Kinds Of Aerosols Research Articles

Evaluation of the direct and indirect radiative and climate effects of aerosols over the western Arctic

From the observations of recent years, there is still not enough evidence to verify the Arctic warming as most global circulation models (GCMs) suggested. This study is dedicated to quantifying the aerosol effect on the Arctic climate change by Northern Aerosol Regional Climate Model (NARCM). The direct and indirect radiative and climate effects of aerosols such as Arctic haze sulfate, black carbon, sea salt, organics, and dust have been evaluated from our NARCM simulations. Within the Arctic Regional Climate Model Intercomparison Project (ARCMIP) our model simulations have been directly compared with the enhanced observation data sets such as the Surface Heat Budget of the Arctic Ocean (SHEBA) and the Atmospheric Radiation Measurement (ARM) in the time period from October 1997 to September 1998. Results show that the climate effects of aerosols strongly depend on the aerosol composition. The surface radiative forcing of pure sulfate aerosols which includes the direct and indirect components reaches up to −7.2 W/m2 in annual mean. The climate responses to radiative forcing of pure sulfate and five kinds of aerosols together are amazingly different. The impacts of aerosols present strong seasonal cycle. In comparison with observations we find the simulation with five kinds of aerosols can better represent the surface temperature from observation. The aerosol radiative and microphysical effects must be taken into account in order to better simulate and predict the change of energy and water cycle occurring in polar climate system.

PM mass concentrations in comparison with aerosol optical depths over the Arabian Sea and Indian Ocean during winter monsoon

Abstract An analysis of PM2.5 mass concentrations and 0.5 μm aerosol optical depths (AODs) during the Northeast winter monsoon seasons of 1996–2000 is performed and intercompared. AODs are found to show diurnal variations over Coastal India (CI) (west coast) while they are relatively smooth over the Arabian Sea (AS) (5–20°N) and tropical Indian Ocean (TIO) (5°N–20°S). PM2.5, PM10 and total mass concentrations show less variations in a day over these oceanic regions. Columnar AODs are found to increase with an increase in the marine boundary layer aerosol concentrations over CI and AS while an opposite trend is seen over TIO. The yearly-mean AODs and mass concentrations are found to increase over CI and AS, over TIO the mass concentrations increased while the AODs decreased during 1996–2000. It is found from the 7-days air back trajectory analyses that at different altitudes air masses can originate from different source regions leading to changes in chemical, physical and optical characteristics of the aerosol between the surface and column. The differences in the surface and columnar measurements could also occur due to changes in the meteorological conditions, wind patterns, in addition to changes in production and subsequently the transport of aerosols. Least-squares fits to the above intercomparison resulted in intercepts of 0.24 and 0.22 over CI and AS indicating that the background AODs over these oceanic regions are higher. An examination of the daily-mean wind speeds and PM2.5 mass concentrations yielded an index of wind dependence of 0.04 for AS and 0.07 for TIO. The background PM2.5 mass concentrations are also found to be high at 36 and 25 μg m−3 over AS and TIO, respectively, indicating a stronger influence from the continent. Frequency distribution figures show that 28% of the PM2.5 values over CI lie in the 60–80 μg m−3 range. Over AS the dominant mode of distribution is 40–60 μg m−3 with a peak value of 42%. Over TIO PM2.5 values are found to peak in the lower mass bin of 0–20 μg m−3 at 33%. A latitudinal gradient is seen in the peak bin value of PM2.5 as the ship moves away from the coast. About half the days over CI and 20% over AS and TIO, PM2.5 values are found unhealthy indicating the influence of anthropogenic pollution and long-range transport of pollutants from the surrounding continental locations across these oceanic regimes. AODs are found to peak in the 0.2–0.4 bin at 52% over CI and 47% over AS. Over AS 32% of the AODs are found to be α values are found to peak in the 1.5–2 range over CI at 55% while they peak in the lower range of 1–1.5 at 49% and 26% over AS and TIO, respectively. Over the Pacific and Atlantic Oceans in more than 90% of the cases α was ⩽1.5, indicating that the amount of smaller and larger particles are higher over the Indian Ocean when compared to the Pacific and Atlantic. The spread in PM2.5 and AOD indicates that it is a challenging task to obtain a good relation without additional inputs on the vertical distribution of aerosols as varied kinds of aerosols from different source regions contribute at different heights over these oceanic regions.

