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The total outgoing long-wave spectral radiances (25.25-2999.75 cm −1 ) constructed from IASI measurements (black) and estimated far infrared radiance (blue) for four instantaneous scenes over: (a) tropical equatorial land, (b) midlatitude land, (c) the Sahara desert and (d) Antarctica. All are night-time scenes from the 17 April 2012.
Source publication
A new method of deriving high-resolution top-of-atmosphere spectral radiances
in 10 181 bands, over the whole outgoing long-wave spectrum of the Earth, is
presented. Correlations between different channels measured by the Infrared
Atmospheric Sounding Interfermeter (IASI) on the MetOp-A (Meteorological Operation) satellite and
unobserved wavenumber...
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... Among them, the LBL method is considered to be the most accurate solution method (Alexander Berk et al., 2015). Some studies have pointed out that using the LBL calculation algorithm can improve the inversion accuracy of polynomial regression algorithms (Gruber et al., 1994;Turner et al., 2015). However, its slow calculation speed makes it infrequently employed in large-scale radiation transfer simulation work. ...
A R T I C L E I N F O Edited by Jing M. Chen Keywords: Outgoing longwave radiation (OLR) Radiation transfer simulation Multi-Dimensional matrix MAPping (MDMAP) Polynomial regression Moderate resolution imaging Spectroradiometer (MODIS) Cloud and Earth's radiant energy system (CERES) A B S T R A C T Outgoing Longwave Radiation (OLR) is an important component of the Earth's radiation budget and a key parameter for coupled models of the atmosphere, ocean, land, and other systems. It is of significant importance in studies related to Earth sciences such as weather forecasting, climate research, and disaster monitoring. Since narrowband sensors are more widely available and have higher spatial resolutions than broadband sensors, high-resolution OLR data are currently frequently estimated using narrowband sensors. This study proposes a novel physical method, namely the Multi-Dimensional matrix MAPping algorithm (MDMAP) framework, inspired by the scene classification ideas of Cloud and Earth's Radiant Energy System (CERES) and the differential absorption theory. The new framework aims to accurately retrieve OLR from the multi-channel infrared sensor, such as Moderate Resolution Imaging Spectroradiometer (MODIS). Corresponding to traditional algorithms, such as the polynomial regression algorithm (POLY) and lookup table algorithm (LUT), the new framework provides two distinct implementations of the MDMAP algorithm framework (MDMAP:POLY and MDMAP:LUT). The performances of both the traditional and the newly proposed algorithms are evaluated based on the radiative transfer simulation dataset and CERES SSF OLR products. The results show that the MDMAP algorithms behave more accurately than the traditional ones under most conditions, especially under clear-sky conditions. Specifically, a comprehensive analysis indicates that the new algorithms demonstrate smaller RMSEs than the traditional ones under various conditions, particularly in desert regions with the RMSE reduction exceeding 3 W/m 2 (>30%). Moreover, the two new algorithms reveal enhanced robustness to noise uncertainties, and demonstrate remarkable generality and computational efficiency, implying their potential and better applicability in deriving believable OLR from most infrared sensors.
... To date, space missions have only sampled part of the Earth's OLR spectral range (only extending up to 25 µm), and only a few spectral measurements have been collected in the FIR region [3,9,10]. Conversely, its has been a long time since planetary atmospheres have been observed in the FIR and TIR spectral regions. ...
