Modeling zenith-angle dependence of outgoing longwave radiation: Implication for flux measurements

Otterman, J.; Starr, David Oc.; Brakke, Thomas W.; Davies, Roger; Jacobowitz, H.; Mehta, A. V.; Chéruy, F.; Prabhakara, C.

doi:10.1016/s0034-4257(97)00084-9

Cited by 16 publications

(7 citation statements)

References 33 publications

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“…If the radiation emitted from the atmosphere was isotropic, F = πL could be established. However, because this radiation is actually anisotropic, the radiance observed from the satellite's VZA must be converted to irradiance [1]. Therefore, the equation given below is used to convert the narrowband radiance observed on the AHI channel into narrowband irradiance (Equations (1)-(3)).…”

Section: Converting Radiance To Irradiancementioning

confidence: 99%

“…Outgoing longwave radiation at the top of the atmosphere (TOA OLR) is an indicator that can describe the overall state of the earth-atmosphere system [1][2][3][4]. Also, OLR is an important radiation budget when balanced with net shortwave radiation at the top of the atmosphere and used in climate studies related to energy balance [5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

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Using the Himawari-8 AHI Multi-Channel to Improve the Calculation Accuracy of Outgoing Longwave Radiation at the Top of the Atmosphere

Kim

Lee

2019

Remote Sensing

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In this study, Himawari-8 Advanced Himawari Imager (AHI) longwave channel data that is sensitive to clouds and absorption gas were used to improve the accuracy of the algorithm used to calculate outgoing longwave radiation (OLR) at the top of the atmosphere. A radiative transfer model with a variety of atmospheric conditions was run using Garand vertical profile data as input data. The results of the simulation showed that changes in AHI channels 8, 12, 15, and 16, which were used to calculate OLR, were sensitive to changes in cloud characteristics (cloud optical thickness and cloud height) and absorption gases (water vapor, O3, CO2, aerosol optical thickness) in the atmosphere. When compared to long-term analysis OLR data from 2017, as recorded by the Cloud and Earth’s Radiant Energy System (CERES), the OLR calculated in this study had an annual mean bias of 2.28 Wm−2 and a root mean square error (RMSE) of 11.03 Wm−2. The new calculation method mitigated the problem of overestimations in OLR in mostly cloudy and overcast regions and underestimated OLR in cloud-free desert regions. It is also an improvement over the result from the existing OLR calculation algorithm, which uses window and water vapor channels.

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Section: Converting Radiance To Irradiancementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Using the Himawari-8 AHI Multi-Channel to Improve the Calculation Accuracy of Outgoing Longwave Radiation at the Top of the Atmosphere

Kim

Lee

2019

Remote Sensing

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“…In particular, the EAV method performs better in SW clear and cloudy land scenes and EAT obtains better comparisons in the LW regime and over SW permanent snow scenes. The better results obtained in the LW domain by EAT were expected, since the oblique views around 55° are known to provide the most accurate LW flux estimations (Otterman et al 1997) and the EAT method reduces significantly the weighting of the nadir view (less than 4% while the obhque views account for the 96% of the effective radiance).…”

Section: Discussion and Summarymentioning

confidence: 88%

Radiative Flux Estimation from a Broadband Radiometer Using Synthetic Angular Models in the EarthCARE Mission Framework. Part II: Evaluation