Continuous observations of Asian dust and other aerosols by polarization lidars in China and Japan during ACE‐Asia

Continuous observations of aerosols in China and Japan were made by polarization lidars during March to May 2001, corresponding with the Asian Pacific Regional Aerosol Characterization Experiment (ACE‐Asia) field campaign period. Lidars in Beijing, Nagasaki, and Tsukuba were continuously operated regardless of weather conditions. Scatterers in the atmosphere were categorized for all vertical profiles, and occurrence frequencies of dust, spherical aerosols, and clouds up to 6 km were calculated. The frequency of dust was highest in Beijing for the whole height range. There was a peak of dust occurrence near the ground in Nagasaki. Dust was frequently detected in the free troposphere in Tsukuba. The contributions of dust and spherical aerosols to the total backscattering coefficient were estimated from the depolarization ratio with the assumption of the external mixture of both kinds of aerosols. Vertical profiles of backscattering by dust and by spherical aerosols represented the different characteristics of these aerosols. The monthly averaged backscattering coefficients by dust near the surface were 0.003/km/sr in Beijing, 0.001–0.002/km/sr in Nagasaki, and 0.0006/km/sr in Tsukuba. The backscattering coefficients by spherical aerosols near the surface were 0.002–0.004/km/sr at all three observatories. We compared the derived backscattering coefficients with aerosol mass concentrations calculated by a numerical model, Chemical Weather Forecasting System (CFORS). CFORS reproduced well the vertical structures of the tall dust events and the enhancements of spherical aerosols throughout the observation period. A specific dust event on 16–19 May 2001 was analyzed by using five lidars in Japan, and its fine structure is described.

Vertical and horizontal aerosol spectral extinction at a rural location in southern Italy

The vertical extinction of the aerosol has been measured with a multiwavelength sunphotometer at a rural location in southern Italy. All measurements were performed during a period with relatively stable weather condition, thus it could be expected to have measured always the same air mass at least within each day. The direct solar radiation was recorded at wavelengths between 400 and 1100 nm with a resolution of 0.5 nm. Calibration of the instrument was performed by means of a Langley plot at an elevation of approximately 3000 m. From these measurements, vertical optical depths have been derived for a series of days in June 1993. The spectral extinction coefficient of the atmospheric aerosol at the same location has been measured by means of a telephotometer. The radiance of a target at a distance of 12 km was measured at nine wavelengths in the visible. Thus the extinction coefficient of the aerosol contained within a conical volume of about 450,000 m3 and a length of 12 km has been measured. The daily variation usually followed the same pattern: a decrease in extinction coefficient in the morning and in the early afternoon and an increase toward the evening. This variation correlated well with the change in humidity, so that it can be assumed that the aerosol particles have decreased their size due to evaporation of water in the morning and uptake of water in the evening. The regular daily pattern of the horizontal aerosol extinction coefficient normally was not followed by the vertical aerosol optical density, but on the other hand, changes in vertical extinction have occurred on some days, which had no effect on the horizontal extinction. Vertical extinction measurements were inverted to obtain aerosol size distributions. Inversions were obtained by the Twomey‐Phillips method and they confirm the presence of a hygroscopic aerosol as suggested directly by the variation of the extinction coefficients against the relative humidity. The aerosol undergoes very clear processes of growth which are well correlated with the behavior of the humidity. Overall, the type of aerosol we have measured could be classified as rural aerosol. This kind of aerosol is typical of the boundary layer of clean continental area and is composed prevalently by water‐soluble substances and in minor abundance by dustlike aerosol.

