scholarly journals Assessing the Errors in Shortwave Radiative Fluxes Inferred from the Geostationary Earth Radiation Budget (GERB) Instrument in the Presence of Dust Aerosol

2008 ◽  
Vol 47 (6) ◽  
pp. 1659-1680 ◽  
Author(s):  
Helen E. Brindley ◽  
Jacqueline E. Russell
Keyword(s):  
Angular Distribution ◽  
Specific Model ◽  
Radiation Budget ◽  
Distribution Model ◽  
Distribution Models ◽  
Radiation Fields ◽  
Time Period ◽  
Earth Radiation Budget ◽  
The Impact ◽  
Earth Radiation

Abstract The Geostationary Earth Radiation Budget (GERB) instruments flying on the Meteosat Second Generation series of satellites provide a unique tool with which to monitor the diurnal evolution of top-of-atmosphere broadband radiation fields. GERB products, which have recently been released to the scientific community, include aerosol information in addition to the observed radiances and inferred fluxes. However, no account of the anisotropic characteristics of aerosol has been incorporated in the radiance-to-flux conversion, which uses angular distribution models developed for clear or cloudy conditions. Here an attempt is made to quantify the impact of this omission in the shortwave (SW), focusing on dust-contaminated scenes. An observationally based representation of dust is used to develop a theoretical angular distribution model, which is tested through comparison with observed GERB radiances. For dusty scenes that have been processed as clear ocean, applying the dust model to convert GERB radiances to fluxes reduces the SW reflected flux by an average of approximately 12 W m−2 relative to the original GERB fluxes. This value ranges from −4 to +55 W m−2, depending on observation geometry and dust loading. For dusty scenes that the GERB processing has treated as cloudy, GERB fluxes are generally smaller than values obtained using the dust-specific model. On average, over the time period studied here, the two effects partially cancel, and the overall mean difference is 2.5 W m−2. However, it is shown that this cancellation is highly sensitive to the location and time period under consideration.

The impact of cloud inhomogeneities on the Earth radiation budget: the 14 October 1989 I.C.E. convective cloud case study

1994 ◽  
Vol 12 (2/3) ◽  
pp. 240-253 ◽  
Author(s):  
F. Parol ◽  
J. C. Buriez ◽  
D. Crétel ◽  
Y. Fouquart
Keyword(s):  
Aspect Ratio ◽  
Water Content ◽  
Liquid Water ◽  
Convective Cloud ◽  
Liquid Water Content ◽  
Radiation Budget ◽  
The Earth ◽  
Earth Radiation Budget ◽  
The Impact ◽  
Earth Radiation

Abstract. Through their multiple interactions with radiation, clouds have an important impact on the climate. Nonetheless, the simulation of clouds in climate models is still coarse. The present evolution of modeling tends to a more realistic representation of the liquid water content; thus the problem of its subgrid scale distribution is crucial. For a convective cloud field observed during ICE 89, Landsat TM data (resolution: 30m) have been analyzed in order to quantify the respective influences of both the horizontal distribution of liquid water content and cloud shape on the Earth radiation budget. The cloud field was found to be rather well-represented by a stochastic distribution of hemi-ellipsoidal clouds whose horizontal aspect ratio is close to 2 and whose vertical aspect ratio decreases as the cloud cell area increases. For that particular cloud field, neglecting the influence of the cloud shape leads to an over-estimate of the outgoing longwave flux; in the shortwave, it leads to an over-estimate of the reflected flux for high solar elevations but strongly depends on cloud cell orientations for low elevations. On the other hand, neglecting the influence of cloud size distribution leads to systematic over-estimate of their impact on the shortwave radiation whereas the effect is close to zero in the thermal range. The overall effect of the heterogeneities is estimated to be of the order of 10 W m-2 for the conditions of that Landsat picture (solar zenith angle 65°, cloud cover 70%); it might reach 40 W m-2 for an overhead sun and overcast cloud conditions.

scholarly journals Global Daytime Mean Shortwave Flux Consistency Under Varying EPIC Viewing Geometries

