Application of the shipborne remote sensing supersite OCEANET for profiling of Arctic aerosols and clouds during Polarstern cruise PS106

Griesche, Hannes; Seifert, Patric; Ansmann, Albert; Baars, Holger; Velasco, Carola Barrientos; Bühl, Johannes; Engelmann, Ronny; Radenz, Martin; Yin, Zhenping

doi:10.5194/amt-2019-434

Cited by 25 publications

(32 citation statements)

References 76 publications

(100 reference statements)

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“…4) was blown up the slope without friction, the vertical wind speed reached about 0.6 m s −1 . The eddy dissipation rate, which is a measure for turbulence, was calculated from the wind profiler and cloud radar measurements as described in Griesche et al (2019) and reached values between 20 cm 2 s −3 and 90 cm 2 s −3 between 1800 m and 2300 m over Wolfgang between 8 and 10 UTC. Such values were reported in stratiform clouds (Borque et al, 2016) as well as in cumulus clouds with weak updrafts (Siebert et al, 2006).…”

Section: Weather Situationmentioning

confidence: 99%

Continuous secondary ice production initiated by updrafts through the melting layer in mountainous regions

Lauber¹,

Henneberger²,

Mignani³

et al. 2020

Preprint

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Abstract. An accurate prediction of the ice crystal number concentration in clouds is important to determine the radiation budget, the lifetime, and the precipitation formation of clouds. Secondary ice production is thought to be responsible for the observed discrepancies between the ice crystal number concentration and the ice nucleating particle concentration in clouds. The Hallett-Mossop process is active between −3 °C and −8 °C and has been implemented into several models while all other secondary ice processes are poorly constrained and lack a well-founded quantification. During two hours of measurements taken on a mountain slope just above the melting layer at temperatures warmer than −3 °C, a continuously high concentration of small plates identified as secondary ice was observed. The presence of drizzle drops suggests droplet fragmentation upon freezing as the responsible secondary ice mechanism. The constant supply of drizzle drops can be explained by a recirculation theory, suggesting that melted snowflakes, which sedimented through the melting layer, were reintroduced into the cloud as drizzle drops by orographically forced updrafts. Here we introduce a parametrization of droplet fragmentation at high temperatures when primary ice nucleation is basically absent and the first ice is initiated by collision of drizzle drops with aged ice crystals sedimenting from higher altitudes. Based on previous measurements, we estimate that a droplet of 200 µm in diameter produces 18 secondary ice crystals when it fragments upon freezing. The application of the parametrization to our measurements shows high uncertainties, but the estimated number of splinters produced per fragmenting droplet (18–43) lies within the range of uncertainty if we assume that all droplets larger than 40 µm fragment when they freeze.

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Section: Weather Situationmentioning

confidence: 99%

Continuous secondary ice production initiated by updrafts through the melting layer in mountainous regions

Lauber¹,

Henneberger²,

Mignani³

et al. 2020

Preprint

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“…The OCEANET-Atmosphere observatory from the Leibniz Institute for Tropospheric Research (TROPOS) in Leipzig (Germany) performed continuous measurements during PS106.1 and PS106.2 (Griesche et al, 2019). Its container houses a multiwavelength Raman polarization lidar Polly-XT and a microwave radiometer HATPRO which was complemented during PS106 by a vertically-pointing motion-stabilized 35-GHz cloud radar Mira-35.…”

Section: Cloudnet Measurementsmentioning

confidence: 99%

Retrieval of microphysical cloud parameters from EM-FTIR spectra measured in Arctic summer 2017

Richter

Palm

Weinzierl

et al. 2020

Preprint

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Abstract. Infrared spectral radiances of optically thin clouds show high sensitivity to changes of the microphysical cloud parameters. Therefore, measurements of infrared spectral radiance of clouds in the spectral range from 770.9 cm−1 to 1163.4 cm−1 using a mobile Fourier Transform Infrared spectrometer were performed on the German research vessel Polarstern in the Arctic in summer 2017. A new retrieval for microphysical cloud parameters of optically thin clouds called Total Cloud Water retrieval, designed to retrieve cloud water optical depth τcw, total effective droplet radius rtotal and condensed water path CWP from infrared spectral radiances without the incorporation of spectral radiances in the far-infrared below 600cm−1, has been developed for application on radiances from the measurement campaign. Validation is performed against derived quantities from a combined cloud radar, lidar and microwave radiometer measurement synergy retrieval, called Cloudnet, performed by the Leibnitz Institute for Trospheric Research. Applied to spectral radiances of synthetic testcases, Total Cloud Water retrieval shows a high ability to retrieve τcw with a correlation of |r| = 0.98, as well as to retrieve CWP with |r| = 0.95 and rtotal with |r| = 0.86. Using the dataset from the campaign, a comparison between CWP from Total Cloud Water retrieval and Cloudnet was performed and showed a correlation of |r| = 0.81. In conclusion, the comparison to artificial clouds and the validation using Cloudnet showed that Total Cloud Water retrieval is able to retrieve the condensed water path from clouds for optically thin clouds and makes it a useful complementation for thin clouds to existing microwave-based measurements.

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“…BELUGA was launched from the ice floe at around 82 • N, 10 • E in the period of 5-14 June 2017. The balloon measurements are complemented by radiosoundings launched every six hours (Schmithüsen, 2017) and ship-based remote sensing data from radar and lidar, which are processed with the Cloudnet algorithm (Griesche et al, 2019a;Griesche et al, 2019).…”

Section: The Pascal Expeditionmentioning

confidence: 99%

Case study of a humidity layer above Arctic stratocumulus using balloon-borne turbulence and radiation measurements and large eddy simulations

Egerer

Ehrlich

Gottschalk

et al. 2020

Preprint

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Abstract. Specific humidity inversions occur frequently in the Arctic. The formation of these inversions is often associated with large scale advection of humid air. However, small-scale boundary layer processes interacting with the humidity inversions are not fully understood yet. In this study, we analyze a three-day period of a persistent layer of increased specific humidity above a stratocumulus cloud observed during an Arctic field campaign in June 2017. The tethered balloon system BELUGA (Balloon-bornE moduLar Utility for profilinG the lower Atmosphere) recorded high-resolution vertical profile measurements of turbulence and radiation in the atmospheric boundary layer. We find that the humidity inversion and the cloud layer are coupled by eddy dissipation, extending above the cloud boundary and linking both layers through turbulent mixing. One case reveals a strong negative virtual sensible heat flux at cloud top (eddy covariance estimate of −15 W/m2), indicating entrainment of humid air from above into the cloud layer. Large Eddy Simulations (LES) based on field campaign data are conducted to supplement the flux measurements. Independent experiments for two days confirm the observed entrainment of humid air, reproducing the observed negative turbulent fluxes of heat and moisture at cloud top. The LES realizations suggest that in the presence of a humidity layer the cloud layer remains thicker and the inversion height is slightly raised, reproducing results from previous idealized LES studies. While this acts to prevent cloud collapse, it remains unclear how the additional moisture is processed in the cloud and how exactly it contributes to the longevity of Arctic cloud layers.

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Application of the shipborne remote sensing supersite OCEANET for profiling of Arctic aerosols and clouds during Polarstern cruise PS106

Cited by 25 publications

References 76 publications

Continuous secondary ice production initiated by updrafts through the melting layer in mountainous regions

Continuous secondary ice production initiated by updrafts through the melting layer in mountainous regions

Retrieval of microphysical cloud parameters from EM-FTIR spectra measured in Arctic summer 2017

Case study of a humidity layer above Arctic stratocumulus using balloon-borne turbulence and radiation measurements and large eddy simulations

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