Static Diffusion Chamber Research Articles

Study of ice nucleating particles in fog-haze weather at New Delhi, India: A case of polluted environment

Ice nucleating particles (INPs) concentration in deposition mode was measured and reported for a polluted urban site in New Delhi, India. The measurements were carried out during the winter period from December 2016 to January 2017. The INPs data, sampled under different meteorological conditions, were analysed using a thermal gradient static diffusion chamber. The observed INPs concentration ranges from 0.05 to 9.55 L−1 at mean nucleation temperature − 18.49 °C (SD = 0.27 °C). The mean INPs number concentration observed under three meteorological conditions was significantly different. No correlation was observed between particles size >0.5 μm, Particulate Matter and BC for the entire observation period, but correlation (r2 = 0.27, p < 0.001) was observed between INPs and BC under foggy conditions for January 2017 period. The activation fraction was ranges from 1:106 to 1:108 for the entire campaign. Scanning electron microscopy analyses revealed that particles chemistry was diverse, and particles were a mixture of BC, mineral dust, and soot. The enrichment factor indicates that elements like Nitrogen, Sulphur, and Chloride were of anthropogenic origin.

Evaluation of Ammonia Recovery from a Laboratory Static Diffusion Chamber System

ABSTRACTAmmoniacal fertilizers are susceptible to ammonia (NH3) volatilization, and multiple methods have been introduced to quantify loss. Methods to quantify differences in NH3 loss are important for evaluating the effectiveness of treatments. Recent research hypothesized that opening chamber enclosures resulted in nitrogen (N) loss (16–30%). Thus, the recovery efficiency of static diffusion chambers used in laboratory experiments was investigated. Chambers with a sand–calcium carbonate (CaCO3) mixture received ammonium-N (NH4-N) solutions. Three time intervals were used to determine if variation in enclosure opening influenced recovery. Acid trap percent recovery and a mass balance approach were used. No differences in cumulative NH3 volatilization were measured from either acid traps or using a mass balance approach. No differences were measured in percent recovery based on N application rate, sample interval, or their interaction, and mean percent N recovery was 99.0%. Thus, diffusion chambers can be reliably used to measure differences in NH3 volatilization.

An observational study of atmospheric ice nuclei number concentration during three fog-haze weather periods in Shenyang, northeastern China

Characteristics of ice nuclei (IN) number concentrations during three fog-haze weather periods from November 2010 to January 2012 in Shenyang were presented in this paper. A static diffusion chamber was used and sampling of IN aerosols was conducted using a membrane filter method. Sampling membrane filter processing conditions were unified in the activation temperature at −15°C under conditions of 20% ice supersaturation and 3% water supersaturation. The variations of natural IN number concentrations in different weather conditions were investigated. The relations between the meteorological factors and the IN number concentrations were analyzed, and relationships between pollutants and IN number concentrations were also studied. The results showed that mean IN number concentration were 38.68L−1 at −20°C in Shenyang, for all measurements. Mean IN number concentrations are higher during haze days (55.92L−1 at −20°C) and lower after rain. Of all meteorological factors, wind speed, boundary stability, and airflow direction appeared to influence IN number concentrations. IN number concentrations were positively correlated with particulate matters PM1, PM2.5, and PM10 during haze weather.

Laboratory investigation of corona initiation by ice crystals and its importance to lightning

This article reports on a new laboratory investigation of the initiation of corona discharges by small vapour‐grown ice crystals. This study was motivated by questions regarding the initiation of lightning and the possible role played by corona discharges on ice hydrometeors. Ice crystals were grown in a static diffusion chamber on a horizontally suspended glass fibre, with environmental conditions selected to mirror those of the thunderstorm environment where initiation of lightning is believed to occur. An in situ parallel plate electrode assembly was then rotated into position, so that the crystals were at the centre. The crystals were then subjected to slowly increasing electric fields until they underwent corona discharge. The discharges were observed and recorded under dark ambient conditions using an image‐intensified video microscope, along with a synchronous record of the applied voltage. The threshold electric fields for corona discharge were determined as a function of air pressure, temperature and ice crystal length in the direction of the applied electric field. The new results are relevant to a better understanding of hydrometeor‐mediated electrical discharge activity in thunderstorms.