2021 ◽  
Vol 2 ◽  
Author(s):  
Wenying Su ◽  
Lusheng Liang ◽  
David P. Duda ◽  
Konstantin Khlopenkov ◽  
Mandana M. Thieman
Keyword(s):  
Radiant Energy ◽  
Energy System ◽  
Field Of View ◽  
Radiation Budget ◽  
Distribution Models ◽  
The Earth ◽  
Imaging Camera ◽  
Earth Radiation Budget ◽  
Mean Square Errors ◽  
Earth Radiation

One of the most crucial tasks of measuring top-of-atmosphere (TOA) radiative flux is to understand the relationships between radiances and fluxes, particularly for the reflected shortwave (SW) fluxes. The radiance-to-flux conversion is accomplished by constructing angular distribution models (ADMs). This conversion depends on solar-viewing geometries as well as the scene types within the field of view. To date, the most comprehensive observation-based ADMs are developed using the Clouds and the Earth’s Radiant Energy System (CERES) observations. These ADMs are used to derive TOA SW fluxes from CERES and other Earth radiation budget instruments which observe the Earth mostly from side-scattering angles. The Earth Polychromatic Imaging Camera (EPIC) onboard Deep Space Climate Observatory observes the Earth at the Lagrange-1 point in the near-backscattering directions and offers a testbed for the CERES ADMs. As the EPIC relative azimuth angles change from 168◦ to 178◦, the global daytime mean SW radiances can increase by as much as 10% though no notable cloud changes are observed. The global daytime mean SW fluxes derived after considering the radiance anisotropies at relative azimuth angles of 168◦ and 178◦ show much smaller differences (<1%), indicating increases in EPIC SW radiances are due mostly to changes in viewing geometries. Furthermore, annual global daytime mean SW fluxes from EPIC agree with the CERES equivalents to within 0.5 Wm−2 with root-mean-square errors less than 3.0 Wm−2. Consistency between SW fluxes from EPIC and CERES inverted from very different viewing geometries indicates that the CERES ADMs accurately quantify the radiance anisotropy and can be used for flux inversion from different viewing perspectives.

scholarly journals Shortwave Radiance to Irradiance Conversion for Earth Radiation Budget Satellite Observations: A Review

2021 ◽  
Vol 13 (13) ◽  
pp. 2640
Author(s):  
Jake J. Gristey ◽  
Wenying Su ◽  
Norman G. Loeb ◽  
Thomas H. Vonder Haar ◽  
Florian Tornow ◽  
...  
Keyword(s):  
Satellite Observations ◽  
Radiation Budget ◽  
Shortwave Radiation ◽  
Distribution Models ◽  
Machine Learning Applications ◽  
Earth Radiation Budget ◽  
Scene Information ◽  
Earth’S Climate ◽  
Observational Record ◽  
Earth Radiation

Observing the Earth radiation budget (ERB) from satellites is crucial for monitoring and understanding Earth’s climate. One of the major challenges for ERB observations, particularly for reflected shortwave radiation, is the conversion of the measured radiance to the more energetically relevant quantity of radiative flux, or irradiance. This conversion depends on the solar-viewing geometry and the scene composition associated with each instantaneous observation. We first outline the theoretical basis for algorithms to convert shortwave radiance to irradiance, most commonly known as empirical angular distribution models (ADMs). We then review the progression from early ERB satellite observations that applied relatively simple ADMs, to current ERB satellite observations that apply highly sophisticated ADMs. A notable development is the dramatic increase in the number of scene types, made possible by both the extended observational record and the enhanced scene information now available from collocated imager information. Compared with their predecessors, current shortwave ADMs result in a more consistent average albedo as a function of viewing zenith angle and lead to more accurate instantaneous and mean regional irradiance estimates. One implication of the increased complexity is that the algorithms may not be directly applicable to observations with insufficient accompanying imager information, or for existing or new satellite instruments where detailed scene information is not available. Recent advances that complement and build on the base of current approaches, including machine learning applications and semi-physical calculations, are highlighted.

scholarly journals Reexamination of the Observed Decadal Variability of the Earth Radiation Budget Using Altitude-Corrected ERBE/ERBS Nonscanner WFOV Data

