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1.
Summary The number and size of salt particles produced by the bursting of air bubbles in sea water has been measured. Bubbles of diameters varying between 1/2 and 2 mm each produced about 300 nuclei the sizes of which, under the electron microscope, were mainly between 0.1 and 0.5 diameter. They appeared to consist mainly of sodium chloride, the smallest ones containing only 10–15 g of salt.These results, together with measurements of the size distribution of salt nuclei collected over the oceans in areas of spray formation, indicate that the total concentrations of salt nuclei over the oceans in winds of up to 15 m sec–1 probably do not exceed 100 cm–3. The corresponding rate of production of salt nuclei at the sea surface is estimated to be 1000 cm–2 sec–1. It is therefore inferred that sea spray contributes perhaps only one-fifth of the nuclei involved in cloud formation, the majority being the products of combustion, either natural or man-made.  相似文献   

2.
Characteristics of cloud drop spectra were studied using 400 samples obtained from 120 warm cumulus clouds formed during the summer monsoon season.The total concentration of cloud drops (N T) varied from 384 to 884 cm–3 and the maximum concentration was observed in the layer below the cloud-top. The width of the drop spectrum was broader in the cloud-base region and in the region below the cloud-top. The spectrum was multimodal at all levels except in the cloud-top region where it was unimodal. The concentration of drops with diameter greater than 50 m (N L) varied from 0.0 to 0.674 cm–3.N L was larger in the cloud-base region.N L decreased with height up to the middle level and thereafter showed an increase. In the cloud-top region no large drops were present. The computed values of the liquid water varied between 0.132 and 0.536 g m–3 and the mean volume diameter (MVD) varied between 8.1 and 12.0 m. The LWC and MVD showed a decrease with height except in the middle region of the cloud where the values were higher than the adjacent levels. The dispersion of the cloud drops was lower (0.65) in the cloud-top region and higher (1.01) in the cloud-base region.The observed cloud microphysical characteristics were attributed to vertical mixing in clouds induced by the cloud-top gravity oscillations (buoyancy oscillations) generated by the intensification of turbulent eddies due to the buoyant production of energy by the microscale-fractional-condensation (MFC) in turbulent eddies.  相似文献   

3.
The atmosphere near the ground contains a mixed population of pollen and spores in the 1 to 90 m diameter range. Continuous sampling at Rothamsted Experimental Station at 2 m above ground level indicated concentrations averaging 12,000 m–3 over 5 summer months, but 1 million m–3 can occur for short periods. Concentrations change rapidly with locality, season, time of day or night and weather. Normally concentration in the troposphere decreases logarithmically with height. The occurrence of long distance transport of pollen and spores by wind is demonstrated by sampling from aircraft, and supported by much circumstantial evidence. Possible effects of this air spora on the atmosphere may be sought in alterations to: opacity, ionization, condensation nuclei, and sinks for minor gases.  相似文献   

4.
Summary Spectrometric experiments performed, in November 1976, within the framework of the Latitude Survey Mission on board the NASA Convair 990 from Ames Research Center are briefly deseribed. The results presented concern odd nitrogen molecules, HCl and water vapor. In terms of vertical column density, HNO3 is predominant over NO+NO2 at all latitudes higher than 40 degrees. A seasonal variation of NO2 abundance is observed, with larger values in the summer hemisphere at high latitude. The mean zenith column density of HCl above 11 km is 1.5×1015 mol.cm–2, with no evidence for any seasonal or climatic variation. Local number densities as high as 1.4×1010 mol.cm–3 for HNO3 and 5.4×1014 mol.cm–3 for water vapor have been measured during the same flight near 11 km.  相似文献   

5.
Summary Airborne particulate matter was sampled at Mt. Cimone, Italy, to determine the size distribution of black spherules in the 1–5 diameter range. The magnetic fraction of airborne particulate matter was separated by forcing air through a strong magnetic sampling device, where ferromagnetic particles accumulated on microscope slides.Sizes of the black spherules were determined by counting under a microscope. Samples were dissolved and analyzed for iron content. Distribution was found to be in agreement with that of deep-sea sediment and satellite high atmosphere samples. The rate of terrestrial accretion of cosmic matter composed of black spherules appears to be approximately 10–15 g cm–2 sec–1.  相似文献   