Atmospheric ice nuclei in the Eyjafjallajökull volcanic ash plume

Abstract. We have sampled atmospheric ice nuclei (IN) and aerosol in Germany and in Israel during spring 2010. IN were analyzed by the static vapor diffusion chamber FRIDGE, as well as by electron microscopy. During the Eyjafjallajökull volcanic eruption of April 2010 we have measured the highest ice nucleus number concentrations (&gt;600 l−1) in our record of 2 yr of daily IN measurements in central Germany. Even in Israel, located about 5000 km away from Iceland, IN were as high as otherwise only during desert dust storms. The fraction of aerosol activated as ice nuclei at −18 °C and 119% rhice and the corresponding area density of ice-active sites per aerosol surface were considerably higher than what we observed during an intense outbreak of Saharan dust over Europe in May 2008. Pure volcanic ash accounts for at least 53–68% of the 239 individual ice nucleating particles that we collected in aerosol samples from the event and analyzed by electron microscopy. Volcanic ash samples that had been collected close to the eruption site were aerosolized in the laboratory and measured by FRIDGE. Our analysis confirms the relatively poor ice nucleating efficiency (at −18 °C and 119% ice-saturation) of such "fresh" volcanic ash, as it had recently been found by other workers. We find that both the fraction of the aerosol that is active as ice nuclei as well as the density of ice-active sites on the aerosol surface are three orders of magnitude larger in the samples collected from ambient air during the volcanic peaks than in the aerosolized samples from the ash collected close to the eruption site. From this we conclude that the ice-nucleating properties of volcanic ash may be altered substantially by aging and processing during long-range transport in the atmosphere, and that global volcanism deserves further attention as a potential source of atmospheric ice nuclei.

Saharan dust and ice nuclei over Central Europe

Abstract. Surface measurements of aerosol and ice nuclei (IN) at a Central European mountain site during an episode of dust transport from the Sahara are presented. Ice nuclei were sampled by electrostatic precipitation on silicon wafers and were analyzed in an isothermal static vapor diffusion chamber. The transport of mineral dust is simulated by the Eulerian regional dust model DREAM. Ice nuclei and mineral dust are significantly correlated, in particular IN number concentration and aerosol surface area. The ice nucleating characteristics of the aerosol as analyzed with respect to temperature and supersaturation are similar during the dust episode than during the course of the year. This suggests that dust may be a main constituent of ice nucleating aerosols in Central Europe.

Ice particle growth under conditions of the upper troposphere

Atmospheric conditions for growth of ice crystals (temperature and ice supersaturation) are often not well constrained and it is necessary to simulate such conditions in the laboratory to investigate such growth under well controlled conditions over many hours. The growth of ice crystals from the vapour in both prism and basal planes was observed at temperatures of −60 °C and −70 °C under ice supersaturation up to 100% (200% relative humidity) at air pressures derived from the standard atmosphere in a static diffusion chamber. Crystals grew outward from a vertical glass filament, thickening in the basal plane by addition of macroscopic layers greater than 2 μm, leading to growth in the prism plane by passing of successive layers conveniently viewed by time-lapse video.

A new method for sampling of atmospheric ice nuclei with subsequent analysis in a static diffusion chamber

A new technique for the sampling of atmospheric ice nuclei is presented. Aerosols are electrostatically precipitated onto silicon discs, and are subsequently analyzed in a diffusion chamber. The method is compared to continuous flow chamber measurements and to membrane filter measurements of ice nuclei. Ice nucleus measurements obtained using this new method compare well to the continuous flow chamber measurements. In contrast, membrane filters were found to lead to serious underestimates of the ice nuclei number concentration when the filters were treated with a pore sealant and analyzed under vacuum. This confirms previous findings of other authors. The electrostatic aerosol collection device is lightweight and easy to handle.

The fast Ice Nucleus chamber FINCH

We present first results of our new developed Ice Nucleus (IN) counter FINCH from the sixth Cloud and Aerosol Characterization Experiment (CLACE 6) campaign at Jungfraujoch station, 3571 m asl. Measurements were made at the total and the ICE CVI inlet. Laboratory measurements of ice onset temperatures by FINCH are compared to those of the static diffusion chamber FRIDGE (FRankfurt Ice Deposition Freezing Experiment). Within the errors of both new instruments the results compare well to published data.

