共查询到20条相似文献，搜索用时 515 毫秒
1.
Tropospheric aerosols affect the radiative forcing of Earth's climate, but their variable concentrations complicate an understanding of their global influence. Model-based estimates of aerosol distributions helped reveal spatial patterns indicative of the presence of tropospheric aerosols in the satellite-observed clear-sky solar radiation budget over the world's oceans. The results show that, although geographical signatures due to both natural and anthropogenic aerosols are manifest in the satellite observations, the naturally occurring sea-salt is the leading aerosol contributor to the global-mean clear-sky radiation balance over oceans. 相似文献
2.
In situ measurements of organics, meteoritic material, mercury, and other elements in aerosols at 5 to 19 kilometers 总被引：1，自引：0，他引：1
In situ measurements of the chemical composition of individual aerosol particles at altitudes between 5 and 19 kilometers reveal that upper tropospheric aerosols often contained more organic material than sulfate. Although stratospheric aerosols primarily consisted of sulfuric acid and water, many also contained meteoritic material. Just above the tropopause, small amounts of mercury were found in over half of the aerosol particles that were analyzed. Overall, there was tremendous variety in aerosol composition. One measure of this diversity is that at least 45 elements were detected in aerosol particles. These results have wide implications for the complexity of aerosol sources and chemistry. They also offer possibilities for understanding the transport of atmospheric aerosols. 相似文献
3.
KW Oum MJ Lakin DO DeHaan T Brauers BJ Finlayson-Pitts 《Science (New York, N.Y.)》1998,279(5347):74-77
Halogen atoms from the reactions of sea-salt particles may play a significant role in the marine boundary layer. Reactions of sodium chloride, the major component of sea-salt particles, with nitrogen oxides generate chlorine atom precursors. However, recent studies suggest there is an additional source of chlorine in the marine troposphere. This study shows that molecular chlorine is generated from the photolysis of ozone in the presence of sea-salt particles above their deliquescence point; this process may also occur in the ocean surface layer. Given the global distribution of ozone, this process may provide a global source of chlorine. 相似文献
4.
A seven-element tracer system shows that regional pollution aerosols of both North America and Europe have characteristic signatures that can be followed into remote areas up to several thousand kilometers downwind. In aerosols of mixed origin, regional contributions to the tracer elements can be resolved by least-squares procedures. After transport of several hundred kilometers, secondary sulfate can also be apportioned satisfactorily. Regional elemental tracers thus offer a way to determine the sources of pollution aerosol in important areas such as the northeastern United States, Scandinavia, and the Arctic. 相似文献
5.
Many types of aerosols have lifetimes long enough for their transcontinental transport, making them potentially important contributors to air quality and climate change in remote locations. We estimate that the mass of aerosols arriving at North American shores from overseas is comparable with the total mass of particulates emitted domestically. Curbing domestic emissions of particulates and precursor gases, therefore, is not sufficient to mitigate aerosol impacts in North America. The imported contribution is dominated by dust leaving Asia, not by combustion-generated particles. Thus, even a reduction of industrial emissions of the emerging economies of Asia could be overwhelmed by an increase of dust emissions due to changes in meteorological conditions and potential desertification. 相似文献
6.
Aerosol effect on cloud droplet size monitored from satellite 总被引：5，自引：0，他引：5
Aerosol concentration and cloud droplet radii derived from space-borne measurements are used to explore the effect of aerosols on cloud microphysics. Cloud droplet size is found to be largest (14 micrometers) over remote tropical oceans and smallest (6 micrometers) over highly polluted continental areas. Small droplets are also present in clouds downwind of continents. By using estimates of droplet radii coupled with aerosol load, a statistical mean relationship is derived. The cloud droplet size appears to be better correlated with an aerosol index that is representative of the aerosol column number under some assumptions than with the aerosol optical thickness. This study reveals that the effect of aerosols on cloud microphysics is significant and occurs on a global scale. 相似文献
7.
由于气溶胶的介电常数不易直接测量,气溶胶的复折射指数的实部与其介电常数之间存在的一定关系,利用这一关系,可以用气溶胶的复折射指数的实部来求出其介电常数,并对4种基本粒子、3种常见类型的气溶胶以及任意体积比混和建立的气溶胶类型的介电常数进行了研究。 相似文献
8.
The multimodal microstructure of the Venus cloud system has been examined. In addition to confirmed H(2)SO(4) droplets and suspected elemental sulfur, a highly concentrated aerosol population has been observed extending above, within, and below the cloud system. These aerosols appear to cycle through the cloud droplets, but can never be removed by the weak precipitation mechanisms present. All cloud particles are likely laced with aerosol contaminants. Sedimentation and decomposition of H(2)SO(4) in the droplets of the lower cloud region contribute more than 7 watts per square meter of heat flux equaling one-fourth of the solar net flux at 50 kilometers. 相似文献
9.
