Model Calculations of Solar Spectral Irradiance in the 3.7-μm Band for Earth Remote Sensing Applications

2008 ◽  
Vol 47 (1) ◽  
pp. 124-134 ◽  
Author(s):  
Steven Platnick ◽  
Juan M. Fontenla
Keyword(s):  
Solar Irradiance ◽  
Spectral Region ◽  
Thermal Emission ◽  
Spectral Irradiance ◽  
Cloud Detection ◽  
Cloud Particle ◽  
Model Calculations ◽  
Solar Spectral Irradiance ◽  
Sensing Applications ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract Since the launch of the first Advanced Very High Resolution Radiometer (AVHRR) instrument aboard the Television and Infrared Observational Satellite (TIROS-N), measurements in the 3.7-μm atmospheric window have been exploited for use in cloud detection and screening, cloud thermodynamic phase and surface snow/ice discrimination, and quantitative cloud particle size retrievals. The utility of the band has led to the incorporation of similar channels on a number of existing satellite imagers and future operational imagers. Daytime observations in the band include both reflected solar and thermal emission energy. Since 3.7-μm channels are calibrated to a radiance scale (via onboard blackbodies), knowledge of the top-of-atmosphere solar irradiance in the spectral region is required to infer reflectance. Despite the ubiquity of 3.7-μm channels, absolute solar spectral irradiance data come from either a single measurement campaign (Thekaekara et al.) or synthetic spectra. In the current study, the historical 3.7-μm band spectral irradiance datasets are compared with the recent semiempirical solar model of the quiet sun by Fontenla et al. The model has expected uncertainties of about 2% in the 3.7-μm spectral region. The channel-averaged spectral irradiances using the observations reported by Thekaekara et al. are found to be 3.2%–4.1% greater than those derived from the Fontenla et al. model for Moderate Resolution Imaging Spectroradiometer (MODIS) and AVHRR instrument bandpasses; the Kurucz spectrum, as included in the Moderate Spectral Resolution Atmospheric Transmittance (MODTRAN4) distribution, gives channel-averaged irradiances 1.2%–1.5% smaller than the Fontenla model. For the MODIS instrument, these solar irradiance uncertainties result in cloud microphysical retrieval uncertainties that are comparable to other fundamental reflectance error sources.

Solar spectral irradiance and total solar irradiance at a solar minimum

2014 ◽  
Vol 54 (7) ◽  
pp. 926-932 ◽  
Author(s):  
E. E. Benevolenskaya ◽  
S. N. Shapovalov ◽  
I. G. Kostuchenko
Keyword(s):  
Solar Irradiance ◽  
Solar Minimum ◽  
Total Solar Irradiance ◽  
Spectral Irradiance ◽  
Solar Spectral Irradiance

scholarly journals Recent variability of the solar spectral irradiance and its impact on climate modelling

2013 ◽  
Vol 13 (8) ◽  
pp. 3945-3977 ◽  
Author(s):  
I. Ermolli ◽  
K. Matthes ◽  
T. Dudok de Wit ◽  
N. A. Krivova ◽  
K. Tourpali ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Solar Radiation ◽  
Spectral Range ◽  
Solar Irradiance ◽  
Spectral Irradiance ◽  
Climate Modelling ◽  
Earth’S Atmosphere ◽  
Solar Spectral Irradiance ◽  
Earth's Atmosphere ◽  
Earth’S Climate

