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Journal Publications

This section contains all refereed journal publications that have some connection either with the Mace Head Research Station or with members, both present and past, of the Atmospheric Physics Research Cluster at NUI, Galway.

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Documents

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Backscatter and extinction measurements in cloud and drizzle at CO2 laser wavelengths Backscatter and extinction measurements in cloud and drizzle at CO2 laser wavelengths

Date added: 07/31/1986
Date modified: 06/30/2009
Filesize: 1.09 MB

Jennings, S.G. (1986). - Backscatter and extinction measurements in cloud and drizzle at CO2 laser wavelengths. Appl. Opt., 25, 2499 - 2505.


Abstract


The backscatter and extinction of laboratory generated cloud and drizzle sized drops have been measured at CO2 laser wavelengths (predominately at λ = 10.591 µm). Measurements of volume backscatter coefficient σb and volume extinction coefficient σe for laboratory cloud of predominantly <20-µm radius droplets are dependent on the form of the size distribution in agreement with numerical prediction. For drops of >˜20 µm at λ = 10.591 µm the relation between σe and σb has the appealingly simple size distribution independent form of σeb =8π/G,[equation] is the asymptotic value of the backscatter gain, where n and k are the real and imaginary indices of refraction. The linear relation is in good agreement with extinction and backscatter measurements made on laboratory generated drizzle sized drops (r > 20 µm). This suggests that the extinction coefficient at CO2 laser wavelengths could be inferred from lidar backscatter return signals without requiring knowledge of the size distribution for drizzle and spherical precipitation sized water drops.

The First Condensation Nucleus Conference And Research In Dublin The First Condensation Nucleus Conference And Research In Dublin

Date added: 08/07/1985
Date modified: 08/18/2008
Filesize: 711.16 kB
 O Connor, The First Condensation Nucleus Conference And Research In Dublin, J Rech. Atmos., 19 (1985) 

Attenuated total reflectance measurements of the complex refractive index of kaolinite powder at CO2 laser wavelengths Attenuated total reflectance measurements of the complex refractive index of kaolinite powder at CO2 laser wavelengths

Date added: 07/31/1985
Date modified: 06/30/2009
Filesize: 1.63 MB

Pinnick, R.G., Jennings, S.G., Boice, D.C., and Cruncleton, J.P. (1985). - Attenuated total reflectance measurement of the complex refractive index of kaolinite powder at CO2 laser wavelengths. Appl. Opt., 24, 3274 - 3285.


Abstract

 

Attenuated total reflectance measurements of the complex refractive index of kaolinite powder-air mixtures are made for nine CO2 laser wavelengths. The Maxwell-Garnett effective medium theory and generalizations of it that account for either the shape distribution of kaolinite grains in the medium (in which the grains are approximated by a shape distribution of small arbitrarily oriented ellipsoids) or the size distribution of grains (in which finite grain sizes are accounted for by considering, in addition to the electric dipole interaction, magnetic dipole and electric quadrupole interactions) are used to deduce from these measurements the complex refractive index of kaolinite. Most success is achieved with a generalization which assumes a shape distribution of small ellipsoidal grains but which neglects all but electric dipole interactions. In spectral regions where kaolinite displays very strong absorption (in the 9.6-10-,um spectral region) all effective medium theory solutions for kaolinite refractive index either are plagued with ill-conditioning or are nonphysical. It appears that the attenuated total reflectance method, at least as we have applied it here to loosely packed powders comprised of nonspherical grains, is not suitable for measurement of powders in spectral regions of strong absorption.

Condensation Nuclei as indicators of air pollution Condensation Nuclei as indicators of air pollution

Date added: 07/31/1984
Date modified: 07/27/2009
Filesize: 2.52 MB

O'Connor, T.C. & O'Dea, J.J.(RTC Sligo) (1984)- Indicators of Air Pollution, Irish Journal of Environmental Science, III, pp. 32-39


Abstract


Condensation Nuclei (CN) are Submicron sized particles found in the atmosphere at concentrations of 10^2 to 10^6 particles per cm^3. They arise from a variety of sources but are mainly produced by combustion processes. Sensitive and reliable CN counters have been developed in Ireland to determine their concentration and size. Results from a variety of locations are presented to illustratetheir use as a general indicator of air pollution levels. The Use of CN measurement as a tool for air quality management is discussed.

Extinction and liquid water content of fog at visible wavelengths Extinction and liquid water content of fog at visible wavelengths

Date added: 07/31/1983
Date modified: 07/01/2009
Filesize: 2.27 MB

Jennings, S.G. (1983)- Extinction and liquid water content of fog at visible wavelengths. Appl. Opt., 22, 2514-2515.


Abstract


Backscatter and Extinction in Water Clouds Backscatter and Extinction in Water Clouds

Date added: 07/31/1983
Date modified: 06/30/2009
Filesize: 2.64 MB

Pinnick, R.G., Jennings, S.G., Chylek, P., Ham, C., and Grandy, W.T. Jr. (1983)- Backscatter and extinction in water clouds. J. Geophys. Res., 88, 6787-6796.


Abstract


An approximate relation between the volume extinction coefficient σe and backscatter coefficient σb of atmospheric cloud at visible and near-infrared wavelengths is derived. The relation is only weakly dependent on the size distribution of droplets and has the form σe/σb=(8π/g){1+k-2/3(<r 4/3>/<r2>) -δ[k2(<r4>/<r2>)+k4/3(< r4/2><r4>/<r2><r2>)]} where the extinction efficiency is approximated by a complex-angular-momentum-theory result and the parameters g and δ are determined by approximating a running mean of the backscatter gain by G(x)=g(1+δx2) (x is droplet size parameter and δ<<1), k is the wave number, and <rn> is the nth moment of the droplet size distribution. To zero order the relation is linear and independent of the droplet size distribution σe=[8π/g(λ)]σb where g(λ) is a slowly varying function of wavelength. At a wavelength λ=1.06 μm the relation is σe (km-1)=18.2 σb (km-1sr-1). Predictions made with this simple zero-order approximation are in good agreement (within 50%) with Mie calculations of extinction and backscatter coefficients based on 156 measurements of cloud droplet spectra in cumulus and stratus type clouds. The linear σe-σb relation is also in agreeement with extinction and backscatter measurements made on laboratory-generated fog droplet distributions. The relation suggests that visible or near-infrared extinction coefficients in cloud of unknown type could be inferred from lidar backscatter measurements alone, without knowledge of the cloud droplet size spectra, barring complications arising from multiple scattering contributions to the lidar return.

The effect of particle size distribution and complex index of refraction of atmospheric aerosols... The effect of particle size distribution and complex index of refraction of atmospheric aerosols...

Date added: 08/01/1981
Date modified: 07/10/2009
Filesize: 1.44 MB
Jennings, S.G. (1981)- The effect of particle size distribution and complex index of refraction of atmospheric aerosols in the visual range. Proc. of the Ninth International Conference in Atmospheric Aerosol, Condensation and Ice Nuclei, Galway University Press, 415 - 420.