Technical Note: Characterization of a static thermal-gradient CCN counter

Abstract. The static (parallel-plate thermal-gradient) diffusion chamber (SDC) was one of the first instruments designed to measure cloud condensation nuclei (CCN) concentrations as a function of supersaturation. It has probably also been the most widely used type of CCN counter. This paper describes the detailed experimental characterization of a SDC CCN counter, including calibration with respect to supersaturation and particle number concentration. In addition, we investigated the proposed effect of lowered supersaturation because of water vapor depletion with increasing particle concentration. The results obtained give a better understanding why and in which way it is necessary to calibrate the SDC CCN counter. The calibration method is described in detail and can, in parts, be used for calibrations also for other types of CCN counters. We conclude the following: 1) it is important to experimentally calibrate SDC CCN counters with respect to supersaturation, and not only base the supersaturation on the theoretical description of the instrument; 2) the number concentration calibration needs to be performed as a function of supersaturation, also for SDC CCN counter using the photographic technique; and 3) we observed no evidence that water vapor depletion lowered the supersaturation.

North American and Asian aerosols over the eastern Pacific Ocean and their role in regulating cloud condensation nuclei

Measurements of aerosol and cloud properties in the Eastern Pacific Ocean were taken during an airborne experiment on the University of Wyoming's King Air during April 2004 as part of the Cloud Indirect Forcing Experiment (CIFEX). We observed a wide variety of aerosols, including those of long‐range transport from Asia, clean marine boundary layer, and North American emissions. These aerosols, classified by their size distribution and history, were found in stratified layers between 500 to 7500 m above sea level and thicknesses from 100 to 3000 m. A comparison of the aerosol size distributions to measurements of cloud condensation nuclei (CCN) provides insight to the CCN activity of the different aerosol types. The overall ratio of measured to predicted CCN concentration (NCCN) is 0.56 ± 0.41 with a relationship of NCCN,measured = NCCN,predicted0.846±0.002 for 23 research flights and 1884 comparisons. Such a relationship does not accurately describe a CCN closure; however, it is consistent with our measurements that high CCN concentrations are more influenced by anthropogenic sources, which are less CCN active. While other CCN closures have obtained results closer to the expected 1:1 relationship, the different aerosol types (and presumably differences in aerosol chemistry) are responsible for the discrepancy. The measured NCCN at 0.3% supersaturation (Sc) ranged from 20 cm−3 (pristine) to 350 cm−3 (anthropogenic) with an average of 106 ± 54 cm−3 over the experiment. The inferred supersaturation in the clouds sampled during this experiment is ∼0.3%. CCN concentrations of cloud‐processed aerosol were well predicted using an ammonium sulfate approximation for Sc ≤ 0.4%. Predicted NCCN for other aerosol types (i.e., Asian and North American aerosols) were high compared to measured values indicating a less CCN active aerosol. This study highlights the importance of chemical effects on CCN measurements and introduces a CCN activation index as a method of classifying the efficiency of an aerosol to serve as CCN relative to an ammonium sulfate particle. This index ranged from close to unity for cloud processed aerosols to as low as 0.31 for aged aerosols transported from Asia. We also compare the performance of two CCN instruments (static thermal diffusion chamber and streamwise continuous flow chamber) on a 45 minute level leg where we observe an aged layer and a nucleation event. More than 50% of the aged aerosol served as CCN at 0.2% Sc, primarily owing to their large size, while CCN concentrations during the nucleation event were close to 0 cm−3. CCN concentrations from both instruments agreed within instrument errors; however, the continuous flow chamber effectively captured the rapid transition in aerosol properties.

Growth Rates and Habits of Ice Crystals between −20° and −70°C

Abstract A laboratory study of ice crystal growth characteristics at temperatures between −20° and −70°C has been performed at ice supersaturations and pressures comparable with those in the atmosphere using a horizontal static diffusion chamber. Maximum dimension, projected area, and volume growth rates, in addition to habit frequency, have been measured for individual habit types as functions of temperature, ice supersaturation, and air pressure. It was found that from −20° to −40°C and at ice supersaturations in excess of 2%, the most frequent habits observed were platelike polycrystals and plates, the complexity of forms increasing with increasing supersaturation. Columns appear with low frequency in this temperature range for all supersaturations. At low ice supersaturation (1%–2%), the habit consists of thick plates, compact polycrystals, and occasional short columns and is the region with the highest frequency of pristine crystals capable of producing halos. Just colder than −40°C, there is a marke...

