scholarly journals Particle Habit Imaging Using Incoherent Light: A First Step toward a Novel Instrument for Cloud Microphysics

2011 ◽  
Vol 28 (4) ◽  
pp. 493-512 ◽  
Author(s):  
Roland Schön ◽  
Martin Schnaiter ◽  
Zbigniew Ulanowski ◽  
Carl Schmitt ◽  
Stefan Benz ◽  
...  
Keyword(s):  
Ccd Camera ◽  
Cloud Microphysics ◽  
Resolving Power ◽  
Ice Crystal ◽  
Ambient Conditions ◽  
Incoherent Light ◽  
Cloud Particle ◽  
Ice Particles ◽  
Institute Of Technology ◽  
A Charge

Abstract The imaging unit of the novel cloud particle instrument Particle Habit Imaging and Polar Scattering (PHIPS) probe has been developed to image individual ice particles produced inside a large cloud chamber. The PHIPS produces images of single airborne ice crystals, illuminated with white light of an ultrafast flashlamp, which are captured at a maximum frequency of ∼5 Hz by a charge-coupled device (CCD) camera with microscope optics. The imaging properties of the instrument were characterized by means of crystalline sodium hexafluorosilicate ice analogs, which are stable at room temperature. The optical resolving power of the system is ∼2 μm. By using dedicated algorithms for image processing and analysis, the ice crystal images can be analyzed automatically in terms of size and selected shape parameters. PHIPS has been operated at the cloud simulation chamber facility Aerosol Interaction and Dynamics in the Atmosphere (AIDA) of the Karlsruhe Institute of Technology at different temperatures between −17° and −4°C in order to study the influence of the ambient conditions, that is, temperature and ice saturation ratio, on ice crystal habits. The area-equivalent size distributions deduced from the PHIPS images are compared with the retrieval results from Fourier transform infrared (FTIR) extinction spectroscopy in case of small (<20 μm) and with single particle data from the cloud particle imager in case of larger (>20 μm) ice particles. Good agreement is found for both particle size regimes.

Optimized intelligent algorithm for classifying cloud particles recorded by a Cloud Particle Imager

2021 ◽  
Author(s):  
Zepei Wu ◽  
Shuo Liu ◽  
Delong Zhao ◽  
Ling Yang ◽  
Zixin Xu ◽  
...  
Keyword(s):  
Processing Speed ◽  
Cloud Microphysics ◽  
Parameter Analysis ◽  
Ice Crystals ◽  
Support Vector ◽  
Svm Classifier ◽  
Ice Crystal ◽  
Cloud Particle ◽  
Average Accuracy ◽  
Cloud Particles

AbstractCloud particles have different shapes in the atmosphere. Research on cloud particle shapes plays an important role in analyzing the growth of ice crystals and the cloud microphysics. To achieve an accurate and efficient classification algorithm on ice crystal images, this study uses image-based morphological processing and principal component analysis, to extract features of images and apply intelligent classification algorithms for the Cloud Particle Imager (CPI). Currently, there are mainly two types of ice-crystal classification methods: one is the mode parameterization scheme, and the other is the artificial intelligence model. Combined with data feature extraction, the dataset was tested on ten types of classifiers, and the highest average accuracy was 99.07%. The fastest processing speed of the real-time data processing test was 2,000 images/s. In actual application, the algorithm should consider the processing speed, because the images are in the order of millions. Therefore, a support vector machine (SVM) classifier was used in this study. The SVM-based optimization algorithm can classify ice crystals into nine classes with an average accuracy of 95%, blurred frame accuracy of 100%, with a processing speed of 2,000 images/s. This method has a relatively high accuracy and faster classification processing speed than the classic neural network model. The new method could be also applied in physical parameter analysis of cloud microphysics.

scholarly journals Relationship between temperature and apparent shape of pristine ice crystals derived from polarimetric cloud radar observations during the ACCEPT campaign

2016 ◽  
Vol 9 (8) ◽  
pp. 3739-3754 ◽  
Author(s):  
Alexander Myagkov ◽  
Patric Seifert ◽  
Ulla Wandinger ◽  
Johannes Bühl ◽  
Ronny Engelmann
Keyword(s):  
Free Fall ◽  
Crystal Shape ◽  
Ice Crystal ◽  
Ambient Conditions ◽  
Axis Ratio ◽  
Microwave Scattering ◽  
Cloud Radar ◽  
Ice Particles ◽  
Rapid Changes ◽  
Good Agreement