Abstract

 

A comprehensive study has been made of the effect of particle size distribution and complex index of refraction on the visual range, with a wavelengrth lamada of 0.55 micrometres. Calculations were performed by using a generalized polydisperse Mie scattering theory, which makes the assumption that the particles are spherical. Several workers have shown that a lognormal distribution can well represent different types of atmospheric aerosol over a wide range of natural conditions. A lognormal distribution wth geometric mean radius rg varying from 0.005 to 10 micrometers and geometric standard deviation sigmag varying from 1.5 up to 3.0 was used in the calculations.

 


 

Attenuated total Reflectance Measurements of the complex refractive index of polystyrene latex at CO2 laser wavelengths Attenuated total Reflectance Measurements of the complex refractive index of polystyrene latex at CO2 laser wavelengths

Date added: 07/31/1981
Date modified: 06/30/2009
Filesize: 1.62 MB
Jennings, S.G. (1981)- Attenuated total Reflectance Measurements of the complex refractive index of polystyrene latex at CO2 laser wavelengths. J. Opt. Soc. Amer., 71, 923-927.
Abstract

 

Attenuated total reflectance (ATR) measurements of the complex refractive index m of 5, 10,15, 20, and 30% water suspensions of polystyrene latex are presented for CO2 laser wavelengths (measurements for the 30% suspension are for X =10.591 ,um only). The use of the Maxwell Garnet mixture rule for the real index and the imaginary index (at X = 9.305 ,um) and an extrapolation scheme for the remaining values of imaginary index yield the values m =
1.709 - 0.07i (X = 9.305 ,tm); m = 1.887 - 0.06i (X = 9.504 Arm); m = 1.705 - 0.04i (X = 9.694 ,um); m = 1.764 - 0.045i (X = 10.591 ,um). ATR measurements of the complex index of water and water-ammonium sulfate solutions are in reasonably good agreement with those previously published.

Relationships Between Extinction, Absorption, Backscattering, and Mass Content of Sulfuric Acid Aer. Relationships Between Extinction, Absorption, Backscattering, and Mass Content of Sulfuric Acid Aer.

Date added: 07/31/1980
Date modified: 07/06/2009
Filesize: 638.52 kB

Pinnick, R.G., Jennings, S.G., and Chylek, P. (1980)- Relationship between extinction, absorption, backscattering and mass content of sulphuric acid aerosols. J. Geophys. Res., 85, 4059-4066.


Abstract


Linear relationships between aerosol extinction, absorption, backscatter, and mass content are derived for polydispersions of sulfuric acid aerosols. These relationships are independent of the form of the size distribution and are a consequence of approximating the corresponding Mie efficiency factors (the extinction efficiency Qe, the absorption efficiency Qa, and the backscatter gain G) by linear functions of the particle size parameter x. The relationships are valid only at particular wavelengths that depend on the range of particle sizes present in a particular polydispersion. For example, at a wavelength λ=0.694 μm the relation between aerosol backscatter coefficient σbs (m-1 sr-1) and mass content M(g m-3) is σbs=0.048M for 75% sulfuric acid (25% water) aerosol, under the restriction that particles in the poly-dispersion have sizes not exceeding about 1.5 μm in radius. Possible applications of the relationships are (1) inference of path-integrated mass content of sulfuric acid aerosol (for example, the clouds of Venus) from an infrared laser transmission measurement through the aerosol cloud, (2) determination of sulfuric acid aerosol mass content at a particular point in an aerosol cloud from aerosol absorption measurements at that point with a CO2(λ=10.6 μm) laser spectrophone, (3) inference of path-integrated stratospheric aerosol mass from aerosol extinction measurements made by solar occultation for wavelengths λ=0.55 and 1 μm, and (4) inference of vertical profiles of stratospheric aerosol mass from ruby lidar (λ=0.694 μm) backscatter measurements.

Relationship between visible extinction absorption and mass concentration of carbonaceous smokes Relationship between visible extinction absorption and mass concentration of carbonaceous smokes

Date added: 07/31/1980
Date modified: 07/06/2009
Filesize: 1.99 MB

Jennings, S.G., and Pinnick, R.G. (1980)- Relationships between visible extinction, absorption and mass concentration of carbonaceous smokes. Atmos. Environ., 14, 1123-1129.


Abstract


A linear relation, independent of the size distribution, between visible and near-i.r. extinction coefficient σe(m−1) and mass concentration M (gm−3) of carbonaceous smokes is predicted. For a wavelength λ = 0.55μm the relation is σe/M = 9.5m2g−1, assuming a particle density of 2gcm−3. The relation is in good agreement with measurements on coal-fired stack plumes, oil smoke, soot and diesel exhaust that are available in the literature. A similar relationship between carbonaceous smoke visible and near-i.r. absorption coefficient σa, and mass concentration is also derived. The relations suggest that integrated mass concentration along a path within a carbonaceous smoke cloud can be inferred from measurement of the transmission from one end of the path to the other, and that the mass concentration at a particular location in the cloud can be determined from an in situ measurement of aerosol absorption at that location with a visible or near-i.r. laser spectrophone.

Relationship between visible extinction absorption and mass concentration of carbonaceous smokes Relationship between visible extinction absorption and mass concentration of carbonaceous smokes

Date added: 07/31/1980
Date modified: 07/22/2009
Filesize: 1.99 MB

Jennings, S.G., and Pinnick, R.G. (1980)- Relationships between visible extinction, absorption and mass concentration of carbonaceous smokes. Atmos. Environ., 14, 1123-1129.


Abstract


A linear relation, independent of the size distribution, between visible and near-i.r. extinction coefficient σe(m−1) and mass concentration M (gm−3) of carbonaceous smokes is predicted. For a wavelength λ = 0.55μm the relation is σe/M = 9.5m2g−1, assuming a particle density of 2gcm−3. The relation is in good agreement with measurements on coal-fired stack plumes, oil smoke, soot and diesel exhaust that are available in the literature. A similar relationship between carbonaceous smoke visible and near-i.r. absorption coefficient σa, and mass concentration is also derived. The relations suggest that integrated mass concentration along a path within a carbonaceous smoke cloud can be inferred from measurement of the transmission from one end of the path to the other, and that the mass concentration at a particular location in the cloud can be determined from an in situ measurement of aerosol absorption at that location with a visible or near-i.r. laser spectrophone.

In situ measurement of the ratio of aerosol absorption to extinction coefficient In situ measurement of the ratio of aerosol absorption to extinction coefficient

Date added: 07/31/1980
Date modified: 07/02/2009
Filesize: 558.49 kB

Bruce, C.W., Yee, Y.P., and Jennings, S.G. (1980)- In situ measurements of the ratio of aerosol absorption to extinction coefficients. Appl. Opt., 19, 1893-1894.


