Angular sampling of a monochromatic, wide-field-of-view camera to augment next-generation Earth radiation budget satellite observations

• Published in: Atmospheric measurement techniques Vol. 16; no. 15; pp. 3609 - 3630
• Main Authors: Gristey, Jake J, Schmidt, K. Sebastian, Chen, Hong, Feldman, Daniel R, Kindel, Bruce C, Mauss, Joshua, van den Heever, Mathew, Hakuba, Maria Z, Pilewskie, Peter
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 08-08-2023; Copernicus Publications
• Subjects: Analysis; Angular distribution; Anisotropy; Atmosphere; Basic converters; Cameras; Channels; Climate system; Climatic analysis; Conversion; Datasets; Earth; Earth radiation budget; Electric waves; Electromagnetic radiation; Electromagnetic waves; Energy balance; Field of view; Irradiance; Lag time; Radiance; Radiation; Radiometers; Remote sensing; Sampling; Satellite observation; Satellites; Short wave radiation; Stratification; Wavelength
• ISSN: 1867-8548; 1867-1381; 1867-8548
• DOI: 10.5194/amt-16-3609-2023

Earth radiation budget (ERB) satellite observations
require conversion of the measured radiance, which is a remotely sensed
quantity, to a derived irradiance, which is the relevant energy balance
quantity routinely used in modeling and analysis of the climate system. The state-of-the-art approach for radiance-to-irradiance conversion taken by the
Clouds and the Earth's Radiant Energy System (CERES) benefits from the
exhaustive sampling of radiance anisotropy by multiple CERES instruments
across many years. Unfortunately, the CERES approach is not easily extended
to new ERB spectral channels that lack previous sampling, such as the
“split-shortwave” planned to be part of the next-generation ERB mission
Libera. As an alternative approach, the capability of a monochromatic,
wide-field-of-view camera to provide dense angular sampling in a much
shorter time frame is assessed. We present a general concept for how this can be achieved and quantify the proficiency of a camera to provide rapid
angular distribution model (ADM) generation for the new Libera
ultraviolet and visible (VIS) sub-band. A single mid-visible camera
wavelength (555 nm) is shown to be ideal for representing the VIS sub-band,
requiring only basic scene stratification for 555 nm to VIS conversion.
Synthetic camera sampling with realistic operating constraints also
demonstrates that the angular radiance field of various scenes can be well
populated within a single day of sampling, a notable advance over existing
approaches. These results provide a path for generating
observationally based VIS ADMs with minimal lag time following Libera's
launch. Coupled with efforts to utilize a camera for scene identification,
this may also pave the way for future ERB satellite systems to develop
stand-alone irradiance products for arbitrary sets of spectral channels,
opening up new measurement and science possibilities.