scholarly journals Cloud microphysical measurements at a mountain observatory: comparison between shadowgraph imaging and phase Doppler interferometry

2021 ◽  
Author(s):  
Moein Mohammadi ◽  
Jakub Lukasz Nowak ◽  
Guus Bertens ◽  
Jan Molacek ◽  
Wojciech Kumala ◽  
...  
Keyword(s):  
Field Experiments ◽  
Droplet Size Distribution ◽  
Number Concentration ◽  
Environmental Research ◽  
Research Station ◽  
Mean Flow ◽  
Cloud Droplets ◽  
Microphysical Properties ◽  
Phase Doppler Interferometry ◽  
Software Algorithms

Abstract. The microphysical properties of cloud droplets, such as droplet size distribution and droplet number concentration, were studied. A series of field experiments were performed in the summer of 2019 at the Umweltforschungsstation Schneefernerhaus (UFS), an environmental research station located just below the peak of Mount Zugspitze in the German Alps. A VisiSize D30 manufactured by Oxford Laser Ltd., which is a shadowgraph imaging instrument, was utilized for the first time to measure the size and velocity of cloud droplets during this campaign. Furthermore, a phase Doppler interferometer (PDI) device, manufactured by Artium Tech. Inc., was simultaneously measuring cloud droplets. After applying modifications to the built-in software algorithms, the results from the two instruments show reasonable agreement regarding droplet sizing and velocimetry for droplet diameters larger than 13 µm. Moreover, discrepancies were observed concerning the droplet number concentration results, especially with smaller droplet sizes. Further investigation by applying appropriate filters to the data allowed the attribution of the discrepancies to two phenomena: the different optical performance of the sensors with regard to small droplets and high turbulent velocity fluctuations relative to the mean flow that result in an uncertain estimate of the volume of air passing through the PDI probe volume.

Employing a shadowgraph imaging technique for cloud microphysical measurements on a mountain observatory

2021 ◽  
Author(s):  
Moein Mohammadi ◽  
Jakub Nowak ◽  
Augustinus Bertens ◽  
Jan Molacek ◽  
Wojciech Kumala ◽  
...  
Keyword(s):  
Size Distribution ◽  
Field Experiments ◽  
Droplet Size Distribution ◽  
Number Concentration ◽  
Depth Of Field ◽  
Research Station ◽  
Mean Flow ◽  
Cloud Droplets ◽  
Probe Volume ◽  
Orographic Clouds

<p>Microphysical properties of cloud droplets, such as droplet size distribution and droplet<br>number concentration have been studied after performing a series of field experiments in<br>summer 2019 at Umweltforschungsstation Schneefernerhaus (UFS), an environmental<br>research station located just below the peak of Zugspitze in the German Alps.<br>“VisiSize D30” manufactured by Oxford Laser Ltd. is a shadowgraph imaging instrument<br>utilized for the first time to measure the size and velocity of cloud droplets during this<br>campaign. It applies a method called “Particle/Droplet Image Analysis” (PDIA) which<br>involves illuminating the region of interest from behind with an infrared pulse laser whilst<br>collecting shadow images of droplets passing through the measurement volume with a<br>high-resolution camera. Droplets detected inside the depth of field are then measured<br>based on their shadow images, and size distribution is built by analyzing a series of<br>images. Furthermore, while turbulent orographic clouds passing our measurement site<br>at UFS observatory during the campaign, a Phase Doppler Interferometer (PDI) device,<br>manufactured by Artium Tech. Inc., was also constantly measuring droplets passing<br>through its probe volume.<br>Analysis of simultaneously collected data from the two instruments, and applying<br>modifications to the original algorithms illustrate a reasonable agreement regarding the<br>droplet sizing and velocimetry between VisiSize D30 and PDI, at least for diameters<br>larger than 13 μm. Moreover, discrepancies have been observed concerning the<br>droplet number concentration results, especially in smaller sizes. Further investigation<br>by applying appropriate filters on data has allowed the attribution of discrepancies to<br>the different optical performance of the sensors regarding small droplets, and to high<br>turbulent velocity fluctuations relative to the mean flow resulting in an uncertain estimate<br>of the volume of air passing through the PDI probe volume.</p>

scholarly journals Observations of high droplet number concentrations in Southern Ocean boundary layer clouds

