National Institute for Space Research

Abstract Tropical deforestation causes substantial changes to local climate including strong local warming. Deforestation is driven by a wide a range of factors including commodity production, shifting agriculture and forestry. However, it is unknown whether the local climate impacts of forest loss vary across these drivers of the deforestation. We used remotely sensed atmospheric and land-surface datasets to explore whether the local warming due to tropical forest loss from 2001 to 2019 varied with the driver of deforestation. In the Amazon, forest loss caused by commodity-driven deforestation caused 0.66 °C of warming, more than double the warming from shifting agriculture (0.31 °C). Across the tropics, forest loss due to commodity-driven deforestation caused a warming of 0.02 °C per percentage point of forest loss, double the warming due to shifting agriculture (0.01 °C per percentage point of forest loss). Compared to commodity-driven deforestation, shifting agriculture leads to smaller reductions in leaf area index and smaller increases in surface albedo likely due to the subsequent land abandonment and regrowth of vegetation that is associated with this driver. Our results suggest that a projected transition from shifting agriculture to commodity-driven deforestation will increase the local climate warming from tropical forest loss with negative impacts for communities living in tropical forest regions.

This study introduces the Hybrid Hydrological Forecast System (HHFS), a dual-stage, data-driven framework for monthly streamflow forecasting at the Santa Branca outlet in the upper Paraíba do Sul River Basin, Brazil. The system combines two nonlinear regressors, Multi-Layer Perceptron (MLP) and extreme Gradient Boosting (XGB), calibrated through a structured four-step evolutionary procedure in GA1 (hydrological weighting, dual-regime Ridge fusion, rolling bias correction, and monthly mean–variance adjustment) and a hydro-adaptive probabilistic optimization in GA2. SHAP-based analysis provides physical interpretability of the learned relations. The regressive stage (GA1) generates a bias-corrected and climatologically consistent central forecast. After the full four-step optimization, GA1 achieves robust generalization skill during the independent test period (2020–2023), yielding NSE = 0.77 ± 0.05, KGE = 0.85 ± 0.05, R2 = 0.77 ± 0.05, and RMSE = 20.2 ± 3.1 m3 s−1, representing a major improvement over raw MLP/XGB outputs (NSE ≈ 0.5). Time-series, scatter, and seasonal diagnostics confirm accurate reproduction of wet- and dry-season dynamics, absence of low-frequency drift, and preservation of seasonal variance. The probabilistic stage (GA2) constructs a hydro-adaptive prediction interval whose width (max-min streamflow) and asymmetry evolve with seasonal hydrological regimes. The optimized configuration achieves comparative coverage COV = 0.86 ± 0.00, hit rate p = 0.96 ± 0.04, and relative width r = 2.40 ± 0.15, correctly expanding uncertainty during wet-season peaks and contracting during dry-season recessions. SHAP analysis reveals a coherent predictor hierarchy dominated by streamflow persistence, precipitation structure, temperature extremes, and evapotranspiration, jointly explaining most of the predictive variance. By combining regressive precision, probabilistic realism, and interpretability within a unified evolutionary architecture, the HHFS provides a transparent, physically grounded, and operationally robust tool for reservoir management, drought monitoring, and hydro-climatic early-warning systems in data-limited regions.