Abstract. This paper presents first quantitative estimations of apparent ice particle shape at the top of liquid-topped clouds. Analyzed ice particles were formed under mixed-phase conditions in the presence of supercooled water and in the temperature range from −20 to −3 °C. The estimation is based on polarizability ratios of ice particles measured by a Ka-band cloud radar MIRA-35 with hybrid polarimetric configuration. Polarizability ratio is a function of the geometrical axis ratio and the dielectric properties of the observed hydrometeors. For this study, 22 cases observed during the ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques) field campaign were used. Polarizability ratios retrieved for cloud layers with the cloud-top temperatures of  ∼ −5,  ∼ −8,  ∼ −15, and  ∼ −20 °C were 1.6, 0.9, 0.6, and 0.9, respectively. Such values correspond to prolate, quasi-isotropic, oblate, and quasi-isotropic particles, respectively. Data from a free-fall chamber were used for the comparison. A good agreement of detected apparent shapes with well-known shape–temperature dependencies observed in laboratories was found. Polarizability ratios used for the analysis were estimated for areas located close to the cloud top, where aggregation and riming processes do not strongly affect ice particles. We concluded that, in microwave scattering models, ice particles detected in these areas can be assumed to have pristine shapes. It was also found that even slight variations of ambient conditions at the cloud top with temperatures warmer than  ∼ −5 °C can lead to rapid changes of ice crystal shape.

scholarly journals Aircraft measurements of microphysical properties of subvisible cirrus in the tropical tropopause layer

2007 ◽  
Vol 7 (3) ◽  
pp. 6255-6292 ◽  
Author(s):  
R. P. Lawson ◽  
B. Pilson ◽  
B. Baker ◽  
Q. Mo ◽  
E. Jensen ◽  
...  
Keyword(s):  
Water Vapor ◽  
Costa Rica ◽  
High Water ◽  
Radiation Budget ◽  
Ambient Conditions ◽  
Cloud Particle ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Ice Particles ◽  
Validation Experiment

Abstract. Subvisible cirrus (SVC) clouds are often observed within the tropical tropopause layer (TTL) and have been shown to have a significant impact on the earth radiation budget. The Costa Rica Aura Validation Experiment (CR-AVE) sponsored by the National Aeronautics and Space Administration (NASA) took place near San Jose, Costa Rica from 14 January–15 February 2006. The NASA WB-57F sampled SVC in the TTL from −75°C to −90°C with an improved set of cloud particle probes. The first digital images of ice particles in the TTL are compared with replicator images of ice particles collected in 1973 by a WB-57F in the TTL. The newer measurements reveal larger particles, on the order of 100 μm compared with <50 μm from the earlier measurements, and also different particle shapes. The 1973 particles were mainly columnar and trigonal, whereas the newer measurements are quasi-spherical and hexagonal plates. The WB-57F also measured very high water vapor contents with some instruments, up to 4 ppmv, and aerosols with mixed organics and sulfates. It is unknown whether these ambient conditions were present in the 1973 studies, and whether such conditions have an influence on particle shape and the development of the large particles. A companion paper (Jensen et al., 2007) presents crystal growth calculations that suggest that the high water vapor measurements are required to grow ice particles to the observed sizes of 100 μm and larger.

scholarly journals Shape-temperature relationships of pristine ice crystals derived from polarimetric cloud radar observations during the ACCEPT campaign

2016 ◽  
Author(s):  
A. Myagkov ◽  
P. Seifert ◽  
U. Wandinger ◽  
J. Bühl ◽  
R. Engelmann
Keyword(s):  
Free Fall ◽  
Ice Crystals ◽  
Crystal Shape ◽  
Ice Crystal ◽  
Ambient Conditions ◽  
Microwave Scattering ◽  
Cloud Radar ◽  
Ice Particles ◽  
Rapid Changes ◽  
Good Agreement