Abstract. The lack of long and reliable time series of solar spectral irradiance (SSI) measurements makes an accurate quantification of solar contributions to recent climate change difficult. Whereas earlier SSI observations and models provided a qualitatively consistent picture of the SSI variability, recent measurements by the SORCE (SOlar Radiation and Climate Experiment) satellite suggest a significantly stronger variability in the ultraviolet (UV) spectral range and changes in the visible and near-infrared (NIR) bands in anti-phase with the solar cycle. A number of recent chemistry-climate model (CCM) simulations have shown that this might have significant implications on the Earth's atmosphere. Motivated by these results, we summarize here our current knowledge of SSI variability and its impact on Earth's climate. We present a detailed overview of existing SSI measurements and provide thorough comparison of models available to date. SSI changes influence the Earth's atmosphere, both directly, through changes in shortwave (SW) heating and therefore, temperature and ozone distributions in the stratosphere, and indirectly, through dynamical feedbacks. We investigate these direct and indirect effects using several state-of-the art CCM simulations forced with measured and modelled SSI changes. A unique asset of this study is the use of a common comprehensive approach for an issue that is usually addressed separately by different communities. We show that the SORCE measurements are difficult to reconcile with earlier observations and with SSI models. Of the five SSI models discussed here, specifically NRLSSI (Naval Research Laboratory Solar Spectral Irradiance), SATIRE-S (Spectral And Total Irradiance REconstructions for the Satellite era), COSI (COde for Solar Irradiance), SRPM (Solar Radiation Physical Modelling), and OAR (Osservatorio Astronomico di Roma), only one shows a behaviour of the UV and visible irradiance qualitatively resembling that of the recent SORCE measurements. However, the integral of the SSI computed with this model over the entire spectral range does not reproduce the measured cyclical changes of the total solar irradiance, which is an essential requisite for realistic evaluations of solar effects on the Earth's climate in CCMs. We show that within the range provided by the recent SSI observations and semi-empirical models discussed here, the NRLSSI model and SORCE observations represent the lower and upper limits in the magnitude of the SSI solar cycle variation. The results of the CCM simulations, forced with the SSI solar cycle variations estimated from the NRLSSI model and from SORCE measurements, show that the direct solar response in the stratosphere is larger for the SORCE than for the NRLSSI data. Correspondingly, larger UV forcing also leads to a larger surface response. Finally, we discuss the reliability of the available data and we propose additional coordinated work, first to build composite SSI data sets out of scattered observations and to refine current SSI models, and second, to run coordinated CCM experiments.

The Sensitivity of Solar Transmittance, Reflectance and Absorptance to Selected Averaging Procedures and Solar Irradiance Distributions

1980 ◽  
Vol 102 (1) ◽  
pp. 34-40 ◽  
Author(s):  
M. A. Lind ◽  
R. B. Pettit ◽  
K. D. Masterson
Keyword(s):  
Optical Properties ◽  
Solar Irradiance ◽  
Thermal Conversion ◽  
Spectral Irradiance ◽  
Solar Thermal ◽  
Computational Techniques ◽  
Spectral Transmittance ◽  
Solar Spectral Irradiance

The sensitivity of the solar weighted optical properties of selected materials to different terrestrial solar spectral irradiance distributions and computational techniques has been investigated. The spectral transmittance, reflectance, and absorptance of typical materials employed in solar thermal conversion systems were used for the calculations. The values obtained for several different solar irradiance distributions and calculational methods show only small differences. A single terrestrial solar irradiance distribution is recommended for use as a standard.

Solar infrared radiation towards building energy efficiency: measurement, data, and modeling

2020 ◽  
Vol 28 (4) ◽  
pp. 457-465
Author(s):  
Yuhui Song ◽  
Qiuhua Duan ◽  
Yanxiao Feng ◽  
Enhe Zhang ◽  
Julian Wang ◽  
...  
Keyword(s):  
Solar Irradiance ◽  
Infrared Radiation ◽  
Measurement Data ◽  
Building Energy ◽  
Energy Performance ◽  
Spectral Irradiance ◽  
Solar Irradiation ◽  
Solar Spectral Irradiance ◽  
Modeling Techniques ◽  
Irradiance Data

With the recent discoveries and engineering solutions emerging in nanomaterials and nanostructures, independent band modulation of solar radiation on building envelopes, including glazing systems, has become increasingly viable as a potential means of improving building energy savings and indoor visual comfort. However, when it comes to the prediction of these new materials’ potential energy performance in buildings, most studies utilize a simple solar irradiance (e.g., global horizontal solar irradiance, direct beam solar irradiance) or a rough estimation of solar infrared (e.g., 50% solar irradiance) as input, which may cause significant errors. Consequently, there is a pressing need for reliable performance estimations of the solar infrared control and response at the building’s scale. To assess this, we need a solar spectral irradiance model, or at least a wideband (visible or infrared) solar irradiance model, as input. To develop this new type of model, one needs to understand the modeling-related key elements, including available solar spectral irradiance datasets, data collection methods, and modeling techniques. As such, this paper reviews the current major measurement methods and tools used in collecting solar spectral irradiance data with a focus on the solar infrared region, identifies the available related resources and datasets that particularly encompass the solar spectral irradiance data with a sufficient wavelength range, and studies existing solar irradiation modeling techniques for building simulations. These investigations will then form the background and backbone for a study scheme of solar infrared radiation modeling and indicate future research paths and opportunities.

