scholarly journals Evaluating CERES angular distribution models for snow using surface reflectance observations from the East Antarctic Plateau

2010 ◽  
Vol 115 (D3) ◽  
Author(s):  
Stephen R. Hudson ◽  
Seiji Kato ◽  
Stephen G. Warren
Keyword(s):  
Angular Distribution ◽  
Surface Reflectance ◽  
Distribution Models ◽  
Antarctic Plateau

scholarly journals Angular Distribution Models for Top-of-Atmosphere Radiative Flux Estimation from the Clouds and the Earth’s Radiant Energy System Instrument on the Terra Satellite. Part I: Methodology

2005 ◽  
Vol 22 (4) ◽  
pp. 338-351 ◽  
Author(s):  
Norman G. Loeb ◽  
Seiji Kato ◽  
Konstantin Loukachine ◽  
Natividad Manalo-Smith
Keyword(s):  
Angular Distribution ◽  
Radiant Energy ◽  
Tropical Rainfall Measuring Mission ◽  
Energy System ◽  
Distribution Models ◽  
Radiative Fluxes ◽  
Earth Observing System ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Terra Satellite

Abstract The Clouds and Earth’s Radiant Energy System (CERES) provides coincident global cloud and aerosol properties together with reflected solar, emitted terrestrial longwave, and infrared window radiative fluxes. These data are needed to improve the understanding and modeling of the interaction between clouds, aerosols, and radiation at the top of the atmosphere, surface, and within the atmosphere. This paper describes the approach used to estimate top-of-atmosphere (TOA) radiative fluxes from instantaneous CERES radiance measurements on the Terra satellite. A key component involves the development of empirical angular distribution models (ADMs) that account for the angular dependence of the earth’s radiation field at the TOA. The CERES Terra ADMs are developed using 24 months of CERES radiances, coincident cloud and aerosol retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS), and meteorological parameters from the Global Modeling and Assimilation Office (GMAO)’s Goddard Earth Observing System (GEOS) Data Assimilation System (DAS) V4.0.3 product. Scene information for the ADMs is from MODIS retrievals and GEOS DAS V4.0.3 properties over the ocean, land, desert, and snow for both clear and cloudy conditions. Because the CERES Terra ADMs are global, and far more CERES data are available on Terra than were available from CERES on the Tropical Rainfall Measuring Mission (TRMM), the methodology used to define CERES Terra ADMs is different in many respects from that used to develop CERES TRMM ADMs, particularly over snow/sea ice, under cloudy conditions, and for clear scenes over land and desert.

scholarly journals Next-generation angular distribution models for top-of-atmosphere radiative flux calculation from CERES instruments: methodology

2015 ◽  
Vol 8 (2) ◽  
pp. 611-632 ◽  
Author(s):  
W. Su ◽  
J. Corbett ◽  
Z. Eitzen ◽  
L. Liang
Keyword(s):  
Angular Distribution ◽  
Sea Ice ◽  
Regional Scale ◽  
Radiant Energy ◽  
Energy System ◽  
Continuous Functions ◽  
Climate Feedback ◽  
Radiative Energy ◽  
Next Generation ◽  
Distribution Models

Abstract. The top-of-atmosphere (TOA) radiative fluxes are critical components to advancing our understanding of the Earth's radiative energy balance, radiative effects of clouds and aerosols, and climate feedback. The Clouds and the Earth's Radiant Energy System (CERES) instruments provide broadband shortwave and longwave radiance measurements. These radiances are converted to fluxes by using scene-type-dependent angular distribution models (ADMs). This paper describes the next-generation ADMs that are developed for Terra and Aqua using all available CERES rotating azimuth plane radiance measurements. Coincident cloud and aerosol retrievals, and radiance measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS), and meteorological parameters from Goddard Earth Observing System (GEOS) data assimilation version 5.4.1 are used to define scene type. CERES radiance measurements are stratified by scene type and by other parameters that are important for determining the anisotropy of the given scene type. Anisotropic factors are then defined either for discrete intervals of relevant parameters or as a continuous functions of combined parameters, depending on the scene type. Significant differences between the ADMs described in this paper and the existing ADMs are over clear-sky scene types and polar scene types. Over clear ocean, we developed a set of shortwave (SW) ADMs that explicitly account for aerosols. Over clear land, the SW ADMs are developed for every 1° latitude × 1° longitude region for every calendar month using a kernel-based bidirectional reflectance model. Over clear Antarctic scenes, SW ADMs are developed by accounting the effects of sastrugi on anisotropy. Over sea ice, a sea-ice brightness index is used to classify the scene type. Under cloudy conditions over all surface types, the longwave (LW) and window (WN) ADMs are developed by combining surface and cloud-top temperature, surface and cloud emissivity, cloud fraction, and precipitable water. Compared to the existing ADMs, the new ADMs change the monthly mean instantaneous fluxes by up to 5 W m−2 on a regional scale of 1° latitude × 1° longitude, but the flux changes are less than 0.5 W m−2 on a global scale.

scholarly journals Development of empirical angular distribution models for smoke aerosols: Methods

2011 ◽  
Vol 116 (D14) ◽  
Author(s):  
Falguni Patadia ◽  
Sundar A. Christopher ◽  
Jianglong Zhang
Keyword(s):  
Angular Distribution ◽  
Distribution Models

Models for the Directional Distribution of the Diffuse Sky Radiance

1990 ◽  
Vol 112 (2) ◽  
pp. 102-109 ◽  
Author(s):  
F. M. F. Siala ◽  
M. A. Rosen ◽  
F. C. Hooper
Keyword(s):  
Angular Distribution ◽  
Stochastic Models ◽  
Continuous Distribution ◽  
Time Dependent ◽  
Distribution Models ◽  
Directional Distribution ◽  
Sky Radiance ◽  
Semi Empirical ◽  
Sky Type

Both traditional and recently proposed models for the angular distribution of diffuse sky radiance are reviewed and compared. The models considered include basic models, sky-type-specific models, empirical and semi-empirical continuous distribution models, models which account for time-dependent cloud effects and stochastic models.