2016 ◽  
Vol 16 (2) ◽  
pp. 971-987 ◽  
Author(s):  
T. Chubb ◽  
Y. Huang ◽  
J. Jensen ◽  
T. Campos ◽  
S. Siems ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Southern Ocean ◽  
Atmospheric Chemistry ◽  
High Performance ◽  
Cloud Droplet ◽  
Environmental Research ◽  
Cloud Droplets ◽  
Back Trajectories ◽  
Boundary Layer Clouds ◽  
Microphysical Properties

Abstract. Cloud physics data collected during the NSF/NCAR High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole-to-Pole Observations (HIPPO) campaigns provide a snapshot of unusual wintertime microphysical conditions in the boundary layer over the Southern Ocean. On 29 June 2011, the HIAPER sampled the boundary layer in a region of pre-frontal warm air advection between 58 and 48° S to the south of Tasmania. Cloud droplet number concentrations were consistent with climatological values in the northernmost profiles but were exceptionally high for wintertime in the Southern Ocean at 100–200 cm−3 in the southernmost profiles. Sub-micron (0.06  < D <  1 µm) aerosol concentrations for the southern profiles were up to 400 cm−3. Analysis of back trajectories and atmospheric chemistry observations revealed that while conditions in the troposphere were more typical of a clean remote ocean airmass, there was some evidence of continental or anthropogenic influence. However, the hypothesis of long-range transport of continental aerosol fails to explain the magnitude of the aerosol and cloud droplet concentration in the boundary layer. Instead, the gale force surface winds in this case (wind speed at 167 m above sea level was  > 25 m s−1) were most likely responsible for production of sea spray aerosol which influenced the microphysical properties of the boundary layer clouds. The smaller size and higher number concentration of cloud droplets is inferred to increase the albedo of these clouds, and these conditions occur regularly, and are expected to increase in frequency, over windy parts of the Southern Ocean.

scholarly journals Characterization and first results of an ice nucleating particle measurement system based on counterflow virtual impactor technique

2014 ◽  
Vol 7 (10) ◽  
pp. 10585-10617 ◽  
Author(s):  
L. P. Schenk ◽  
S. Mertes ◽  
U. Kästner ◽  
F. Frank ◽  
B. Nillius ◽  
...  
Keyword(s):  
Field Experiments ◽  
Water Saturation ◽  
Chemical Characterization ◽  
Number Concentration ◽  
Research Station ◽  
Virtual Impactor ◽  
First Results ◽  
Aerosol Instrumentation ◽  
Set Up

Abstract. A specific instrument combination was developed to achieve a better microphysical and chemical characterization of atmospheric aerosol particles that have the potential to act as ice nucleating particles (INP). For this purpose a pumped counterflow virtual impactor system called IN-PCVI was set up and characterized to separate ice particles that had been activated on INP in the Fast Ice Nucleus Chamber (FINCH) from interstitial, non-activated particles. This coupled setup consisting of FINCH (ice particle activation and counting), IN-PCVI (INP separation and preparation), and further aerosol instrumentation (INP characterization) had been developed for the application in field experiments. The separated INP were characterized on-line with regard to their total number concentration, number size distribution and chemical composition, especially with the Aircraft-based Laser Ablation Aerosol Mass Spectrometer ALABAMA. Moreover, impactor samples for electron microscopy were taken. Due to the coupling the IN-PCVI had to be operated with different flow settings than known from literature, which required a further characterization of its cut-off-behavior. Taking the changed cut-off-behavior into account, the INP number concentration measured by the IN-PCVI system was in good agreement with the one detected by the FINCH optics for water saturation ratios up to 1.01 (ice saturation ratios between 1.21–1.34 and temperatures between −18 and −26 °C). First field results of INP properties are presented which were gained during the INUIT-JFJ/CLACE 2013 campaign at the high altitude research station Jungfraujoch in the Bernese Alps, Switzerland (3580 m a.s.l.).