Abstract


A knowledge of the proportion of absorbed to scattered radiation for countermeasure smokes is necessary for modeling battlefield effects. Measurement of the total scattered component, however, is difficult. This report presents results obtained by using a new and simpler approach focussing on the extinction and the absorption coefficients (the total scattering coefficient is the difference quantity). Measurements of the absorption and extinction coefficients due to smoke produced by the combustion of 'red phosphorous' are simultaneously obtained in a small test chamber. The same CO2 laser beam at lambda = 9.55 micron is used to produce both results. A form of aerosol spectrophone cell was used to measure the absorption coefficient while functioning as a transmission cell from which the extinction coefficient was calculated. The ratio of the absorption to extinction coefficients was then compared with estimates of the same quantities based on calculated particle sizes, the particle size estimates being obtained from characteristics of the settling process. The ratio agreed with that predicted within the experimental error.

Remote Sensing of Air Pollution Remote Sensing of Air Pollution

Date added: 08/07/1979
Date modified: 07/06/2009
Filesize: 1.35 MB

O'Connor T.C,Remote Sensing of Air Pollution , Proceedings of Seminar: Airpollution- Impacts and Controls, National Board for Science and Technology, 1979, pp. 93-96


Abstract

 

Recent technological advances have enabled man to extend his remote sensing capabilities from looking at the visible world around him into other parts of the Electromagnetic spectrum and his vantage point from a tower or hill to an orbiting satellite. one can now stufy air pollution problems over widespread areas and at all levels in the atmosphere. The techniques used are reviewed briefly and their application to air pollution in the lower atmosphere considered.

Remote sensing instruments may be categorised by the region of the electromagnetic spectrum concerned; the purpose for which they are used the mode of action as passive or active; the signal recovery and data handling techniques; the platform used - ground, aircraft or satellite; and or fixed location instruments. Remote sensing techniques can be used to study aerosols and/or specific gases. They may be used to study pollution distribution in the horizontal and vertical directions, general air quality, plume tracking, source monitoring and other applications. Their advantages and disadvantages for air quality management are given.

Verification of a Linear Relation between IR Extinction Absorption and Liquid Water Content of Fogs Verification of a Linear Relation between IR Extinction Absorption and Liquid Water Content of Fogs

Date added: 08/01/1979
Date modified: 07/27/2009
Filesize: 761.93 kB

Pinnick, R. G.; Jennings, S. G.; Chýlek, Petr; Auvermann, H. J., Verification of a Linear Relation between IR Extinction, Absorption and Liquid Water Content of Fogs., Journal of Atmospheric Sciences, vol. 36, Issue 8, pp.1577-1586


Abstract


A linear relationship, independent of the form of the size-distribution, between extinction at wave-lengths around = 11 µm, absorption around = 3.8 and 9.5 µm, and liquid water content of atmospheric fogs has been verified using 341 droplet size distribution measurements made under a variety of meteorological conditions. The results suggest that integrated liquid water content along a path in fog can be determined from measurement of CO2 laser ( = 10.6 µm) transmission along the path, and that liquid water content at a particular point in fog can be inferred from in situ measurement of fog-droplet absorption with a deuterium fluoride laser ( = 3.8 µm) or a suitably tuned C02 laser ( = 9.5 µm) spectrophone.

Relation between absorption coefficient and imaginary index of atmospheric aerosol constituents Relation between absorption coefficient and imaginary index of atmospheric aerosol constituents

Date added: 07/31/1979
Date modified: 07/06/2009
Filesize: 512.02 kB
Jennings, S.G., Pinnick, R.G., and Gillespie, J.B. (1979)- Relation between absorption coefficient and imaginary index of atmospheric aerosol constituents. Appl. Opt., 18, 1368-1371.

Abstract


The absorption coefficient per unit mass α(cm2g-l) for aerosols in the wavelength range λ = 1.06–10.6 µm is shown to be a sensitive function of particle size distribution and of both imaginary and real indexes of refraction. Hence the imaginary index of refraction cannot be accurately determined from absorption measurements on an aerosol sample as attempted by S. A. Schleusener et al., Appl. Opt. 15, 2546 (1976), unless the size distribution and real index of the aerosol material are known. Similar difficulties arise in attempts to infer imaginary index from transmission measurements through aerosol samples as done by F. E. Volz, Appl. Opt. 11, 755 (1972); 12, 564 (1973) and K. Fischer, Beitr. Phys. Atmos. 43, 244 (1970). In addition, scattering losses can further complicate the determination of imaginary index from transmission measurements.

Vertical Structure in Atmospheric Fog and Haze and Its Effects on Visible and Infrared Extinction Vertical Structure in Atmospheric Fog and Haze and Its Effects on Visible and Infrared Extinction

Date added: 08/01/1978
Date modified: 07/08/2009
Filesize: 1004.22 kB
R. G. Pinnick, D. L. Hoijelle, G. Fernandez, E. B. Stenmark, J. D. Lindberg, G. B. Hoidale, and S. G. Jennings,, "Vertical structure in atmospheric fog and haze and its effects on visible and infrared extinction," J. Atmos. Sci.35, 2020 (1978).

Abstract

 

Vertical structure of the size distribution and number concentration of particulates in atmospheric fog and haze near Grafenwöhr, West Germany, were measured with a balloonborne light-scattering aerosol counter for periods spanning parts of eight days in February 1976. For haze (5 km visibility) conditions, little vertical variation is seen; but for low visibility (<1 km) fog conditions, significant vertical increases in concentration of droplets with radii larger than 4 μm are seen over the first 150 m altitude. For haze, the particle size distribution is approximated by a log-normal with geometric mean radius rg ≈ 0.2 μm and geometric standard deviation  σo ≈1.9. For fog, a bimodal distribution is found with a relative maximum for the larger particle mode at radii of 4 to 6 μm and corresponding values rg ≈ 5 m and σo ≈1.6; the smaller particle mode has values of rg ≈ 0.3 μm to rg ≈ 0.6 μm and σo  ≈1.8 to ≈2.5. Liquid water content values for haze and fog range from 10-4 to 0.45 g m-3. Extinction calculated from the particle size distributions shows an approximate 1/ λ wavelength dependence for haze conditions, but nearly neutral (wavelength independent) extinction for heavy fog. A correlation exists between calculated particulate extinction and calculated liquid water content, independent of particle size distribution, for the fogs and hues studied.