Citation: Dinelli, B.M.; Del Bianco, S.; Castelli, E.; Di Roma, A.; Lorenzi, G.; Premuda, M.; Barbara, F.; Gai, M.; Raspollini, P.; Di Natale, G. GBB-Nadir and KLIMA: Two Full Physics Codes for the Computation of the Infrared Spectrum of the Planetary Radiation Escaping to Space. Remote Sens. 2023, 15, 2532. Abstract: In 2019 the Far-Infrared Outgoing Radiation Understanding and Monitoring (FORUM) mission was selected to be the 9th Earth Explorer mission of the European Space Agency (ESA). In the preparatory phase of the mission there was the need for accurate and versatile codes to compute the spectrally resolved Earth radiation escaping to space (outgoing long-wave radiation, OLR), targets for the FORUM measurements.Moreover, for the study of planetary atmospheres, several instruments measuring the planetary radiation escaping to space have been deployed (i.e., the planetary Fourier spectrometer on Mars express or composite infrared spectrometer on Cassini). For both the analysis of the measurements of these instruments and the design of new instruments, reliable radiative transfer codes need to be available. In this paper, we describe two full physics codes, Geofit broadband-Nadir (GBB-Nadir) and Kyoto protocol-informed management of adaptation (KLIMA), both able to compute the OLR spectrum, while GBB-Nadir is only a forward model, and therefore computes the spectra only, KLIMA implements the computation of spectral radiance derivatives with respect to atmospheric parameters and therefore it is suitable to be used in retrieval codes. The GBB-Nadir code can be interfaced with radiative transfer solvers that include representations of multiple scatterings, making it suitable to compute the radiances in all-sky conditions. KLIMA has been extensively validated comparing its radiances to ones generated by the widely used line-by-line radiative transfer model (LBLRTM) code. In this paper, we describe the latest version of both codes and their comparison. We compared the optical depth computed by GBB-Nadir and KLIMA for given values of pressure, temperature and gas columns for most gases active in the far-infrared and thermal-infrared spectral regions. We show that the optical depths computed by the two codes are in very good agreement. We compared the simulated spectra in clear sky conditions for three different atmospheres (equatorial, mid-latitude and polar) at resolutions of the FORUM instrument. The differences found are well below the expected noise of the FORUM instrument. The KLIMA code has already been used to simulate the observations of the Mars atmosphere, while the limb version of the GBB code has been used to simulate the radiances measured in the limb geometry of planetary atmospheres (Titan and Jupiter). Therefore, we may safely affirm that both codes can be used to simulate the nadir measurements of planetary atmospheres.
... In the following, we will refer to them as seasonal and interannual variability, respectively. Following ref. 30, we use a prediction model based on ℒ ν simulations to extend our estimate of λ ν to the far infrared (FIR), which is not covered by IASI. This way, we provide an observational estimate of the global mean all-sky λ ν , covering the full spectrum of Earth's outgoing long-wave radiation. ...
... As mentioned, the λ ν values derived from IASI observations for the FIR are based on a prediction model introduced by Turner et al. 30 . Future missions such as the Far-infrared Outgoing Radiation Understanding and Monitoring (FORUM) and the Polar Radiant Energy in the Far Infrared Experiment (PREFIRE) will provide spectrally resolved observations of the entire FIR. ...
... The simulated monthly clear-sky ℒ ν spectra are used to set up a prediction model, closely following ref. 30. For every channel between 100 cm −1 and 645 cm −1 , we calculate the correlation coefficient of ln(ℒ ν ) with every IASI channel from 645 cm −1 to 2,760 cm −1 . ...
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... In this study we have used REFIR-PAD downwelling radiance observations covering the spectral range 100-1400 cm −1 for clear-sky cases from 2013 over Dome C in Antarctica to assess whether it is currently possible to build a model which uses MIR spectral radiances to predict spectral values in the FIR to an acceptable level of accuracy. The motivation for this work comes from a number of studies that have estimated the FIR spectrum from satellite observations of MIR radiances (Huang et al., 2008;Turner et al., 2015). While these have shown encouraging agreement with broadband observations, the results have not been tested with spectrally resolved measurements due to the lack of such observations. ...
... While these have shown encouraging agreement with broadband observations, the results have not been tested with spectrally resolved measurements due to the lack of such observations. We have described a correlation-and regression-based methodology based on Turner et al. (2015), which we have used to search for predictor wavenumbers and to extract regression coefficients at these specified wavenumbers. In addition to the observations, radiosonde soundings are used to create a corresponding simulated spectral database with the radiative transfer model LBLRTM. ...