Soot carbon and excess fine potassium: long-range transport of combustion-derived aerosols 总被引：2，自引：0，他引：2
Andreae MO 《Science (New York, N.Y.)》1983,220(4602):1148-1151
During a cruise from Hamburg to Montevideo, aerosol samples representing air masses from Europe, the Sahara, tropical Africa, South America, and open oceanic regions were collected. They showed significant amounts of soot carbon over large areas of the remote Atlantic, often similar to concentrations in rural continental areas. Back-trajectories and the ratios of soot carbon to total fine (less than 1.7 micrometers in diameter) carbon and of excess fine potassium (the portion not attributable to soil dust or sea salt) to soot carbon indicate that biomass burning in tropical regions is an important source of soot carbon to the world atmosphere. The ratio of excess potassium to soot carbon in the fine fraction of aerosols is proposed as an indicator of the relative contributions of biomass and fossil-fuel burning to soot carbon aerosols. The ratio of soot carbon to fine carbon suggests that most of the particulate organic carbon over the Atlantic is of continental origin. 相似文献
10.
Jaenicke R 《Science (New York, N.Y.)》2005,308(5718):73
Suspended atmospheric particles play a crucial role in any global climate scenario: They can both enforce and suppress radiative forcing. In developing climate modeling further, a deeper understanding of atmospheric aerosol is needed. Because of extreme local and temporal variations, proper incorporation of aerosols into models requires modeling of the aerosol itself. It turns out that cellular material and proteins compose up to 25% of the atmospheric aerosol. Consequently, the source strength of the biogenic aerosol in general must be corrected and should be estimated on the order of other major aerosol sources. 相似文献
11.
de Gouw JA Middlebrook AM Warneke C Ahmadov R Atlas EL Bahreini R Blake DR Brock CA Brioude J Fahey DW Fehsenfeld FC Holloway JS Le Henaff M Lueb RA McKeen SA Meagher JF Murphy DM Paris C Parrish DD Perring AE Pollack IB Ravishankara AR Robinson AL Ryerson TB Schwarz JP Spackman JR Srinivasan A Watts LA 《Science (New York, N.Y.)》2011,331(6022):1295-1299
A large fraction of atmospheric aerosols are derived from organic compounds with various volatilities. A National Oceanic and Atmospheric Administration (NOAA) WP-3D research aircraft made airborne measurements of the gaseous and aerosol composition of air over the Deepwater Horizon (DWH) oil spill in the Gulf of Mexico that occurred from April to August 2010. A narrow plume of hydrocarbons was observed downwind of DWH that is attributed to the evaporation of fresh oil on the sea surface. A much wider plume with high concentrations of organic aerosol (>25 micrograms per cubic meter) was attributed to the formation of secondary organic aerosol (SOA) from unmeasured, less volatile hydrocarbons that were emitted from a wider area around DWH. These observations provide direct and compelling evidence for the importance of formation of SOA from less volatile hydrocarbons. 相似文献
12.
Particulate air pollution has been shown to strongly suppress precipitation from convective clouds over land. New observations show that precipitation from similar polluted clouds over oceans is much less affected, because large sea salt nuclei override the precipitation suppression effect of the large number of small pollution nuclei. Raindrops initiated by the sea salt grow by collecting small cloud droplets that form on the pollution particles, thereby cleansing the air. Therefore, sea salt helps cleanse the atmosphere of the air pollution via cloud processes. This implies that over oceans, the climatic aerosol indirect effects are significantly smaller than current estimates. 相似文献
13.
Falkowski PG Kim Y Kolber Z Wilson C Wirick C Cess R 《Science (New York, N.Y.)》1992,256(5061):1311-1313
Cloud albedo plays a key role in regulating Earth's climate. Cloud albedo depends on column-integrated liquid water content and the density of cloud condensation nuclei, which consists primarily of submicrometer-sized aerosol sulfate particles. A comparison of two independent satellite data sets suggests that, although anthropogenic sulfate emissions may enhance cloud albedo immediately adjacent to the east coast of the United States, over the central North Atlantic Ocean the variability in albedo can be largely accounted for by natural marine and atmospheric processes that probably have remained relatively constant since the beginning of the industrial revolution. 相似文献
14.