Domenech

López-Baeza

Donovan

et al. 2012

Journal of Applied Meteorology and Climatology

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The instantaneous top-of-atmosphere (TOA) radiance-to-flux conversion for the broadband radiometer (BBR) on board the Earth Clouds. Aerosols, and Radiation Explorer (EarthCARE) was assessed in Part I of this paper, by developing theoretical angular distribution models (ADMs) specifically designed for the instrument viewing configuration. This paper validates the BBR ADMs by comparing derived flux estimates with flux retrievals obtained from the Clouds and the Earth's Radiant Energy System (CERES) Terra models. A CERES BBR-like database is employed in the assessment, which is an optimum dataset to validate the BBR algorithms and to determine the benefits of the multiangular conversion procedures in the BBR instrument. The validation of theoretical results with empirical data is essential to prepare the conversion algorithms prior to the launch of EarthCARE. This paper demonstrates that the application of a linear combination method is not recommended when outgoing radiances do not follow the response modeled in the radiative transfer calculations. An effective radiance averaged model outperforms all other developed models, in terms of the coefficient of variation of the root-mean-square error, in the validation study of the shortwave (SW) regime (clear sky 1.9%; cloudy 7.1%) while an effective radiance along-track model obtains the best comparisons for the longwave (LW) regime (clear sky 1.4%: cloudy 1.5%). The evaluation of the multiangular models with scenes with high anisotropy shows that multiview flux conversion algorithms can statistically improve CERES ADM results when CERES flux discrepancies of a target are higher than 4 W m"" in the LW domain and SW clear-sky scenes and higher than 20 W m"^ in scenes with cloudy conditions.

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“…The results do not show large differences in the TOA flux retrievals because of the smooth anisotropic nature of LW radiance field. The lowest error is associated with the observation at 50° because of the low dependence on the scene type and the reduced anisotropic effect around this angle [ Bodas‐Salcedo et al , 2003; Otterman et al , 1997]. On the other hand, as expected the worst inversion is obtained for the nadir view.…”

Section: Methodsmentioning

confidence: 89%

Toward an Earth Clouds, Aerosols and Radiation Explore (EarthCARE) thermal flux determination: Evaluation using Clouds and the Earth's Radiant Energy System (CERES) true along-track data

Domenech¹,

Wehr²,

Fischer³

2011

J. Geophys. Res.

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[1] The Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) mission developed by the European Space Agency and the Japan Aerospace Exploration Agency addresses the need to improve the understanding of the interactions between cloud, aerosol, and radiation processes. The broadband radiometer (BBR) instrument on board the EarthCARE spacecraft provides measurements of broadband reflected solar and emitted thermal radiances at the top of atmosphere (TOA) over the along-track satellite path at three fixed viewing zenith angles. The multiangular information provided by the BBR, combined with the spectral information from the EarthCARE's multispectral imager (MSI) can be exploited to construct accurate thermal radiance-to-flux conversion algorithms on the basis of radiative transfer modeling. In this study, the methodology to derive longwave (LW) fluxes from BBR and MSI data is described, and the performance of the LW BBR angular models is compared with the Clouds and the Earth's Radiant Energy System (CERES) Terra flux retrievals in order to evaluate the reliability of the BBR synthetic models when applied to satellite-based radiances. For this purpose, the BBR methodology proposed in this work is adapted to the CERES and the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument specifications, and new LW angular models for CERES are developed. According to plane-parallel simulations, the BBR LW flux uncertainty caused by flux inversion could be reduced up to 0.4 W m −2. The intercomparison between CERES BBR-like adapted and CERES original angular models is performed over a BBR-like database of CERES true along track, and the averaged instantaneous retrievals agree to within 2 W m −2 .Citation: Domenech, C., T. Wehr, and J. Fischer (2011), Toward an Earth Clouds, Aerosols and Radiation Explore (EarthCARE) thermal flux determination: Evaluation using Clouds and the Earth's Radiant Energy System (CERES) true along-track data,

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Modeling zenith-angle dependence of outgoing longwave radiation: Implication for flux measurements

Cited by 16 publications

References 33 publications

Using the Himawari-8 AHI Multi-Channel to Improve the Calculation Accuracy of Outgoing Longwave Radiation at the Top of the Atmosphere

Using the Himawari-8 AHI Multi-Channel to Improve the Calculation Accuracy of Outgoing Longwave Radiation at the Top of the Atmosphere

Radiative Flux Estimation from a Broadband Radiometer Using Synthetic Angular Models in the EarthCARE Mission Framework. Part II: Evaluation

Toward an Earth Clouds, Aerosols and Radiation Explore (EarthCARE) thermal flux determination: Evaluation using Clouds and the Earth's Radiant Energy System (CERES) true along-track data

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