A radiação solar ou irradiância constitui um importante fator que influencia os processos químicos, físicos e biológicos na Terra. Essa radiação emitida por diferentes camadas da atmosfera solar afeta a atmosfera superior e também o clima da Terra. Neste artigo serão descritos os conceitos físicos sobre a irradiância total e irradiância espectral. Essas medidas são fundamentais para a modelagem do clima da Terra. Também alguns modelos utilizados são descritos. A relação entre a irradiância solar e o clima da Terra será discutido. Palavras-chave: Sol, Irradiância, Radiação eletromagnética, Fenômenos solares, Clima da Terra.The solar radiation or irradiance influences chemical, physical and biological processes on the Earth. This radiation emitted from the solar atmosphere through different layers can affect the Earth's upper atmosphere and climate. An overview about the Sun were presented. The physical description of Total Solar Irradiance (TSI) and Solar Spectral Irradiance (SSI) are explained. Some models of irradiance are briefly described. The relationship between the solar irradiance and the Earth's climate were discussed. Keywords: Sun, Irradiance, Electromagnetic radiation, Solar features, Earth's climate. IntroduçãoA energia solar esta diretamente relacionada com os processos químicos, físicos e biológicos, ou seja, esta associada com a vida na Terra. As variações dessa energia têm impacto na atmosfera e no clima da Terra em largas escalas de tempo [1]. Além disso, a química da atmosfera superior, da ionosfera e da estratosfera também são influenciadas [2,3].A radiação solar é o fluxo de energia emitida pelo Sol e transmitida sob a forma de radiação eletromagnética. Durante muitos anos foi considerada uma constante em torno de 1. A obtenção de valores da irradiância solar com alta precisão são importantes nos modelos climáticos e atmosféricos [5]. Apesar da radiação solar ser a principal fonte de energia da Terra o clima também é influenciado pelo efeito estufa, emissões de vulcões [6,7], raios cósmi-* Endereço de correspondência: jemfisi@gmail.com.cos [8] e energia radiante da supernova [9]. Além disso, mudanças de longo prazo na órbita da Terra modulam a irradiância solar que atinge o topo da atmosfera. As variações nas inclinações orbitais também podem causar pequenas diferenças na TSI [10].O principal motivo para abordar o estudo da irradiân-cia solar é conhecer qual é a verdadeira influência dela, nas variações do clima da Terra já que elas afetam nossa vida diária. Assim, como determinar qual é a influência dos processos humanos (efeito estufa e emissões de CO 2 , por exemplo) no clima e sua variabilidade. Esse trabalho fornece uma visão geral desde os conceitos básicos da radiação solar, a estrutura do Sol, a geração de campo magnético do Sol, a descrição física da irradiância solar, modelos de reconstrução da irradiância e a relação da irradiância solar e o clima da Terra. Conceitos básicos da radiação solarA radiação eletromagnética está relacionada com cargas elétricas aceleradas que irradiam en...
The total solar irradiance at the top of the atmosphere is the primary source of energy of the Earth’s highly coupled atmosphere–land–ocean system. Small fluctuations of the solar flux density in scales from years to millennia could impact the energy balance of this system due to nonlinear effects. The quantification of this variability depends on absolute radiometers on board of space-based platforms. Although there has been significant improvement in the design and calibration of absolute radiometers during the last decades, the uncertainties in the measurements have not allowed us to untangle the natural and anthropogenic drivers of the observed changes of the climatic patterns appropriately. One of the critical components of the absolute radiometers is the coating of the sensor elements, which should absorb the radiation efficiently. Here we discuss the optical characteristics of ultra-black Nickel–Phosphorus (Ni–P) and its relations with the surface morphology. The ultra-black Ni–P has important unique properties such as low reflectance and uniformity of deposition in complex geometries. Ni–P multilayer was deposited by electroless on aluminum substrates. The surface was etched by oxidizing acid to produce ultra-black Ni–P. Characterization techniques were used to describe the properties of the material. We describe the directional reflectance employing the bidirectional reflectance distribution function. Additionally, we used reflectance maps to show the influence of the pores on the reflectance. Ultra-black Ni–P exhibited a high absorptance and dependence with the light incidence angle. Based on the results, the material demonstrated the opportunity of many terrestrial and space applications as a black coating absorber.
Absolute radiometers are based on electrical substitution radiometers, which compare optical and electrical power. The same physical principle applies to standard reference detectors operating at cryogenic temperatures and room temperature radiometers for total solar irradiance (TSI) measurements. Both types rely on the cavity with an internal low-reflectance coating to absorb incident radiation similar to a black body. The cavity shape design requires an analysis of the coating reflection properties. Like many materials, ultra-black Ni-P exhibits a mixture of diffuse and specular reflection that depends on the angle of incidence of light in the pores. We employed ray-tracing software to study the impact of the geometry on the absorptivity and distribution of the scattered rays. We describe the scattering model of the black coating in terms of the bidirectional reflectance distribution function. Also, we examined the difficulties of Ni-P electroless deposition and blackening inside the cavity. The measured absorptance of the cavity showed some discrepancies of the simulated absorptance mostly probably due to Ni-P non-uniformity coating.