Simulation of remote sensing of sea surface temperature from space: influences of cirrus clouds and stratospheric aerosols on sea surface temperatures derived from the VISSR Atmospheric Sounder

Abstract This simulation study demonstrates that cirrus clouds and volcanic aerosols with atmospheric gases would greatly affect the transmission functions and brightness temperatures of infrared window channels in the VISSR Atmospheric Sounder (VAS), and VAS-derived sea surface temperature (SST) determinations. The ;clear air (CLR) retrieval equations should not be used in the presence of cirrus and high stratospheric aerosol loadings. An alternative five-window channel algorithm could be found that would work in arbitrary clear, cirrus or aerosol conditions, but the retrieval accuracy would decrease in comparison with the multi-channel SST (MCSST) algorithms for simply cirrus clouds, or aerosols only. In MCSST algorithms, channel 12 (3–94μ) is most important for CLR, or tenuous cirrus with any kind of aerosols, or moderate cirrus with weak aerosols, whereas for moderate cirrus combined with the strong aerosol, or dense cirrus with any kind of aerosols, channel 5 (13‐34μ) or channel 8 (11–22μ) becomes the most important. In addition, the effects of variations of water vapour profile, aerosol concentration, and sea surface reflection (SSR) on SST retrievals need to be considered.

Response of a quartz crystal aerosol mass monitor to sulfate and nitrate aerosols

Response of two commercial quartz crystal aerosol mass monitor (TSI Model 3200A and 3500) to several sulfate and nitrate aerosols has been examined in terms of linerity, mass sensitivity and hygroscopicity. For all the aerosols tested, the mass monitor responded linearly (± 15% variation) to mass loadings on the sensing crystal up to an accumulated frequency change of 1000 Hz in Model 3200A and 4000 Hz in Model 3500. Within this linearity limit, the mass sensitivity tended to increase gradually with increase of mass loading. The mass sensitivity coefficient ( S) of the monitor varied from 135 to 219 Hz/μg with 0.5 μm MMAD (GSD = 1.5) aerosols, depending upon the kind of aerosols and was 10–26% higher with 1.2 μm MMAD aerosols. The monitors responded sensitively and correctly to hygroscopic nature of the aerosols tested. showing sharp increases of frequency change at known deliquescent points of the aerosols.

Experimental studies of long-term aerosol inhalation. An inhalation apparatus for long-term exposure with concentration regulation facilities (author's transl)

A "multipurpose" inhalation system for long-term experiments was developed to study health effects of the exposure to various kinds of aerosols appearing in general working environments as well as in the ambient atmosphere. In order to carry out a continuous inhalation study on animals for their life-span, at least two essential conditions should continuously be fulfilled. (1) Steady maintenance of the appropriate sanitary conditions for the animals placed in the inhalation box. (2) Constant feeding of aerosol at an appropriately regulated concentration level. The developed system described in the present paper has been proved to be satisfactory from the above viewpoints. This inhalation system was applied to an experimental study attempting to simulate the polluted lungs in the urban dwellers. Heavy oil combustion products were chosen as the inhalation material, which were made to be inhaled by the male rats of SD-JCL strain for their life-span. The present report is mainly concerned with the construction of the inhalation system including a newly devised regulation facility of the aerosol concentration. Operating characteristics and actual data obtained are described. Details of the exposure conditions and pathological findings obtained will be described in the succeeding reports.

The Effect of Organic Vapors on the Stability of Aerosols

The stabilities of aerosols depending on the nature of the added vapors as well us on their concentrations are discussed. The role of the vapors in stabilizing the aerosols and the rate of coagulation in the presence of such vapors were observed by means of the ultramicroscopic method using three kinds of aerosols. e.g.. the fogs of aqueous ammonium chloride solution, glycerol, and dioctyl phthalate. (J.E.D.)

A PHOTO-ELECTRONIC FOG COUNTER

A photo-electronic fog counter has been developed on the principle of counting flashes of light scattered from individual fog droplets with a photomultiplier. Since a photomultiplier appears to act very rapidly and reponse in a time of the order of 10-8 sec. is possible, the maximum counting rate is limited only by the sealer which is associated with the counter. If a Berkeley Sealer (Model 1000B) is used, this counter is capable of counting fog droplets at a rate of 300,000/min. with very small error and the chance of coincidence countings is therefore small. This counter will prove useful for even very dense fogs or any other kind of aerosols. The optical theory of scattering which may lead to the determination of particle size from size of electric pulse has been introduced.Preliminary experiments show the applicability of this counter for droplet size measurement. There seems to be of no doubt that this counter could register the smallest droplets that occur in natural fogs (i.e., of the order of r≈1 micron) and a better sensitivity can be achieved by reducing stray-light noise level and improving signal to noise ratio. Possibilities of further improvements of the present instrument both as a fog counter and as a droplet size indicator have been discussed.