scholarly journals In-situ observations of aerosol particles remaining from evaporated cirrus crystals: Comparing clean and polluted air masses

2003 ◽  
Vol 3 (4) ◽  
pp. 1037-1049 ◽  
Author(s):  
M. Seifert ◽  
J. Ström ◽  
R. Krejci ◽  
A. Minikin ◽  
A. Petzold ◽  
...  
Keyword(s):  
Size Distribution ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Aerosol Particles ◽  
Pollution Level ◽  
Size Distributions ◽  
Number Density ◽  
Particle Volume ◽  
In Situ Observations

Abstract. In-situ observations of aerosol particles contained in cirrus crystals are presented and compared to interstitial aerosol size distributions (non-activated particles in between the cirrus crystals). The observations were conducted in cirrus clouds in the Southern and Northern Hemisphere mid-latitudes during the INCA project. The first campaign in March and April 2000 was performed from Punta Arenas, Chile (54°S) in pristine air. The second campaign in September and October 2000 was performed from Prestwick, Scotland (53°N) in the vicinity of the North Atlantic flight corridor. Size distribution measurements of crystal residuals (particles remaining after evaporation of the crystals) show that small aerosol particles (Dp< 0.1 mm) dominate the number density of residuals. The crystal residual size distributions were significantly different in the two campaigns. On average the residual size distributions were shifted towards larger sizes in the Southern Hemisphere. For a given integral residual number density, the calculated particle volume was on average three times larger in the Southern Hemisphere. This may be of significance to the vertical redistribution of aerosol mass by clouds in the tropopause region. In both campaigns the mean residual size increased slightly with increasing crystal number density. The form of the residual size distribution did not depend on temperature as one might have expected considering different modes of nucleation. The observations of ambient aerosol particles were consistent with the expected higher pollution level in the Northern Hemisphere. The fraction of residual particles only contributes to approximately a percent or less of the total number of particles, which is the sum of the residual and interstitial particles. Excellent agreement between the CVI and FSSP-300 probes was found supporting the assumption that each crystal is associated with only one residual particle.

scholarly journals In situ observations of aerosol particles remaining from evaporated cirrus crystals: Comparing clean and polluted air masses

2002 ◽  
Vol 2 (5) ◽  
pp. 1599-1633 ◽  
Author(s):  
M. Seifert ◽  
J. Ström ◽  
R. Krejci ◽  
A. Minikin ◽  
A. Petzold ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Aerosol Particles ◽  
Pollution Level ◽  
Size Distributions ◽  
Number Density ◽  
Particle Volume ◽  
The North ◽  
In Situ Observations

Abstract. In situ observations of aerosol particles contained in cirrus crystals are presented and compared to interstitial aerosol size distributions (non-activated particles in between the cirrus crystals). The observations were conducted in cirrus clouds in the Southern and Northern Hemisphere mid-latitudes during the INCA project. The first campaign in March and April 2000 was performed from Punta Arenas, Chile (54° S) in pristine air. The second campaign in September and October 2000 was performed from Prestwick, Scotland (53° N) in the vicinity of the North Atlantic flight corridor. Size distribution measurements of crystal residuals (particles remaining after evaporation of the crystals) show that small aerosol particles (Dp < 0.1µm) dominate the number density of residuals. The crystal residual size distributions were significantly different in the two campaigns. On average the residual size distributions were shifted towards larger sizes in the Southern Hemisphere. For a given integral residual number density, the calculated particle volume was on average three times larger in the Southern Hemisphere. This may be of significance to the vertical redistribution of aerosol mass by clouds in the tropopause region. In both campaigns the mean residual size increased with increasing crystal number density. The observations of ambient aerosol particles were consistent with the expected higher pollution level in the Northern Hemisphere. The fraction of residual particles only contributes to approximately a percent or less of the total number of particles, which is the sum of the residual and interstitial particles.

scholarly journals Snow Depth Fusion Based on Machine Learning Methods for the Northern Hemisphere

2021 ◽  
Vol 13 (7) ◽  
pp. 1250
Author(s):  
Yanxing Hu ◽  
Tao Che ◽  
Liyun Dai ◽  
Lin Xiao
Keyword(s):  
Machine Learning ◽  
Northern Hemisphere ◽  
Snow Depth ◽  
Learning Algorithm ◽  
Random Forest Regression ◽  
Machine Learning Methods ◽  
Long Time ◽  
In Situ Observations ◽  
Input Variables