Resumo A irradiância solar total (TSI) é definida como a energia emitida pelo Sol por unidade de área e recebida pela Terra. Durante muitos anos essa energia foi considerada constante, no entanto, hoje se sabe que há variações em diferentes escalas de tempo. A medição do valor absoluto da TSI precisar ser realizada em ambiente extraterrestre devido à influência da atmosfera na irradiância solar que atinge a superfície da Terra. Sendo a TSI uma variável imprescindível para quantificar a influência solar nas mudanças climáticas da Terra, a obtenção de medidas com a precisão e estabilidade necessária têm se demonstrado um grande desafio tecnológico. Nesse artigo é descrito o princípio de funcionamento e as particularidades dos radiômetros de substituição elétrica utilizados para medir a TSI no espaço.
The study of solar radiation in space has become something necessary, motivating the launch of radiometers on board satellites dedicated to perform TSI measurements and to build a record of their behavior over the years, making these data essential for meteorology and climatology. In this work, a simplified model was proposed to understand the thermal behavior of absolute radiometers, which are dedicated to this type of measurement. The model considers the heat transfer between parts through conduction and loss only by radiation since the instrument operates in a space environment. The goal is to understand how each component interferes with sensitivity and response time of the instrument depending on its design, material, volume and thermal contact. The model was applied to data generated by a prototype for validation.
Luminosity, which is the total amount of radiant energy emitted by an object, is one of the most critical quantities in astrophysics for characterizing stars. Equally important is the temporal evolution of a star’s luminosity because of its intimate connection with the stellar energy budget, large-scale convective motion, and heat storage in the stellar interior. The Sun’s luminosity and its variation have not been measured to date because current observations of the solar radiative output have been restricted to vantage points near the Earth. Here, we model the solar luminosity by extending a semiempirical total solar irradiance (TSI) model that uses solar-surface magnetism to reconstruct solar irradiance over the entire 4π solid angle around the Sun. This model was constrained by comparing its output to the irradiance in the Earth’s direction with the measured TSI. Comparing the solar luminosity to the TSI on timescales from days to solar cycles for cycles 23 and 24, we find poor agreement on short timescales (<solar rotation). This is not unexpected due to the Earth-centric viewing geometry and short-term irradiance dependence on surface features on the Earth-facing solar disk. On longer timescales, however, we find good agreement between the luminosity model and the TSI, which suggests that the extrapolation of luminosities to multicycle timescales based on TSI reconstructions may be possible. We show that the solar luminosity is not constant but varies in phase with the solar cycle. This variation has an amplitude of 0.14% from minimum to maximum for Solar Cycle 23. Considering the energetics in the solar convection zone, it is therefore obvious that a steady-state input from the radiative zone at the solar minimum level would lead to a gradual reduction in the energy content in the convection zone over multicentury timescales. We show that the luminosity at the base of the convection zone should be approximately 0.032% higher than that at the solar surface during solar minimum to maintain net energy equilibrium through the solar cycle. These different energy-input scenarios place constraints on the long-term evolution of the TSI and its impact on the solar forcing of climate variability. These results highlight the convection zone’s role as an energy reservoir on solar-cycle timescales and set constraints for dynamo models intending to understand the long-term evolution of the Sun and solar analogs.
The Total Solar Irradiance (TSI), which is the total radiation arriving at Earth's atmosphere from the Sun, is one of the most important forcing of the Earths climate. Measurements of the TSI have been made employing instruments on board several space-based platforms during the last four solar cycles. However, combining these measurements is still challenging due to the degradation of the sensor elements and the long-term stability of the electronics. Here we describe the preliminary efforts to design an absolute radiometer based on the principle of electrical substitution that is under development at Brazilian's National Institute for Space Research (INPE).
Long and reliable total solar irradiance (TSI) time series is one of the essential parameters for understanding solar contributions to climate change. The minor fluctuations of TSI in long timescales could impact the energy balance. Despite the improvement of accurate measurements provided by the instruments, at the time, long-term TSI variability and its effects had not been established. The space-borne radiometer era provided observations in short timescales from minutes to years. Therefore, this study presents an overview of irradiance observations, highlighting the importance of following its variability in different time scales. In this context, the Galileo Solar Space Telescope that has been developed by the Institute for Space Research (INPE), Brazil, includes the Irradiance Monitor Module with a radiometer cavity like the classical design and a next-generation compact radiometer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
334 Leonard St
Brooklyn, NY 11211
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.