the years 2011 and 2013. Evaluation of mean global simulated fields, such as 200‐hPa wind, 500‐hPa geopotential height, 850‐hPa temperature and wind, and MSLP at the surface, for the SON period indicates high level of agreement with reanalyses and observations, both in spatial distribution and intensity for most of the variables. The variable of the lowest skill is precipitation, which is overestimated over some tropical oceanic regions and underestimated over tropical continental regions, including South America. The onset of the rainy season is determined using methods based on precipitation and outgoing long‐wave radiation (OLR). The threshold based on simulated precipitation is also calculated as an alternative method for defining monsoon onset. Comparison of the 5‐day averaged values (pentads) of precipitation and OLR of all members of the ensemble and the ensemble mean against the observed data shows the ability of GEF to reproduce the typical pattern of transition from dry to wet season in WCB, although most of ensemble members tend to underestimate precipitation and overestimate OLR. The onset date is delayed for few pentads in the model simulations.

Use of rapidly evolving molecular markers to distinguish species and clarify range uncertainties in the spearfishes (Istiophoridae, Tetrapturus)

Despite broad spatial distributions in the Atlantic, Pacific, and Indian oceans, relatively little is known about spearfishes (family Istiophoridae, genus Tetrapturus) due to their pelagic nature and relative scarcity. The limited biological understanding of spearfishes includes uncertain taxonomic relationships complicated by conserved morphology, thus specific identification relies heavily on geographic location of capture. Previous phylogenetic studies incorporating a limited number of loci and few representatives of each species have been unable to consistently resolve the four currently recognized species comprising Tetrapturus. In the present study, we surveyed 14 nuclear microsatellite loci and the mitochondrial DNA control region across relatively large numbers of samples per species to genetically discriminate spearfish species. Molecular data resolved roundscale spearfish (n = 89) (Tetrapturus georgii Lowe, 1841) and Mediterranean spearfish (n = 12) (Tetrapturus belone Rafinesque, 1810) as genetically distinct groups. Longbill spearfish (n = 79) (Tetrapturus pfluegeri Robins and de Sylva, 1963) and shortbill spearfish (n = 29) (Tetrapturus angustirostris Tanaka, 1915) were not consistently resolved. A single individual collected in the western central Atlantic Ocean off Brazil assigned to shortbill spearfish and likely represents a vagrant. Additionally, a spearfish sampled from the Indian Ocean off eastern South Africa was morphologically identified as a longbill spearfish, and the molecular profile of this specimen was consistent with the morphological identification. Our study represents the most extensive molecular evaluation of the spearfishes to date. Results reported here underscore the substantial level of genetic similarity between longbill and shortbill spearfishes, and suggest high-resolution genomic methods may be required to unambiguously resolve these species.

Ectoparasites of small-mammals: determinants of community structure in South American savannah.

This study aimed to assess the contribution of hosts characteristics (rodents and marsupials) in the organization of ectoparasite communities present in woodland patches in western central Brazil. We verified the effect of host species, sex, body mass and vertical strata in addition to the role of seasonality on the ectoparasite composition, richness and abundance. The total sampling effort was 22 032 trap-nights equally distributed in 54 woodland patches. Variance partition and principal coordinate analysis were used to verify the existence of significant relationships between response variables and predictors. As expected, host species was the most important variable in ectoparasite community assembly. The composition, richness and abundance of mites and lice were highly influenced by host species, although higher for mites than for lice. Host body mass had a determining role on the richness and abundance of tick species. Vertical stratification and seasonality had weak influence, while the sex of the host had no influence on the organization of these communities. The results are closely related to the evolutionary characteristics of the species involved, as well as with local environmental characteristics of the study area.

Moisture and heat budgets of the south American monsoon system: climatological aspects

The climatology of the moisture and heat budget equation terms for subareas within the South American Monsoon System (SAMS) region is investigated for the 1958–2014 period considering the distinct phases of the Pacific Decadal Oscillation (PDO). These budget equations are applied to the data from the National Centers for Environmental Prediction (NCEP) Reanalysis project. Sources or sinks of moisture and heat are equation residues, referred to as residue and diabatic terms, respectively. Analyses are done for the Central Amazon Basin (CAM) and Western-Central Brazil (WCB) for three distinct periods, 1958–1976, 1977–1995, and 1996–2014, that correspond to the cold, warm, and undefined PDO phases. The differences among the PDO phases for each term are discussed. The CAM region acts dominantly as a moisture sink and heat source in all months during the three phases. On the other hand, in the WCB region, the monsoon characteristics are better defined, with a moisture sink (source) and a heat source (sink) during the wet (dry) season. The main result of the present analysis is the persistence of SAMS intensification signs in both CAM and WCB areas up to the last analyzed period (1996–2014), which is consistent with intense flooding in the Amazon Basin in 2008/2009, 2012, and 2014.

