Publicações

Soil nitrogen dynamics in terrestrial ecosystems can be evaluated by analyzing the natural abundances of N isotope ratio mass spectrometry (δ15N) because δ15N integrates decades of organic matter transformations in the soil. On a large scale, the δ15N of soil organic matter across climate gradients may provide critical insights into understanding regional patterns of N cycling. However, the mechanisms that control N cycling in some tropical regions still present critical gaps, particularly in dry ecosystems. We evaluated the variation of soil δ15N in Alisols along the climatic gradient of three physiographic regions in Northeast Brazil: Zona da Mata (humid, rainfall well distributed throughout the year), Agreste (subhumid, rainfall concentrated in 57 months), and Sertão (semiarid, rainfall in highly intense events, concentrated over 35 months). Soil samples were collected at the 020 cm depth layer and analyzed for physical and chemical characteristics, including soil δ15N, by mass spectrometry. A linear model with physical biological, chemical, and climatic variables was generated to explain the spatial distribution of the soil δ15N. The map modeled values δ15N for Pernambuco State was produced using all observed values and the best-performing explicit spatial predictive variables in the model selection pH, clay content, mean temperature, mean precipitation, and potential of evapotranspiration. Soil δ15N was positively related to clay content and negatively associated with the pH, temperature, rain, and evapotranspiration, expressing differences in nitrogen dynamics along the climatic gradient. In the Sertão, the low and erratic rainfall combined with a neutral pH and high temperature provide adequate conditions for nitrogen transformations and cause high soil δ15N.

The Brazilian Equatorial Shelf (BES) is a very dynamic region due to the influence of various forcings: trade winds, macrotides, the Amazon River, and the North Brazil Current (NBC). To investigate each forcing’s role in BES circulation, a control simulation and three sensitivity simulations (without rivers, without tides, and without winds) were performed using the Regional Ocean Modeling System (ROMS) with a horizontal resolution of 1/24° and realistic forcings. The results showed that the NBC advected low-salinity waters from the Amazon River northwestward to Caribbean Sea and occasionally eastward through the NBC retroflection. The NBC exhibited the strongest flow when all forcings were included in the simulation. On the other hand, southeasterly winds inhibited the NBC retroflection system and, thus reducing its contribution to North Equatorial Counter Current (NECC) and Equatorial Undercurrent (EUC). The simulation without tides showed a plume more advected by the NBC and constricted to the first 10 m of the water column, while in the simulation without wind the plume was less advected northwestward by the weakened NBC and spread more toward the shelf break. The correlation analysis highlighted the complexity of the system, the complementarity of the forcings and their time-variable interdependence. The three sensitivity simulations and correlation analysis demonstrated the wind to be the main mechanism of the circulation in the BES. The sensitivity simulations also gave insight of how circulation would respond in a future scenario if climate changes persist. Previous studies suggest that the reduced Amazon runoff may indirectly weaken Atlantic ITCZ and thus trade winds causing a weakened circulation in tropical Atlantic. Our results show that this weakened circulation would advect even less fresh water northward, worsening the disturbances in North Atlantic due to the reduced freshwater supply.

Over the last decades, the Amazon rainforest has been hit by multiple severe drought events. Here, we assess the severity and spatial extent of the extreme drought years 2005, 2010 and 2015/16 in the Amazon region and their impacts on the regional carbon cycle. As an indicator of drought stress in the Amazon rainforest, we use the widely applied maximum cumulative water deficit (MCWD). Evaluating nine state-of-the-art precipitation datasets for the Amazon region, we find that the spatial extent of the drought in 2005 ranges from 2.2 to 3.0 (mean = 2.7) ×106 km2 (37 % 51 % of the Amazon basin, mean = 45 %), where MCWD indicates at least moderate drought conditions (relative MCWD anomaly < −0.5). In 2010, the affected area was about 16 % larger, ranging from 3.0 up to 4.4 (mean = 3.6) ×106 km2 (51 %74 %, mean = 61 %). In 2016, the mean area affected by drought stress was between 2005 and 2010 (mean = 3.2 × 106 km2 ; 55 % of the Amazon basin), but the general disagreement between datasets was larger, ranging from 2.4 up to 4.1 × 106 km2 (40 %69 %). In addition, we compare differences and similarities among datasets using the self-calibrating Palmer Drought Severity Index (scPDSI) and a dry-season rainfall anomaly index (RAI). We find that scPDSI shows a stronger and RAI a much weaker drought impact in terms of extent and severity for the year 2016 compared to MCWD. We further investigate the impact of varying evapotranspiration on the drought indicators using two state-of-the-art evapotranspiration datasets. Generally, the variability in drought stress is most dependent on the drought indicator (60 %), followed by the choice of the precipitation dataset (20 %) and the evapotranspiration dataset (20 %). Using a fixed, constant evapotranspiration rate instead of variable evapotranspiration can lead to an overestimation of drought stress in the parts of Amazon basin that have a more pronounced dry season (for example in 2010). We highlight that even for well-known drought events the spatial extent and intensity can strongly depend upon the drought indicator and the data sources it is calculated with. Using only one data source and drought indicator has the potential danger of under- or overestimating drought stress in regions with high measurement uncertainty, such as the Amazon basin.