6.
Summary Based on the qualitative microspectrophotometric analysis of 287 atmospheric dust samples taken within the surface boundary layer over south central New Mexico, U.S.A. from May 1966 through October 1967, a representative infrared absorption spectrum from 4000 to 250 cm–1 (2.5 to 40 m) is presented. The strongest absorption band is centered at 1027 cm–1 (9,7 m), within the 1250 to 770 cm–1 (8 to 13 m) atmospheric window, and is silicate induced. Two other strong broad absorption bands are the carbonate band at 1425 cm–1 (7.0 m) and the silicate band at 468 cm–1 (21.4 m). Temporal variations in the absorption spectra of the dust are observed primarily in the varying relative intensities of the 1027 and 1425 cm–1 (9.7 and 7.0 m) absorption bands and in the occasional enhancement of the 1027 cm–1 (9.7 m) band caused by sulfates in the dust. This study indicates that there is a close similarity between the absorption spectra of the atmospheric dust and the spectra of the small particle fraction of area soils, and between the representative dust spectrum and a spectrum of a synthetic mixture (by weight) of 80% silicates, 16% carbonates, and 4% nitrates.  相似文献   

7.
Summary Theoretical considerations are put forward for identifying the Dynamic and Static Methods of Diffusion measurements of aerosol particles. On the basic of this equality the Exhaustion Method of Diffusion developed byPollak andMetnieks for the size-frequency resolution of a heterogeneous aerosol by Dynamic Diffusion Methods should be applicable to Static Methods. This hypothesis is tested using a Pollak-Nolan nucleus counter as decay vessel. It is shown that turbulence in the counter is the most serious obstacle against this type of approach to finding the size components of an aerosol. The time involved, the high humidity in the counter and a hypothetical nucleus-free zone are other major difficulties for relatively large Aitken nuclei. It is established, however, that for particles whose diffusion coefficient is of the order of 10–3 cm2 sec–1, the proposed method should be quite workable.  相似文献   

8.
The authors conducted a Rn222 survey in wells of the Larderello geothermal field (Italy) and observed considerable variations in concentrations. Simple models show that flow-rate plays an important part in the Rn222 content of each well, as it directly affects the fluid transit time in the reservoirs. Rn222 has been sampled from two wells of the Serrazzano area during flow-rate drawdown tests. The apparent volume of the steam reservoir of each of these two wells has been estimated from the Rn222 concentration versus flow-rate curves.List of symbols Q Flow-rate (kg h–1) - Decay constant of Rn222 (=7.553×10–3 h–1) - Porosity of the reservoir (volume of fluid/volume of rock) - 1 Density of the fluid in the reservoir (kg m–3) - 2 Density of the rock in the reservoir (kg m–3) - M Stationary mass of fluid filling the reservoir (kg). - E Emanating power of the rock in the reservoir (nCi kg rock –1 h–1). - P Production rate of Rn222 in the reservoir: number of atoms of Rn222 (divided by 1.764×107) transferred by the rock to the mass unit of fluid per unit time (nCi kg fluid –1 h–1). - N Specific concentration of Rn222 in the fluid (nCi kg–1) - Characteristic time of the steam reservoir at maximum flow-rate (=M/Q)  相似文献   

9.
Profiles of electrical conductivity in the troposphere and stratosphere were measured by balloon-borne conductivity sondes at Garmisch-Partenkirchen, West Germany, from January to May, 1980, when volcanic activity was low. The aerosol concentration has been deduced from the relative decrease of conductivity from surrounding values by assuming the effective attachment coefficient of ions to aerosols. A prominent decrease of the conductivity near the tropopause is usually observed indicating high concentrations of Aitken particles (500–1000 cm–3). A decrease of conductivity, well above the tropopause, is sometimes observed, probably due to the transport of tropospheric Aitken particles with high concentration (200–400 cm–3) into the stratosphere.  相似文献   

10.
Summary The present paper contains studies of the nocturnal radiation at some Indian Stations (Madras, Waltair, Nagpur, New Delhi and Poona) with the help of the Ångström compensation Pyrgeometer. The technique of measurement is also described briefly. A study of the mean monthly variation of sky radiation during clear as well as all nights has been discussed. A comparitive study of mean monthly values of sky and other nocturnal radiation components at these stations is also presented. Ångström, [4]2) expressed the dependence of sky radiationS—on water vapour pressuree (mm of mercury) at the earth's surface and air temperatureT (degrees absolute), near the instrument to be given byS=T 4 (0.75–0.32×10–0.069e ) cal/cm2/min. According to this semi-empirical relationship, the calculated values of sky radiation for clear nights are smaller than the observed values of sky radiation at all the above stations. It is for this reason the authors obtained a new formula with different constants using nine years observed data at all the stations. To investigate the value of the constant, the mean annual observations presented for nine years from clear skies were analysed for correlations betweenB (black body radiation) versesS (sky radiation),N (net radiation) andE (absolute error) and obtained a good correlation co-efficients 0.90, 1 and 0.98 respectively. The new suggested formula isS=T 4 (0.88–0.32×10–0.069e ) cal/cm2/min, 267° A<T<313° A. It is also verified using with observed data of different years of the stations. The agreement between the computed values with the new formula of sky radiation and observed sky radiation is found to be good.  相似文献   