Vertical Inhomogeneity in Atmospheric Fog and Haze and it's effects on IR extinction Vertical Inhomogeneity in Atmospheric Fog and Haze and it's effects on IR extinction

Date added: 08/01/1978
Date modified: 07/08/2009
Filesize: 2.32 MB
Pinnick, R. G.; Hoihjelle, D. L.; Stenmark, E. B.; Lindberg, James D., Vertical inhomogeneity in atmospheric fog and haze and its effects on infrared extinction, J. Opt. Soc. Am, Vol.68, Page 540

Abstract

 

The presence of atmospheric fog and haze is important to radiative transfer in the atmosphere. For quantitative estimates of scattering and absorption by fod and haze particles, the size distribution is needed. Previously, fog and haze particulate size distributions have been measured by impaction techniques (Garland, 1971; Pilie, 1975; Krasikov and Chikirova, 1956; Kumai, 1973; low, 1975; May, 1961; barteneva and Polyakova, 1965; and Goodman, 1977), by collection of particles on spiderwebs (Arnulf et al., 1957), by a laser hologram camera (Kumkelm, 1971), and by light-scattering single particle counters (Eldridge, 1961; Laktionov, 1967). All of these techniques have serious limitations which restrict their usefulness and require measurements made with them to be regarded with caution. For example, impaction techniques involve laborious microsope measuremtn of droplets or droplet replicas, and corrections must be made to obtain true droplet size. Furthermore, impaction collection efficiencies must be applied to obtain relative particle concentrations.

 

In this article we present measurements of the size distribution of fog and haze particles made with a balloon-borne light-scattering single-particle counter, with emphasis on their effect on Infrared radiation. The primary advantages of using a light-scattering counter is that the measurement is donw in situ in real time, with minimal disturbance to the particles during measurement. Also, measurment of vertical structure is possible with this technique because a statistically significant size distribution measurement can be completed in a relatively short time (on the order of 1/2 minute), permitting a vertical upleg and lownleg to 200m altitude to be completed in 15 to 30 minutes. Measurements made during upleg and downleg portions of each tranverse show that temporal changes during such times scales were relatively small compared to vertical changes for most measurement periods.

Results from measurement of four haze and fog profiles presented here are typical of 19 profiles measured during February 1976 near Grafenwohr, a town located 100 km north of Nurnberg near the eastern border of West Germany. The local terrain consists of rollong hills and is partially forested; some of the land is tilled for farming.

Use of an Average complex refractive index in atmospheric propagation calculations Use of an Average complex refractive index in atmospheric propagation calculations

Date added: 08/01/1978
Date modified: 07/08/2009
Filesize: 932.35 kB
. B. Gillespie, S. G. Jennings, and J. D. Lindberg, "Use of an average complex refractive index in atmospheric propagation calculations," Appl. Opt. 17, 989-991 (1978)

Abstract

 

In most atmospheric propagation calculation it is generally ssumed that atmospheric dust is composed of homogeneous spherical particles all with the same average complex refractive index and all distributed by the same size distribution. As pointed out by Bergstrom, it is perhaps more realisitc to assume that since diiferent optical constants and each component will have an associated size distribution characteristic of its production. In particular, the free carbon type particles and the soil derived particles should be different. Previous work in our laboratory  with commericallly available cascade impactors has shown that, for some minerals characteristic of the local envirorment, the imaginary refractive index of desert dust is a strong function of particle size.

Effects of particulate complex refractive index and particle size distribution variations on atmospheric extinction Effects of particulate complex refractive index and particle size distribution variations on atmospheric extinction

Date added: 08/01/1978
Date modified: 07/01/2009
Filesize: 851.05 kB
Jennings, S.G., and Pinnick, R.G.  (1978)- Effects of particulate refractive index and particle size distribution variations on atmospheric extinction and absorption for visible to middle-IR wavelengths. American Meteorological Society Third Conference on Atmospheric Radiation, Davis, California, 6-9.

Abstract


A comprehensive sensitivity study has been made, using Mie theory, to determine the effect of realistic variations in values of real and imaginary parts of the complex index of refraction on volume extinction and absorption coefficients for a wide range of lognormal particle size distributions (defined by geometric mean radius r sub g and geometric standard deviation sigma sub g). Wavelengths lambda from visible (0.55 micrometers) through middle-infrared (10.6 micrometers) were considered. Extinction is independent of complex index to within 20 percent for the majority of realistic particle size distributions, providing lambda < or = 2 micrometers. However, changes in extinction by up to an order of magnitude are caused by realistic variations in refractive indexes for 2 < or = lambda < or = 10.6 micrometers, with real index being more important in affecting extinction than imaginary index.

Combination coefficients of small positive ions with sub micrometer aerosol particles Combination coefficients of small positive ions with sub micrometer aerosol particles

Date added: 02/14/1978
Date modified: 07/01/2009
Filesize: 745.64 kB

Dixon, A.M., and Jennings, S.G. (1978).- Combination coefficients of small ions with submicrometre aerosol particles. J. Phys. D: Appl. Phys., 11, 125-136.


Abstract


The work was concerned with the simultaneous measurement of the combination coefficients b and eta 0, between small ions and aerosol particles, and between small ions and uncharged aerosol particle respectively, for different particle radii. The ion-ion mutual repulsion coefficient gamma had a mean experimental value of 2.39 (+or-0.14)*10-6 cm3 s-1. The decay of ions in the presence of aerosol particles in a mylar vessel was recorded and compared with a family of computed theoretical ion-aerosol decay curves to determine b. eta 0 could then be determined from concentration of uncharged nuclei present. Satisfactory agreement was found between the b eta 0 versus radius results and various theoretically computed values. Possible reasons for discrepancies between theory and experiment are indicated.

Experiments on water drop interactions Experiments on water drop interactions

Date added: 09/06/1977
Date modified: 08/06/2009
Filesize: 1.27 MB

Jennings, S.G. (1977)- Experiments on water drop interactions. Phys. Ed., 12, 381-385.


Abstract

 

A series of experiments is described which demonstrate the interactions of water drops. These experiments were used in a project with second year undergraduates and should be easy to adapt for school use. Photographic, stroboscopic and droplet stream formation techniques are used. Droplet-droplet collisions and collisions with plane and curved air-water interfaces are involved. It is considered that the experiments provide a good basis for the understanding of the relative roles of kinetic energy and surface energy in governing water droplet behaviour.

The influence of the complex index of refraction on the volume extinction, scattering and absorption The influence of the complex index of refraction on the volume extinction, scattering and absorption

Date added: 08/01/1977
Date modified: 07/08/2009
Filesize: 496.46 kB
The influence of the complex index of refraction on the volume extinction, scattering and absorption coefficient of particle size distributions. Topical Optical Society of America Meeting on Optical Propagation Through Turbulence, Rain and Fog, Boulder, Colorado, U.S.A., pp. WD  7-1  to  7-4.

Abstract

 


Tracking electrically charged puff,....,by ground level electric field measurements Tracking electrically charged puff,....,by ground level electric field measurements

Date added: 07/31/1977
Date modified: 07/08/2009
Filesize: 1003.89 kB

Jennings, S.G., and Jones, C.D. (1977)- Tracking electrically charged puffs, as used in short range atmospheric diffusion investigations, by ground level electric field measurements. J. Electrostatics, 2, 367-373.