The biosphereatmosphere interactions associated with the rainy season onset in South America (SA) are not well understood. This study aimed to analyze the atmospheric and surface patterns associated with early, neutral, and late rainy season onset in tropical regions of SA. The following years represented each rainy season onset: 1998, 2006, 2009 (early), 2001, 2004, 2005 (neutral), 2000, 2007, 2008 (late). The early (late) onset were negative (positive) rainy season onset date anomalies in comparison to the climatological mean (19982016) over central SA. Distinct atmospheric conditions were identified in the early and late rainy season onset. In the early onset, the northwesterly moisture flux and moisture advection were higher than average over central-east SA, where the precipitation increased. In the late onset, precipitation was enhanced in northwest SA and the configuration of multiple atmospheric blocking episodes contributed to delay the rainy season onset. Surface conditions also contributed to both the early/late rainy season onset. In the early onset, wetter and cooler pre-onset conditions over the central-east SA were verified. In the late onset, surface conditions were dry and warm before onset. Even though the atmospheric instability was promoted by the increase in sensible heating, dry atmospheric conditions were not favorable to deep convection, thus delaying the onset. These findings highlight how the onset variability promotes different atmospheric and surface patterns in SA. The results will contribute to the development of weather and climate models to better represent the rainy season onset focusing on biosphereatmosphere processes improvements.

Although income inequality has been often pointed out as an important cause of crime, it is yet unclear how spatial patterns of income in a city can explain its geography of crime. In this study, we apply a model to test the influence of income inequality on the spatial concentration of residential burglaries in the city of Campinas, Brazil. Following criminological theory, our model decomposes income inequality into two hypothetical effects: that of local income, which determines how attractive residences are to burglary, and exposure to poverty, where poverty boosts criminal motivation through economic hardship. Our study reveals that higher local income is indeed significant and positively associated to higher burglary risk, but that exposure to poverty does not increase risk. Therefore, higher income areas more surrounded by poor areas do not feature a particularly increased burglary risk if compared to other higher income areas, contrary to what could be expected from some criminological frameworks such as relative deprivation and strain theories. Instead, our findings suggest that the geography of residential burglaries can be explained by the distribution of burglary opportunities, that is, of where the most profitable targets are. To conclude, we compare our findings to other existing studies.

The solar radiation has been monitored through ground-based and satellite instruments all over the world for decades. This is also important for both checking and validation of satellite probing. In this work, we compare spectral irradiances at 305 nm (UV-B) and 380 nm (UV-A) from a ground-based radiometer and the Ozone monitoring instrument (OMI) for a tropical site in 2019-2020. Measurements had the auxiliary support of a ground-based imager to identify cloud cover. The presence of clouds introduces the largest differences between satellite and ground-based measurements. In fact, on average, for all-sky (AS, only cloudy skies) conditions such differences (satellite – ground-based) were 46% and 30% at 305 nm and 380 nm, respectively, while for cloud-free-sky (CFS) conditions, the differences dropped to 17% and 8%. In addition, the linear fitting between ground-based and satellite measurements yielded a coefficient of determination (r(2)) of 0.857 (for AS) and 0.984 (for CFS) at 305 nm and 0.774 (for AS) and 0.950 (for CFS) at 380 nm. The differences between these AS and CFS values of r(2) were 95% statistically significant. Such results imply the hindrance clouds (and also aerosols based on the results for CFS) still set to obtain UV-B and UV-A surface irradiance from satellite probing.

