Florian Tornow- Aug 28

Weather and Climate Seminar

Broadband Radiometry during EarthCARE: An Improved Solar Radiance-to-Flux Conversion

Florian Tornow

Wednesday, August 28^th

NWC 5930/3:00 pm

Outgoing radiative fluxes at top-of-atmosphere (TOA) are driven by the interaction of clouds, aerosols, and radiation. The upcoming satellite mission EarthCARE aims at an improved understanding of this interaction through a radiative closure assessment based on TOA fluxes. This assessment compares (1) shortwave (SW) and longwave TOA fluxes inferred from an onboard broadband radiometer (BBR) with (2) fluxes from radiative transfer calculations acting on cloud and aerosol properties that were retrieved from onboard active and passive instruments. Comparing instantaneous fluxes over horizontal domains of (~10km)², the radiative closure is considered successful for flux differences smaller 10 W/m².

When converting a BBR-measured radiance into a flux, the main challenge is assuming the present hemispheric field of outgoing radiances. Angular Distributions Models (ADMs) – mostly based on several years of satellite observations – provide these radiance fields. This work explores a new approach to SW ADMs and incorporates additional parameters (cloud-top effective radius and cloud-topped water vapor). When comparing against state-of-the-art methodology, new ADMs produce significantly different flux estimates of the order of 10 W/m².