Far-infrared (FIR: 100cm-1<wavenumber, ν<667 cm-1) radiation emitted by the Earth and its atmosphere plays a key role in the Earth's energy budget. However, because of a lack of spectrally resolved measurements, radiation schemes in climate models suffer from a lack of constraint across this spectral range. Exploiting a method developed to estimate upwelling far-infrared radiation from mid-infrared (MIR: 667cm-1<ν<1400 cm-1) observations, we explore the possibility of inferring zenith FIR downwelling radiances in zenith-looking observation geometry, focusing on clear-sky conditions in Antarctica. The methodology selects a MIR predictor wavenumber for each FIR wavenumber based on the maximum correlation seen between the different spectral ranges. Observations from the REFIR-PAD instrument (Radiation Explorer in the Far Infrared – Prototype for Application and Development) and high-resolution radiance simulations generated from co-located radio soundings are used to develop and assess the method. We highlight the impact of noise on the correlation between MIR and FIR radiances by comparing the observational and theoretical cases. Using the observed values in isolation, between 150 and 360 cm-1, differences between the “true” and “extended” radiances are less than 5 %. However, in spectral bands of low signal, between 360 and 667 cm-1, the impact of instrument noise is strong and increases the differences seen. When the extension of the observed spectra is performed using regression coefficients based on noise-free radiative transfer simulations the results show strong biases, exceeding 100 % where the signal is low. These biases are reduced to just a few percent if the noise in the observations is accounted for in the simulation procedure. Our results imply that while it is feasible to use this type of approach to extend mid-infrared spectral measurements to the far-infrared, the quality of the extension will be strongly dependent on the noise characteristics of the observations. A good knowledge of the atmospheric state associated with the measurements is also required in order to build a representative regression model.
... This approach has also been applied to satellite obser-G. Bianchini et al.: An FTS for ground-based remote sensing of the atmospheric emission vations to derive CERES fluxes from IASI spectral measurements (Turner et al., 2015). ...
The Radiation Explorer in the Far Infrared – Prototype for Applications and Development (REFIR-PAD) is a Fourier transform spectroradiometer that has been designed to operate from both stratospheric balloon platforms and the ground. It has been successfully deployed in a stratospheric balloon flight and several ground-based campaigns from high-altitude sites, including the current installation at the Italian–French Concordia Antarctic station. The instrument is capable of operating autonomously with only a limited need of remote control and monitoring and provides a multiyear dataset of spectrally resolved atmospheric downwelling radiances, measured in the 100–1500 cm-1 spectral range with 0.4 cm-1 resolution and a radiometric uncertainty of better than 0.85 mW(m2srcm-1)-1.
... In this study we have used REFIR-PAD downwelling observations for clear-sky cases from 2013 over Dome C in Antarctica to assess whether it is possible to build a model capable of using MIR radiances to predict values in the FIR. We have described 15 a correlation and regression based methodology based on Turner et al. (2015) which we have used to search for predictor wavenumbers and to extract regression coefficients at these specified wavenumbers. In addition to the observations, radiosonde soundings are used to create a corresponding simulated spectral database with the radiative transfer model LBLRTM. ...
Far-infrared (FIR: 100cm−1wavenumber, ν667cm−1) radiation emitted by the Earth and its atmosphere plays a key role in the Earth's energy budget. However, because of a lack of spectrally resolved measurements, radiation schemes in climate models suffer from a lack of constraint across this spectral range. Exploiting a method developed to estimate upwelling far-infrared radiation from mid-infrared (MIR: 667cm−1ν1400cm−1) observations, we explore the possibility of inferring zenith FIR downwelling radiances in zenith-looking observation geometry, focusing on clear-sky conditions in Antarctica. The methodology selects a MIR predictor wavenumber for each FIR wavenumber based on the maximum correlation seen between the different spectral ranges. Observations from the REFIR-PAD instrument (Radiation Explorer in the Far Infrared – Prototype for Application and Development) and high resolution radiance simulations generated from co-located radio soundings are used to develop and assess the method. We highlight the impact of noise on the correlation between MIR and FIR radiances by comparing the observational and theoretical cases. Using the observed values in isolation, between 150 and 360cm−1, differences between the true and extended radiances are less than 5%. However, in spectral bands of low signal, between 360 and 667cm−1, the impact of instrument noise is strong and increases the differences seen. When the extension of the observed spectra is performed using regression coefficients based on noise-free radiative-transfer simulations the results show strong biases, exceeding 100% where the signal is low. These biases are reduced to just a few percent if the noise in the observations is accounted for the simulation procedure. Our results imply that while it is feasible to use this type of approach to extend mid infrared spectral measurements to the far-infrared, the quality of the extension will be strongly dependent on the noise characteristics of the observations. A good knowledge of the atmospheric state associated with the measurements is also required in order to build a representative regression model.
