Recent meetings of the CERES Science Team examined how the instruments are coping with changes in spacecraft operations and orbital geometry. Terra and Aqua CERES units now often operate in Rotating Azimuth Plane, or RAP, mode to sample a wider range of solar zenith angles as their orbits drift. Suomi NPP's FM5 instrument spent four years in a rotating-azimuth configuration before returning to cross-track mode in late 2023, and NOAA-20's FM6 has shown intermittent shortwave channel noise in space-view data that does not appear to affect Earth-view radiances. The team has also reported progress on maintaining cross-mission calibration and on extending the record as older platforms approach the end of their lifetimes.
CERES observations place recent temperature and radiation anomalies in context. Analyses presented to the team showed that 2023 global mean surface temperatures, based on the ERA5 reanalysis, displayed record-high anomalies, with September 2023 standing out over the 1979 - 2023 period. CERES data indicated that absorbed solar radiation exceeded the 90 percent confidence interval anomaly for most months from March through September 2023, and that net radiation anomalies surpassed earlier peaks associated with the 2016 El Nino event. Outgoing longwave radiation shifted beyond the negative 90 percent confidence interval starting in June 2023, signalling enhanced energy loss to space even as the net radiation declined later in the year. Elevated absorbed solar and longwave flux signatures persisted into early 2024.
The team used these observations to link CERES findings with broader climate research initiatives. One focus is the World Climate Research Programme's Explaining and Predicting Earth System Change effort, which examines Earth's energy imbalance and its drivers. CERES data underpin experiments in the CERES Model Intercomparison Project, designed to extend overlap between model output and radiative observations beyond the period covered in earlier Coupled Model Intercomparison Project activities. Model forcings such as sea surface temperature, sea ice, aerosols, volcanic emissions, and solar irradiance are being revisited to capture pronounced variability in energy imbalance and ocean conditions since 2014.
Work is also underway to understand how orbital drift and cross-platform differences affect top-of-atmosphere fluxes. Presentations at recent meetings described how shifts in Terra's local equatorial crossing time change the sampling of solar illumination and hence shortwave fluxes when compared with NOAA-20. Differences in shortwave top-of-atmosphere flux between the two satellites appear smaller in the Northern Hemisphere than in the Southern Hemisphere, reflecting closer overpass times. Longwave flux differences show less hemispheric contrast. CERES scientists are comparing their broadband fluxes with those from the European Space Agency's EarthCARE Broadband Radiometer. Early results indicate that EarthCARE's shortwave channel runs about 8 percent brighter than CERES, while its longwave channel aligns well with CERES except in very cold scenes, and the joint data now support a 25-year radiation budget record from March 2000 through February 2025.
Algorithm development remains central to sustaining the climate data record. The Edition 5 cloud algorithms aim to keep derived cloud properties consistent between MODIS instruments on Terra and Aqua and VIIRS sensors on Suomi NPP and NOAA-20, despite differences in spectral bands. Researchers reported progress in harmonizing geostationary imager data from multiple generations of GOES, Meteosat, and Japanese geostationary satellites to cover 25 years of global observations. Comparisons with CALIPSO lidar data show improvements in cloud detection and classification, particularly for high clouds, though some underestimation of low clouds below about 3 kilometers remains. Geostationary algorithms that rely on three-channel cloud retrievals now produce more consistent day and night cloud fractions across platforms, with additional refinements targeting cloud optical depth and particle size discrepancies.
Other team members are refining the angular distribution models that convert radiances to fluxes, including sensitivity to different climate modes. Analyses that built separate Terra ADMs from El Nino and La Nina periods found small global shortwave flux differences on the order of half a watt per square meter, with similar spatial patterns regardless of phase. Researchers also presented methods to partition CERES shortwave flux into visible and near-infrared components using MODTRAN-based lookup tables and VIIRS spectral radiances. These studies show that water clouds have much higher albedo in the visible than in the near-infrared because absorption is stronger at longer wavelengths, while ice clouds show closer visible and near-infrared albedos due to their different scattering characteristics and overlying water vapor structure.
Additional ADM work uses RAP-mode data from Terra collected after its orbit began drifting away from the historical 10:30 a.m. local crossing time. The extended angular sampling improves flux estimates, especially for clear land and cloudy ocean scenes. New unfiltering coefficients based on updated MODTRAN versions, refined cloud properties, and more viewing and solar geometry bins have also been introduced. Tests indicate that the resulting changes to shortwave and longwave fluxes are modest but help reduce biases and reconcile differences between total-channel and spectrally separated measurements, particularly for NOAA-20's longwave channel.
The team is also advancing methods to compare Earth radiation budget instruments and prepare for future missions. One approach uses invariant Earth targets such as the Libya-4 desert site and deep convective cloud fields in the tropical western Pacific to cross-calibrate instruments like CERES on NOAA-20 and future sensors such as Libera on JPSS-4. Tests that match scanning modes between polar-orbiting and geostationary platforms show that longwave flux regressions between Terra and Aqua and geostationary imagers can agree within a few tenths of a percent. Machine learning methods applied to geostationary radiances have reduced longwave broadband bias and root-mean-square error compared with earlier multilinear regression schemes, and similar techniques are being used with VIIRS data to allocate shortwave and longwave fluxes to cloud layers while keeping global biases within about 1 watt per square meter.
