Distribution Of Condensation Nuclei Research Articles

Disdrometer, Polarimetric Radar, and Condensation Nuclei Observations of Supercell and Multicell Storms on 11 June 2018 in Eastern Nebraska

Disdrometer and condensation nuclei (CN) data are compared with operational polarimetric radar data for one multicell and one supercell storm in eastern Nebraska on 11 June 2018. The radar was located ~14.3 km from the instrumentation location and provided excellent observation time series with new low-level samples every 1–2 min. Reflectivity derived by the disdrometer and radar compared well, especially in regions with high number concentration of drops and reflectivity <45 dBZ. Differential reflectivity also compared well between the datasets, though it was most similar in the supercell storm. Rain rate calculated by the disdrometer closely matched values estimated by the radar when reflectivity and differential reflectivity were used to produce the estimate. Concentration of CN generally followed precipitation intensity for the leading convective cell, with evidence for higher particle concentration on the edges of the convective cell associated with outflow. The distribution of CN in the supercell was more complex and generally did not follow precipitation intensity.

Anthropogenic Effects on Cloud Condensation Nuclei Distribution and Rain Initiation in East Asia

Key Points The activated cloud condensation nuclei (CCN) into cloud droplets were nearly equally low (<300 cm−3) in inland areas with little anthropogenic emissions Anthropogenic emissions were responsible to the greatly elevated concentrations of CCN over and downwind of urban agglomeration The enhanced CCN increased cloud depth for rain initiation up to 4 km, further delayed and suppressed the precipitation over the most polluted regions

Enhanced persistence of fog under illumination for carbon nanotube fog condensation nuclei

Black carbon (BC) emissions have increased over South Asia and more persistent winter fogs are common during last decade. However, a physical mechanism connecting these two is still unknown. A significant fraction of BC is known to be in the form of carbon-nanotube (CNT). We have investigated the effects of two different sets of fog condensation nuclei, viz., inorganic salts (sodium chloride and ammonium sulphate) and BC (graphite and CNT) on the dissipation of chamber generated fog under dark and halogen lamp illuminated conditions at a controlled temperature, relative humidity, and fog condensation nuclei distribution. We found that, for inorganic salts, fog dissipates at a faster rate under illumination than in dark conditions showing similar trends for both sodium chloride and ammonium chloride. On the contrary, fog is found to be more persistent, for illuminated conditions, in the case of BC. Moreover, fog persistence is found to be more than twice for CNT compared to graphite in illuminated conditions. CNT is known to be an extremely effective absorber of light which leads to microscopic heating and subsequent evaporation which inhibits droplet growth. Small droplets have large residence time leading to longer fog persistence. This hitherto unknown mechanism may be responsible for persistent fog in India during last decade.

Cosmic ray-induced stratospheric aerosols: A possible connection to polar ozone depletions

Abstract. The model calculations of altitude distribution of CN (condensation nuclei), plausible centers of sulfate aerosol formation after the occurrence of GLE, are presented. Events with relativistic solar protons (i.e. protons with energies >450MeV) are observed at ground level by neutron monitors and called ground-level events (GLEs) (Shea and Smart, 2001). Analysis of experimental data and model calculations permits us to explain some distinctions observed in ozone total content (OTC) variations during several GLEs. For example, model simulations show a significant CN concentration enhancement during the May 1990 GLEs of relatively "moderate" magnitude, when polar ozone "mini-holes" (OTC depletions up to 20%) have been observed, while no OTC variations and considerable aerosol enhancements were seen during more powerful GLEs (4 August 1972, 2 May 1998, 14 July 2000) (Reagan et al., 1981; Shumilov et al., 1995, 2003). Our results demonstrate that "moderate" GLEs may increase aerosol content significantly and cause ozone "mini-hole" creation.