Revised method to detect the onset and demise dates of the rainy season in the South American Monsoon areas

This paper proposes the detection of dates for the onset and demise of the rainy season (ONR and DER, respectively) for some areas within the South American monsoon system (SAMS) region using procedures based on indices which could be easily calculated and subjected to very simple criterion. Previously, the time series of the averaged antisymmetric outgoing longwave radiation ([AOLR]) in each region of interest was used by some authors to detect ONR and DER. This method is referred to as OLD. First, it was proposed in this paper to smooth this time series with the five-pentad running mean ([RM_AOLR]). This modified method is called NEW. Then, an additional modification was adopted by smoothing the [AOLR] with the three-pentad running mean but with the [AOLR] in the most recent pentad being replaced by its climatological value ([RM_AOLRCLI]). This method is called NEW_CLI. For these methods, the criterion was that the first pentad with negative (positive) [AOLR] (or [RM_AOLR] or [RM_AOLRCLI]) is the ONR (DER) date in the region of interest. All these methods were applied for the Central Amazon (CAM) and Western-Central Brazil (WCB) regions during the rainy seasons in the 2001–2013 period. The efficiency of these methods was analyzed using the precipitation estimated from the Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis. The spatial average of the TRMM ([TRMM]) time series with threshold values, which depends on the area and season, was used to determine the ONR and DER dates. In this case, the single method based on the threshold value is called RAIN, and the method which considers the persistence of dry or wet condition is referred to as NEW_RAIN. Comparisons between the methods were performed by calculating the root mean square error (RMSE) when ONR and DER dates obtained from a given method were considered as the true dates. The advantages and disadvantages of the methods were discussed here. It was previously noted that the [AOLR] time series during the transition from dry (wet) to wet (dry) season showed several signs of oscillation. This was a weakness when detecting the ONR and DER dates; however, using the NEW and NEW_CLI methods eliminated this problem. The NEW_CLI method has more advantages than the other methods and will be useful for monitoring the ONR and DER dates of the SAMS regions.

New species of Tanytarsus van der Wulp (Diptera: Chironomidae: Tanytarsini) from Brazil

Five new species of Tanytarsus van der Wulp (Diptera: Chironomidae: Tanytarsini) from Brazil are described and illustrated. T. longitubuli sp. n. and T. pseudocurvicristatus sp. n., are described as larva, pupa and male; T. hirsutus sp. n., as male and pupa, and T. corumba sp. n. and T. jatai sp. n. as males. Except for one species from Pantanal (western central Brazil), most species were collected in southeast Brazil, from lowland streams and lakes. New occurrences of known species of Tanytarsus in Brazil, Mato Grosso do Sul and Mato Grosso states, are also given.

Integrated Water Resource Management in Brazil

The complex interactions between water resources, land-use change and water technologies are a major issue in many emerging countries of Southern America. Usable water resources are affected by natural conditions, such as, strong seasonal contrasts and high climatic variability, and rapid changes of land use and land cover that is caused by the dramatic expansion of agricultural land and urbanization processes.So far, the effects of the changing climate have had minor effects on water resources. Although regional data is rather scarce, global climate models predict substantial changes of climatic conditions in the future. A further pressure is that demand for water supply and waste water, both in terms of amount and spatial expansion, is increasing rapidly due to higher population densities caused by natural population growth and migration as well as higher per capita consumption.Integrated Water Resource Management in Brazil aims to present the results of the joint project IWAS-AGUA DF which deals with problems, causes and solutions in water supply in scope of integrated water resource management in western Central Brazil. The basic idea of the IWRM approach to be presented is to show how natural conditions and human interference are interacting and how technologies as well as concepts might help to manage such water resource systems in a sustainable way.ISBN: 9781780404905 (eBook)ISBN: 9781780404899 (Print)

Análise da Estrutura Termodinâmica Associada ao Desenvolvimento de Tempestade Ocorrida entre 17 e 18 de Março de 2013 no Estado do Rio de Janeiro, Brasil

This paper presents an analysis of the thermodynamic structure of the atmosphere with the processes related to a thunderstorm occurred on 17 and 18 March 2013 in the State of Rio de Janeiro. The coupling of a stationary cold front in the Atlantic Ocean with a moisture channel over western central Brazil, resulted in elevated precipitation in the northern part of the Metropolitan Region of Rio de Janeiro (MARJ) and of the surroundings areas (northward highlands). Among the consequences caused by this event are: landslides and urban floods, 34 deaths and material damage. The result was obtained from analysis of radiosonde data, which indicated strong conditional instability, presence of strong advection hot air and wet associate with wind shear in the surface boundary layer, as registered in the International Airport Tom Jobim in late afternoon of March, 17th 2013. The thermodynamic conditions was plenty favorable to the organization and maintenance of deep forced convection, which provided alarming values of precipitation.

