Continuous in situ measurements of stable isotopes in liquid water

2012 ◽  
Vol 48 (3) ◽  
Author(s):  
Barbara Herbstritt ◽  
Benjamin Gralher ◽  
Markus Weiler
Keyword(s):  
Stable Isotopes ◽  
Liquid Water ◽  
In Situ Measurements

scholarly journals In situ measurements of cloud microphysics and aerosol over coastal Antarctica during the MAC campaign

2017 ◽  
Vol 17 (21) ◽  
pp. 13049-13070 ◽  
Author(s):  
Sebastian J. O'Shea ◽  
Thomas W. Choularton ◽  
Michael Flynn ◽  
Keith N. Bower ◽  
Martin Gallagher ◽  
...  
Keyword(s):  
Liquid Water ◽  
Cloud Microphysics ◽  
Effective Radius ◽  
In Situ Measurements ◽  
Weddell Sea ◽  
Interquartile Range ◽  
Future Climate Change ◽  
Cloud Base ◽  
Ice Production

Abstract. During austral summer 2015, the Microphysics of Antarctic Clouds (MAC) field campaign collected unique and detailed airborne and ground-based in situ measurements of cloud and aerosol properties over coastal Antarctica and the Weddell Sea. This paper presents the first results from the experiment and discusses the key processes important in this region, which is critical to predicting future climate change. The sampling was predominantly of stratus clouds, at temperatures between −20 and 0 °C. These clouds were dominated by supercooled liquid water droplets, which had a median concentration of 113 cm−3 and an interquartile range of 86 cm−3. Both cloud liquid water content and effective radius increased closer to cloud top. The cloud droplet effective radius increased from 4 ± 2 µm near cloud base to 8 ± 3 µm near cloud top. Cloud ice particle concentrations were highly variable with the ice tending to occur in small, isolated patches. Below approximately 1000 m, glaciated cloud regions were more common at higher temperatures; however, the clouds were still predominantly liquid throughout. When ice was present at temperatures higher than −10 °C, secondary ice production most likely through the Hallett–Mossop mechanism led to ice concentrations 1 to 3 orders of magnitude higher than the number predicted by commonly used primary ice nucleation parameterisations. The drivers of the ice crystal variability are investigated. No clear dependence on the droplet size distribution was found. The source of first ice in the clouds remains uncertain but may include contributions from biogenic particles, blowing snow or other surface ice production mechanisms. The concentration of large aerosols (diameters 0.5 to 1.6 µm) decreased with altitude and were depleted in air masses that originated over the Antarctic continent compared to those more heavily influenced by the Southern Ocean and sea ice regions. The dominant aerosol in the region was hygroscopic in nature, with the hygroscopicity parameter κ having a median value for the campaign of 0.66 (interquartile range of 0.38). This is consistent with other remote marine locations that are dominated by sea salt/sulfate.

In situ measurements of liquid water content profiles in midlatitude stratiform clouds

2007 ◽  
Vol 133 (628) ◽  
pp. 1693-1699 ◽  
Author(s):  
A. V. Korolev ◽  
G. A. Isaac ◽  
J. W. Strapp ◽  
S. G. Cober ◽  
H. W. Barker
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Liquid Water Content ◽  
In Situ Measurements ◽  
Stratiform Clouds

scholarly journals Continuous in situ measurements of water stable isotopes in soils, tree trunk and root xylem: field approval

2021 ◽  
Author(s):  
Kathrin Kühnhammer ◽  
Adrian Dahlmann ◽  
Alberto Iraheta ◽  
Malkin Gerchow ◽  
Christian Birkel ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
In Situ Measurements ◽  
Tree Trunk

scholarly journals Microphysical and optical properties of Arctic mixed-phase clouds. The 9 April 2007 case study.

