Guest seminar, Tristan L'Equyer, University of Wisconsin-Madison, WI, USA
Seminar
Date: Tuesday 23 September 2025
Time: 11.15 – 12.15
Location: C609 Rossbysalen, MISU, Svante Arrhenius väg 16C, 6th floor
Title: Taking Earth’s Temperature: Insights into Earth’s Emission from One Year of PREFIRE Observations.
Climate models and observations unequivocally confirm that the climate is warming in response to increasing greenhouse gas concentrations, but future projections of the societal impacts, including Arctic warming and the resultant sea level rise, remain uncertain. This can be attributed, in part, to a significant gap in current Earth observations. While more than a century has passed since Max Planck won the Nobel Prize in Physics, we have yet to fully characterize our planet’s emission spectrum. NASA’s Polar Radiant Energy in the Far Infrared Experiment (PREFIRE) mission launched in summer 2024 with the goal of filling this gap and providing a more complete depiction of the spectral character of Earth’s longwave emission. The Thermal InfraRed Spectrometers (TIRS) aboard both of PREFIRE’s 6U CubeSats, measure emitted radiation from 5 to 53 micrometers. These near-complete spectra include the first measurements of far-infrared radiation (wavelengths greater than 15 micrometers) of Earth since experimental missions in the 1970’s and 80’s.
This presentation will introduce the PREFIRE mission and summarize results from its CubeSats’ first full year in orbit. When analyzed using state-of-the-art remote sensing methods PREFIRE’s measurements yield new insights into energy flows between the surface, atmosphere, and space in the polar atmosphere. For example, PREFIRE’s top of atmosphere (TOA) spectral radiance measurements capture variations in the role clouds and water vapor play in defining the spectral character of emission around the globe. In polar regions, surface emissivity retrievals reveal important distinctions in the emissivities of polar surfaces that depend on elevation and evolve with the seasons. Taken together, polar TOA spectral radiances and emissivity estimates yield a new spectrally-resolved measure of the atmospheric greenhouse effect (AGHE) that reflects seasonal shifts in how atmospheric constituents modulate emission in the cold, dry polar environments.
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Last updated: August 4, 2025
Source: MISU