Dandonneau Y Vega A Loisel H du Penhoat Y Menkes C 《Science (New York, N.Y.)》2003,302(5650):1548-1551
Recent satellite observations of Rossby waves and chlorophyll anomalies propagating in subtropical gyres have suggested that wave-induced upwelling could stimulate photosynthesis. Instead, we show that chlorophyll maxima are located in abnormally warm water, in Rossby wave-induced convergences. This excludes inputs of nutrients from deeper water. We argue that the sea color anomalies are not caused by chlorophyll but by floating particles evolved from the ecosystem and accumulated by Rossby waves, acting as "marine hay rakes," in convergence zones. Such processes may be determinant for the distribution of living organisms in oligotrophic areas. 相似文献
15.
The anthropogenic indirect aerosol effects of modifying cloud albedo and cloud lifetime cannot be deduced from observations alone but require a modeling component. Here we validate a climate model, with and without indirect aerosol effects, by using satellite observations. The model agrees better with observations when both indirect aerosol effects are included. However, the simulated clouds are more susceptible to aerosols than the observed clouds from the POLDER satellite, thus overestimating the indirect aerosol effect. By taking the difference in susceptibilities into account, the global mean total anthropogenic aerosol effect is reduced from -1.4 to -0.85 watts per square meter. 相似文献
16.
Measurements of mass concentration and size distribution of aerosols from eruptions of Mount St. Helens as well as morphological and elemental analyses were obtained between 7 April and 7 August 1980. In situ measurements were made in early phreatic and later, minor phreatomagmatic eruption clouds near the vent of the volcano and in plumes injected into the stratosphere from the major eruptions of 18 and 25 May. The phreatic aerosol was characterized by an essentially monomodal size distribution dominated by silicate particles larger than 10 micrometers in diameter. The phreatomagmatic eruption cloud was multimodal; the large size mode consisted of silicate particles and the small size modes were made up of mixtures of sulfuric acid and silicate particles. The stratospheric aerosol from the main eruption exhibited a characteristic narrow single mode with particles less than 1 micrometer in diameter and nearly all of the mass made up of sulfuric acid droplets. 相似文献
17.
Cassar N Bender ML Barnett BA Fan S Moxim WJ Levy H Tilbrook B 《Science (New York, N.Y.)》2007,317(5841):1067-1070
Biogeochemical rate processes in the Southern Ocean have an important impact on the global environment. Here, we summarize an extensive set of published and new data that establishes the pattern of gross primary production and net community production over large areas of the Southern Ocean. We compare these rates with model estimates of dissolved iron that is added to surface waters by aerosols. This comparison shows that net community production, which is comparable to export production, is proportional to modeled input of soluble iron in aerosols. Our results strengthen the evidence that the addition of aerosol iron fertilizes export production in the Southern Ocean. The data also show that aerosol iron input particularly enhances gross primary production over the large area of the Southern Ocean downwind of dry continental areas. 相似文献
18.
The light-scattering and light-absorption coefficients of the global background aerosol define its single-scatter albedo. Continuous, simultaneous measurements of these optical coefficients were made on a daily basis for the remote marine mid-troposphere; such measurements are essential for assessment of the effects of aerosol on atmospheric radiative transfer. Measurements of light-absorption coefficients made at the Mauna Loa Observatory in Hawaii were higher than expected, and the single-scatter albedo was lower than the value often used in radiative transfer models. Soot appears to be the most likely primary absorber, and hemispheric dispersal of this combustion-derived material is suggested. 相似文献
19.
Atmospheric aerosols play a substantial role in climate change through radiative forcing. Combustion-produced carbonaceous particles are the main light-absorbing aerosols; thus, quantifying their optical properties is essential for determining the magnitude of direct forcing. By using the electron energy-loss spectrum in the transmission electron microscope, we quantified the optical properties of individual, submicrometer amorphous carbon spheres that are ubiquitous in East Asian-Pacific outflow. The data indicate that these common spheres are brown, not black, with a mean refractive index of 1.67 - 0.27i (where i = square root 1) at a wavelength of 550 nanometers. The results suggest that brown carbon aerosols should be explicitly included in radiative forcing models. 相似文献
20.
Laskin A Gaspar DJ Wang W Hunt SW Cowin JP Colson SD Finlayson-Pitts BJ 《Science (New York, N.Y.)》2003,301(5631):340-344
Understanding the formation of sulfate particles in the troposphere is critical because of their health effects and their direct and indirect effects on radiative forcing, and hence on climate. Laboratory studies of the chemical and physical changes in sodium chloride, the major component of sea-salt particles, show that sodium hydroxide is generated upon reaction of deliquesced sodium chloride particles with gas-phase hydroxide. The increase in alkalinity will lead to an increase in the uptake and oxidation of sulfur dioxide to sulfate in sea-salt particles. This chemistry is missing from current models but is consistent with a number of previously unexplained field study observations. 相似文献