scholarly journals Differences in liquid cloud droplet effective radius and number concentration estimates between MODIS collections 5.1 and 6 over global oceans

2017 ◽  
Vol 10 (6) ◽  
pp. 2105-2116 ◽  
Author(s):  
John Rausch ◽  
Kerry Meyer ◽  
Ralf Bennartz ◽  
Steven Platnick
Keyword(s):  
Solar Irradiance ◽  
Thermal Emission ◽  
Cloud Droplet ◽  
Number Concentration ◽  
Effective Radius ◽  
Spectral Channel ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Cloud Top Pressure ◽  
Global Oceans

Abstract. Differences in cloud droplet effective radius and cloud droplet number concentration (CDNC) estimates inferred from the Aqua–MODIS (Moderate Resolution Imaging Spectroradiometer) collections 5.1 (C5.1) and 6 (C6) cloud products (MYD06) are examined for warm clouds over global oceans for the year 2008. Individual pixel level retrievals for both collections are aggregated to 1°  ×  1° and compared globally and regionally for the three main spectral channel pairs used for MODIS cloud optical property retrievals. Comparisons between both collections are performed for cases in which all three effective radii retrievals are classified by the MODIS cloud product as valid. The contribution to the observed differences of several key MYD06 Collection 6 algorithm updates are also explored, with a focus on changes to the surface reflectance model, assumed solar irradiance, above-cloud emission, cloud-top pressure (CTP), and pixel registration. Global results show a neutral to positive (> 50 cm−3) change for C6-derived CDNC relative to C5.1 for the 1.6 and 2.1 µm channel retrievals, corresponding to a neutral to −2 µm difference in droplet effective radius (re). For 3.7 µm retrievals, CDNC results show a negative change in the tropics, with differences transitioning toward positive values with increasing latitude spanning −25 to +50 cm−3 related to a +2.5 to −1 µm transition in effective radius. Cloud optical thickness (τ) differences were small relative to effective radius and found to not significantly impact CDNC estimates. Regionally, the magnitude and behavior of the annual CDNC cycle are compared for each effective radius retrieval. Results from this study indicate significant inter-collection differences in aggregated values of effective radius due to changes to the precomputed retrieval lookup tables (LUTs) for ocean scenes, changes to retrieved cloud-top pressure, solar irradiance, or above-cloud thermal emission, depending upon spectral channel. The observed differences between collections may have implications for existing MODIS-derived climatologies and validation studies of effective radius and CDNC.

scholarly journals Mathematical Assessment of the Effects of Substituting the Band Radiative Transfer Equation (RTE) for the Spectral RTE in the Applications of Earth’s Surface Temperature Retrievals from Spaceborne Infrared Imageries

2019 ◽  
Vol 11 (3) ◽  
pp. 226
Author(s):  
Chunguang Liu ◽  
Jiancheng Shi ◽  
Tianxing Wang ◽  
Kirpa Ram ◽  
Tianjie Zhao
Keyword(s):  
Radiative Transfer ◽  
Surface Temperature ◽  
Spectral Region ◽  
Transfer Equation ◽  
Thermal Emission ◽  
Radiative Transfer Equation ◽  
Spectral Response ◽  
Conservation Of Energy ◽  
Surface Emission ◽  
Moderate Resolution Imaging Spectroradiometer