Physical and chemical analyses of bare soil sites in Western Central Brazil: a case study

The extent of degraded areas in Brazil, mostly caused by human activities, is increasing. Degradation leads frequently to bare soils, which, due to lack of vegetation cover, are liable to erosion and, therefore, might be the main source of sediments. The objective of this study is to analyze the physical and chemical soil properties of a degraded site (bare soil) in the Federal District of Brazil, which is located in the Cerrado biome, one of the global frontiers for agricultural expansion and urbanization as well as a major global biodiversity ‘hotspot’. Soil samples from degraded and reference sites were collected in this area and analyzed. The results of this study confirm that several soil physical and chemical factors are altered by compaction and topsoil removal. In particular, our study shows that degraded soils are rather low in nutrients and have unfavorable physical soil properties compared to reference soils under native vegetation of Cerrado with dynamic nutrient cycling and low bulk densities.

Assessing hydrological and provisioning ecosystem services in a case study in Western Central Brazil

IntroductionCurrent land use in the Federal District, Western Central Brazil, causes problems related to the water supply which are linked to the regulation of ecosystem services (ES). In scope of an Integrated Water Resources Management concept, we further developed the web-based planning support tool GISCAME for the Pipiripau river basin case study.MethodsWe introduced analyses on ecosystem potentials in the raster-based tool to assess, in a spatially explicit manner, the scenario impact on water purification, sediment retention, water retention, and provision of food and fodder in order to identify potential pathways for conserving water resources. To demonstrate the method, we assess ES depending on a number of land use/land cover change (LULCC) scenarios.ResultsWe found that a considerable increase of water purification and sediment retention is difficult to achieve with realistic small scale LULCC, mainly because in areas with a low potential to provide hydrological ES and thus with a high demand for sustainable land use, such as native Savanna (Cerrado) and natural forests (Mata), favorable land uses were often already existing. We observed synergies in the response of regulating hydrological ES to LULCC but at the same time also trade-offs with provision of food and fodder.ConclusionsOur findings suggest that further degradation and loss of Cerrado and Mata must be avoided and their restoration should be promoted in order to safeguard water resources. We suggest that restoration measures should be focused on arable land located at steep slopes near surface waters to effectively increase hydrological ES through the marginal reduction of provision services.

Reproductive potential and stock recruitment of the Caribbean and Brazilian metapopulations of the spiny lobster, Panulirus argus (Latreille, 1804)

The spiny lobsterPanulirus argus(Latreille, 1804) is the most important commercial fishing resource in the western central Atlantic and Brazil. Field studies covering the waters off southwestern Cuba and northern Brazil have improved our understanding of the variations in the reproductive potential (number of eggs), stock recruitment and reproductive efficiency of spiny lobsters according to location, depth and size class. Using the spawner-recruitment model, the reproductive potential index was correlated with the index of subsequent recruitment based on field sampling. Spiny lobster habitats in deeper waters need special attention in order to protect the species from overfishing of the recruitment. Considering the longevity and absence of reproductive senility in spiny lobsters, management strategies should ideally include the creation of spawner sanctuaries (marine protected areas) capable of restoring and maintaining the biomass of the spawning stock and the establishment of a maximum catch size of 135 mm (CL) for both sexes along the entire Brazilian coast. Based on our findings, we propose to establish spiny lobster sanctuaries (50-100 m) on the continental shelf off northern Brazil, from Amapá (5°25′N 51°0′W) to the western reaches of the coast of Pará (1°11′N 46°27′W, 0°42′N 46°45′W), covering a total surface area of 64 230 km2.

