scholarly journals In situ cloud particle tracking experiment

2021 ◽  
Vol 92 (12) ◽  
pp. 125105
Author(s):  
G. Bertens ◽  
G. Bagheri ◽  
H. Xu ◽  
E. Bodenschatz ◽  
J. Moláček
Keyword(s):  
Particle Tracking ◽  
Cloud Particle

scholarly journals Microphysical properties of synoptic-scale polar stratospheric clouds: in situ measurements of unexpectedly large HNO<sub>3</sub>-containing particles in the Arctic vortex

2014 ◽  
Vol 14 (19) ◽  
pp. 10785-10801 ◽  
Author(s):  
S. Molleker ◽  
S. Borrmann ◽  
H. Schlager ◽  
B. Luo ◽  
W. Frey ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Scattered Light ◽  
Stratospheric Ozone ◽  
The Arctic ◽  
Size Distributions ◽  
Synoptic Scale ◽  
Cloud Particle ◽  
Regular Feature ◽  
Particle Composition

Abstract. In January 2010 and December 2011, synoptic-scale polar stratospheric cloud (PSC) fields were probed during seven flights of the high-altitude research aircraft M-55 Geophysica within the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interaction) and the ESSenCe (ESSenCe: ESA Sounder Campaign) projects. Particle size distributions in a diameter range between 0.46 and 40μm were recorded by four different optical in situ instruments. Three of these particle instruments are based on the detection of forward-scattered light by single particles. The fourth instrument is a grayscale optical array imaging probe. Optical particle diameters of up to 35μm were detected with particle number densities and total particle volumes exceeding previous Arctic measurements. Also, gas-phase and particle-bound NOy was measured, as well as water vapor concentrations. The optical characteristics of the clouds were measured by the remote sensing lidar MAL (Miniature Aerosol Lidar) and by the in situ backscatter sonde MAS (Multiwavelength Aerosol Scatterometer), showing the synoptic scale of the encountered PSCs. The particle mode below 2μm in size diameter has been identified as supercooled ternary solution (STS) droplets. The PSC particles in the size range above 2μm in diameter are considered to consist of nitric acid hydrates, and the particles' high HNO3 content was confirmed by the NOy instrument. Assuming a particle composition of nitric acid trihydrate (NAT), the optically measured size distributions result in particle-phase HNO3 mixing ratios exceeding available stratospheric values. Therefore the measurement uncertainties concerning probable overestimations of measured particle sizes and volumes are discussed in detail. We hypothesize that either a strong asphericity or an alternate particle composition (e.g., water ice coated with NAT) could explain our observations. In particular, with respect to the denitrification by sedimentation of large HNO3-containing particles, generally considered to be NAT, our new measurements raise questions concerning composition, shape and nucleation pathways. Answering these would improve the numerical simulation of PSC microphysical processes like cloud particle formation, growth and denitrification, which is necessary for better predictions of future polar ozone losses, especially under changing global climate conditions. Generally, it seems that the occurrence of large NAT particles – sometimes termed "NAT rocks" – are a regular feature of synoptic-scale PSCs in the Arctic.

scholarly journals Particle-by-Particle in Situ Characterization of the Protein Corona via Real-Time 3D Single Particle Tracking Microscopy

2021 ◽  
Author(s):  
Xiaochen Tan ◽  
Kevin Welsher
Keyword(s):  
Real Time ◽  
Particle Tracking ◽  
Single Particle ◽  
Biological Fluids ◽  
Protein Corona ◽  
Single Particle Tracking ◽  
Ex Situ ◽  
High Background ◽  
Particle Nature

<p>Nanoparticles (NPs) adsorb proteins when exposed to biological fluids, forming a dynamic protein corona that affects their fate in biological environments. A comprehensive understanding of the protein corona is lacking due to the inability of current techniques to precisely measure the full corona <i>in situ</i> at the single particle level. Herein, we introduce a 3D real-time single-particle tracking spectroscopy to "lock-on" to single freely-diffusing polystyrene NPs and probe their individual protein coronas. The diffusive motions of the tracked NPs enable quantification of the "hard corona" using mean-squared displacement analysis. Critically, this method's particle-by-particle nature enabled a lock-in-type frequency filtering approach to extract the full protein corona, despite the typically confounding effect of high background signal from unbound proteins. From these results, the dynamic <i>in situ </i>full protein corona is observed to contain double the number of proteins than are observed in the <i>ex situ</i> measured "hard" protein corona.</p><br>

scholarly journals Post-flight analysis of detailed size distributions of warm cloud droplets, as determined in situ by cloud and aerosol spectrometers