Abstract


The use of ionized air as a tracer in short range atmospheric diffusion investigations raises the possibility of cloud location using electric field measurements. In this short communication a simple analysis is developed which enables the trajectory of a charged cloud to be ascertained from electric field measurements at three points at ground level (assuming the charge is known). Alternatively, if the charge is not known, it is shown that five-position electric field measurements are needed to find both its position and magnitude.

Large Electric fields due to industrial chimney stack plumes Large Electric fields due to industrial chimney stack plumes

Date added: 07/30/1977
Date modified: 07/23/2009
Filesize: 2.08 MB

Jones, C.D., and Jennings, S.G. (1977).- Large electric fields due to industrial chimney stack plumes. Atmos. Environ.,11, 1197-1207.


Abstract


Large values of electric field due to a charged plume from an industrial chimney stack have been observed. Downwind and crosswind profiles of the electric field were measured using 4 field mills. Average values of between 5 and 6 kV m−1 over 10 minute periods were measured at distances within 200 m of the stack. Electric field values as large as 3.5 kV m−1 were present at a distance of 3 km from the stack. It was found that the electric field did not return to its normal fair-weather value until the downwind distance from the stack had exceeded 9 km.

The decrease in the average value of the electric field, Ep, under the plume gave good agreement with an equation derived from line charge theory, modified by an empirical decay factor exp(−R/D)

.[1+Image ] where λ is the charge per unit length, h the plume height, R the distance of the position P downwind, and D the distance at which λ is reduced by Image . The experimental results yielded a value for D of about 1.5 km.

 

Point discharge currents as large as 3 μA were measured at a distance of 700 m from the stack. Measurements at heights ranging from 9.25 m to 3.25 m agreed with the theoretical relation i = k(E-E0) where E is the measured value of electric field at a distance 10 m upwind from the discharge point, E0 the critical value of electric field above which point discharge will occur and k is a constant. Values of E0 of about 2kV m−1 were found for the two highest points.

The results suggest that electric field measurements may be a valuable supplement to concentration data in atmospheric diffusion experiments using charged plumes.

Aerosol particle size distribution in the 0.25-5.0 micron radius range in Northern England Aerosol particle size distribution in the 0.25-5.0 micron radius range in Northern England

Date added: 07/30/1977
Date modified: 06/30/2009
Filesize: 1.3 MB

Jennings, S.G., and Elleson, R.K. (1977)- Aerosol size distributions in the 0.25 to 5 micrometre radius range. Atmos. Environ., 11, 361-366.


Abstract


An analysis has been made of continuous measurements on the particle size distribution of the atmospheric aerosol in five particle radius categories between 0.25 and 5.0 μm. An automatic Royco model 225 optical particle counter together with a digital line printer was used to obtain the measurements at a 10 min sampling frequency from 21 July to 8 September 1975 at Durham Observatory, 2 km SSW of Durham City in the North East of England. Measurements were also taken every 10 min from 15 December to 6 January 1976 on the summit of Great Dun Fell, 842 msl, on the Northern Pennine Range, England.

Diurnal variation associated with the particle number concentration shows maximum concentration from about 02:00–08:00 h BST and a minimum over the period 14:00–20:00 h BST.

The particle size distribution for both the Durham and Great Dun Fell site follows the shape of a Junge log-radius type distribution with slopes β equal to 3.04 and 2.74 respectively. The distributions show that the number concentration over the five radius intervals is an order of magnitude lower at the mountain site of Great Dun Fell than at Durham Observatory.

An analysis of the sampling frequency of particle concentrations showed that the measurements could be made less frequently by factors up to 20, without loss of accurate information.

A method of measurement of the Dielectric Constant of some liquids A method of measurement of the Dielectric Constant of some liquids

Date added: 01/01/1977
Date modified: 08/06/2009
Filesize: 1.3 MB

Jennings S.G., A method of measurement of the dielectric constant of some liquids. Phys. Educ. Vol 12, January 1977. pp. 40-42.


Abstract


The method depends on the existence of a driving force on a liquid dielectric in an electric field. The force leads to a rise in the liquid level between the plates of a capacitor. The capacitor plates were placed just above a reservoir of the dielectric liquid, the level of which was monitored by a travelling microscope. The rise in liquid level (h) was measured for selected values of voltage (v) until sparking between the plates occurred. A plot of h against V2 was obtained, and the dielectric constant was determined from the slope of the graph.

Continuous Measurements of the natural aerosol size distribution at rural mountain and maritime sites Continuous Measurements of the natural aerosol size distribution at rural mountain and maritime sites

Date added: 08/01/1976
Date modified: 07/01/2009
Filesize: 937.82 kB

Jennings, S.G.  (1976)- Continuous measurements of the natural aerosol size distribution at rural, mountain and maritime sites. Conference on the Atmospheric Aerosols: Their Optical Properties and Effects. NASA Conference Publication CP-2004, MB 4-1  to  4-4.


Abstract


 


High Electric fields from industrial stack plumes High Electric fields from industrial stack plumes

Date added: 01/01/1976
Date modified: 07/02/2009
Filesize: 338.61 kB

Jennings, S.G., and Jones, C.D. (1976)- High electric fields due to industrial stack plumes. Nature, 264, 236-237.


Abstract


THE use of electrostatic precipitators on an industrial stack to remove particulate matter and aerosol particles is now quite common. The plume emanating from such an installation is likely to be highly electrically charged, and consequently associated electrical effects should be observable downwind of the stack.

The Electrical conductivity within water droplet clouds The Electrical conductivity within water droplet clouds

Date added: 08/01/1975
Date modified: 07/22/2009
Filesize: 1.58 MB
Jennings,S.G.   (1975)- The electrical conductivity within water droplet clouds. Proc.  4th Conf. Static Electrification. Inst. Phys. Conf. Series, No 27,  34-43.

Abstract

 

Studies have been made of the reduction of small positive ion concentration, produced by a weak americium alpha source in the presence of small water droplet clouds. The droplet clouds which possessed values of clou-water content ranging from about 1.0 up to 6 g m-3 and mean radius from 0.75 up to approximately 2.25 μm were produced by a steam condenser method which yielded relatively stable clouds.

Measurements of the number concentration of aitken nuclei at mountain and rural sites Measurements of the number concentration of aitken nuclei at mountain and rural sites

Date added: 08/01/1975
Date modified: 07/03/2009
Filesize: 1.25 MB
Jennings, S.G.  (1975)- Measurements of condensation Aitken nuclei at rural and mountain sites. Jnl. de Rech. Atmos., No. 2,  59-66.

Abstract

 

A study of the number concentration at Aitken nuclei has been carried out using automated Nolan Pollak photoelectric nucleus ountain site, a sparsely populated site and in a rural envirorment. It has been found that the nucleus counter assembly operates very satisfactorily over long periods under field conditions.

The appuratus has proven to be particularly senstive in detecting pertubations in the background count due to localized nuclei sources. Frequency distribution curves of the individual observations follow closely a log-normal distribution for each measurement period. It is shown that te two minute sampling frequency can be increased by about an order of magnitude without causing a significant change in the nuclei number distribution.