Abstract This study investigates the ionospheric response to the intense geomagnetic storm of 20–21 December 2015 over the equatorial and low‐latitude South American sector. Ionosonde data from São Luís (2.6°S, 44.2°W; dip angle: 3.9°S) and four additional Brazilian stations were analyzed to examine variations in the peak height of the F2 layer (hmF2) and vertical plasma drift velocities. A notable feature of this event was the occurrence of post‐midnight equatorial plasma bubbles (EPBs) during the recovery phase, an uncommon storm‐time response. In contrast, a suppression of post‐sunset EPBs was observed on 20 December, despite enhanced vertical drifts associated with the pre‐reversal enhancement. The post‐midnight EPBs are attributed to disturbance dynamo electric fields (DDEFs), which uplifted the F layer to higher altitudes and created favorable conditions for the Rayleigh‐Taylor instability (RTI) growth rate . On 20 December evening, the vertical drifts exceeded quiet‐time reference at equatorial stations, reflecting undershielding Prompt Penetration Electric Field activity. However, the absence of post‐sunset EPBs under seemingly favorable RTI conditions suggests the influence of additional suppressive mechanisms. The suppression of EPBs may be attributed to disturbance meridional winds driven by DDEFs, which generate interhemispheric asymmetries in the Equatorial Ionization Anomaly. These asymmetries can increase the integrated flux‐tube E‐region conductivity along magnetic field lines. Additionally, enhanced chemical recombination—associated with storm‐time variations in the ratio—may further reduce under geomagnetically disturbed conditions.

The rocket propulsion community is actively seeking nontoxic, stable propellants to replace hazardous hydrazine-based options. This study provides a comprehensive analysis of the hypergolic ignition and spray characteristics of a newly developed eco-friendly self-igniting fuel (named PAHyp 3) with rocket-grade hydrogen peroxide (RGHP), using an impinging jet apparatus. Using synchronized high-speed visible shadowgraph and infrared imaging, the transition from standard atomization to reactive bubbly atomization was revealed by modulating propellant reactivity. Infrared imaging aids in tracking spray breakup, mixing, and the liquid-to-gas transition of droplets, providing valuable insights. To better understand the mixing and reactive bubbly dynamics before ignition, a simplified oxidation mechanism is proposed based on infrared imaging of hypergolic and non-hypergolic samples. This work reveals key multiphase reaction behaviors, including bubble nucleation and growth, bubbly droplet burst (microexplosion), and gas-phase combustion dynamics, along with insights into the reaction kinetics. Unlike non-hypergolic propellants, hypergolic combinations exhibit unique droplet dynamics characterized by bubble nucleation, expansion, and rapid consumption via internal and external evaporation. These mechanisms result in accelerated droplet disintegration and a shorter lifespan. The findings provide insights applicable to other hydrogen-peroxide-based bipropellants as well as to conventional hydrazine-based systems.

Long period (1–10 000 s) magnetotelluric (MT) data were acquired along a 400 km north–south transect across the Ceará Central domain in northwestern Borborema Province to investigate the electrical structure of the lithosphere. The data were inverted for 3D resistivity models, which revealed a thinned lithosphere between the Transbrasiliano Lineament and the Senador Pompeu Shear Zone in the Ceará Central domain. The basic structure across Ceará Central consists of a steep, electrically resistive lithospheric block (R3) bounded by deep-reaching conductors extending to depths of c . 100 km overlying a deeper conductive substratum (C3). In the upper crust, the raised thickest parts of R1a coincide spatially with the Archean inlier Tróia–Tauá massif, whereas R1b coincides with the Tamboril Santa Quitéria calc-alkaline magmatic arc downdip, implying northward subduction. Our results are consistent with the past 3D MT models for the region, and we show that the above basic structure is repeated to the north and south in the adjoining tectonic domains. Integrating past and present results reveals a consistent lithospheric structure along-strike whereas dip-sections show lithospheric segmentation with structural wavelengths of c . 180–250 km and coinciding with the compartmentalization of surface-mapped tectonic terrains. We interpret the gross structure across the region as suggesting the presence of multiple north-dipping (or south-verging) deep lithospheric roots or fossil subduction (and roll-back) systems. The shear zones are through-going, their high conductivity suggesting the reactivation of inherited structures, mineralization or deep fluid circulation. Some of the shear zones are also associated with rift basin inversion. We therefore suggest that such terrains may be important for future exploration for geothermal and natural hydrogen resources.