Exploratory analysis of the distribution of condensation nuclei in the northern hemisphere upper troposphere and lower stratosphere during the late 1970s

Data obtained from the Global Atmospheric Sampling Program (GASP) during the late 1970s are used to evaluate the hypothesis that particulate emissions by aircraft are a significant source for the upper tropospheric/lower stratospheric fine and ultrafine aerosol. Measurements of condensation nuclei (CN) were acquired above 6 km mean sea level as part of GASP from October 1977 through June 1979, using automated packages on up to four commercial airliners simultaneously flying their normal daily routes. These routes spanned much of the midlatitude Northern Hemisphere, with the notable exceptions of the former Soviet Union and China. The GASP measurements are analyzed to determine the vertical, geographical, and seasonal distribution of upper tropospheric/lower stratospheric CN in clear air, spanning an altitude range from several kilometers above to several kilometers below the tropopause. The general lack of vertical gradients in median CN mixing ratio at altitudes in the troposphere suggests that CN in the clear troposphere are generally well mixed. CN mixing ratios decrease with distance above the tropopause, consistent with a tropospheric source for stratospheric CN. Median CN mixing ratios for selected regions were compared to the Northern Hemisphere median, by altitude and season. Regional median CN mixing ratios can differ from the hemispheric median by more than a factor of 2 but never an order of magnitude. The lack of vertical variation of CN concentrations in the troposphere is not at all consistent with the vertical variation of fuel consumed by aircraft, which peaks at altitudes near the tropopause. The observations of CN show some regional medians exceeding Northern Hemisphere medians in some seasons and not others, but the regions with the highest medians are not always those with the highest aircraft fuel consumption. We conclude that aircraft emissions are not a major component of the global clear air background CN measured during GASP.

Number concentration and size distribution of aerosol particles in the middle troposphere over the Western Pacific Ocean

Number concentration and size distribution of aerosol particles were measured on board aircraft during the PACE (Pacific Atmospheric Chemistry Experiment) campaign from Australia to Japan in January 1994. The spatial distribution of condensation nuclei (CN) ( r ⩾ 4 nm) at 5–6 km altitude showed large variabilities in concentrations from 10 2 to 10 3 mg −1 that is, the concentrations were low (70–500 mg −1) in the intertropical convergence zone, high (400–1500 mg −1) in the subtropical highpressure area, and low again in the higher latitudes. An apparent opposite tendency was present between CN and large particle ( r ⩾ 0.15 μm) concentrations. The size distributions in the subtropical region exhibited high number concentrations of very fine particles ( r < 0.02 μm). Together with the horizontal observation, vertical observations of aerosols were carried out over some areas. In the subtropical area (Saipan), CN concentration increased with altitude in contrast to the large particle concentration. Also most of the particles collected at 6 km altitude over Saipan contained sulfuric acid. These results are consistent with the results of Clarke (1993, J. geophys. Res. 98, 20,633–20,647) that new particle formation is favored in the upper troposphere.

Ozone and Aitken nuclei over equatorial Africa: Airborne observations during DECAFE 88

We determined the distribution of ozone (O3) and Aitken condensation nuclei (CN) over the rain forest in equatorial Africa during February 12–25, 1988. A pronounced O3 maximum with levels up to 70 ppbv was present in a layer between 1 and 3 km altitude throughout the period. It coincided with a CO maximum and with high levels of CO2 and gaseous organic acids. In general, the vertical distribution of CN was similar to that of O3, with number densities ranging up to approximately 3000 cm−3. Dense haze was visible within this layer. O3 and CN decreased sharply above the haze layer to values typical of the remote troposphere. Survey flights showed little change in levels of O3 and CN or in their vertical distribution over distances of hundreds of kilometers. Meteorological observations suggest that this ozone and particulate enriched layer is formed from air masses which originate in northern Africa and subsequently advect over dry tropical regions where biomass burning emits large amounts of aerosols, CO, NO, and hydrocarbons. These air masses then become trapped in the equatorial region between the near‐surface monsoon flow from the southeast and the permanent easterly flow above 3–4 km. Differences in the vertical distribution of O3 and CN result from the removal of O3 by surface uptake and reactions with NO and hydrocarbons, leading to surface O3 concentrations near zero and a steep O3 gradient through the subcloud layer at night. During the day this gradient is reduced by convective mixing. CN concentrations showed no pronounced gradients in the subcloud layer, consistent with the absence of a strong sink for CN at the ground. CN gradients near the surface suggest emission of particles from the forest vegetation or from biomass burning.