Electrical charging of water drops in polarizing electric fields. Electrical charging of water drops in polarizing electric fields.

Date added: 08/01/1975
Date modified: 07/01/2009
Filesize: 2.02 MB

Jennings, S.G.  (1974)- Electrical charging of water drops in polarizing electric fields.  J. Electrostatics, 1,  15-25.


Abstract


Measurements were made of the electric charge acquired by drops of mean radius of about 750 μm as they fell through a cloud of water droplets of mean radius 16 μm, in the presence of a vertical electric field E, the value of which could be varied from 4.5 to 27 kV m−1. It was found that the proportion of interactions which resulted in separation (and, therefore, in electric charge transfer, as a consequence of the inductive process of electrification) decreased from about 1% in the weaker fields to about 0.2% in the strongest ones.

This work suggests that the collisions between polarised raindrops and cloud droplets in natural clouds could give rise, very effectively, to the production of electric fields of about 30 kV m−1 but that significantly larger fields could not be produced since all collisions in higher fields would result in permanent coalescence.

Charge separation due to water drop and cloud droplet interactions in an electric field Charge separation due to water drop and cloud droplet interactions in an electric field

Date added: 01/01/1975
Date modified: 07/01/2009
Filesize: 2.09 MB
Jennings, S.G. (1975)- Charge separation due to water drop and cloud droplet interactions in an electric field. Quart. J. Roy. Met. Soc., 101, 227-233.   
Abstract

Measurements were made of the electric charge acquired by drops of mean radius of about 750m, in the presence of a vertical electric field E, the value of which could be varied from 4·5 to 27kV/m. It was found that the average charge acquired by the water drop as a consequence of the inductive process increased from 0·1fC to about 0·25fC as the electric field strength increased from 5kV/m to about 15kV/m, but there-after decreased with increasing values of electric field.
This work suggests that the collisions between polarized rain-drops and cloud droplets in natural clouds could give rise, very effectively, to the production of electric fields of about 30kV/m; but that significantly larger fields could not be produced since all collisions in the higher fields would result in permanent coalescence.

The influence of evaporation and drop-interaction on a rainshaft : Comments and Notes The influence of evaporation and drop-interaction on a rainshaft : Comments and Notes

Date added: 09/14/1974
Date modified: 07/08/2009
Filesize: 326.53 kB

Brazier-Smith, P.R., and Jennings, S.G., and Latham, J. (1974)- The influence of evaporation and drop-interaction on a rainshaft Reply. Quart. J. Roy. Met. Soc., 99, 704-722.


Abstract


Calculations have been made of the variations with fall-depth z of the liquid water content, L, rainfall rate, p, radar reflectivity, Z, drop concentration, NT, and raindrop size distribution n(r), within a steady-state rainshaft as a result of the evaporation and interaction of the drops. The interactions were described by a generalized stochastic equation which takes account, as described by Brazier-Smith, Jennings and Latham (1973), of the variation of coalescence efficiency s with drop radii R, r and the fact that satellite drops are produced when drops separate after collision. The relative humidity is assumed to fall linearly from 100 per cent at cloud base (z = 0, T = 8°C) with a gradient 8. The lapse rate within the rainshaft was taken to be 8°C krn- and the initial size distribution was generally given by the Marshall-Palmer equation. Calculations were made for 3 different situations in order to isolate the physical processes which most affect the rainfall:
(l), evaporation without interaction; (2) interaction without evaporation; (3) both interaction and evaporation. The calculations for Case (1) indicate that the numbers of drops in all size classes are diminished with increasing Z, with a preferential reduction at the small-radius end of the spectrum. In Case (2) the interactions of the raindrops introduce considerable detail into n(r), with bimodal curves associated with satellite drop production, the highly efficient consumption of small drops by larger ones and the variations of E and fall-velocity V with drop-radius r.
The main feature of the calculations for Case (3) is the rBle of coalescence in preserving within the spectrum a considerable amount of liquid water that would otherwise be lost by evaporation. For example, whereas the rainwater content at z = 1.5 km for 8 = 20 per cent km- and Lo = 1.0 gm m- is 0.28 gm m-3 if interactions are absent, their presence elevates L to 0.57 gm m-3 at this level. This retention effect is significant for all values considered of 8, L, p, and the initial slope of the raindrop size distribution (varied from half to twice that of the Marshall-Palmerequation). It is alsofound that the structure introduced into the size distributions as a result of interactions is partially smoothed out by evaporation, which replaces a substantial proportion of the smallest drops consumed by coalescence.

Mass absorption Coefficient of natural Aerosol Particles in the 0.4 - 2.4um Wavelength Interval.. Mass absorption Coefficient of natural Aerosol Particles in the 0.4 - 2.4um Wavelength Interval..

Date added: 08/26/1973
Date modified: 07/22/2009
Filesize: 8.15 MB
K. Fischer, "Bestimmung der Absorption von sichtbarer Strahlung durch Aerosolpartikeln," Contrib. Atmos. Phys. 43, 244 (1970); "Mass Absorption Coefficient of Natural Aerosol Particles in the 0.4–2.4 µm Wavelength Interval," Contrib. Atmos. Phys. 46, 89 (1973), "Mass Absorption Indices of Various Types of Natural Aerosol Particles in the Infrared," Appl. Opt. 14, 2851 (1975).

Abstract

 

Theoretical investigation have predicted that absorption of solar radiation by particulate matter- suspended as aerosol particles in the air - plays an important part in the radiation budget of the atmosphere.

In the present study the mass absorption coeffiecnet K/P (i.e. the imaginary part of the refractive index related to density) is determined for the 0.4 - 2.4 um wavelength intercal wavelength interval. The measuremetn are performed on films of aerosol particles which were collected by an automatic jet impactor at several urban and remote sites.

Increased rates of rainfall production in Electrified clouds Increased rates of rainfall production in Electrified clouds

Date added: 07/30/1973
Date modified: 07/22/2009
Filesize: 822.23 kB

Brazier-Smith, P.R., Jennings, S.G., and Latham, J. (1973)- Increasing rates of rainfall production in electrified clouds. Quart. J. Roy. Met. Soc., 99, 776-779


Abstract

The influence of evaporation and drop-interaction on a rainshaft The influence of evaporation and drop-interaction on a rainshaft

Date added: 07/30/1973
Date modified: 07/08/2009
Filesize: 1.13 MB

Brazier-Smith, P.R., and Jennings, S.G., and Latham, J. (1973)- The influence of evaporation and drop-interaction on a rainshaft. Quart. J. Roy. Met. Soc., 99, 704-722.