Airborne bacteria as cloud condensation nuclei

Bacteria cultivated from aerosol and cloud water samples collected at a remote Austrian mountain site under wintry conditions were tested for their ability to act as cloud condensation nuclei (CCN). The experiment was carried out with a cloud condensation nuclei counter (CCNC) operating on the principle of a static thermal diffusion chamber. Average concentrations of cultivable airborne bacteria amounted to 8 colony forming units (CFU) m−3 in aerosol samples and to 79 CFU mL−1 in cloud water. The set of tested bacteria comprised Gram positive and Gram negative but no known ice nucleating species. At supersaturations between 0.07 and 0.11% all types of bacteria were activated as CCN. As the sizes of the bacteria were smaller than the Kelvin diameters for the respective supersaturations, the physico‐chemical properties of their outer cell walls must have enhanced their CCN activity.

CCN activation of oxalic and malonic acid test aerosols with the University of Vienna cloud condensation nuclei counter

The cloud droplet activation of monodisperse laboratory aerosols consisting of single organic and inorganic substances as well as a mixture of several substances was investigated using the University of Vienna cloud condensation nuclei counter (CCNC). The CCNC operates on the principle of a static thermal diffusion chamber. Water vapour supersaturations can be set in the range from 0.1% to 2%. Aqueous solutions of oxalic acid and malonic acid as well as solutions of inorganic compounds (NaCl and (NH 4) 2SO 4) were nebulized in a Collison atomizer and then passed through a closed-loop differential mobility particle spectrometer to produce monodispersed particles. An internally mixed aerosol consisting of ammonium sulphate, oxalic acid and malonic acid with relative concentrations resembling those found in cloud water at a mountain station [Löflund, Kasper-Giebl, Schuster, Giebl, Hitzenberger, Reischl et al. (2002) Atmos. Environ. 36, 1553] was also investigated for cloud condensation nuclei (CCN) activation. All these particles were activated at supersaturations expected from Köhler theory. Oxalic and malonic acid particles are therefore expected to be good atmospheric CCN both as pure particles and as internally mixed particles containing other chemical compounds.

Nucleation effects on the habit of vapour grown ice crystals from −18 to −42°C

AbstractIce crystals have been nucleated and grown by a new method where supersaturation is controlled by combining static diffusion chamber and expansion chamber techniques. Crystals were nucleated and grown on $50\ \mu \hbox{m}$ diameter glass filaments at pressures of 500 to 300 hPa, typical of clouds with temperatures from −18 to −42°C, respectively. Crystals were also nucleated on particles of finely powdered silver iodide and kaolinite adhering to glass filaments, in order to investigate effects on habit due to different nucleating materials. Critical supersaturations for nucleation were measured for each case and were in good agreement with previous nucleation studies. Crystals were grown at ice supersaturations which ranged from less than 1% to just above water saturation. For ice growth below a critical supersaturation, nucleation was achieved by applying a brief adiabatic expansion to the static diffusion chamber with a filament in place and the chamber evacuated to the target pressure for the temperature of interest. Nucleation occurred at a critical supersaturation, followed by growth at a lower value. A review of past laboratory experiments and recent in situ observations reveals good agreement between laboratory and field observations when the effects of nucleating methods and growth times are taken into account. Contrary to studies which report the habit of ice as ‘prism’‐like or columnar below approximately −22°C, the habit is found to be plate‐like for temperatures ranging from −18°C to −40°C at ice supersaturations relevant to the atmosphere. Additionally, the plate‐like‐habit distribution is dominated by polycrystalline forms, which is consistent with aspects of past laboratory studies and recent observations obtained with improved aircraft instrumentation. The habits and habit distributions obtained from glass and kaolinite most closely resemble those observed in the atmosphere, while the results from silver iodide show large differences. Below −40°C, the habit becomes columnar except at low supersaturation, and is still dominated by polycrystals which appear as rosettes for ice supersaturations greater than about 20%. ‘Bullet rosettes’ were observed to nucleate and grow on clean glass threads below −40°C but not on kaolinite which predominantly grew single columns and irregular polycrystals with columnar components; silver iodide produced single columns with few polycrystals. This behaviour indicates that rosettes result from ice nuclei which share few or no crystallographic similarities with ice, and is consistent with that expected from homogeneous nucleation. Critical supersaturation measurements for nucleation were extended down to −70°C, and revealed that below −40°C ice crystals can nucleate on glass at ice supersaturations of 25%, and at values of approximately 15% on kaolinite or silver iodide. Copyright © 2002 Royal Meteorological Society

