In situ sounding of radiative flux profiles through the Arctic lower troposphere

• Published in: Bulletin of Atmospheric Science and Technology
• Main Authors: Becker, Ralf, Maturilli, Marion, Philipona, Rolf, Behrens, Klaus
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2020
• Subjects: Atmosphere; Arctic; Heating rates; Clouds; Albedo; Research Article; In-situ profiling; albedo; Ny Ålesund; Ny-Ålesund; Svalbard
• Online Access: https://repository.publisso.de/resource/frl:6472092; https://doi.org/10.1007/s42865-020-00011-8

<jats:title>Abstract</jats:title><jats:p>In situ profiles and fixed-altitude time series of all four components of net radiation were obtained at Ny-Ålesund, Svalbard (78.9° N, 11.9° E), in the period May 04–21, 2015. Measurements were performed using adapted high-quality instrumentation classified as “secondary standard” carried by a tethered balloon system. Balloon-lifted measurements of albedo under clear-sky conditions demonstrate the local dependence on altitude and on the surface inhomogeneity of this parameter over coastal terrain of Ny-Ålesund. Depending on the surface composition within the sensor’s footprint near the coastline, the albedo over predominantly snow-covered surfaces was found to decrease to 0.548 and 0.452 at 494 m and 881 m altitude compared with 0.731 and 0.788 measured with near-surface references, respectively. Albedo profiles show an all-sky maximum at 150 m above surface level due to local surface inhomogeneity, and an averaged vertical change rate of − 0.040/100 up to 750 m aboveground level (clear sky) and − 0.034/100 m (overcast). Profiling of arctic low-level clouds reveals distinct vertical gradients in all radiative fluxes but longwave upward at the cloud top. Observed radiative cooling at the top of a partly dissolving stratus cloud with heating rates of − 40.4 to − 62.1 Kd<jats:sup>−1</jats:sup> in subsequent observations is exemplified.</jats:p>