In this study, a machine learning algorithm was introduced to fuse gridded snow depth datasets. The input variables of the machine learning method included geolocation (latitude and longitude), topographic data (elevation), gridded snow depth datasets and in situ observations. A total of 29,565 in situ observations were used to train and optimize the machine learning algorithm. A total of five gridded snow depth datasets—Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) snow depth, Global Snow Monitoring for Climate Research (GlobSnow) snow depth, Long time series of daily snow depth over the Northern Hemisphere (NHSD) snow depth, ERA-Interim snow depth and Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) snow depth—were used as input variables. The first three snow depth datasets are retrieved from passive microwave brightness temperature or assimilation with in situ observations, while the last two are snow depth datasets obtained from meteorological reanalysis data with a land surface model and data assimilation system. Then, three machine learning methods, i.e., Artificial Neural Networks (ANN), Support Vector Regression (SVR), and Random Forest Regression (RFR), were used to produce a fused snow depth dataset from 2002 to 2004. The RFR model performed best and was thus used to produce a new snow depth product from the fusion of the five snow depth datasets and auxiliary data over the Northern Hemisphere from 2002 to 2011. The fused snow-depth product was verified at five well-known snow observation sites. The R2 of Sodankylä, Old Aspen, and Reynolds Mountains East were 0.88, 0.69, and 0.63, respectively. At the Swamp Angel Study Plot and Weissfluhjoch observation sites, which have an average snow depth exceeding 200 cm, the fused snow depth did not perform well. The spatial patterns of the average snow depth were analyzed seasonally, and the average snow depths of autumn, winter, and spring were 5.7, 25.8, and 21.5 cm, respectively. In the future, random forest regression will be used to produce a long time series of a fused snow depth dataset over the Northern Hemisphere or other specific regions.

scholarly journals Methodology for determining rom size distribution

2014 ◽  
Vol 67 (4) ◽  
pp. 405-412
Author(s):  
Christiane Ribeiro da Silva ◽  
Vládia C. G. de Souza ◽  
Jair C. Koppe
Keyword(s):  
Size Distribution ◽  
Distribution Curve ◽  
Size Distributions ◽  
Sampling Protocol ◽  
Product Size ◽  
Operational Conditions ◽  
Specific Protocol ◽  
Open Side ◽  
Ore Dressing

A methodology to determine the size distribution curve of the ROM was developed in a Brazilian iron ore mine. The size of the larger fragments was determined taking photographs and setting the scale of the images to analyze their dimensions (length of their edges and areas). This was implemented according to a specific protocol of sampling that involves split and homogenization stages in situ of a considerable quantity of ore (about 259 metric tonnes). During the sampling process, larger fragments were separated and smaller size material was screened. The methodology was developed initially in order to preview the performance of a primary gyratory crusher that is fed directly from trucks. Operational conditions of the equipment such as closed and open-side settings could be adjusted previously, obtaining different product size distributions. Variability of size of the fragments affects subsequent stages of crushing and can increase circulating load in the circuit. This leads to a decrease of productivity or recovery of the ore dressing. The results showed insignificant errors of accuracy and reproducibility of the sampling protocol when applied to friable itabirite rocks.

scholarly journals Normalized Hail Particle Size Distributions from the T-28 Storm-Penetrating Aircraft

2019 ◽  
Vol 58 (2) ◽  
pp. 231-245 ◽  
Author(s):  
Paul R. Field ◽  
Andrew J. Heymsfield ◽  
Andrew G. Detwiler ◽  
Jonathan M. Wilkinson
Keyword(s):  
Particle Size ◽  
Water Content ◽  
Size Distribution ◽  
Optical Probe ◽  
Particle Size Distributions ◽  
South Dakota School ◽  
Significant Damage ◽  
In Situ Observations ◽  
Cloud Evolution

AbstractHail and graupel are linked to lightning production and are important components of cloud evolution. Hail can also cause significant damage when it precipitates to the surface. The accurate prediction of the amount and location of hail and graupel and the effects on the other hydrometeor species depends upon the size distribution assumed. Here, we use ~310 km of in situ observations from flights of the South Dakota School of Mines and Technology T-28 storm-penetrating aircraft to constrain the representation of the particle size distribution (PSD) of hail. The maximum ~1-km hail water content encountered was 9 g m−3. Optical probe PSD measurements are normalized using two-moment normalization relations to obtain an underlying exponential shape. By linking the two normalizing moments through a power law, a parameterization of the hail PSD is provided based on the hail water content only. Preliminary numerical weather simulations indicate that the new parameterization produces increased radar reflectivity relative to commonly used PSD representations.

scholarly journals On the Quantitative Low-Level Aerosol Measurements Using Ceilometer-Type Lidar

2009 ◽  
Vol 26 (11) ◽  
pp. 2340-2352 ◽  
Author(s):  
Anu-Maija Sundström ◽  
Timo Nousiainen ◽  
Tuukka Petäjä
Keyword(s):  
Size Distribution ◽  
Theoretical Calculations ◽  
Measurement Instrument ◽  
Aerosol Size Distribution ◽  
Lidar Measurement ◽  
Size Distributions ◽  
Absolute Accuracy ◽  
Particle Composition ◽  
Aerosol Measurement