Transport in the static diffusion cloud chamber revisited

The static diffusion chamber (SDC) allows the measurement of critical supersaturation and of nucleation rates and it is a powerful instrument for the vapor nucleation study. Earlier, within the scope of the International Nucleation Workshop Group, nucleation rates of the n-pentanol–helium system have been measured using different experimental techniques. Disagreement of experimental data obtained using the static diffusion chamber and data obtained using other methods, particularly the laminar flow diffusion chamber, can be explained by re-examining the mass and energy transport analysis used to describe static diffusion chamber operation. In the present research we describe the mass and energy transport in the SDC modeled as an effectively open system with mass and energy transport in one direction with a nonzero diffusion flux at the system boundaries. Calculated values for vapor supersaturation are compared with the n-pentanol nucleation rate experimental results of the American–Czech group [M. Rudek, J. L. Katz, I. Y. Vidensky et al., J. Chem. Phys. 111, 3623 (1999)] and with a nucleation rate Reference Equation obtained from an earlier investigation involving the n-pentanol–helium system. From our results one can see that there is a significant difference in the calculated supersaturation for all of the data. The magnitude of this difference is quite large even for the relatively small vapor mass fractions at a nucleation temperature of 260 K. We also note that the calculated nucleation temperatures from our analysis are slightly larger than those reported in the work of Rudek et al.4 We performed our calculations with and without the thermal diffusion term. We observed that the effect of thermal diffusion on the transport process is relativelly small and is not particularly essential to include in this comparison that we are making the effects of the different flux boundary conditions.

Corrected model for one-dimension transport in static diffusion chamber

Corrected model for one-dimension transport in static diffusion chamber

n -Pentanol–helium homogeneous nucleation rates

An international collaboration to examine the effects of different experimental systems on nucleation measurements has resulted in a series of nucleation experiments on the n-pentanol–helium system. In particular, using a laminar flow diffusion chamber, nucleation rate data were obtained for temperatures between 258 and 266 K and total pressures of 0.10, 0.20, and 0.30 MPa. These results are compared with other data on nucleation measured experimentally using an expansion wave tube, a two-piston expansion chamber, a flow diffusion chamber, and a static diffusion chamber. The influence of the carrier gas pressure on nucleation rates was explored. It was concluded that the critical embryo phase transitions should be detectable in an analogous manner to the recently reported phase transitions in the glycerin–carbon dioxide system. The experimental detection of the melting point is suggested as a critical test for the ability of an experimental system to provide adequate measurements of nucleation rates. For example, the glycerin melting point can be used for these tests. A reference equation for nucleation rates of n-pentanol–helium is proposed as a practical test of any experimental measurement system for total pressures of 0.10, 0.20, and 0.30 MPa. The use of this equation is recommended even if the reference equation is not completely accurate, because it provides a scale for comparison of the results for different research groups and methods.

Calibration of a Photometric Cloud Condensation Nucleus Counter Designed for Deployment on a Balloon Package

Abstract The importance of atmospheric aerosols in understanding global climate changes has renewed interest in measurements of cloud condensation nuclei (CCN). To obtain high-resolution (125 m) vertical profiles of CCN number concentration, a balloon-borne instrument was developed. The instrument deduces the CCN concentration from measurements of laser light scattered by water droplets that condense on CCN within a static thermal-gradient diffusion chamber. The amount of light scattering is linearly proportional to the number of droplets within the diffusion chamber. Correlating the number of droplets within the sample volume with the amount of light scattered by the droplets provides the calibration constant that relates scattered light to CCN concentration. The calibration was tested by comparisons between the CCN counter and a condensation nuclei counter when sampling monodisperse aerosol larger than the CCN counter’s critical activation size. The calibration constant depends on supersaturation, and d...

Joint experiments on homogeneous nucleation: static diffusion chamber results

Joint experiments on homogeneous nucleation: static diffusion chamber results