scholarly journals A Multisensor Approach Toward a Better Understanding of Snowfall Microphysics: The TOSCA Project

2011 ◽  
Vol 92 (5) ◽  
pp. 613-628 ◽  
Author(s):  
U. Löhnert ◽  
S. Kneifel ◽  
A. Battaglia ◽  
M. Hagen ◽  
L. Hirsch ◽  
...  
Keyword(s):  
Microwave Radiometer ◽  
Optimal Estimation ◽  
Supercooled Liquid ◽  
Environmental Research ◽  
Research Station ◽  
Vertical Column ◽  
Microphysical Properties ◽  
Snow Water ◽  
Snow Crystals

The Towards an Optimal estimation based Snow Characterization Algorithm (TOSCA) project addresses possible novel measurement synergies for deriving snowfall microphysical parameters from the ground by combining the unique information obtained from a suite of ground-based sensors: microwave radiometers (22–150 GHz), 24- and 36-GHz radar, lidar, and in situ optical disdrometer methods. During the winter of 2008/09, such instruments were deployed at the Environmental Research Station Schneefernerhaus (UFS; at 2650 m MSL) at the Zugspitze Mountain in Germany for deriving microphysical properties of snowfall. This contribution gives an overview of the measurements carried out and discusses the potential for the developments of synergetic retrieval algorithms for deriving snow water content within the vertical column. The identification of potentially valuable ground-based instrument synergy for the retrieval of snowfall parameters from the surface will also be of importance for the development of new space-borne observational techniques. Microwave radiometer measurements show that brightness temperature enhancements at 90 and 150 GHz are correlated with the radar-derived snow water path, which is supported by radiative transfer simulations. The synergy of these measurements toward an improved snow mass content, however, needs to be augmented by knowledge on water vapor, supercooled liquid water, particle size distribution, and shape, thus making clear the necessity of synergetic remote sensing and in situ measurements. The radiometric measurements also reveal the very frequent presence of supercooled water within snow clouds and its importance to microphysical diffusion and aggregation growth of snow crystals. Analysis of the disdrometer measurements shows a “secondary aggregation peak” around −12° to −15°C, a temperature range where the Wegener–Bergeron–Findeisen process is most effective and typically dendrite snow crystals forms dominate.

scholarly journals Observations of high droplet number concentrations in Southern Ocean boundary layer clouds

2015 ◽  
Vol 15 (18) ◽  
pp. 25503-25545
Author(s):  
T. Chubb ◽  
Y. Huang ◽  
J. Jensen ◽  
T. Campos ◽  
S. Siems ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Southern Ocean ◽  
High Performance ◽  
Cloud Droplet ◽  
Environmental Research ◽  
Cloud Droplets ◽  
Boundary Layer Clouds ◽  
Microphysical Properties ◽  
Sea Spray Aerosol ◽  
Abstract Data

Abstract. Data from the standard cloud physics payload during the NSF/NCAR High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole-to-Pole Observations (HIPPO) campaigns provide a snapshot of unusual wintertime microphysical conditions in the boundary layer over the Southern Ocean. On 29 June 2011, the HIAPER sampled the boundary layer in a region of pre-frontal warm air advection between 58 and 48° S to the south of Tasmania. Cloud droplet number concentrations were consistent with climatological values in the northernmost profiles but were exceptionally high for wintertime in the Southern Ocean at 100–200 cm−3 in the southernmost profiles. Sub-micron (0.0625 m s−1) were most likely responsible for production of sea spray aerosol which influenced the microphysical properties of the boundary layer clouds. The smaller size and higher number concentration of cloud droplets is inferred to increase the albedo of these clouds, and these conditions occur regularly, and are expected to increase in frequency, over windy parts of the Southern Ocean.