Comparison of four luminance and radiance angular distribution models for radiance estimation

Solar Energy ◽  
2011 ◽  
Vol 85 (9) ◽  
pp. 2202-2216 ◽  
Author(s):  
A. Gracia ◽  
J.L. Torres ◽  
M. De Blas ◽  
A. García ◽  
R. Perez
Keyword(s):  
Angular Distribution ◽  
Distribution Models ◽  
Radiance Estimation

Changes in TOA SW Fluxes over Marine Clouds When Estimated via Semi-Physical Angular Distribution Models

2021 ◽  
Author(s):  
F. Tornow ◽  
C. Domenech ◽  
J. N. S. Cole ◽  
N. Madenach ◽  
J. Fischer
Keyword(s):  
Angular Distribution ◽  
Optical Depth ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Cloud Water ◽  
Effective Radius ◽  
Distribution Models ◽  
Radiative Fluxes ◽  
Cloud Optical Depth ◽  
Aerosol Indirect Effects

AbstractTop-of-atmosphere (TOA) shortwave (SW) angular distribution models (ADMs) approximate – per angular direction of an imagined upward hemisphere – the intensity of sunlight scattered back from a specific Earth-atmosphere scene. ADMs are, thus, critical when converting satellite-borne broadband radiometry into estimated radiative fluxes. This paper applies a set of newly developed ADMs with a more refined scene definition and demonstrates tenable changes in estimated fluxes compared to currently operational ADMs. Newly developed ADMs use a semi-physical framework to consider cloud-top effective radius, , and above-cloud water vapor, ACWV, in addition to accounting for surface wind speed and clouds’ phase, fraction, and optical depth. In effect, instantaneous TOA SWfluxes for marine liquid-phase clouds had the largest flux differences (of up to 25 W m−2) for lower solar zenith angles and cloud optical depth greater than 10 due to extremes in or ACWV. In regions where clouds had persistently extreme levels of (here mostly for <7μm and >15μm) or ACWV, instantaneous fluxes estimated from Aqua, Terra, and Meteosat 8 and 9 satellites using the two ADMs differed systematically, resulting in significant deviations in daily mean fluxes (up to ±10 W m−2) and monthly mean fluxes (up to ±5 W m−2). Flux estimates using newly developed, semi-physical ADMs may contribute to a better understanding of solar fluxes over low-level clouds. It remains to be seen whether aerosol indirect effects are impacted by these updates.

scholarly journals Next-generation angular distribution models for top-of-atmosphere radiative flux calculation from the CERES instruments: validation

2015 ◽  
Vol 8 (5) ◽  
pp. 4489-4536 ◽  
Author(s):  
W. Su ◽  
J. Corbett ◽  
Z. Eitzen ◽  
L. Liang
Keyword(s):  
Angular Distribution ◽  
Radiant Energy ◽  
Energy System ◽  
Direct Integration ◽  
Distribution Models ◽  
Radiative Fluxes ◽  
Rms Error ◽  
Sky Conditions ◽  
Along Track ◽  
Scene Identification

Abstract. Radiative fluxes at the top of the atmosphere (TOA) from the Clouds and the Earth's Radiant Energy System (CERES) instrument are fundamental variables for understanding the Earth's energy balance and how it changes with time. TOA radiative fluxes are derived from the CERES radiance measurements using empirical angular distribution models (ADMs). This paper evaluates the accuracy of CERES TOA fluxes using direct integration and flux consistency tests. Direct integration tests show that the overall bias in regional monthly mean TOA shortwave (SW) flux is less than 0.2 W m−2 and the RMS error is less than 1.1 W m−2. The bias and RMS error are very similar between Terra and Aqua. The bias in regional monthly mean TOA LW fluxes is less than 0.5 W m−2 and the RMS error is less than 0.8 W m−2 for both Terra and Aqua. The accuracy of the TOA instantaneous flux is assessed by performing tests using fluxes inverted from nadir- and oblique-viewing angles using CERES along-track observations and temporally- and spatially-matched MODIS observations, and using fluxes inverted from multi-angle MISR observations. The TOA instantaneous SW flux uncertainties are about 2.3% (1.9 W m−2) over clear ocean, 1.6% (4.5 W m−2) over clear land, and 2.0% (6.0 W m−2) over clear snow/ice; and are about 3.3% (9.0 W m−2), 2.7% (8.4 W m−2), and 3.7% (9.9 W m−2) over ocean, land, and snow/ice under all-sky conditions. The TOA SW flux uncertainties are generally larger for thin broken clouds than for moderate and thick overcast clouds. The TOA instantaneous daytime LW flux uncertainties are 0.5% (1.5 W m−2), 0.8% (2.4 W m−2), and 0.7 % (1.3 W m−2) over clear ocean, land, and snow/ice; and are about 1.5% (3.5 W m−2), 1.0% (2.9 W m−2), and 1.1 % (2.1 W m−2) over ocean, land, and snow/ice under all-sky conditions. The TOA instantaneous nighttime LW flux uncertainties are about 0.5–1% (< 2.0 W m−2) for all surface types. Flux uncertainties caused by errors in scene identification are also assessed by using the collocated CALIPSO, CloudSat, CERES and MODIS data product. Errors in scene identification tend to underestimate TOA SW flux by about 0.6 W m−2 and overestimate TOA daytime (nighttime) LW flux by 0.4 (0.2) W m−2 when all CERES viewing angles are considered.

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