Abstract. This paper presents first quantitative estimations of ice particle shape at the top of liquid-topped clouds. Analyzed ice particles were formed in the presence of supercooled water and in the temperature range from −20 to −3 °C. The estimation is based on polarizability ratios of ice particles measured by a Ka-band cloud radar MIRA-35 with hybrid polarimetric configuration, manufactured by METEK GmbH. For this study, 22 cases observed during the ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques) field campaign were used. Polarizability ratios retrieved for cloud layers with the cloud top temperatures of ~−5, ~−8, ~−15, and ~−20 °C were 1.6, 0.9, 0.6, and 0.9, respectively. Such values correspond to prolate, quasi-isotropic, oblate, and quasi-isotropic particles, respectively. Data from a free-fall chamber were used for the comparison. A good agreement of detected shapes with well-known shape-temperature dependencies observed in laboratories was found. Polarizability ratios used for the analysis were estimated for areas located close to the cloud top where aggregation and riming processes do not strongly affect ice particles. We concluded, that in microwave scattering models ice particles detected in these areas can be assumed to have pristine shapes. It was also found that even slight variations of ambient conditions at the cloud top with temperatures warmer than ~−5 °C can lead to rapid changes of ice crystal shape.

scholarly journals In-situ measurements of tropical cloud properties in the West African monsoon: upper tropospheric ice clouds, mesoscale convective system outflow, and subvisual cirrus

2011 ◽  
Vol 11 (1) ◽  
pp. 745-812 ◽  
Author(s):  
W. Frey ◽  
S. Borrmann ◽  
D. Kunkel ◽  
R. Weigel ◽  
M. de Reus ◽  
...  
Keyword(s):  
Water Content ◽  
Potential Temperature ◽  
In Situ Measurements ◽  
Size Distributions ◽  
Ice Crystal ◽  
Cloud Particle ◽  
Ice Particles ◽  
Ice Water Content ◽  
Ice Water

Abstract. In-situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS) clouds were performed during the SCOUT-AMMA campaign over West Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP) operated aboard the Russian high altitude research aircraft M-55 ''Geophysica'' with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS). Two or three modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionate more large ice particles compared to former measurements above maritime regions. With the help of trace gas measurements of NO, NOy, CO2, CO, and O3, and satellite images clouds in young and aged MCS outflow were identified. These events were observed at altitudes of 11.0 km to 14.2 km corresponding to potential temperature levels of 346 K to 356 K. In a young outflow (developing MCS) ice crystal number concentrations of up to 8.3 cm−3 and rimed ice particles with maximum dimensions exceeding 1.5 mm were found. A maximum ice water content of 0.05 g m−3 was observed and an effective radius of about 90 μm. In contrast the aged outflow events were more diluted and showed a maximum number concentration of 0.03 cm−3, an ice water content of 2.3 × 10−4 g m−3, an effective radius of about 18 μm, while the largest particles had a maximum dimension of 61 μm. Close to the tropopause subvisual cirrus were encountered four times at altitudes of 15 km to 16.4 km. The mean ice particle number concentration of these encounters was 0.01 cm−3 with maximum particle sizes of 130 μm, and the mean ice water content was about 1.4 × 10−4 g m−3. All known in-situ measurements of subvisual tropopause cirrus are compared and an exponential fit on the size distributions is established in order to give a parameterisation for modelling. A comparison of aerosol to ice crystal number concentrations, in order to obtain an estimate on how many ice particles result from activation of the present aerosol, yielded low activation ratios for the subvisual cirrus cases of roughly one cloud particle per 30 000 aerosol particles, while for the MCS outflow cases this resulted in a high ratio of one cloud particle per 300 aerosol particles.

scholarly journals Box model trajectory studies of contrail formation using a particle-based cloud microphysics scheme

2021 ◽  
Author(s):  
Andreas Bier ◽  
Simon Unterstrasser ◽  
Xavier Vancassel
Keyword(s):  
Relative Humidity ◽  
Geometric Mean ◽  
Cloud Microphysics ◽  
Ice Crystals ◽  
Box Model ◽  
Radial Dependence ◽  
Ice Crystal ◽  
Ambient Conditions ◽  
Microphysics Scheme ◽  
Soot Particles

