EOL Seminar - Sebastian Hoch - University of Utah

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TITLE: Observations of radiative heating and cooling in the atmospheric boundary layer under clear sky and fog conditions

SPEAKER: Sebastian Hoch - University of Utah

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ABSTRACT: Radiative flux divergence (RFD) or clear-air radiative cooling is one of several physical processes governing the diurnal heating and cooling cycle in the near-surface atmosphere. Although its importance has been stressed in past studies, the precise role of RFD in the evolution of the temperature structure is still under debate. While some studies emphasize the importance of RFD in the onset of nocturnal cooling, other studies indicate that RFD actually leads to warming near the ground under inversion conditions. Other aspects under investigation are radiative cooling in complex terrain, where the lowest temperatures are often recorded in basins or valleys, and the role of radiative cooling in the fog life cycle.  

This presentation will revisit past investigations of RFD, including theoretical and model approaches and observations, and discuss their complexities, challenges, and potential contradictions. Direct tower-based observations from past field campaigns (METCRAX, MATERHORN-FOG, CFACT) are presented, and the need to develop a new observational platform is explained. Such a new observational approach using balloon-borne, gimbal-stabilized radiometers is then introduced, and initial results from its application during two field campaigns focusing on fog formation (CFACT, FATIMA) are presented.