CERES Top-of-Atmosphere Earth Radiation Budget Climate Data Record: Accounting for in-Orbit Changes in Instrument Calibration

Abstract

Abstract:The Clouds and the Earth's Radiant Energy System (CERES) project provides observations of Earth's radiation budget using measurements from CERES instruments onboard the Terra, Aqua and Suomi National Polar-orbiting Partnership (S-NPP) satellites. As the objective is to create a long-term climate data record, it is necessary to periodically reprocess the data in order to incorporate the latest calibration changes and algorithm improvements. Here, we focus on the improvements and validation of CERES Terra and Aqua radiances in Edition 4, which are used to generate higher-level climate data products. Onboard sources indicate that the total (TOT) channel response to longwave (LW) radiation has increased relative to the start of the missions by 0.4% to 1%. In the shortwave (SW), the sensor response change ranges from´0.4% to 0.6%. To account for in-orbit changes in SW spectral response function (SRF), direct nadir radiance comparisons between instrument pairs on the same satellite are made and an improved wavelength dependent degradation model is used to adjust the SRF of the instrument operating in a rotating azimuth plane scan mode. After applying SRF corrections independently to CERES Terra and Aqua, monthly variations amongst these instruments are highly correlated and the standard deviation in the difference of monthly anomalies is 0.2 Wm´2 for ocean and 0.3 Wm´2 for land/desert. Additionally, trends in CERES Terra and Aqua monthly anomalies are consistent to 0.21 Wm´2 per decade for ocean and 0.31 Wm´2 per decade for land/desert. In the LW, adjustments to the TOT channel SRF are made to ensure that removal of the contribution from the SW portion of the TOT channel with SW channel radiance measurements during daytime is consistent throughout the mission. Accordingly, anomalies in day-night LW difference in Edition 4 are more consistent compared to Edition 3, particularly for the Aqua land/desert case.

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].…”

Constraining the Global Ocean Heat Content Through Assimilation of CERES‐Derived TOA Energy Imbalance Estimates

“…Such an error is assumed equal to 0.3 W m −2 , corresponding to the EEI monthly global anomaly for nonocean components, as suggested by Trenberth et al (). The instrumental error is assumed equal to 0.3 W m −2 , estimated by Loeb et al () as standard deviation of the differences of CERES measurements from different satellite platforms.…”

“…We use in this study CERES Energy Balanced and Filled Top-of-Atmosphere (EBAF-TOA) Edition 4.0 (Loeb et al, 2016), released during early 2017. This version presents improvements with respect to the previous Geophysical Research Letters 10.1002/2017GL075396 version (version 2.8) in many aspects, such as the instrument calibration and the retrieval of cloud properties.…”

Multi-Instrument Inter-Calibration (MIIC) System

“…Shape and bandwidth differences of spectral response functions (SRF) must be accounted for when comparing radiances from separate instruments. The CERES project tracks calibration relative stability of multiple CERES instruments using vicarious techniques, including tropical mean and deep convective cloud comparisons referenced to the FM1 instrument [7]. CERES performs inter-satellite direct comparisons by commanding its two-axis gimbal pointing system to rotate in the azimuth direction so that observations from multiple instruments match near satellite orbit crossings.…”