2021 ◽  
Author(s):  
Sorin Nicolae Vâjâiac ◽  
Andreea Calcan ◽  
Robert Oscar David ◽  
Denisa-Elena Moacă ◽  
Gabriela Iorga ◽  
...  
Keyword(s):  
Cross Section ◽  
Forward Scattering ◽  
Scattering Cross Section ◽  
Size Distributions ◽  
Cloud Droplets ◽  
Cloud Particle ◽  
Fine Grid ◽  
Scattering Cross ◽  
Cloud Parameters

Abstract. Warm clouds, consisting of liquid cloud droplets, play an important role in modulating the amount of incoming solar radiation to Earth’s surface and thus, the climate. The size and number concentration of these cloud droplets control the reflectance of the cloud, the formation of precipitation and ultimately, the lifetime of the cloud. Therefore, in situ observations of the number and diameter of cloud droplets are frequently performed with cloud and aerosol spectrometers, which determine the optical diameters of cloud particles (in the range of up to a few tens of microns) by measuring their forward scattering cross sections in visible light and comparing these values with Mie-theoretical computations. The use of such instruments must rely on a fast working scheme consisting of a limited pre-defined uneven grid of cross section values that corresponds to a theoretically derived uneven set of size intervals (bins). However, as more detailed structural analyses of warm clouds are needed to improve future climate projects, we present a new numerical post-flight methodology using recorded particle-by-particle sample files. The Mie formalism produces a complicated relationship between a particle’s diameter and its forward scattering cross section. This relationship cannot be expressed in an analytically closed form and it should be numerically computed point by point, over a certain grid of diameter values. The optimal resolution required for constructing the diagram of this relationship is therefore analysed. Cloud particle statistics are further assessed using a fine grid of particle diameters in order to capture the finest details of the cloud particle size distributions. The possibility and the usefulness of using coarser size grids, with either uneven or equal intervals is also discussed. For coarse equidistant size grids, the general expressions of cloud microphysical parameters are calculated and the ensuing relative errors are discussed in detail. The proposed methodology is further applied to a subset of measured data and it is shown that the overall uncertainties in computing various cloud parameters are mainly driven by the measurement errors of the forward scattering cross section for each particle. Finally, the influence of the relatively large imprecision in the real and imaginary parts of the refractive index of cloud droplets on the size distributions and on the ensuing cloud parameters is analysed. It is concluded that, in the presence of high atmospheric loads of hydrophilic and light absorbing aerosols, such imprecisions may drastically affect the reliability of the cloud data obtained with cloud and aerosol spectrometers. Some complementary measurements for improving the quality of the cloud droplet size distributions obtained in post-flight analyses are suggested.

Ground-Based Remote Sensing of Cloud Particle Sizes during the 26 November 1991 FIRE II Cirrus Case: Comparisons with In Situ Data

1995 ◽  
Vol 52 (23) ◽  
pp. 4128-4142 ◽  
Author(s):  
S. Y. Matrosov ◽  
A. J. Heymsfield ◽  
J. M. Intrieri ◽  
B. W. Orr ◽  
J. B. Snider
Keyword(s):  
Remote Sensing ◽  
Particle Sizes ◽  
Cloud Particle ◽  
In Situ Data

Determination of polar stratospheric cloud particle refractive indices by use of in situ optical measurements and T-matrix calculations