The first time-resolved leader spectra associated with a downward Terrestrial Gamma-ray Flash (TGF) observed by the Telescope Array Surface Detector (TASD) were recently reported by \citeA{kieu2024first}. Building on that study, this paper presents th

Abstract Over the past decade, the Brazilian electricity sector has undergone a profound transformation, driven by the large-scale deployment of wind and solar photovoltaic power plants, a trend that is expected to continue in the years ahead. Although the transition to these variable renewable energy resources helps to reduce greenhouse gas emissions and mitigate the climate crisis, they are vulnerable to the very climate changes they help to avert. This study uses projections from CMIP6 global climate models under two future scenarios (SSP2-4.5 and SSP5-8.5) to assess potential impacts on power generation in the existing centralized wind and solar power facilities in Brazil. The study innovates by assessing the effects of climate change on the future performance of the power plants using measured historical capacity factors as a proxy, thereby eliminating the need for climate bias correction and standardized manufacturer power curves. Projections indicate a nationwide increase in wind potential between 6% and 15% by the end of the century, contributing to an extended wind season in the northeastern region and a stronger seasonality in the southern region. In contrast, the photovoltaic potential reveals modest change; the positive effects of increasing surface radiation are counterbalanced by the negative effects of warmer air temperatures across the assessed scenarios. These findings offer valuable insights for strengthening Brazil’s energy security under future climate conditions.

This paper proposes a novel Particle Swarm Optimized (PSO) PID controller for buck converters that combines conventional PID robustness with PSO's global search capability. The hybrid architecture enables real-time self-tuning of controller parameters. We present a Lyapunov-based stability proof, parametric sensitivity analysis, and robustness evaluation against disturbances. Simulated on a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$48 ~\mathrm{V} / 12 ~\mathrm{V}$</tex> buck converter (300 kHz), the controller achieves precise voltage regulation with less than 0.1 % overshoot and rapid disturbance rejection. High-fidelity simulation in PSIM demonstrates superior performance compared to conventional approaches. The system maintains stability under <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 10 \%$</tex> input voltage variations and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 50 \%$</tex> load changes.

Abstract Ground-based astronomical and solar observations are strongly influenced by atmospheric turbulence, a dynamic phenomenon that degrades optical resolution through refractive index fluctuations. This study evaluates daytime sky quality and the refractive index structure parameter ( C n 2 ) at the Pico dos Dias Observatory (OPD) in Brazil, integrating in situ meteorological data with the European Centre for Medium-Range Weather Forecasts Reanalysis version 5 product. Variables such as air temperature, wind speed, relative humidity, and cloud cover are analyzed across vertical and temporal scales, providing insights into diurnal, seasonal, and altitudinal atmospheric behaviors. The study highlights the distinct challenges posed by daytime turbulence, driven by solar heating and convection, on adaptive optics (AO) systems and high-precision solar spectropolarimetric instruments, such as the prototype of the Galileo Solar Space Telescope. To provide context for the atmospheric conditions at the OPD, this study characterizes several key meteorological variables. Typical daytime conditions feature median air temperatures of 15°C–20°C and surface winds of 1.0–4.0 m s −1 , predominantly from the north, while nighttime conditions are cooler (10°C–15°C) with weaker winds shifting south–southeast. Relative humidity generally remains below 70%, especially in the June–July–August months, making it favorable for astronomical observations. Cloud cover shows seasonality, with clear-sky fractions of about 32% at night and 28% by day, peaking in austral winter and minimizing in summer. Our quantitative analysis of refractive index variability underscores the necessity of advanced AO technologies. Seasonal and vertical profiles of C n 2 present pronounced variability, influenced by solar heating, terrain-induced airflow, and jet stream dynamics. These findings stress the importance of strategic scheduling and turbulence modeling to optimize performance. This comprehensive characterization advances understanding of atmospheric conditions for solar and nighttime astronomy, refining AO systems, and enabling progress in high-precision astrophysics.