... TOA BT and OLR represent longwave radiation variations of the entire surface-atmosphere system and are significantly affected by atmospheric conditions. The height and coverage of clouds have a dominating influence on the total intensity of longwave radiative fluxes received at the TOA (Turner et al., 2015). Therefore, eliminating cloud effects is necessary in applications, which can be difficult when working with low-resolution data. ...
Detecting various anomalies using optical satellite data prior to strong earthquakes is key to understanding and forecasting earthquake activities because of its recognition of thermal-radiation-related phenomena in seismic preparation phases. Data from satellite observations serve as a powerful tool in monitoring earthquake preparation areas at a global scale and in a nearly real-time manner. Over the past several decades, many new different data sources have been utilized in this field, and progressive anomaly detection approaches have been developed. This paper reviews the progress and development of pre-seismic anomaly detection technology in this decade. First, precursor parameters, including parameters from the top of the atmosphere, in the atmosphere, and on the Earth's surface, are stated and discussed. Second, different anomaly detection methods, which are used to extract anomalous signals that probably indicate future seismic events, are presented. Finally, certain critical problems with the current research are highlighted, and new developing trends and perspectives for future work are discussed. The development of Earth observation satellites and anomaly detection algorithms can enrich available information sources, provide advanced tools for multilevel earthquake monitoring, and improve short- and medium-term forecasting, which play a large and growing role in pre-seismic anomaly detection research.
... При этом в общем случае также следует учитывать различия в интенсивности излучения в зависимости от географических точек наблюдения, условий освещенности, сезонности, климатических и погодных условий. На рис. 3 приведены данные для ночного времени суток, апрель 2012 г. [6]. Целью исследования является разработка математической модели и проведение расчетов излучения системы поверхность Земли -атмосфера в среднем и дальнем ИК-диапазонах электромагнитного спектра для формирования исходных данных в заданном угловом направлении на лимб Земли. ...
The study proposes some methods of engineering calculation of outgoing infrared radiation on the basis of the solution of the energy transfer equation for a stationary radiation field in the Earth surface – atmosphere system with allowance for permissible approximations. According to the experimental data, a mathematical model has been developed and verified, which makes it possible to calculate the spectral distributions and integral values of the infrared radiation intensity for a given angular position of the observer outside the atmosphere.
... There has been increased interest within the climate sciences in the far-infrared spectrum, typically taken as 2000-20 000 GHz (15-150 µm), e.g. see Harries et al. (2008); Turner et al. (2015). This has also been sparsely measured in the atmosphere for similar reasons to those of the submillimetre, despite representing up to half of the total outgoing longwave radiation and three quarters of the total incoming longwave radiation. ...
The submillimetre is an understudied region of the Earth's atmospheric
electromagnetic spectrum. Prior technological gaps and relatively high
opacity due to the prevalence of rotational water vapour lines at these
wavelengths have slowed progress from a ground-based remote sensing
perspective; however, emerging superconducting detector technologies in the
fields of astronomy offer the potential to address key atmospheric science
challenges with new instrumental methods. A site study, with a focus on the
polar regions, is performed to assess theoretical feasibility by simulating
the downwelling (zenith angle = 0°) clear-sky submillimetre spectrum
from 30 mm (10 GHz) to 150 µm (2000 GHz) at six locations under
annual mean, summer, winter, daytime, night-time and low-humidity conditions.