11.
Pyroclastic flow emplacement is strongly influenced by eruption column height. A surface along which kinetic energy is zero theoretically connects the loci of eruption column collapse with all coeval ignimbrite termini. This surface is reconstructed as a two-dimensional energy line for the 1912 Katmai pyroclastic flow in the Valley of Ten Thousand Smokes from mapped flow termini and the runup of the ignimbrite onto obstructions and through passes. Extrapolation of the energy line to the vicinity of the source vent at Novarupta suggests the eruption column which generated the ignimbrite eruption was approximately 425 m high. The 1912 pyroclastic flow travelled about 25 km downvalley. Empirical velocity data calculated from runup elevations and surveyed centrifugal superelevations indicate initial velocities near Novarupta were greater than 79–88 m s–1. The flow progressively decelerated and was travelling only 2–8 m s–1 when it crossed a moraine 16 km downvalley. The constant slope of the energy line away from Novarupta suggests the flow was systematically slowed by internal and basal friction. Using a simple physical model to calculate flow velocities and a constant kinetic friction coefficient (Heim coefficient) of 0.04 derived from the reconstructed energy line, the flow is estimated to have decelerated at an average rate of –0.16 m s–2 and to have taken approximately 9.5 minutes to travel 25 km down the Valley of Ten Thousand Smokes. The shear strength of the flowing ignimbrite at the moraine was approximately 0.5 kPa, and its Bingham viscosity when it crossed the moraine was 3.5 × 103 P. If the flow was Newtonian, its viscosity was 4.2 × 103 P. Reynolds and Froude numbers at the moraine were only 41–62 and 0.84–1.04, respectively, indicating laminar, subcritical flow.  相似文献   

12.
Summary The measurement of condensation nucleus concentration from an aircraft is considered and preliminary observations made with a photo-electric condensation nucleus counter discussed. It is concluded that at heights up to 6000 ft concentrations of condensation nuclei vary, from 200 cm–3 in clean maritime air to 5 × 103 cm–3 generally over large industrial areas and 35 × 103 cm–3 downwind of specific industrial sources. It appears that sea spray makes a contribution to the nucleus population.Mr. G. J.Day, B. Sc., Meteorological Research Flight, Royal Aircraft Establishment,Farnborough, Hants. (Great Britain).  相似文献   

13.
Quantitative measurements of crystal size distributions (CSDs) have been used to obtain kinetic information on crystallization of industrial compounds (Randolph and Larson 1971) and more recently on Hawaiian basalts (Cashman and Marsh 1988). The technique is based on a population balance resulting in a differential equation relating the population densityn of crystals to crystal sizeL, i.e., at steady staten =n o exp(–L/itG), wheren o is nucleation density,G is the average crystal growth rate, is the average growth time, and the nucleation rateJ =n o G. CSD (Inn vsL) plots of plagioclase phenocrysts in 12 samples of Mount St. Helens blast dacite and 14 samples of dacite from the 1980–1986 Mount St. Helens dome are similar and averageG = 9.6 (± 1.1) × 10–3 cm andn o = 1–2 × 106 cm–4. Reproducibility of the measurements was tested by measuring CSDs of 12 sections cut from a single sample in three mutually perpendicular directions; precision of the size distributions is good in terms of relative, but not necessarily absolute values (± 10%). Growth and nucleation rates for plagioclase have been calculated from these measurements using time brackets of = 30–150 years; growth ratesG are 3–10 × 10–12cm/s, and nucleation ratesJ are 5–21 × 10–6/cm3 s.G andJ for Fe-Ti oxides calculated from CSD data areG = 2–13 ± 10–13 cm/sec andJ = 7–33 × 10–5/cm3 s, respectively. The higher nucleation rate and lower growth rate of oxides resulted in a smaller average crystal size than for plagioclase. Sizes of plagioclase microlites (<0.01 mm) in the blast dacite groundmass have been measured from backscatter SEM photographs. Nucleation of these microlites was probably triggered by intrusion of material into the cone of Mount St. Helens in spring 1980. This residence time of 52 days gives minimum crystallization estimates ofG = 1–3 × 10–11 cm/s andJ = 9–16 × 1O3/cm3 s. The skeletal form of the microlites provides evidence for nucleation and growth at high values of undercooling (T) relative to the phenocrysts. A comparison of nucleation and growth rates for the two crystal populations (phenocrysts vs microlites) suggests that while growth rate seems to be only slightly affected by changes inT, nucleation rate is a very strong function of undercooling. A comparison of plagioclase nucleation and growth rates measured in the Mount St. Helens dacite and in basalt from Makaopuhi lava lake in Hawaii suggests that plagioclase nucleation rates are not as dependent on composition. Groundmass textures suggest that plagioclase microphenocrysts crystallized at depth rather than in the conduit, in the dome, or after extrusion onto the surface. Most of this crystallization appears to be in the form of crystal growth (coarsening) of groundmass microphenocrysts at small degrees of undercooling rather than extensive nucleation of new crystals. This continuous crystallization in a shallow magmatic reservoir may provide the overpressurization needed to drive the continuing periodic domebuilding extrusions, which have been the pattern of activity at Mount St. Helens since December 1980.  相似文献   