Abstract. We investigate the microphysics of contrail formation behind commercial aircraft by means of the particle-based LCM (Lagrangian Cloud Module) box model. We extend the original LCM to cover the basic pathway of contrail formation of soot particles being activated into liquid droplets that soon after freeze into ice crystals. In our particle-based microphysical approach, simulation particles are used to represent different particle types (soot, droplets, ice crystals) and properties (mass/radius, number). The box model is applied in two frameworks. In the classical framework, we prescribe the dilution along one average trajectory in a single box model run. In the second framework, we perform a large ensemble of box model runs using 25000 different trajectories inside an expanding exhaust jet as simulated by the LES (large-eddy simulation) model FLUDILES. In the ensemble runs, we see a strong radial dependence of the temperature and relative humidity evolution. Droplet formation on soot particles happens first near the plume edge and a few tenths of seconds later in the plume centre. Averaging over the ensemble runs, the number of formed droplets/ice crystals increases more smoothly over time than for the single box model run with the average dilution. Consistent with previous studies, contrail ice crystal number varies strongly with atmospheric parameters like temperature and relative humidity near the contrail formation threshold. Close to this threshold, the freezing fraction of soot particles depends strongly on the geometric-mean dry core radius and the hygroscopicity parameter of soot particles. This sensitivity is quite low at ambient conditions far away from the formation threshold. Absolute ice crystal numbers, on the other hand, are controlled by the soot number emission index for all atmospheric conditions. The comparison with a recent contrail formation study by Lewellen (2020) (using similar microphysics) shows a later onset of our contrail formation due to a weaker prescribed plume dilution. If we use the same dilution data, our and Lewellen's evolution in contrail ice nucleation show an excellent agreement cross-validating both microphysics implementations. This means that differences in contrail properties mainly result from different representations of the plume mixing and not from the microphysical modelling. The presented aerosol and microphysics scheme describing contrail formation is of intermediate complexity and thus suited to be incorporated in an LES model for 3D contrail formation studies explicitly simulating the jet expansion. The presented box model results will help interpreting the upcoming, more complex 3D results.

scholarly journals In situ measurements of tropical cloud properties in the West African Monsoon: upper tropospheric ice clouds, Mesoscale Convective System outflow, and subvisual cirrus

2011 ◽  
Vol 11 (12) ◽  
pp. 5569-5590 ◽  
Author(s):  
W. Frey ◽  
S. Borrmann ◽  
D. Kunkel ◽  
R. Weigel ◽  
M. de Reus ◽  
...  
Keyword(s):  
Water Content ◽  
Potential Temperature ◽  
In Situ Measurements ◽  
Size Distributions ◽  
Ice Crystal ◽  
Cloud Particle ◽  
Ice Particles ◽  
Ice Water Content ◽  
Ice Water

Abstract. In situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS) clouds were performed during the SCOUT-AMMA campaign over West Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP) operated aboard the Russian high altitude research aircraft M-55 Geophysica with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS). Two to four modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionately more large ice particles compared to former measurements above maritime regions. With the help of trace gas measurements of NO, NOy, CO2, CO, and O3 and satellite images, clouds in young and aged MCS outflow were identified. These events were observed at altitudes of 11.0 km to 14.2 km corresponding to potential temperature levels of 346 K to 356 K. In a young outflow from a developing MCS ice crystal number concentrations of up to (8.3 ± 1.6) cm−3 and rimed ice particles with maximum dimensions exceeding 1.5 mm were found. A maximum ice water content of 0.05 g m−3 was observed and an effective radius of about 90 μm. In contrast the aged outflow events were more diluted and showed a maximum number concentration of 0.03 cm−3, an ice water content of 2.3 × 10−4 g m−3, an effective radius of about 18 μm, while the largest particles had a maximum dimension of 61 μm. Close to the tropopause subvisual cirrus were encountered four times at altitudes of 15 km to 16.4 km. The mean ice particle number concentration of these encounters was 0.01 cm−3 with maximum particle sizes of 130 μm, and the mean ice water content was about 1.4 × 10−4 g m−3. All known in situ measurements of subvisual tropopause cirrus are compared and an exponential fit on the size distributions is established for modelling purposes. A comparison of aerosol to ice crystal number concentrations, in order to obtain an estimate on how many ice particles may result from activation of the present aerosol, yielded low ratios for the subvisual cirrus cases of roughly one cloud particle per 30 000 aerosol particles, while for the MCS outflow cases this resulted in a high ratio of one cloud particle per 300 aerosol particles.

scholarly journals Aircraft measurements of microphysical properties of subvisible cirrus in the tropical tropopause layer

2008 ◽  
Vol 8 (6) ◽  
pp. 1609-1620 ◽  
Author(s):  
R. P. Lawson ◽  
B. Pilson ◽  
B. Baker ◽  
Q. Mo ◽  
E. Jensen ◽  
...  
Keyword(s):  
Water Vapor ◽  
Costa Rica ◽  
High Water ◽  
Radiation Budget ◽  
Ambient Conditions ◽  
Cloud Particle ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Ice Particles ◽  
Validation Experiment