2009 ◽  
Vol 9 (17) ◽  
pp. 6581-6595 ◽  
Author(s):  
J.-F. Gayet ◽  
G. Mioche ◽  
A. Dörnbrack ◽  
A. Ehrlich ◽  
A. Lampert ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Liquid Water ◽  
In Situ Measurements ◽  
Mixed Phase ◽  
Ice Crystals ◽  
The Arctic ◽  
Small Scale ◽  
Water Droplets ◽  
Tropospheric Aerosol

Abstract. Airborne measurements in Arctic boundary-layer stratocumulus were carried out near Spitsbergen on 9 April 2007 during the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) campaign. A unique set of co-located observations is used to describe the cloud properties, including detailed in situ cloud microphysical and radiation measurements along with airborne and co-located spaceborne remote sensing data (CALIPSO lidar and CloudSat radar). CALIPSO profiles indicate cloud top levels at temperature between −24°C and −21°C. In situ measurements confirm that the cloud-top lidar attenuated backscatter signal along the aircraft trajectory is linked with the presence of liquid water, a common feature observed in Arctic mixed-phase stratocumulus clouds. A low concentration of large ice crystals is also observed up to the cloud top resulting in significant CloudSat radar echoes. Since the ratio of the extinction of liquid water droplets to ice crystals is high, broadband radiative effects near the cloud top are mostly dominated by water droplets. CloudSat observations and in situ measurements reveal high reflectivity factors (up to 15 dBZ) and precipitation rates (1 mm h−1). This feature results from efficient ice growth processes. About 25% of the theoretically available liquid water is converted into ice water with large precipitating ice crystals. Using an estimate of mean cloud cover, a considerable value of 106 m3 h−1 of fresh water could be settled over the Greenland sea pool. European Centre for Medium-Range Weather Forecast (ECMWF) operational analyses reproduces the boundary layer height variation along the flight track. However, small-scale features in the observed cloud field cannot be resolved by ECMWF analysis. Furthermore, ECMWF's diagnostic partitioning of the condensed water into ice and liquid reveals serious shortcomings for Arctic mixed-phased clouds. Too much ice is modelled.

The Carbon:²³⁴Thorium ratios of sinking particles in the California Current Ecosystem 2: Examination of a thorium sorption, desorption, and particle transport model

2019 ◽  
Author(s):  
Michael Stukel ◽  
Thomas Kelly
Keyword(s):  
Organic Carbon ◽  
Water Column ◽  
Particulate Organic Carbon ◽  
Transport Model ◽  
California Current ◽  
In Situ Measurements ◽  
Power Law Distribution ◽  
Sinking Particles ◽  
Organic Carbon Concentration

Thorium-234 (234Th) is a powerful tracer of particle dynamics and the biological pump in the surface ocean; however, variability in carbon:thorium ratios of sinking particles adds substantial uncertainty to estimates of organic carbon export. We coupled a mechanistic thorium sorption and desorption model to a one-dimensional particle sinking model that uses realistic particle settling velocity spectra. The model generates estimates of 238U-234Th disequilibrium, particulate organic carbon concentration, and the C:234Th ratio of sinking particles, which are then compared to in situ measurements from quasi-Lagrangian studies conducted on six cruises in the California Current Ecosystem. Broad patterns observed in in situ measurements, including decreasing C:234Th ratios with depth and a strong correlation between sinking C:234Th and the ratio of vertically-integrated particulate organic carbon (POC) to vertically-integrated total water column 234Th, were accurately recovered by models assuming either a power law distribution of sinking speeds or a double log normal distribution of sinking speeds. Simulations suggested that the observed decrease in C:234Th with depth may be driven by preferential remineralization of carbon by particle-attached microbes. However, an alternate model structure featuring complete consumption and/or disaggregation of particles by mesozooplankton (e.g. no preferential remineralization of carbon) was also able to simulate decreasing C:234Th with depth (although the decrease was weaker), driven by 234Th adsorption onto slowly sinking particles. Model results also suggest that during bloom decays C:234Th ratios of sinking particles should be higher than expected (based on contemporaneous water column POC), because high settling velocities minimize carbon remineralization during sinking.

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