Kienast-Sjögren, Erika
[VerfasserIn];
Rolf, Christian
[VerfasserIn];
Seifert, Patric
[VerfasserIn];
Krieger, Ulrich K.
[VerfasserIn];
Luo, Bei P.
[VerfasserIn];
Krämer, Martina
[VerfasserIn];
Peter, Thomas
[VerfasserIn]
Climatological and radiative properties of midlatitude cirrus clouds derived by automatic evaluation of lidar measurements
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Medientyp:
E-Artikel
Titel:
Climatological and radiative properties of midlatitude cirrus clouds derived by automatic evaluation of lidar measurements
Beteiligte:
Kienast-Sjögren, Erika
[VerfasserIn];
Rolf, Christian
[VerfasserIn];
Seifert, Patric
[VerfasserIn];
Krieger, Ulrich K.
[VerfasserIn];
Luo, Bei P.
[VerfasserIn];
Krämer, Martina
[VerfasserIn];
Peter, Thomas
[VerfasserIn]
Anmerkungen:
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Beschreibung:
Cirrus, i.e., high, thin clouds that are fully glaciated, play an important role in the Earth's radiation budget as they interact with both long- and shortwave radiation and affect the water vapor budget of the upper troposphere and stratosphere. Here, we present a climatology of midlatitude cirrus clouds measured with the same type of ground-based lidar at three midlatitude research stations: at the Swiss high alpine Jungfraujoch station (3580 m a.s.l.), in Zürich (Switzerland, 510 m a.s.l.), and in Jülich (Germany, 100 m a.s.l.). The analysis is based on 13 000 h of measurements from 2010 to 2014. To automatically evaluate this extensive data set, we have developed the Fast LIdar Cirrus Algorithm (FLICA), which combines a pixel-based cloud-detection scheme with the classic lidar evaluation techniques. We find mean cirrus optical depths of 0.12 on Jungfraujoch and of 0.14 and 0.17 in Zürich and Jülich, respectively.Above Jungfraujoch, subvisible cirrus clouds (τ < 0.03) have been observed during 6 % of the observation time, whereas above Zürich and Jülich fewer clouds of that type were observed. Cirrus have been observed up to altitudes of 14.4 km a.s.l. above Jungfraujoch, whereas they have only been observed to about 1 km lower at the other stations. These features highlight the advantage of the high-altitude station Jungfraujoch, which is often in the free troposphere above the polluted boundary layer, thus enabling lidar measurements of thinner and higher clouds. In addition, the measurements suggest a change in cloud morphology at Jungfraujoch above ∼ 13 km, possibly because high particle number densities form in the observed cirrus clouds, when many ice crystals nucleate in the high supersaturations following rapid uplifts in lee waves above mountainous terrain.The retrieved optical properties are used as input for a radiative transfer model to estimate the net cloud radiative forcing, CRFNET, for the analyzed cirrus clouds. All cirrus detected here have a positive CRFNET. This confirms that these ...