Abstract. Subvisible cirrus (SVC) clouds are often observed within the tropical tropopause layer (TTL). Some studies suggest that SVC has a significant impact on the earth radiation budget. The Costa Rica Aura Validation Experiment (CR-AVE) sponsored by the National Aeronautics and Space Administration (NASA) took place near San Jose, Costa Rica from 14 January–15 February 2006. The NASA WB-57F sampled SVC in the TTL from −75°C to −90°C with an improved set of cloud particle probes. The first digital images of ice particles in the TTL are compared with replicator images of ice particles collected in 1973 by a WB-57F in the TTL. The newer measurements reveal larger particles, on the order of 100 μm compared with <50 μm from the earlier measurements, and also different particle shapes. The 1973 particles were mainly columnar and trigonal, whereas the newer measurements are quasi-spherical and hexagonal plates. The WB-57F also measured very high water vapor contents with some instruments, up to 4 ppmv, and aerosols with mixed organics and sulfates. It is unknown whether these ambient conditions were present in the 1973 studies, and whether such conditions have an influence on particle shape and the development of the large particles. A companion paper (Jensen et al., 2008) presents crystal growth calculations that suggest that the high water vapor measurements are required to grow ice particles to the observed sizes of 100 μm and larger.

Development of a bio-monitoring system for toxicants in water with fish

2001 ◽  
Vol 1 (2) ◽  
pp. 9-17
Author(s):  
Y.-H. Lee ◽  
H.-K. Lee ◽  
C.-H. Chang ◽  
W.-H. Kim
Keyword(s):  
Monitoring System ◽  
Treatment Plant ◽  
Ccd Camera ◽  
Water Treatment Plant ◽  
Abnormal Behavior ◽  
Time Interval ◽  
Toxic Substances ◽  
Bio Monitoring ◽  
Index Value ◽  
A Charge

A bio-monitoring system for toxicants in water has been developed and verified for actual applications. This system is based on the motionality of five Acheilognathus lanceolata, a fish known to be very sensitive to toxic substances, moving around in an aquarium. Their movements are continuously monitored with a charge coupled device (CCD) camera and analyzed to find and quantify any abnormal behavior in their motional characteristics in comparison with the pre-acquired data. That is, the images of fish captured by a CCD camera are digitalized to identify the location of fish in a constant time interval and the locations of each fish were then analyzed mathematically with a personal computer using the equations proposed to determine the motional characteristics such as floatness, fledness and mobility(agility). These data are then converted by means of fuzzy estimation to an index value, defined as the contamination index (CI), by which the system provides the information about the overall toxic strength of the toxicant in the water flowing into the aquarium. If the fish are exposed to toxicant(s), the CI value will be proportional to the strength of its toxicity. The pilot test was performed in a water treatment plant for six months in order to verify the reproducibility of the system over the unstable conditions such as highly turbid water after rainfall as well as in normal conditions. The test results revealed that this monitoring system has good reproducibility and sensitivity, proving our approach, described in this paper, is reliable. As a result, this approach seems to enable us to make a quick and easy detection of toxic substances contained in water, therefore, this system can be applied to a source of water supply as a toxicant watching system.

scholarly journals Spectroscopic flat-fields can be used for precision CCD gain and noise tests

2021 ◽  
Vol 38 ◽  
Author(s):  
J. Gordon Robertson
Keyword(s):  
Ccd Camera ◽  
Matched Pair ◽  
Optical Fibres ◽  
Charge Coupled Device ◽  
Small Areas ◽  
Flat Field ◽  
Basic Parameters ◽  
The Mean ◽  
A Charge ◽  
Analogue To Digital

Abstract One of the basic parameters of a charge coupled device (CCD) camera is its gain, that is, the number of detected electrons per output Analogue to Digital Unit (ADU). This is normally determined by finding the statistical variances from a series of flat-field exposures with nearly constant levels over substantial areas, and making use of the fact that photon (Poisson) noise has variance equal to the mean. However, when a CCD has been installed in a spectroscopic instrument fed by numerous optical fibres, or with an echelle format, it is no longer possible to obtain illumination that is constant over large areas. Instead of making do with selected small areas, it is shown here that the wide variation of signal level in a spectroscopic ‘flat-field’ can be used to obtain accurate values of the CCD gain, needing only a matched pair of exposures (that differ in their realisation of the noise). Once the gain is known, the CCD readout noise (in electrons) is easily found from a pair of bias frames. Spatial stability of the image in the two flat-fields is important, although correction of minor shifts is shown to be possible, at the expense of further analysis.

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