14.
Résumé En assimilant à des petits ions les atomes RaA provenant de la désintégration du Radon présent dans l'air, on évalue par le calcul la fraction de ces particules fixées sur les poussières et les noyaux de condensation, ainsi que leur durée de fixation.Pour vérifier ces considérations, on compte les petits et gros ions radioactifs par la méthode deZeleny, en maintenant l'électrode axiale des tubes sous tension négative, les autres particules sont fixées par captation électrostatique ou avec un filtre papier et les activités des différents échantillons sont étudiées par comptage . On trouve une concentration de l'air en petits ions RaA de 1.5·10–4 atome par cm3. Connaissant la teneur de l'air en Radon, et en admettant que l'équilibre radioactif est atteint entre le Radon et le Radium A qui en provient, on obtient par différence les concentrations de RaA fixée sur les autres particules.
Summary The proportion and free life time of RaA atoms arising from the radioactivity of atmospheric radon, and catched by dust particles, large ions and condensation nuclei, is evaluated, with assumption that these atoms are identical to the ordinary small ions.Experimental verification of the calculation are made by catching small and large ions withZeleny tubes, axial electrode being negatively charged. Other particles being catched with electrical precipitation and filter paper, activities of different samples are measured by counting. 1.5·10–4 per cm3 small ions RaA concentration is found. Knowing the air radon value concentration, and with the assumption of radioactive equilibrium only between radon and RaA in free air, it is possible to evaluate the concentration of RaA catched by other particles.
  相似文献   