Abstract


Calculations have been made of the variations with fall-depth z of the liquid water content, L, rainfall rate, p, radar reflectivity, Z, drop concentration, NT, and raindrop size distribution n(r), within a steady-state rainshaft as a result of the evaporation and interaction of the drops. The interactions were described by a generalized stochastic equation which takes account, as described by Brazier-Smith, Jennings and Latham (1973), of the variation of coalescence efficiency s with drop radii R, r and the fact that satellite drops are produced when drops separate after collision. The relative humidity is assumed to fall linearly from 100 per cent at cloud base (z = 0, T = 8°C) with a gradient 8. The lapse rate within the rainshaft was taken to be 8°C krn- and the initial size distribution was generally given by the Marshall-Palmer equation. Calculations were made for 3 different situations in order to isolate the physical processes which most affect the rainfall:
(l), evaporation without interaction; (2) interaction without evaporation; (3) both interaction and evaporation. The calculations for Case (1) indicate that the numbers of drops in all size classes are diminished with increasing Z, with a preferential reduction at the small-radius end of the spectrum. In Case (2) the interactions of the raindrops introduce considerable detail into n(r), with bimodal curves associated with satellite drop production, the highly efficient consumption of small drops by larger ones and the variations of E and fall-velocity V with drop-radius r.
The main feature of the calculations for Case (3) is the rBle of coalescence in preserving within the spectrum a considerable amount of liquid water that would otherwise be lost by evaporation. For example, whereas the rainwater content at z = 1.5 km for 8 = 20 per cent km- and Lo = 1.0 gm m- is 0.28 gm m-3 if interactions are absent, their presence elevates L to 0.57 gm m-3 at this level. This retention effect is significant for all values considered of 8, L, p, and the initial slope of the raindrop size distribution (varied from half to twice that of the Marshall-Palmerequation). It is alsofound that the structure introduced into the size distributions as a result of interactions is partially smoothed out by evaporation, which replaces a substantial proportion of the smallest drops consumed by coalescence.

Raindrop interactions and rainfall rates within clouds Raindrop interactions and rainfall rates within clouds

Date added: 11/30/1972
Date modified: 07/06/2009
Filesize: 787.75 kB

Brazier-Smith, P.R., Jennings, S.G., and Latham, J. (1973)- Raindrop interactions and rainfall rates within clouds. Quart. J. Roy. Met. Soc., 99, 260-272.


Abstract

 

Experiments showed that when a pair of water drops of raindrop dimensions collide and separate in air at their relative terminal velocities satellite drops are generally produced. Although the numbers and sizes of satellites resulting from individual interactions are highly variable a typical event produces about 3 satellites each having a volume of 0.04 ViVj/(Vi + Vj), where Vi and Vj are the volumes of the parent drops.

A full stochastic treatment is presented of the development of rainfall in a volume within a cloud where water is being released by condensation at a constant rate J. The production of satellites and an experimentally verified expression for the coalescence efficiency are incorporated into these calculations. Computations are made of the variation with time of the cloud water content, C, the rainwater content, L, the radar reflectivity, Z, the rainfall rate, P, and the drop-size distribution. The calculations show that the crucial parameter in governing the intensity and duration of rainfall is J, and that the microphysical processes are of secondary importance; C, L and P are all insensitive to and the production of satellite drops. The influence upon rainfall development of the break-up of large raindrops on attaining their maximum size within a cloud is found to be even less than that of the satellites.

The drop size distribution after several minutes of growth is insensitive to the initial spectrum but is markedly dependent upon and the production of satellites, which tend eventually to produce a bimodal spectrum. The radar reflectivity increases very rapidly with time (typically by about an order of magnitude every 2 1/2 minutes) and depends quite strongly on , but is unaffected by the production of satellites.


 

The Photo-Electric Counter The Photo-Electric Counter

Date added: 08/31/1972
Date modified: 08/31/2008
Filesize: 3.79 MB

How falling raindrops collide How falling raindrops collide

Date added: 08/01/1972
Date modified: 07/02/2009
Filesize: 470.45 kB

S.G Jennings, P.R. Brazier-Smith, J. Latham, ,How falling raindrops collide,Page 313, New Scientist, 10 February 1972


Abstract

The Interaction of Falling Water drops:Coalescene The Interaction of Falling Water drops:Coalescene

Date added: 07/30/1972
Date modified: 07/08/2009
Filesize: 802.92 kB

Brazier-Smith, P.R., Jennings, S.G., and Latham, J. (1972)- The interaction of falling water drops: coalescence. Proc. Roy. Soc.., A326, 393-408.


Abstract


Experimental studies have been conducted of the interaction of falling water drops of radii R and r (R > r), density p and surface tension or colliding in air with a relative velocity U and a perpendicular distance X between the centre of one drop and the undeflected trajec- tory of the other. R and r were varied from 150 to 750 /m, R/r from 1.0 to 2.5, U from 0.3 to 3.0 m s-1 and X from 0 (head-on collisions) to the maximum value for contact, R+r. Four types of interaction were observed: (1) bouncing; (2) permanent coalescence; (3) coalescence followed by separation; (4) coalescence followed by separation and the formation of satellite drops. The principal effort was devoted to a study of the critical conditions under which drops will separate after coalescence. It was found that there was a critical value of X, denoted by Xc, below which the coalesced drops remained united and above which there was sufficient angular momentum for the drops to separate after coalescence. For a wide range of values of r, R and U the coalescence efficiency e = Xc(R + r)2 was found to lie between 0.1 and 0.4 for drops of identical size and about 0.2 and 0.6 for drops with Rlr = 2.0. A theoretical analysis based on energy concepts predicted that the coalescence efficiency is given by the equation = 2.40(Up f (r) wheref (Rlr) is a function which varies from 1.3 for Rlr = 1 and 3.8 for R/r = 3. The predic- tions of this equation were in excellent agreement with the experimental results over the entire range of conditions studied. Investigations are also described of the critical conditions for the bouncing of colliding drops, the influence of electric charges upon the interactions and the elongation and splitting of a rotating drop.

Advance, 12 the growth of snowflakes and hail Advance, 12 the growth of snowflakes and hail

Date added: 06/01/1972
Date modified: 08/01/2008
Filesize: 330.33 kB

The charging of water drops falling and colliding in an electric field The charging of water drops falling and colliding in an electric field

Date added: 01/01/1972
Date modified: 07/07/2009
Filesize: 1.67 MB

O'Connor, T.C. and Sharkey, W.P.F. (1960)- Ionization equilibrium in maritime air, Proc. Roy. Ir. Acad., 61, p.15-27.


Abstract


Studies have been made of the charge transfer resulting from the collision and separation of water drops falling in an electric field. The charge transferq was measured for values of field strengthE, impact velocityV, drop radiiR, r, radius ratioR/r, and angle THgr ranging from 0.5 to 80 kV/m, 0.5 to 3 m·sec–1, 200 to 600 mgr, 1.0 to 3.0 and 0 to 90 degrees respectively, where THgr is the angle between the field and the line of centres of the drops at the moment of separation.