Vertical profiles of temperature, pressure and 28 atmospheric gases are
constructed by combining radiosonde, meteorological reanalysis and
atmospheric chemistry model data. The sensitivity of the simulated spectra to
the choice of water vapour continuum model and spectroscopic line database is
explored. For the atmospheric trace species hypobromous acid (HOBr), hydrogen
bromide (HBr), perhydroxyl radical (HO2) and nitrous oxide (N2O)
the emission lines producing the largest change in brightness temperature are
identified. Signal strengths, centre frequencies, bandwidths, estimated
minimum integration times and maximum receiver noise temperatures are
determined for all cases. HOBr, HBr and HO2 produce brightness
temperature peaks in the mK to µK range, whereas the N2O peaks
are in the K range. The optimal submillimetre remote sensing lines for the
four species are shown to vary significantly between location and scenario,
strengthening the case for future hyperspectral instruments that measure over
a broad wavelength range. The techniques presented here provide a framework
that can be applied to additional species of interest and taken forward to
simulate retrievals and guide the design of future submillimetre
instruments.
L’évolution des flux radiatifs atmosphériques à grande longueur d’onde en réponse aux émissions de gaz à effet de serre anthropiques est à la source des changements du climat actuellement observés. Ce forçage radiatif positif du système climatique terrestre est d’une grande importance puisqu’il entraine par exemple des changements dans la circulation atmosphérique et le cycle hydrologique. Ce forçage radiatif correspond à l’évolution du flux radiatif sortant à grande longueur d’onde nommé Outgoing Longwave Radiation (OLR). Les sources et puits de cette énergie radiatives à chaque niveau atmosphérique définissent le taux de chauffage vertical à grande longueur d’onde. L’OLR et le taux de chauffage vertical sont deux des principales grandeurs radiatives importantes utilisées pour suivre et analyser le bilan radiatif terrestre et pour modéliser l’évolution du climat. L’étude de ces grandeurs radiatives prend tout son sens sur des échelles de temps climatiques (plus de vingt ans) et à l’échelle globale, ce que permet l’observation spatiale de la Terre. L’objectif de cette thèse est de déterminer l’apport du sondeur infrarouge hyperspectral IASI (Infrared Atmospheric Sounding Interferometer) à la détermination des grandeurs radiatives à grandes longueurs d’onde.Ces travaux s’appuient sur le développement de 4A-Flux : un module de calcul des flux radiatifs et du taux de chauffage vertical intégré au code de transfert radiatif raie-par-raie et couche-par-couche 4A/OP. Ce code a été validé dans le cadre de l’exercice international d’intercomparaison des codes de transfert radiatifs RFMIP. 4A-Flux a permis de réaliser des études de sensibilité des grandeurs radiatives aux différents paramètres atmosphériques et de surface.Bien que très précise, la modélisation raie-par-raie du transfert radiatif requiert un temps de calcul conséquent qui ne permet pas d’envisager la mise à l’échelle à la multitude d’observations spatiales réalisées par IASI. Nous avons donc développé une méthode basée sur les réseaux de neurones afin d’estimer les grandeurs radiatives directement à partir des spectres de température de brillance observés par IASI. Cette méthode repose sur l’apprentissage d’un perceptron multicouches à partir des bases de données construites avec 4A-Flux à partir des bases de données atmosphériques TIGR et ARSA développées au LMD.Nous démontrons ainsi la possibilité d’estimer à partir des observations à haute résolution spectrale du sondeur infrarouge IASI, sur une vingtaine d’années, période pertinente pour les études climatiques, non seulement l’évolution de l’OLR mais aussi, pour la première fois, du taux de chauffage associé. L’OLR estimé à partir de IASI est comparé et validé par rapport aux mesures réalisées par des radiomètres larges bandes (CERES, SCARAB) et sont analysées en rapport avec des signaux climatiques classiques tels que l'ENSO démontrant ainsi le grand intérêt de la mesure hyperspectrale de IASI pour le suivi des grandeurs radiatives pour le climat.