A web-based planning support tool for sediment management in a meso-scale river basin in Western Central Brazil

In scope of an IWRM concept for the Federal District, Western Central Brazil we developed a planning support tool, which enables non-experts to test the effects of land-use and land-cover change (LULCC) on landscape processes and landscape functions (LPF) related to sediment generation and retention. For this purpose we developed the web-based tool Letsmap do Brasil. The tool has two principal layers. The upper layer contains information on land use and its effect on LPF, i.e. sediment retention, runoff control, nitrogen loss control and agronomic value. The parameterized relation between land use and LPF is the core of the whole system. For each LPF a value specific to land use has been assigned. A second layer contains information on landscape properties and potentials (LPP), e.g. potential for sediment input in river networks and runoff potential. By linking land use and LPPs the system provides a spatially explicit assessment of effects of LULCC on landscape processes and functions (LPF).Letsmap do Brasil might have two major purposes. (1) It will support decision-making in river basin management and sediment management. By creating their own land-use/cover pattern non-expert users are enabled to test effects of LULCC on LPFs. (2) It will support and train non-experts to participate in decision processes in land-use planning. Because of its high adaptability, transparency, and simple handling Letsmap do Brasil might be used as tool in river basin management and land-use planning.

A new species of Solanum sect. Acanthophora (Solanaceae) from Argentina and Brazil

A new species of Solanum belonging to section Acanthophora (subgenus Leptostemonum) from Argentina and Brazil is described. Solanum neei Chiarini & L.A.Mentz, sp. nov. is found in clearings of semideciduous forests and in secondary formations, from the states of Paraná, Rio Grande do Sul and Santa Catarina in Brazil to the Misiones province in Argentina. It is morphologically similar to Solanum incarceratum Ruiz & Pav. from Peru, Bolivia and Western-Central Brazil, differing mainly by its pedunculate inflorescences. A key to related species is provided, as well a photograph of the holotype, a distribution map and illustration.

Sediment characteristics and sedimentations rates of a small river in Western Central Brazil

The purpose of this study is to characterise the alluvial sediments and to quantify sedimentation rates of a small river system, the Ribeirao do Torto in Central Western Brazil. The study area provides an excellent opportunity to examine the effect of land use on sedimentation rates in the region for the first time and thus contributes to understanding sediment transport processes into water reservoirs (silting). 137Cs, 210Pb and 14C dating techniques were used to estimate natural sedimentation rates and those associated with land use development. Complementary use of physical and chemical analyses of the sediments and contained anthropogenic materials revealed that sedimentation dynamics had varied over time. Natural sedimentation rates are more than ten times lower than in the period since the mid-1950s for the alluvial system of the Ribeirao do Torto. The results indicated that human impact had accelerated the sedimentation dynamics, which resulted in higher sediment quantities and sand content and changes of sediment sources. The variation of sedimentation rates may reflect also several other factors, e.g. natural fluctuation in flow energy or geomorphologic changes within the alluvial system. However, the multiple dating techniques and supplementary interpretation employed in this study show the potential use of radionuclides and soil/sediment parameters to identify changes in sedimentation rate, stream energy and sediment characteristics in floodplains.

Some considerations on onset dates of the rainy season in Western‐Central Brazil with antisymmetric outgoing longwave radiation relative to the equator

AbstractA new method to determine the onset dates of the rainy season (ONR) in the Central Amazon area using the antisymmetric in relation to the equator outgoing longwave radiation (OLR) data was developed in a previous paper. This method is adjusted and used here to determine the ONR in Western‐Central Brazil (WCB). The adjustment is needed because of the northwest‐southeast (NW‐SE) orientation of the American monsoon‐related convection displacement. The area averages of the OLR (AOLR) are used to identify the ONR dates. The ONR dates in WCB based on the precipitation index determined in a previous work are used as reference for comparisons. The differences between the results with the AOLR method and those shown in previous papers, as well as the advantages of this method are discussed, using composite maps of OLR and maps of the Tropical Rainfall Measuring Mission (TRMM) precipitation data for individual years. The results obtained here for the WCB indicate a potential of the new method for monitoring purposes because the OLR data can easily be obtained and the AOLR calculation is very simple. Copyright © 2011 Royal Meteorological Society

Challenges of an integrated water resource management for the Distrito Federal, Western Central Brazil: climate, land-use and water resources

Land-use/cover change (LUCC) and climate change are major controlling factors for water resources in the Distrito Federal in Western Central Brazil. Dynamic LUCC in the region has severe impacts on water resources, while climate changes during the last three decades is thought to have only moderate effects. LUCC affects water quantity mostly during base flow conditions. River basins with substantial expansion of agriculture since the end 1970s show a dramatic decrease of base flow discharge by 40–70%, presumably due to irrigation. In contrast, the effects of urbanization on runoff are less distinct, since factors controlling runoff generation might be more variable. For water quality, we found urban areas to have a strong influence on the parameters CSB, NH4+, and suspended solids. In addition, we assume emerging pollutants, e.g. organic (micro)pollutants, might play a major role in the future. The project IWAS-AGUA DF focuses on creating the scientific base to face these problems in frame of an IWRM concept for the region. Results of our study will be a contribution to an IRWM concept for the Distrito Federal and will help to maintain high standards in water supply for the region.