2005 ◽  
Vol 44 (16) ◽  
pp. 3302 ◽  
Author(s):  
Claudio Scarchilli ◽  
Alberto Adriani ◽  
Francesco Cairo ◽  
Guido Di Donfrancesco ◽  
Carlo Buontempo ◽  
...  
Keyword(s):  
Optical Measurements ◽  
Refractive Indices ◽  
Cloud Particle ◽  
Polar Stratospheric Cloud ◽  
T Matrix

scholarly journals Particle-by-Particle in Situ Characterization of the Protein Corona via Real-Time 3D Single Particle Tracking Microscopy

2021 ◽  
Author(s):  
Xiaochen Tan ◽  
Kevin Welsher
Keyword(s):  
Real Time ◽  
Particle Tracking ◽  
Single Particle ◽  
Biological Fluids ◽  
Protein Corona ◽  
Single Particle Tracking ◽  
Ex Situ ◽  
High Background ◽  
Particle Nature

<p>Nanoparticles (NPs) adsorb proteins when exposed to biological fluids, forming a dynamic protein corona that affects their fate in biological environments. A comprehensive understanding of the protein corona is lacking due to the inability of current techniques to precisely measure the full corona <i>in situ</i> at the single particle level. Herein, we introduce a 3D real-time single-particle tracking spectroscopy to "lock-on" to single freely-diffusing polystyrene NPs and probe their individual protein coronas. The diffusive motions of the tracked NPs enable quantification of the "hard corona" using mean-squared displacement analysis. Critically, this method's particle-by-particle nature enabled a lock-in-type frequency filtering approach to extract the full protein corona, despite the typically confounding effect of high background signal from unbound proteins. From these results, the dynamic <i>in situ </i>full protein corona is observed to contain double the number of proteins than are observed in the <i>ex situ</i> measured "hard" protein corona.</p><br>

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.

Post-flight analysis of the aerosol impact on size distributions of warm clouds’ droplets, as determined in situ by cloud and aerosol spectrometers

2020 ◽  
Author(s):  
Denisa Elena Moacă ◽  
Sorin Nicolae Vâjâiac ◽  
Andreea Calcan ◽  
Valeriu Filip
Keyword(s):  
Size Distribution ◽  
Pure Water ◽  
Weather Forecast ◽  
Cloud Microphysics ◽  
Atmospheric Environment ◽  
Size Distributions ◽  
Cloud Droplets ◽  
Cloud Particle ◽  
Microphysical Properties

&lt;p&gt;The influence of aerosol on the various aspects of the atmospheric properties as well as on the energetic balance is widely recognised in the scientific community and this issue is currently subject to worldwide intense investigations. Among the multiple ways aerosol particles are impacting the atmospheric environment, their interference with the phase transformations of the atmospheric water is of particular importance. Cloud microphysics, on the other hand, is one of the key components in weather forecast and, therefore, in pursuing daily domestic activities ranging from agriculture to energy harvesting and aviation. The micro-physical processes taking place in clouds are strongly influenced by the spatiotemporal variation of the size distribution of the cloud droplets. In this context, as in situ investigations of clouds seem appropriate, one of the most useful types of instruments is casted into the generic name of Cloud and Aerosol Spectrometer (CAS) that can be mounted on specialized research aircraft. The CAS working principle relies basically on measuring the forward scattering cross section (FWSCS) of light with a certain wavelength on a cloud particle and comparing it to the FWSCS computed for pure water spheres. The eventual matching of these values leads to assigning a certain value for the measured particle&amp;#8217;s diameter. The light wavelength is usually chosen in a range where pure water has virtually no absorption. However, atmospheric aerosol frequently mixes up with cloud droplets (starting even from the nucleation processes) and alters their optical properties. By increasing absorption and/or refractivity with respect to those of pure water, one can easily show that the FWSCS-diameter diagram changes drastically by becoming smoother and with an overall significant decrease in absolute values. This means that a CAS will systematically count &amp;#8220;contaminated&amp;#8221; cloud droplets in a lower range of diameters, thus distorting their real size distribution. This effect is inherently degrading the objectivity of CAS measurements and should be more pronounced when levels of sub-micrometer sized aerosol increase at the cloud altitude. The present study aims at pointing out such correlation in order to estimate the reliability of size distributions (and of the ensuing cloud microphysical properties) obtained by CAS.&lt;/p&gt;

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