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

Abstract

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 Wm −2 and the RMSE is less than 1.1 Wm −2 . The bias and RMSE are very similar between Terra and Aqua. The bias in regional monthly mean TOA LW fluxes is less than 0.5 Wm −2 and the RMSE is less than 0.8 Wm −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 averaged TOA instantaneous SW flux uncertainties from these two tests are about 2.3 % (1.9 Wm −2 ) over clear ocean, 1.6 % (4.5 Wm −2 ) over clear land, and 2.0 % (6.0 Wm −2 ) over clear snow/ice; and are about 3.3 % (9.0 Wm −2 ), 2.7 % (8.4 Wm −2 ), and 3.7 % (9.9 Wm −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 derived from the CERES-MODIS test are 0.5 % (1.5 Wm −2 ), 0.8 % (2.4 Wm −2 ), and 0.7 % (1.3 Wm −2 ) over clear ocean, land, and snow/ice; and are about 1.5 % (3.5 Wm −2 ), 1.0 % (2.9 Wm −2 ), and 1.1 % (2.1 Wm −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 Wm −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 Wm −2 and overestimate TOA daytime (nighttime) LW flux by 0.4 (0.2) Wm −2 when all CERES viewing angles are considered.

Estimation of the Dust Aerosol Shortwave Direct Forcing Over Land Based on an Equi‐albedo Method From Satellite Measurements

“…The ADMs are a function of varying scene types, such as land, ocean, cloud cover, and aerosols. Research shows that the uncertainty of TOA instantaneous shortwave flux is about 1.6% (4.5 W/m 2 ) over clear‐sky land, and about 2.7% (8.4 W/m 2 ) over land under all‐sky conditions (Su et al, ). Thus, TOA radiative fluxes derived from the CERES measuring radiance are reliable which could be used to estimate DRF dust .…”

Bias and Sensitivity of Boundary Layer Clouds and Surface Radiative Fluxes in MERRA‐2 and Airborne Observations Over the Beaufort Sea During the ARISE Campaign

“…While satellite observations have been widely employed to study the Arctic climate system and to evaluate climate models, large discrepancies between and among satellites and models remain in the representation of boundary layer (BL) clouds, and surface fluxes and properties. This in turn contributes to continued large uncertainty in the estimation of the Arctic surface radiative budget determined from models and satellites (Chaudhuri et al, ; de Boer et al, ; Jakobson et al, ; Su et al, ). Many atmospheric reanalysis products used to evaluate climate models in the Arctic have substantial uncertainties and biases in the BL, especially in vertical profiles of specific and relative humidity (RH) and temperature (e.g., Jakobson et al, ; Lindsay et al, ; Liu et al, ; Tjernström et al, ).…”

Cloud occurrences and cloud radiative effects (CREs) from CERES‐CALIPSO‐CloudSat‐MODIS (CCCM) and CloudSat radar‐lidar (RL) products

“…The Clouds and the Earth's Radiant Energy System (CERES) instrument, aboard Aqua as a part of the A-Train Earth Observing System [Wielicki et al, 1996], measures shortwave (SW) and longwave (LW) broadband radiation at top-of-atmosphere (TOA). After many years of improving instrument calibration [Loeb et al, 2016] and angular distribution model (ADM) [Loeb et al, 2005[Loeb et al, , 2007Su et al, 2015aSu et al, , 2015b, the CERES instrument gives unprecedented accuracy for TOA radiation budget estimates [Loeb et al, 2012a[Loeb et al, , 2016, and it has been widely used for examination of Earth energy imbalance and related climate changes [e.g., Loeb et al, 2012b;Trenberth et al, 2014;Allan et al, 2015]. Unlike TOA irradiance estimates, estimating surface or atmosphere radiation budget involves radiative transfer computations that require appropriate model inputs Su et al, 2005;Kato et al, 2008Kato et al, , 2011Kato et al, , 2013Wild et al, 2013;Stephens et al, 2012].…”