2006 ◽  
Vol 19 (16) ◽  
pp. 4028-4040 ◽  
Author(s):  
Takmeng Wong ◽  
Bruce A. Wielicki ◽  
Robert B. Lee ◽  
G. Louis Smith ◽  
Kathryn A. Bush ◽  
...  
Keyword(s):  
High Resolution ◽  
Decadal Variability ◽  
Radiation Budget ◽  
Wide Field ◽  
Net Radiation ◽  
The Earth ◽  
Time Period ◽  
Data User ◽  
Earth Radiation Budget ◽  
Earth Radiation

Abstract This paper gives an update on the observed decadal variability of the earth radiation budget (ERB) using the latest altitude-corrected Earth Radiation Budget Experiment (ERBE)/Earth Radiation Budget Satellite (ERBS) Nonscanner Wide Field of View (WFOV) instrument Edition3 dataset. The effects of the altitude correction are to modify the original reported decadal changes in tropical mean (20°N to 20°S) longwave (LW), shortwave (SW), and net radiation between the 1980s and the 1990s from 3.1, −2.4, and −0.7 to 1.6, −3.0, and 1.4 W m−2, respectively. In addition, a small SW instrument drift over the 15-yr period was discovered during the validation of the WFOV Edition3 dataset. A correction was developed and applied to the Edition3 dataset at the data user level to produce the WFOV Edition3_Rev1 dataset. With this final correction, the ERBS Nonscanner-observed decadal changes in tropical mean LW, SW, and net radiation between the 1980s and the 1990s now stand at 0.7, −2.1, and 1.4 W m−2, respectively, which are similar to the observed decadal changes in the High-Resolution Infrared Radiometer Sounder (HIRS) Pathfinder OLR and the International Satellite Cloud Climatology Project (ISCCP) version FD record but disagree with the Advanced Very High Resolution Radiometer (AVHRR) Pathfinder ERB record. Furthermore, the observed interannual variability of near-global ERBS WFOV Edition3_Rev1 net radiation is found to be remarkably consistent with the latest ocean heat storage record for the overlapping time period of 1993 to 1999. Both datasets show variations of roughly 1.5 W m−2 in planetary net heat balance during the 1990s.

scholarly journals Radiometric and Spectral Characteristics of the ScaRaB-3 Instrument on Megha-Tropiques: Comparisons with ERBE, CERES, and GERB

2010 ◽  
Vol 27 (3) ◽  
pp. 428-442 ◽  
Author(s):  
Michel Viollier ◽  
Patrick Raberanto
Keyword(s):  
Spectral Response ◽  
Spectral Characteristics ◽  
Radiant Energy ◽  
Radiation Budget ◽  
Practical Reasons ◽  
Radiometric Calibration ◽  
Distribution Models ◽  
Earth Radiation Budget ◽  
The Difference ◽  
Earth Radiation

Abstract The Indian–French Megha-Tropiques mission, scheduled to be launched in 2010, will carry radiation and microwave sensors to study the energy and water cycle in the tropics. The radiation sensor, the third model of the Scanner for Radiation Budget (ScaRaB-3), is dedicated to the earth’s radiation budget, the difference between the solar absorbed flux and the terrestrial emitted flux. These fluxes are calculated from satellite measurements of outgoing shortwave (SW) and longwave (LW) radiances using angular distribution models (ADMs). For practical reasons, the LW radiation is calculated from the difference between a total (T) channel (0.2–100 μm) and an SW channel (0.2–4 μm). With the ADM application, the radiance calibration remains the most critical issue in the radiation budget estimation. The 1% accuracy goal is difficult to achieve, specifically in the SW domain. The authors explain their efforts to improve the radiometric calibration of ScaRaB-3. The internal calibration module is improved: the sensor is switched between SW and T channels by rotating the filter wheel on which the SW filter is now installed. Because the pyroelectric detector is sensitive to the thermal effect of the electromagnetic radiation independently of its spectral range, this plan allows calibrating the SW channel as a T channel by viewing a blackbody. Indeed, the transfer of the T calibration to the SW domain requires perfect knowledge of the total spectral response and of the transmittance of the SW filter, which is discussed in the article. Spectral errors are calculated with updated data. In the SW domain, they are found to be the smallest compared to those of the Earth Radiation Budget Experiment (ERBE), the Clouds and the Earth’s Radiant Energy System (CERES), and the Geostationary Earth Radiation Budget (GERB).

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