CERES-derived products continue to evolve as underlying meteorological datasets and radiative transfer schemes are updated. A shift from the GEOS 5.4.1 reanalysis to MERRA-2 for producing single-scanner footprint and synoptic one-degree products yields small global mean differences in longwave downward surface flux, although zonal biases can reach several watts per square meter. Upcoming SYN1deg Edition 4B products will reprocess earlier two-channel geostationary satellites, incorporate interpolated cloud retrievals at large solar zenith angles, and rely on NOAA-20 and MERRA-2 after early 2022. New CERES Cloud and Radiative Swath products on a one-degree grid provide hourly top-of-atmosphere and surface fluxes from 2018 through 2022, with Edition 5 Fu-Liou radiative transfer changes reducing longwave top-of-atmosphere biases to well below a watt per square meter.
Radiative transfer updates are expanding spectral resolution and gas treatment for future editions. Plans call for increasing the number of bands in the Fu-Liou calculations from 18 to 29 and for tracking nine gas species per band instead of up to four in a single band previously. The updated line-by-line gas database and band structure produce relatively small changes, generally under about 2 watts per square meter, in broadband shortwave and longwave fluxes when compared with current editions, but detailed spectral comparisons show improved performance. Parallel work on irradiance trends indicates that top-of-atmosphere shortwave flux under all-sky conditions is adding energy to the system, while longwave flux is removing energy more slowly, yielding an increase in net energy. At the surface, shortwave gains and longwave losses nearly balance, and aerosol direct radiative effects remain consistent with earlier estimates.
Several presentations examined how CERES data connect to fast-response flux products and operational applications. Updates to the FLASHFlux product now use a meteorological input tailored for instrument teams, with tests showing global mean daytime longwave surface downward flux differences of less than half a watt per square meter relative to earlier configurations, though some latitudinal bands exhibit biases of several watts per square meter. Team members also highlighted changes to synoptic products and ongoing efforts to keep radiation datasets consistent as input meteorology and satellite coverage change.
Beyond instrument and algorithm work, the meetings featured invited talks on greenhouse gas forcing, aerosol-cloud interactions, hemispheric albedo symmetry, spectral radiative changes, and feedback pattern effects. One analysis combined multiple satellite records to decompose Earth's energy imbalance into radiative forcing and feedback contributions, attributing part of the imbalance to greenhouse gas forcing of about a few tenths of a watt per square meter and showing how changes in aerosols over regions such as China alter shortwave radiative forcing. Other model-based studies assessed how aerosol direct and indirect effects evolved over the twentieth century, with indirect effects dominating and peaking in the early twenty-first century before declining as pollution controls reduced aerosol loads.
A presentation on hemispheric albedo symmetry showed that despite much higher clear-sky albedo over the land-dominated Northern Hemisphere, Earth's total all-sky albedo remains nearly balanced between hemispheres. The speaker described how changes in clouds and aerosols in both hemispheres, as well as transport in the atmosphere and ocean, act together to maintain this balance, even through events such as Arctic sea ice loss, shifts in Antarctic sea ice, changes in shipping emissions, and major wildfire and volcanic aerosol episodes. Another talk explored how aerosol-driven changes in droplet number concentration and liquid water path influence cloud radiative feedbacks, and used models and observations to narrow uncertainties in aerosol - cloud effective radiative forcing by constraining how clouds respond to pollution-driven aerosol increases.
Spectrally resolved radiation studies used line-by-line codes driven by reanalysis data to calculate top-of-atmosphere flux spectra and compared them with AIRS satellite observations. These comparisons showed that, while broadband all-sky outgoing longwave radiation trends from CERES, AIRS, and the line-by-line calculations generally align, some spectral bands exhibit larger discrepancies. The work highlighted where models capture or miss observed changes in greenhouse gas absorption features across the infrared spectrum. Another analysis introduced a method that relates global-mean radiative feedback to local surface temperature variations, emphasizing the role of regions such as the eastern and western tropical Pacific in shaping global feedback parameters and evaluating how well climate models reproduce the observed spatial pattern.
The CERES meetings also reviewed progress on new and planned Earth radiation budget missions. A pathfinder project, Athena EPIC, used a small satellite platform carrying a spare CERES longwave detector and calibration hardware to test a modular spacecraft concept for potential future instruments, though the mission encountered post-launch tumbling that prevented operations. The Polar Radiant Energy in the Far InfraRed Experiment, PREFIRE, launched two CubeSats into near-polar orbits to measure far-infrared emission beyond 15 micrometers, a spectral range that carries more than half of the outgoing longwave radiation over polar regions and responds sensitively to thin clouds and low water vapor. PREFIRE uses a compact spectrometer spanning roughly 5 to 53 micrometers and is intended to clarify feedbacks linked to Arctic warming, sea ice loss, and ice sheet melt.
Looking ahead, the Libera mission will fly on JPSS-4 and is designed to extend the CERES radiation budget record with new detectors, building on lessons from a CubeSat instrument that uses the same vertically aligned carbon nanotube absorbers. Comparisons between CTIM CubeSat measurements and CERES have shown relative differences of around a few percent across multiple CERES instruments, indicating reasonable consistency despite CTIM's larger footprint. Together with ongoing algorithm updates and cross-calibration efforts, Libera and related missions are expected to continue the radiation budget record as older CERES platforms age and retire.
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