CER_SYN1deg-Day_Terra-NOAA20_Edition4A is the Clouds and the Earth's Radiant Energy System (CERES) and geostationary (GEO)-Enhanced Top-of-Atmosphere (TOA), Within-Atmosphere and Surface Fluxes, Clouds and Aerosols Daily Terra-NOAA20 Edition4A data product. Data was collected using the following instruments and platforms: Imaging Radiometers on the Geostationary Satellites platform, CERES Flight Model 1 (FM1), CERES FM2, CERES Scanner, and MODIS on Terra; and CERES FM6 and VIIRS on NOAA-20. Data collection for this product is ongoing.The CERES Synoptic Radiative Fluxes and Clouds (SYN) 1degree products provide CERES-observed temporally interpolated TOA radiative fluxes and coincident imager-derived cloud and aerosol properties and include geostationary-derived cloud properties and broadband fluxes that have been carefully normalized with CERES fluxes to maintain the CERES calibration. They also contain computed initial TOA, in-atmosphere, surface fluxes, and computed fluxes adjusted or constrained to the CERES-observed TOA fluxes. The calculated fluxes are produced using the Langley Fu-Liou radiative transfer model. Computations use MODIS, geostationary satellite cloud properties, and atmospheric profiles provided by the Global Modeling and Assimilation Office (GMAO). The adjustments to clouds and atmospheric properties are also provided. The computations are for all-sky, clear-sky, pristine (clear-sky without aerosols), and all-sky without aerosol conditions. This product provides parameters on a daily temporal resolution and 1°-regional spatial scales. Fluxes are provided for clear-sky and all-sky conditions in the longwave (LW), shortwave (SW), and window (WN) regions. The CERES SYN1deg products use 1-hourly radiances and cloud property data from GEO imagers to model variability between CERES observations accurately. Several steps are involved in using GEO data to enhance diurnal sampling. First, GEO radiances are cross-calibrated with the MODIS imager using only data that is coincident in time and ray-matched in angle. Next, the GEO cloud retrievals are inferred from the calibrated GEO radiances. The GEO radiances are converted from narrowband to broadband using empirical regressions and then to broadband GEO TOA fluxes using Angular Distribution Models (ADMs) and directional models. A normalization technique ensures GEO and CERES TOA fluxes are consistent. Instantaneous matched gridded fluxes from CERES and GEO are regressed against one another over a month from 5°x5 ° latitude-longitude regions. The regression relation is then applied to all GEO fluxes to remove biases that depend upon cloud amount, solar and view zenith angles, and regional dependencies. The regional means are determined for 1° equal-angle grid boxes calculated by first interpolating each parameter for any missing times of the CERES/GEO observations to produce a complete 1-hourly time series for the month. Daily means are calculated using the combination of observed and interpolated parameters from all days containing at least one CERES observation.CERES is a key Earth Observing System (EOS) program component. The CERES instruments provide radiometric measurements of the Earth's atmosphere from three broadband channels. The CERES missions follow the successful Earth Radiation Budget Experiment (ERBE) mission. The first CERES instrument, the protoflight model (PFM), was launched on November 27, 1997, as part of the Tropical Rainfall Measuring Mission (TRMM). Two CERES instruments (FM1 and FM2) were launched into polar orbit on board the Earth Observing System (EOS) flagship Terra on December 18, 1999. Two additional CERES instruments (FM3 and FM4) were launched on board Earth Observing System (EOS) Aqua on May 4, 2002. The CERES FM5 instrument was launched on board the Suomi National Polar-orbiting Partnership (NPP) satellite on October 28, 2011. The newest CERES instrument (FM6) was launched on board the Joint Polar-Orbiting Satellite System 1 (JPSS-1) satellite, now called NOAA-20, on November 18, 2017.