Measurements of condensation nuclei above the jet stream: Evidence for cross jet transport by waves and new particle formation at high altitudes

Condensation nuclei (CN) were used as a tracer in mid‐latitude aircraft experiments in April and May 1984 designed to study transport in the stratosphere. A very large scale, mean distribution of CN was determined for April 20 in the plane perpendicular to the jet stream using smoothed CN measurements and very large scale, mean potential vorticity isopleths. This very large scale, mean distribution was constructed to exclude the structures associated with waves of short vertical wavelengths. A second analysis was done on filtered CN data by Danielsen et al. [this issue] to produce a CN cross section which included the effects of waves having vertical wavelengths of the order of 1 to 3 km. These two analyses and the waves inferred from the meteorological and tracer data produce a self‐consistent explanation for the observed spatial distribution of CN on April 20. The very large scale, mean CN distribution was distorted by waves which had the effect of transporting air with anticyclonic properties several degrees to the cyclonic side of the jet and created a strongly layered structure in the CN distribution.The unfiltered CN data revealed short wavelength oscillations in the CN distribution at the interface between the transported anticyclonic air parcel and the adjacent cyclonic air mass. These oscillations were also seen in the ozone data, and they increase the potential for mixing along that interface. If the mixing does occur, then a wave mechanism for cross jet transport has been observed.At altitudes above about 17 km, CN mixing ratios were affected by a high altitude source of new particles.

Effect of size distribution of condensation nuclei on pressure in an expansion counter

Pressure in the sample chamber of a pressure defined expansion type nucleus counter and optical attenuation are measured using a sensitive pressure transducer, an optical sensor and an electronic recorder for different samples of aerosols. It is observed that first and second derivatives of pressure, as a function of time, display inflections characteristic of the samples. Details of the experimental work, theoretical background and an analysis of results are presented in this paper. It is concluded that the inflections are likely to indicate the number of modes in the size distribution of condensation nuclei in the sample. Measurements of optical attenuation and its derivative as a function of time support the interpretation.

Analytical Solutions for Cloud-Drop Concentration

This note compares and evaluates the analytical solutions of Squires and Twomey for cloud droplet concentration. Either solution is likely to be fairly accurate (±30%) when the slope parameter (β) of the cloud condensation nuclei distribution is small (β<0.8). For large β errors increase rapidly and both solutions are likely to underestimate the actual drop concentration by a wide margin.

The main features of condensation nuclei distribution in the free atmosphere over the European territory of the USSR

According to the numerous observations from airplanes the mean profiles of the condensation nuclei concentration up to the height of 6 km in different geographical points have been obtained and the regularity of their vertical distribution has been specified. It has been shown that the theoretical diffusion-coagulation formula (6) is in good agreement with the empirical data. According to the relations obtained the total of the condensation nuclei content in the troposphere (1.15· 10 27 nuclei) has been estimated. Basing on the data of stationary soundings and on a great number of additional horizontal flights the peculiarities of geographical condensation nuclei distribution in the lower troposphere over the European territory of the USSR have been cleared up. The schematic maps of nuclei distribution at levels 2 and 3 km are given which are compared with the distribution of the atmospheric precipitation mineralization. DOI: 10.1111/j.2153-3490.1966.tb00265.x

The main features of condensation nuclei distribution in the free atmosphere over the European territory of the USSR

The main features of condensation nuclei distribution in the free atmosphere over the European territory of the USSR

The vertical distribution of condensation nuclei near the ground

Measurements have been made of the concentration of condensation nuclei, Z, at four heights between the ground and 300 cms in country air close to Cambridge. When the results are averaged over sufficiently long periods a systematic variation of Z with height is found and this variation itself has a diurnal variation. The results imply the production of nuclei in the atmosphere in this region. With the aid of simplifying assumptions, estimates of the rate of production are made for various periods of the day and night.

Some characteristics of condensation nuclei stored in a large vessel

The coagulation coefficient, size and charge distribution of condensation nuclei from room air when stored in a 4000 litre rubber balloon gasometer were studied. The results indicate that the acquisition of water vapour contributes to the growth of stored nuclei. A preliminary trial was made to see ifJunge's approximate rule that the number of particles in an aerosol varies inversely as the third power of their radius, also holds forAitken nuclei. Further confirmation of the relationship between the percentage of stored nuclei electrically charged and their average radius was obtained.