As previsões climáticas para o Semiárido Brasileiro nesse século incluem aumento da temperatura do ar, redução das chuvas e aridização. As previsões alertam também para danos em sistemas humanos que já enfrentam uma infinidade de outras ameaças, requerendo que a vulnerabilidade nesses sistemas seja melhor identificada, para contribuir na gestão da convivência e adaptação às mudanças climáticas. A pesquisa teve por objetivo analisar vulnerabilidades municipais no estado do Ceará e identificar potenciais Tecnologias Sociais (TS) para redução da vulnerabilidade climática. Para tanto, utilizou-se do Índice Municipal de Alerta, período 2010 a 2020 e informações sobre TS disponíveis, seguindo um percurso metodológico com quatro etapas. Os resultados mostraram que os municípios cearenses se distribuem em três classes de vulnerabilidade: Classe (1) com 10 municípios em expansão; Classe (2) com 15 municípios em retração e; Classe (3) com 159 municípios sem alteração significativa. As TS instaladas no Ceará totalizam 375.708 unidades de 17 tipos com destaque para o Tanque de Pedra e a Cisterna 16 mil litros, com 61% e 26% das unidades, respectivamente. Para melhorar os resultados de convivência e de enfrentamento às mudanças climáticas é necessário levar em conta a aderência entre número/tipo das TS com as demandas locais.

Observations of concentric gravity waves (CGWs) in the OH airglow emission over the Brazilian equatorial region are presented. An all-sky imager installed at Sao Joao do Cariri [7.4 degrees S, 36.5 degrees W] was used to acquire near-infrared OH images. Using over 19 years of observational data from 2000 to 2019, more than 1,052 clear sky nights of airglow data were acquired with a total of 25 observed CGW cases. Three CGW events were selected for this study. These waves had small-scale characteristics and well-defined concentric structures. The selected CGW events showed horizontal wavelengths lambda(H) similar to 31.9, 42.5, and 30.9 km, horizontal phase speeds c(H) similar to 49.2, 57.6, and 74.1 m/s, and periods tau similar to 10.8, 12.3, and 7.0 min, respectively. The CGW structures were well defined, with coherent wave patterns expanding concentrically from the source point, with the observed events having semi-circle or arc-like and semi-elliptical shapes. We found the occurrence of the CGWs to coincide with the seasons of intense tropospheric convective activity and low background winds. This suggests little or no wave breaking, critical level absorption, and filtering or reflection, thereby allowing the CGWs to propagate up to the mesosphere and lower thermosphere region. Using backward ray tracing, we also found the positions and times where and when the ray paths reached the tropopause. The tropopause positions and times of two of the CGW events coincide with active convective systems with cold cloud top temperatures. However, the tropopause position of one of the 3 CGW events did not coincide with any active convective system, suggesting that this CGW was most likely generated in-situ.

The atmospheric boundary layer height ((Formula presented.)) is a key parameter in the vertical transport of mass, energy, moisture, and chemical species between the surface and the free atmosphere. There is a lack of long-term and continuous observations of (Formula presented.), however, particularly for remote regions, such as the Amazon forest. Reanalysis products, such as ERA5, can fill this gap by providing temporally and spatially resolved information on (Formula presented.). In this work, we evaluate the ERA5 estimates of (Formula presented.) ((Formula presented.) -ERA5) for two locations in the Amazon and corrected them by means of ceilometer, radiosondes, and SODAR measurements ((Formula presented.) -experimental). The experimental data were obtained at the remote Amazon Tall Tower Observatory (ATTO) with its pristine tropical forest cover and the T3 site downwind of the city of Manaus with a mixture of forest ((Formula presented.)), pasture ((Formula presented.)), and rivers ((Formula presented.)). We focus on the rather typical year 2014 and the El Niño year 2015. The comparison of the experimental vs. ERA5 (Formula presented.) data yielded the following results: (i) (Formula presented.) -ERA5 underestimates (Formula presented.) -experimental daytime at the T3 site for both years 2014 (30%, underestimate) and 2015 (15%, underestimate); (ii) (Formula presented.) -ERA5 overestimates (Formula presented.) -experimental daytime at ATTO site (12%, overestimate); (iii) during nighttime, no significant correlation between the (Formula presented.) -experimental and (Formula presented.) -ERA5 was observed. Based on these findings, we propose a correction for the daytime (Formula presented.) -ERA5, for both sites and for both years, which yields a better agreement between experimental and ERA5 data. These results and corrections are relevant for studies at ATTO and the T3 site and can likely also be applied at further locations in the Amazon.