scholarly journals Multi-View Polarimetric Scattering Cloud Tomography and Retrieval of Droplet Size

2020 ◽  
Vol 12 (17) ◽  
pp. 2831 ◽  
Author(s):  
Aviad Levis ◽  
Yoav Y. Schechner ◽  
Anthony B. Davis ◽  
Jesse Loveridge
Keyword(s):  
Remote Sensing ◽  
Droplet Size ◽  
Polarization State ◽  
Optimization Technique ◽  
Three Dimensional ◽  
Cloud Droplet ◽  
Droplet Size Distribution ◽  
Cloud Droplets ◽  
Passive Remote Sensing ◽  
Microphysical Properties

Tomography aims to recover a three-dimensional (3D) density map of a medium or an object. In medical imaging, it is extensively used for diagnostics via X-ray computed tomography (CT). We define and derive a tomography of cloud droplet distributions via passive remote sensing. We use multi-view polarimetric images to fit a 3D polarized radiative transfer (RT) forward model. Our motivation is 3D volumetric probing of vertically-developed convectively-driven clouds that are ill-served by current methods in operational passive remote sensing. Current techniques are based on strictly 1D RT modeling and applied to a single cloudy pixel, where cloud geometry defaults to that of a plane-parallel slab. Incident unpolarized sunlight, once scattered by cloud-droplets, changes its polarization state according to droplet size. Therefore, polarimetric measurements in the rainbow and glory angular regions can be used to infer the droplet size distribution. This work defines and derives a framework for a full 3D tomography of cloud droplets for both their mass concentration in space and their distribution across a range of sizes. This 3D retrieval of key microphysical properties is made tractable by our novel approach that involves a restructuring and differentiation of an open-source polarized 3D RT code to accommodate a special two-step optimization technique. Physically-realistic synthetic clouds are used to demonstrate the methodology with rigorous uncertainty quantification.

scholarly journals Atmospheric new particle formation at the research station Melpitz, Germany: connection with gaseous precursors and meteorological parameters

2018 ◽  
Vol 18 (3) ◽  
pp. 1835-1861 ◽  
Author(s):  
Johannes Größ ◽  
Amar Hamed ◽  
André Sonntag ◽  
Gerald Spindler ◽  
Hanna Elina Manninen ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Solar Radiation ◽  
Gas Phase ◽  
Meteorological Parameters ◽  
Particle Formation ◽  
Number Concentration ◽  
Independent Effect ◽  
Research Station ◽  
New Particle Formation ◽  
Automated Method

Abstract. This paper revisits the atmospheric new particle formation (NPF) process in the polluted Central European troposphere, focusing on the connection with gas-phase precursors and meteorological parameters. Observations were made at the research station Melpitz (former East Germany) between 2008 and 2011 involving a neutral cluster and air ion spectrometer (NAIS). Particle formation events were classified by a new automated method based on the convolution integral of particle number concentration in the diameter interval 2–20 nm. To study the relevance of gaseous sulfuric acid as a precursor for nucleation, a proxy was derived on the basis of direct measurements during a 1-month campaign in May 2008. As a major result, the number concentration of freshly produced particles correlated significantly with the concentration of sulfur dioxide as the main precursor of sulfuric acid. The condensation sink, a factor potentially inhibiting NPF events, played a subordinate role only. The same held for experimentally determined ammonia concentrations. The analysis of meteorological parameters confirmed the absolute need for solar radiation to induce NPF events and demonstrated the presence of significant turbulence during those events. Due to its tight correlation with solar radiation, however, an independent effect of turbulence for NPF could not be established. Based on the diurnal evolution of aerosol, gas-phase, and meteorological parameters near the ground, we further conclude that the particle formation process is likely to start in elevated parts of the boundary layer rather than near ground level.