Abstract The objective of this work is to investigate whether a commercial ceilometer-type lidar can be used as a quantitative aerosol measurement instrument. To this end, lidar backscattering measurements are compared with exact theoretical calculations of backscattering, which are based on in situ–measured size distributions and account for uncertainties in particle composition and shape. The results show that the differences between simulated and measured backscattering remain nearly constant and within the uncertainties involved. The differences are most plausibly explained by an error in the overlap function of the lidar and/or errors in the calibration of either the lidar or the in situ instruments used to measure the aerosol size distribution. Occasionally, large differences occur that are obviously connected to the unrepresentativeness of the in situ and lidar measurement volumes because of insufficient atmospheric mixing. The results imply that the absolute accuracy of the instrument investigated might be sufficient for quantitative aerosol measurements in some applications. A fix for the overlap function, however, would be desirable.

scholarly journals Aerosol size distributions during the Atmospheric Tomography Mission (ATom): methods, uncertainties, and data products

2019 ◽  
Vol 12 (6) ◽  
pp. 3081-3099 ◽  
Author(s):  
Charles A. Brock ◽  
Christina Williamson ◽  
Agnieszka Kupc ◽  
Karl D. Froyd ◽  
Frank Erdesz ◽  
...  
Keyword(s):  
High Resolution ◽  
Size Distribution ◽  
Atmospheric Composition ◽  
The Arctic ◽  
Distribution Data ◽  
Size Distributions ◽  
Aerosol Composition ◽  
Aerosol Mass ◽  
Data Products

Abstract. From 2016 to 2018 a DC-8 aircraft operated by the US National Aeronautics and Space Administration (NASA) made four series of flights, profiling the atmosphere from 180 m to ∼12 km above sea level (km a.s.l.) from the Arctic to the Antarctic over both the Pacific and Atlantic oceans. This program, the Atmospheric Tomography Mission (ATom), sought to sample the troposphere in a representative manner, making measurements of atmospheric composition in each season. This paper describes the aerosol microphysical measurements and derived quantities obtained during this mission. Dry size distributions from 2.7 nm to 4.8 µm in diameter were measured in situ at 1 Hz using a battery of instruments: 10 condensation particle counters with different nucleation diameters, two ultra-high-sensitivity aerosol size spectrometers (UHSASs), one of which measured particles surviving heating to 300 ∘C, and a laser aerosol spectrometer (LAS). The dry aerosol measurements were complemented by size distribution measurements from 0.5 to 930 µm diameter at near-ambient conditions using a cloud, aerosol, and precipitation spectrometer (CAPS) mounted under the wing of the DC-8. Dry aerosol number, surface area, and volume, and optical scattering and asymmetry parameters at several wavelengths from the near-UV to the near-IR ranges were calculated from the measured dry size distributions (2.7 nm to 4.8 µm). Dry aerosol mass was estimated by combining the size distribution data with particle density estimated from independent measurements of aerosol composition with a high-resolution aerosol mass spectrometer and a single-particle soot photometer. We describe the instrumentation and fully document the aircraft inlet and flow distribution system, the derivation of uncertainties, and the calculation of data products from combined size distributions. Comparisons between the instruments and direct measurements of some aerosol properties confirm that in-flight performance was consistent with calibrations and within stated uncertainties for the two deployments analyzed. The unique ATom dataset contains accurate, precise, high-resolution in situ measurements of dry aerosol size distributions, and integral parameters, and estimates and measurements of optical properties, for particles < 4.8 µm in diameter that can be used to evaluate aerosol abundance and processes in global models.

The Impact of Facies Variability within the Harwich Formation on Ground Engineering in the London Area, UK.

2021 ◽  
pp. qjegh2020-136
Author(s):  
Justyna Edgar ◽  
Richard C. Ghail ◽  
James Lawrence ◽  
Jacqueline Skipper ◽  
Philippa J. Mason
Keyword(s):  
Particle Size ◽  
Fault Zones ◽  
Size Distributions ◽  
Infrastructure Projects ◽  
Particle Size Distributions ◽  
Facies Model ◽  
In Situ Observations ◽  
The Impact

The Eocene Harwich Formation, underlying the Greater London (UK) area, presents many construction problems for design and location of tunnels, pipelines, and other engineering infrastructure projects. Variable deposits make up the sequence of the Harwich Formation. These include cemented fault zones, hard grounds, loose gravel and sand that, when unexpectedly encountered, can cause construction delays and increase costs. Here, we interpret borehole cores and logs, in-situ observations coupled with borehole derived samples, and calculate particle-size distributions to develop a general facies model that accounts for the lithological distribution within the Harwich Formation. This provides an improved geological framework for proposed subsurface construction that can reduce inherent engineering uncertainties, not only in the London region, but potentially in other similar geological environments.