Two uniformly sized drop-streams were ejected from hypodermic needles by modulating the flow of water through them and then collided between a pair of electrodes across which a potential difference existed. The drops coalesced temporarily, swung around each other and separated, each resulting stream being collected in a vessel connected to an electrometer in order to measure the charge. The measured values ofq were generally in good agreement with theoretical values derived from the equationq = 1.1 · 10-10 gamma1 E r 2 Cos THgr, where gamma1 is a function ofR/r.
Calculations based on this equation, the Marshall-Palmer drop-size distribution and established values of separation probabilities of colliding drops showed that collisions between raindrops within electrified clouds will act powerfully to dissipate the existing fields.

An investigation of the behaviour of drops and drop-pairs subjected to strong electrical forces An investigation of the behaviour of drops and drop-pairs subjected to strong electrical forces

Date added: 09/12/1971
Date modified: 07/23/2009
Filesize: 703.62 kB

Brazier-Smith, P.R., Jennings, S.G., and Latham, J.  (1971)- An investigation of the behaviour of drops and drop-pairs subjected to strong electrical forces. Proc. Roy. Soc., A325, 363-376.


Abstract


A numerical model is described which simulates irrotational, incompressible flow on a computer. It has been applied to the problems of the deformation of uncharged drop-pairs separated in an electric field of critical strength and isolated drops charged to the Rayleigh limit in the absence of an electric field. In the case of pairs of drops of radius R, separated by an initial distance X in an electric field equal to that predicted by Brazier-Smith (1971) to cause disruption two types of interaction were identified. For values of X/R less than about 1.2 the drops deform and their surfaces accelerate towards each other and make contact. For X/R greater than about 1.2 the drops deform, a concavity appears at the near poles and then the near surfaces assume a conical profile of angle equal to that predicted by Taylor (1964). The subsequent issuance of liquid from these jets could not be studied with the present model. The computations predict that an isolated drop carrying the critical charge calculated by Rayleigh (1882) will deform, while retaining an approximately spheroidal shape, until the axial ratio achieves a value of about 2.5, whereupon cones possessing the Taylor angle are formed at each end of the drop, from which liquid will issue in the form of a jet. Experiments were performed in which uncharged water drops of radius R and surface tension T were directed towards a highly polished, earthed electrode at a shallow angle in an electric field of strength E. Each drop experienced the same electric forces as would result if the earthed electrode were removed and replaced by an identical drop twice as far away. Stroboscopic photographs of drops and their optical image in the polished electrode illustrated their deformation and eventual disintegration. The experimentally determined relation between normalized disintegration field E(R/T)1/4 and both X/R and the elongation a/b agreed well with theory over a wide range of separations.

Weather: Understanding rainfall Weather: Understanding rainfall

Date added: 08/01/1971
Date modified: 07/22/2009
Filesize: 336.23 kB
Weather: Understanding rainfall,1971
Abstract

Nature-times Weather Understanding rainfall Nature-times Weather Understanding rainfall

Date added: 08/01/1971
Date modified: 09/11/2009
Filesize: 336.23 kB

Nature-times Weather Understanding rainfall Nature-times Weather Understanding rainfall

Date added: 08/01/1971
Date modified: 08/01/2008
Filesize: 336.23 kB

Accelerated Rates of Rainfall Accelerated Rates of Rainfall

Date added: 07/09/1971
Date modified: 06/30/2009
Filesize: 384.37 kB
P. R. BRAZIER-SMITH, S. G. JENNINGS & J. LATHAM, Accelerated Rates of Rainfall,  Nature 232, 112 - 113 (09 July 1971); doi:10.1038/232112b0

Abstract

 

RAINFALL intensity within clouds may be greatly increased by the production of satellite drops when raindrops collide, and this process could explain the extremely high rates of rainfall development reported in certain clouds1,2. We have set out to test this possibility by laboratory experiments.

Atmospheric Sulphur Levels in Western Ireland Atmospheric Sulphur Levels in Western Ireland

Date added: 08/07/1969
Date modified: 07/27/2009
Filesize: 2.97 MB
O'Connor. TC., Atmospheric Sulphur Levels In Western Ireland, Sulphur in Agriculture, AN Foras Taluntais, Dublin, 1969

Abstract

 

Sulphur compounds can exist in the atmosphere in the solid, liquid or gaseous form, depending on their origin and subsequent history. They have deleterious effect on the health of humans, plants and animals and by their corrosive action on buildings and other materials. They have also been studied for their beneficial effects, for example, the nutrition of plants and other natural processes in soils and weathering. They can also be involved in processes of cloud formation and the geochemistry around the world. Although there have been many studies or atmospheric sulphur levels in polluted areas there is little data available on the natural background concentrations of sulphur dioxide in unpolluted areas in temperate latitudes.

This paper is concerned with some aspects of the atmospheric portion of the natural cycle of sulphur. it describes some investigations into the concentrations of sulphur dioxide at a variety of sites. in Galway city, Sine references to recent paper on specific aspects of the sulpur cycle are also given.

Electrostatic Deposition in ionic Diffussion Electrostatic Deposition in ionic Diffussion

Date added: 08/31/1968
Date modified: 07/21/2009
Filesize: 1.69 MB
F. Anderson, P.J Nolan and T.C. O'Connor, Electrostatic Deposition in ionic Diffussion, Volume 66, Section A, No. 5, 1968

Abstract

 

Errors in the determination of ionic diffusion coefficients caused by the neglect of electrostatic deposition are examined. Correction formulae applicable to low ionic concentrations are derived for cylindrical channels. These are similiar to the Fuchs formulae for rectangular channels. Formulae applicable in the case of high ionic concentration are also derived.

For singly charged particles the correction tot the diffusion coefficient under the usual experimental conditions is about two or three per cent. The error becomes large when the number electronic charges per ion aproaches 100. Previous Dublin experiments with multiply charged nuclei are examined in this connection and corrections applied. The Corrections do not invalidate the main conclusion of these experiments that the Einstein equation B=D/KT does not apply in the absence of charge equilibrium.

Deposition in ionic Diffussion Deposition in ionic Diffussion

Date added: 08/07/1968
Date modified: 07/27/2009
Filesize: 1.69 MB

TC OConnor, F Anderson, PJ Nolan, Electrostatic Deposition in ionic Diffussion ,Proceeding of the Royal Irish Academy 1968, Volume 66 Section A No. 5


Abstract

 

Errors in the determination of ionic diffusion coefficients caused by the neglect of electrostatic deposition are examined. Correction formulae applicable to low ionic concentrations are derived for cylindrical channels. These are similiar to the Fuchs formulae for rectangular channels. Formulae applicable in the case of high ionic concentration are also derived.

For singly charged particles the correction tot the diffusion coefficient under the usual experimental conditions is about two or three per cent. The error becomes large when the number electronic charges per ion aproaches 100. Previous Dublin experiments with multiply charged nuclei are examined in this connection and corrections applied. The Corrections do not invalidate the main conclusion of these experiments that the Einstein equation B=D/KT does not apply in the absence of charge equilibrium.

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