scholarly journals Technical note: GUARD – An automated fluid sampler preventing sample alteration by contamination, evaporation and gas exchange, suitable for remote areas and harsh conditions

2018 ◽  
Author(s):  
Arno Hartmann ◽  
Marc Luetscher ◽  
Ralf Wachter ◽  
Philipp Holz ◽  
Elisabeth Eiche ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Field Experiments ◽  
Hydrological Cycle ◽  
Technical Note ◽  
Production Costs ◽  
Environmental Research ◽  
Remote Areas ◽  
Wide Range ◽  
Public And Private Sector

Abstract. Automated water sampling devices adapted to field operation have proven highly useful for environmental research as well as in the public and private sector, where natural or artificial waters need to be tested regularly for compliance with environmental and health regulations. Such autosamplers are already available on the market in slightly differing versions, but none of these devices are capable of sealing the collected samples to prevent sample alteration by contamination, evaporation or gas exchange. In many sampling cases, however, this feature is essential, for instance for studying the hydrological cycle based on isotopes in rainwater, or for monitoring waters contaminated with toxic gases or other volatile compounds detrimental to biota and human health. Therefore, we have developed a new mobile autosampler, which injects water samples directly into airtight vials, thus preventing any sample alteration. Further advantages include low production costs, compact dimensions and low weight allowing for easy transport, a wide range of selectable sampling intervals as well as a low power consumption, which make it suitable for long-term applications even in remote areas and harsh (outdoor) conditions due to its heavy-duty water-proof casing. In this paper, we demonstrate (1) the sampler's mechanical functioning, (2) the long-term stability of the collected samples with regard to evaporation and gas exchange and (3) the potential of our device in a wide variety of applications drawing on laboratory and field experiments in different karst caves, which represent one of the most challenging sampling environments.

scholarly journals Validation of Target Yield based Fertilizer Prescription for Rabi Castor in Alfisol

2020 ◽  
pp. 166-173
Author(s):  
Kasthuri Rajamani ◽  
A. Madhavi ◽  
T. Srijaya ◽  
P. Surendra Babu ◽  
Pradip Dey
Keyword(s):  
Field Experiments ◽  
Agricultural Research ◽  
Organic Fertilizers ◽  
Research Station ◽  
Agricultural Research Station ◽  
Target Yield ◽  
Test Verification ◽  
Absolute Control ◽  
Inorganic And Organic

Field experiments were conducted from 2015-16 to 2017-18 on a Typic Rhodustalfs (Alfisol) soils of Telangana at Regional Agricultural Research Station, Palem, Nagarkurnool, Southern Telangana Zone, India to validate targeted yield based fertilizer prescription equations which developed for hybrid castor by adopting eight treatments viz., Blanket recommendation (100% RDF:80:40:30 kg N, P2O5 and K2O ha-1), Blanket+5 t ha-1 of vermin-compost (VC), STCR-Target yield with NPK alone at 25q ha-1, STCR-Target yield with IPNS at 25q ha-1, STCR-Target yield with NPK alone at 30q ha-1, STCR-Target yield with IPNS at 30q ha-1, Farmer’s practice (40:20:0kg N, P2O5 and K2O ha-1) and Absolute control (without inorganic and organic fertilizers). The findings of these test verification trials clearly revealed that the percent achievement of the aimed yield target was within + 10 percent variation confirming the validity of the equations. Using STCR-NPK@25 and 30q ha-1 recorded significantly higher seed (20.74 and 22.30q ha-1) and stalk (24.63 and 26.36q ha-1) yield over blanket recommendation (19.40 and 23.13 q ha-1), while STCR-IPNS at 25 and 30 q ha-1recorde relatively higher seed (20.98 and 22.69q ha-1) and stalk (25.88 and 27.13q ha-1) yield over STCR-NPK alone treatments. The magnitude of built-up was higher with STCR-IPNS treatments as compared to STCR-NPK alone, blanket recommendations, farmer’s practice and absolute control.

Sign in / Sign up

Export Citation Format

Share Document