Continuous monitoring of forest disturbance on tropical forests is a fundamental tool to support proactive preservation actions and to stop further destruction of native vegetation. Currently most of the monitoring systems in operation are based on optical imagery, and thus are flaw-prone on areas with frequent cloud cover. As this, several Synthetic Aperture Radar (SAR)-based systems have been developed recently, aiming all-weather disturbance detection. This article presents the main aspects and the results of the first year of operation of the SAR based Near Real-Time Deforestation Detection System (DETER-R), an automated deforestation detection system focused on the Brazilian Amazon. DETER-R uses the Google Earth Engine platform to preprocess and analyze Sentinel-1 SAR time series. New images are treated and analyzed daily. After the automated analysis, the system vectorizes clusters of deforested pixels and sends the corresponding polygons to the environmental enforcement agency. After 12 months of operational life, the system has produced 88,572 forest disturbance warnings. Human validation of the warning polygons showed a extremely low rate of misdetections, with less than 0.2% of the detected area corresponding to false positives. During the first year of operation, DETER-R provided 33,234 warnings of interest to national monitoring agencies which were not detected by its optical counterpart DETER in the same period, corresponding to an area of 105,238.5 ha, or approximately 5% of the total detections. During the rainy season, the rate of additional detections increased as expected, reaching 8.1%.

Aim Our aim was to quantify the influence of climate and land use on major fires that occurred during the 2020 drought over the Brazilian Pantanal region. Location Alto Paraguay Basin, central-western flank of Brazil. Time period 2003-2020. Methods We calculated climatic and burned area anomalies and Spearman’s correlation between precipitation and sea surface temperature (SST). We assessed water coverage to identify the impact of the 2020 drought. We produced fire recurrence maps, identified the areas that burned for the first time in 2020, and estimated the carbon loss. Lastly, we assessed the burned areas within land-use classes and land tenure. Results The anomalies showed that climatic variables in 2020 had an atypical behaviour, being hotter and drier than the historical average. The water surface area in the Pantanal has been decreasing annually from 2003, and in 2020 the reduction was 34% greater than the annual average. Burned areas in 2020 were 200% greater than the long-term average, and 35% of the burned areas occurred for the first time in this year. We showed that 84% of these new fires occurred within natural vegetation, with 39% of the burned areas occurring in forests, an increase of 514%. Forest fires were responsible for 47% of the carbon loss in 2020. Finally, 70% of the fires in 2020 occurred within rural properties, 5% in indigenous lands and 10% in protected areas. Main conclusions The unprecedented fires in 2020 were not only a result of atypical climate, but also a consequence of the intensification of fire-related human activities. Rural properties play a major role in Pantanal fires, requiring law enforcement and a consistent plan for increasing the protection of the conservation areas. We argue that ineffective fire prevention and the lack of suppression strategies were also key in enhancing the magnitude of these fires.

Liquid insulation is used in high voltage equipment such as power transformers as both dielectric medium and coolant. Breakdown in liquid insulation tends to be governed either by streamer initiation under more uniform fields, or by streamer propagation under more non-uniform fields. A model streamer propagation study, which screens the effectiveness of additives based on cyclohexane and mixtures with diethylaniline (DEA) and toluene, is presented in this paper. The effect of additives, at different concentrations, on streamer propagation velocity in cyclohexane under an applied lightning impulse voltage of positive polarity is studied. Cyclohexane (ionisation potential 9.88 eV) was chosen because, being a hydrocarbon, it shares similarities with the constituents of common insulating liquids. Previous studies have also shown how, in general, the addition of additives of lower ionization potential than the bulk liquid can slow down streamer propagation in insulating liquids. A point-plane electrode configuration of 70 mm gap with a 5 mu m tip radius is used and subjected to an applied positive polarity impulse of 1.2/50 mu s. A high velocity imaging system is also used to capture streamer images to validate a Time-To-Breakdown (TTB) measurement approach used in inferring approximate streamer velocity. The DEA (ionisation potential 6.98 eV) was found to be an effective additive to slow down positive polarity streamers in cyclohexane in the applied voltage range (approximate to 220-280 kV peak) in concentrations above approximately 0.33% (by volume). Toluene (ionisation potential 8.82 eV) was found not to significantly slow down streamers in cyclohexane, even at 10% concentration, for the same voltage range. This is postulated to be due to the fact that toluene does not have a low enough ionisation potential (with respect to that of the cyclohexane) to change the streamer branching characteristics sufficiently during propagation.