15.
Zusammenfassung Es werden die Grundgleichungen der Ionisations-Neutralisationsbilanz in derE-Schicht präzisiert und auf die Notwendigkeit der Berücksichtigung des Einflusses der lokalen ionisierenden Strahlungsquellen auf der Sonnenscheibe, der dynamischen ionosphärischen Vorgängen und der Veränderungen des äquivalenten Rekombinationskoeffizienten hingewiesen. Ferner wird eine Methodik zur Bestimmung der charakteristischen Grössen der Ionisations-Rekombinationsbilanz (q 0m ,q d, ) dargelegt. Zu dem Zweck werden die Messergebnisse aus der Periode der Sonnenfinsternis von zwei unweit voneinander gelegenen Ionosphärenstationen verwendet. Die Methodik wird auf die während der totalen Sonnenfinsternis am 15. Februar 1961 auf den Ionosphärenstationen in Sofia und Nesebar erhaltenen Ergebnisse angewandt. Für den Rekombinationskoeffizienten werden Werte zwischen 0,63·10–7 cm3sec–1 und 2,32·10–7 cm3sec–1 und für die Elektronenproduktion unter dem Einfluss der ionisierenden Strahlung von der homogenen Sonnenscheibeq 0m 1700 cm–3sec–1 erhalten.
Summary The basic equations for the ionisation-neutralisation balance in theE layer have been shown the necessity to take in account the influence of the local ionisation sources on the disk of the sun, the dynamic ionospheric processes and the variations in the equivalent recombination coefficient. The method for determining the characteristic quantities of the ionisation-recombination balance (q 0m ,q d, ) has been exhibited for this purpose are used measurement data from two ionospheric stations located not far from each other, in the period of the solar eclips on 15 February, 1961. The quantity of the recombination coefficient lay between 0.63×10–7 sec–1 cm3 and 2.32×10–7 sec–1 cm3; the electron production under the action of the ionising radiation of the homogen disk showsq 0m 1700 sec–1 cm–3.
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16.
The seasonal variation of microbial biomass and activity in the surface sediments (0–10 cm) of the shallow, eutrophic Lake Vallentunasjön was followed during one year. OverwinteringMicrocystis colonies dominated the microbial community during all seasons, constituting 60–90% of the total microbial biomass. Expressed on an areal basis, the benthic biomass was, throughout the year, larger than or similar to the planktonic biomass during the peak of the summer bloom, indicating an ability of the colonies to survive in the sediments for extended periods. Abundance of other, non-photosynthetic bacteria varied in the range 3.0–15.5 · 1010 cells g–1 d. w. over the year with minimum values in summer and maximum values in autumn in connection with the sedimentation of theMicrocystis bloom. A substantial part of the non-photosynthetic bacteria, up to circa 40%, was associated with the mucilage of healthyMicrocystis colonies. Bacterial production (3H-thymidine incorporation) appeared to be strongly temperature dependent and less influenced by the seasonal sedimentation pattern. Our data indicate an increasing proportion of non-growing cells in autumn and winter. Biomass-bound phosphorus constituted a significant portion, circa 10%, of the phosphorus content in Lake Vallentunasjön sediments. This pool has normally been overlooked in studies on phosphorus dynamics in lake sediments. Different mechanisms whereby organic phosphorus can be released from the sediments are discussed.  相似文献   

17.
Summary The residues of cloud droplets collected at the summit of a mountain were examined with an electron microscope and their materials were identified with the aid of micro-electron-diffraction method. About 30% of nuclei of cloud droplets larger than 5 in radius were mainly composed of sodium chloride and their masses were 10–1210–13 gr. We also found salt particles in snow crystals. Some discussions are made about the process of the capture of these particles by snow crystals.  相似文献   

18.
An automatic condensation nuclei counter was developed for the concentration range of about 1 to 400 particles per cubic centimeter. After expansion, the water droplets are photographed when they are still suspended in the air so that the counter can be considered an absolute one. The volume in which the droplets are counted is determined by the size of the picture of the droplets as a function of their distance from the focal plane. To eliminate any effect of decreasing pressure with altitude, the cloud chamber is filled with clean air prior to expansion to about half an atmosphere above ambient pressure. This counter was used to obtain vertical profiles of condensation nuclei up to altitudes of 27 km with high altitude balloons. A total of seven profiles was obtained over a period of about one year at 47° N over the United States. Because of the restrictions in the range of the meter no data could be obtained below 5 km. The profiles show the following main features:
  1. 1.
    Although there are pronounced fluctuations in the individual flights the average nuclei concentration of 200 to 300/cm3 remains fairly constant from 5 km to the tropopause.  相似文献   

19.
Summary Auroral spectra taken from within the auroral zone reveal H-emission as not limited to the magnetic zenith but as extending over the sky. The surface brightness forH andH may tentatively be estimated to a few airglows. The assumption is made that some of this emission may extend to the very low gm latitudes and be practically universal and the possible mode of excitation of neutral hydrogen in space is speculated upon. At the earth's orbit the density number of the cosmic, infalling, hydrogen accreted from beyond the solar system towards the sun is about 102 neutral atoms cm–3 and coronal plasma contributions cannot encrease this number by more than a factor of two. If an exceptionally violent solar disturbance ejects stream-electrons attaining velocities-of 2,200 km sec–1 corresponding to the threshold energy forH excitation of 12.8 eV and if these electrons, at the earth's orbit, have a density number of 103 cm–3, then a shell about 100,000 km thick may contributeH emission having a surface brightness of about 0.1 airglow this being the higher probable value. Such anH-emission could be detectable from all latitudes during, or, most probably, just before the occurence of an auroral storm.  相似文献   

20.
Summary The geothermal gradient in the Carpathian Basin lies between 40–70 C/km. According to careful measurements in shafts the value of terrestrial heat flow in the southern part of Hungary is (2.055–3.066)·10–6 cal/cm2 sec. These measurements are believed the first ever attempted in continental Europe. Systematic heat flow measurement are being extended to other part of this country.  相似文献   

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