The Planck’s thermal emission function, the reflectivity-emissivity decoupled Kirchhoff’s law and the associated atmospheric radiative transfer equation (RTE) is a theoretical base for Earth surface temperature (ST) retrievals from spaceborne infrared imageries. The infrared (IR) instruments generally collect band averaged radiance which are usually different from the RT codes simulated spectral one. Although IR band RTE is widely used, the effects of substituting the band-averaged RTE for the corresponding spectral one for those broadband observations (e.g., the Moderate Resolution Imaging Spectroradiometer (MODIS) thermal IR bands) have not been evaluated. In this paper, mathematical analysis and numerical experiments have been conducted to clarify the uncertainties arising from this substitution treatment. Firstly, we present the IR spectral RTE in a concise manner, and then, based on the law of conservation of energy and the integral assumption, a detailed mathematical derivation of the commonly-used IR band RTE has been derived. The significant improvement of the derivation is the validation of the integral assumption, which states that over a small spectral region, the integral of a product is approximately equal to the product of integrals. In the IR spectral region, taking the most significant term of the IR band RTE as an example (i.e., the surface emission term), we confirmed that, for the satellite collected IR signals emitted from the Earth’s surface, over any bandwidth at any band-location and under any instrument spectral response function (SRF), the integral approximation (IA) is a well-founded approximation and thus the IR band RTEs are good approximations for the corresponding spectral ones. Furthermore, in the ST, especially the land ST, product validation investigations, the ST errors introduced by the substituting treatment are negligible and do not need to be taken into consideration.

scholarly journals Field Quality Control of Spectral Solar Irradiance Measurements by Comparison with Broadband Measurements

2021 ◽  
Vol 13 (19) ◽  
pp. 10585
Author(s):  
Aitor Marzo ◽  
Jesús Ballestrín ◽  
Joaquín Alonso-Montesinos ◽  
Pablo Ferrada ◽  
Jesús Polo ◽  
...  
Keyword(s):  
Solar Irradiance ◽  
Spectral Estimation ◽  
Strong Dependence ◽  
High Sensitivity ◽  
Ground Level ◽  
Spectral Irradiance ◽  
Simulation Code ◽  
Solar Spectral Irradiance ◽  
Direct Normal Irradiance ◽  
Atmospheric Transmittance

Measurement of solar spectral irradiance is required in an increasingly wide variety of technical applications, such as atmospheric studies, health, and solar energy, among others. The solar spectral irradiance at ground level has a strong dependence on many atmospheric parameters. In addition, spectroradiometer optics and detectors have high sensitivity. Because of this, it is necessary to compare with a reference instrumentation or light source to verify the quality of measurements. A simple and realistic test for validating solar spectral irradiance measurements is presented in this study. This methodology is applicable for a specific spectral range inside the broadband range from 280 to 4000 nm under cloudless sky conditions. The method compares solar spectral irradiance measurements with both predictions of clear-sky solar spectral irradiance and measurements of broadband instruments such as pyrheliometers. For the spectral estimation, a free atmospheric transmittance simulation code with the air mass calculation as the mean parameter was used. The spectral direct normal irradiance (Gbλ) measurements of two different spectroradiometers were tested at Plataforma Solar de Almería, Spain. The results are presented in this article. Although only Gbλ measurements were considered in this study, the same methodology can be applied to the other solar irradiance components.

scholarly journals How Does the Sun’s Spectrum Vary?

2012 ◽  
Vol 25 (7) ◽  
pp. 2555-2560 ◽  
Author(s):  
Judith L. Lean ◽  
Matthew T. DeLand
Keyword(s):  
Solar Activity ◽  
Solar Irradiance ◽  
Solar Spectrum ◽  
Total Solar Irradiance ◽  
Spectral Irradiance ◽  
Model Calculations ◽  
Uv Irradiance ◽  
Infrared Spectral ◽  
Total Irradiance ◽  
Solar Ultraviolet

Abstract Recent observations made by the Spectral Irradiance Monitor (SIM) on the Solar Radiation and Climate Experiment (SORCE) spacecraft suggest that the Sun’s visible and infrared spectral irradiance increased from 2004 to 2008, even as the total solar irradiance measured simultaneously by SORCE’s Total Irradiance Monitor (TIM) decreased. At the same time, solar ultraviolet (UV) irradiance decreased 3–10 times more than expected from prior observations and model calculations of the known effects of sunspot and facular solar features. Analysis of the SIM spectral irradiance observations during the solar minimum epoch of 2008, when solar activity was essentially invariant, exposes trends in the SIM observations relative to both total solar irradiance and solar activity that are unlikely to be solar in origin. The authors suggest that the SIM’s radically different solar variability characterization is a consequence of undetected instrument sensitivity drifts, not true solar spectrum changes. It is thus doubtful that simulations of climate and atmospheric change using SIM measurements are indicative of real terrestrial behavior.

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