Neoproterozoic glacial deposits from the Araçuaí orogen, Brazil: Age, provenance and correlations with the São Francisco craton and West Congo belt

Glacigenic diamictite successions of the Macaúbas Group are widespread in the western domain of the Araçuaí orogen, east of the São Francisco craton (Brazil). Diamictites also occur on this craton and in the African counterpart of the Araçuaí orogen, the West Congo belt. Detrital zircon grains from the matrix of diamictites and sandstones from the Macaúbas Group were dated by the U–Pb SHRIMP technique. The geochronological study sets the maximum depositional age of the glacial diamictites at 900Ma, and indicates multiple sources for the Macaúbas basin with ages ranging from 900 to 2800Ma. Sm–Nd TDM model ages, determined on whole rock samples, range from 1.8Ga to 2.5Ga and get older up-section. Comparison of our data with those from the cratonic area suggest that these glacial deposits can be correlated to the Jequitaí and Carrancas diamictites in the São Francisco craton, and to the Lower Mixtite Formation of the West Congolian Group, exposed in Africa. The 900–1000Ma source is most probably represented by the Zadinian–Mayumbian volcanic rocks and related granites from the West Congo belt. However, one of the most voluminous sources, with ages in the 1.1–1.3Ga interval, has not been detected in the São Francisco-Congo craton. Possible sources for these grains could occur elsewhere in Africa, or possibly from within the Brasília Belt in western central Brazil.

Moisture and heat budgets associated with the South American monsoon system and the Atlantic ITCZ

AbstractMoisture and heat budgets in selected areas of the South American monsoon system (SAMS) and the equatorial Atlantic are examined for the 1979–2006 period. These areas are the Central Amazon (CAM), western Central Brazil (WCB), South Atlantic convergence zone (SACZ) and the Atlantic inter‐tropical convergence zone (ITCZ). The moisture and heat budget terms are calculated using daily reanalyzed data, and filtered for the 0.4–1.2 year scale. Analyses are based on the correlation maps between these terms and the expansion coefficient of the SAMS mode, previously identified. The vertical structures of the moisture and heat budget terms are discussed and allow us to examine the thermodynamic reasoning of the SAMS relationship with the Atlantic ITCZ. Important differences in the moisture and heat budgets have been found among the analyzed areas. Except for the horizontal advection of q and T, indications of a wet and dry season appear in the anomalies of other terms 4 pentads earlier in the WCB than in the CAM. The SAMS and the ITCZ relate to each other through the moisture and heat budgets. A time lag of approximately 8 pentads is noted for the moisture sink (source) and heat source (sink) between the CAM and ITCZ regions during the wet (dry) season of both regions. Indeed, the largest negative (positive) values of the residue term and the largest positive (negative) values of the diabatic term occur at pentad 12 (44) for the CAM and at pentad 20 (52) for the ITCZ. The results here provide observational support to the relationship between the SAMS and the Atlantic ITCZ. Copyright © 2010 Royal Meteorological Society

Quaternary colluvial episodes (Upper Paraná River Hydrographic Basin, Brazil)

Colluvial deposits occur extensively in the Upper Paraná River Hydrographic Basin (UPRHB) in Southeastern,Southern, and Western central Brazil. These deposits were recognized as an allostratigraphic unit and related to creeping during the Quaternary. Every studied colluvial profile is homogeneous, which indicates relatively long periods of landscape stability that is sufficient for the development of a thick soil cover. The deposits were dated by luminescence and indicate periods of more intense colluvial deposition between 6 and 220 ky B.P. These events correspond approximately to the transitions between the oxygen isotope stages 2-3-4 and 5-6, suggesting that this aggradation was influenced by climatic changes. However, the most important alluviation episode was tentatively correlated with the Middle to Upper Pleniglacial of the Wisconsin glaciation. The most intensive and frequent periods of precipitation that occurred during climate transitions are probably correlated with aggradation events. The regularity of the colluvial deposits suggests continuous uplift accompanied by sediment deposition throughout the UPRHB due to neotectonic activity during the last million years.