Size distribution functions of submicron aerosol and approximation based on the direct Kolmogorov equation

2020 ◽  
Author(s):  
Otto Chkhetiani ◽  
Evgeny Gledzer ◽  
Natalia Vazaeva
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Aerosol Particles ◽  
Distribution Functions ◽  
Dust Aerosol ◽  
Fragmentation Process ◽  
Aral Sea ◽  
Kolmogorov Equation ◽  
Radiation Budget ◽  
Size Distributions

&lt;p&gt;The particle size distribution function is one of the characteristics reflecting the composition of aerosol during sand lifting and removal in desert regions. This characteristic, in addition to known practical applications, is important in describing radiation processes during the exchange of heat fluxes and in forming cloud systems in the models of atmospheric dynamics. Fine dust-aerosol fractions (less than 2 &amp;#181;m in diameter) are especially important for the atmospheric radiation budget, because such fractions (having a significant lifetime) most efficiently interact with short-wave solar radiation. One of the central regularities in considering the size distributions of simulated dust-aerosol particles is the following formula based on the so-called fragmentation process and verified using a large amount of empirical data &lt;em&gt;N &lt;/em&gt;(&lt;em&gt;d&lt;/em&gt;) ~ &lt;em&gt;d &lt;/em&gt;&lt;sup&gt;-2&lt;/sup&gt;. Similar dependence for particles with size &lt;em&gt;d &lt;/em&gt;&gt; 1 &amp;#181;m is associated with the consideration of the fragmentation process as a particle splitting according to the log-normal distribution.&lt;/p&gt;&lt;p&gt;Results of field measurements taken in the near&amp;#8211;Caspian (2002, 2003, 2007, 2009, 2010, 2011, 2013, 2014, 2016 years) and near&amp;#8211;Aral-sea (1998) deserts under the conditions of weak winds (almost in the absence of saltation processes) and strong heating of the land surface are given. These results show that the fine mineral dust aerosol (0.1-1 &amp;#181;m) considerably contributes to the total aerosol content of the atmospheric surface layer under such conditions. The scaling of daytime mean size &lt;em&gt;d&lt;/em&gt; distribution at a height of 2 m is close to &lt;em&gt;d &lt;/em&gt;&lt;sup&gt;-5&lt;/sup&gt;&amp;#160;in contrast to the law &lt;em&gt;d &lt;/em&gt;&lt;sup&gt;-2&lt;/sup&gt; for fraction&amp;#160;&lt;em&gt;d&lt;/em&gt; &gt;1 &amp;#181;m.&lt;/p&gt;&lt;p&gt;Different compositions of aerosol particles at 0.1 &lt; &lt;em&gt;d &lt;/em&gt;&lt; 1 &amp;#181;m, and &lt;em&gt;d&lt;/em&gt; &gt;1 &amp;#181;m, including multicomponent fractions (less than 1 &amp;#181;m) may result in different probabilities of their integration and disintegration, which, finally, determine equilibrium particle size distributions. The simplest distribution approximations based on the Kolmogorov direct differential equation are given.&amp;#160;&lt;/p&gt;&lt;p&gt;This study was supported by the RFBR (19-05-50110) and the Presidium of the Russian Academy of Sciences (programs 12 and 20).&lt;/p&gt;

scholarly journals A Study of Cirrus Ice Particle Size Distribution Using TC4 Observations

2010 ◽  
Vol 67 (1) ◽  
pp. 195-216 ◽  
Author(s):  
Lin Tian ◽  
Gerald M. Heymsfield ◽  
Lihua Li ◽  
Andrew J. Heymsfield ◽  
Aaron Bansemer ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Size Spectra ◽  
Lognormal Distributions ◽  
Characteristic Particle ◽  
In Situ Observations

Abstract An analysis of two days of in situ observations of ice particle size spectra, in convectively generated cirrus, obtained during NASA’s Tropical Composition, Cloud, and Climate Coupling (TC4) mission is presented. The observed spectra are examined for their fit to the exponential, gamma, and lognormal function distributions. Characteristic particle size and concentration density scales are determined using two (for the exponential) or three (for the gamma and lognormal functions) moments of the spectra. It is shown that transformed exponential, gamma, and lognormal distributions should collapse onto standard curves. An examination of the transformed spectra, and of deviations of the transformed spectra from the standard curves, shows that the lognormal function provides a better fit to the observed spectra.

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