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1.
The spectral aerosol-extinction coefficients (SAECs) obtained from SAGE III measurements are used to study the physical and integral microphysical characteristics of polar stratospheric clouds (PSCs). Different criteria for PSC identification from SAEC measurements are considered and analyzed based on model and field measurements. An intercomparison of them is performed, and the agreement and difference of the results obtained with the use of different criteria are shown. A new criterion is proposed for PSC identification, which is based on the estimate of how close the measured vector of the spectral attenuation coefficient is to a model distribution of the PSC ensemble. On the basis of different criteria, cases of PSCs are isolated from all SAGE III observations (over 30000). All selection criteria lead to a qualitatively and quantitatively similar space-time distribution of the regions of PSC localization. The PSCs observed in the region accessible to SAGE III measurements are localized in the latitudinal zones 65°–80° in the Northern Hemisphere and 45°–60° in the Southern Hemisphere during the winter-spring period. In the Northern Hemisphere, PSCs are observed within the longitudinal zone 120° W–100° E with the maximum frequency of PSC observation in the vicinity of the Greenwich meridian. In the Southern Hemisphere, the region of PSC observation is almost the same in longitude but with a certain shift in the maximum frequency of PSC observation to the west. This maximum is observed in the vicinity of 40°W, and the region of usual PSC observation is the neighborhood of 60° of the maximum’s longitude. The physical parameters of PSCs are estimated: the mean heights of the lower and upper boundaries of PSCs are 19.5 and 21.9 km, respectively, and the mean cloud temperature is 191.8 K. The integral microphysical parameters of PSCs are estimated: the total surface of NAT particles S NAT = 0.41 μm2/cm3; the total volume of NAT particles V NAT = 1.1 μm3/cm3; and, for all aerosol and cloud particles together, S is 2.9 ± 1.5 at a standard deviation of 2.7 μm2/cm3 and V is 2.8 ± 1.5 at a standard deviation of 4.2 μm3/cm3. A high frequency of PSC occurrence and high values of S and V in PSCs both for all particles and for NAT particles have been noted in January–February 2005 as compared to the rest of the period of SAGE III measurements for 2002–2005.  相似文献   

2.
The surface area and volume densities (S and V) of the particles of stratospheric background aerosol in the 15–20 km and 20–25 km layers for 2002–2005 were obtained from measurements of the aerosol extinction coefficient with the SAGE III instrument by using the linear-regression method of solving the inverse problem. The measurements were taken within the latitudinal belts 43°–80°N and 34°–58°S. The spatial and temporal dependences of S and V demonstrate homogeneous distribution fields in summer, whereas noticeable inhomogeneities are observed in winter and early spring. In all years of the measurements, an increase in the integral characteristics of stratospheric background aerosol was observed during the fall-to-winter transition period. Longitudinal variations in S and V can be both slight and significant (50–70%). Analysis of the interannual variability of the mean areas and volumes of aerosol particles shows that their minima (as a rule) were observed in 2002 and their maxima were observed in 2005. In most of the cases, no monotonic annual variations in the aerosol characteristics are noted. The dependence of the aerosol parameters on the phase of the quasi-biennial oscillations of zonal wind in the stratosphere is observed. The data obtained for 2002–2005 are, on the whole, in good agreement with the climatological data obtained for 1996–1999.  相似文献   

3.
A method for reconstructing the parameters of postvolcanic stratospheric aerosol from the results of joint measurements of the aerosol backscattering coefficient with lidar systems based on the Nd:YAG laser and the aerosol extinction coefficient with the SAGE III satellite instrumentation is developed. The most informative set of optical characteristics is determined for each of the microphysical parameters under consideration (concentration, surface area, volume, and effective size of particles of the fine and coarse aerosol fractions). Multiple polynomial regressions between optical and microphysical characteristics of aerosol are obtained. These regressions make it possible to determine the microphysical characteristics of aerosol within a wide range without solving incorrect inverse problems. The results are compared with independent experimental data. The errors of reconstructing microphysical parameters of aerosol are estimated for different situations in the stratosphere. The influence of the shape of particles of the dust fraction on the results of a reconstruction of the microphysical parameters of aerosol is considered.  相似文献   

4.
Spectroradiometric measurements of the ocean skin temperature and thermometric measurements of the bulk temperature at a depth of about 5 cm taken from the R/V Tangaroa during SAGE (SOLAS/SAGE: surface-ocean lower-atmosphere studies air-sea gas exchange experiment) off New Zealand are analyzed to reveal the wind speed dependence of the temperature difference across the thermal skin layer (??T). The wind speeds used here are corrected for flow distortion by the ship. Unlike most previously published measurements of ??T, these data include those taken during the day, prior analyses being usually restricted to night-time measurements to avoid contamination of the data by diurnal heating. The results show the same dependence of ??T on wind speed at night-time measurements, with an asymptotic behavior at a value of −0.13 K at high winds. These data show larger ??T at low wind speeds than previous studies, and there is an indication that this may reveal a dependence on sea surface temperature.  相似文献   

5.
Based on the optimum P-wave model, the S-wave velocity structure of a wide angle seismic profile (OBS2006-1), across the northwestern sub-basin (NWSB) and the Macclesfield, is simulated by a 2-D ray-tracing method. The results indicate the S-wave velocities in the upper and lower crust of the NWSB are 3.2–3.6 km/s and 3.6–4.0 km/s, with Vp/Vs ratios of 1.82–1.88 and 1.74–1.82, respectively, which reflect typical oceanic crust characteristics. The S-wave velocity in the upper crust of the NWSB is a little higher in the NNW segment than that in the SSE segment, while the lateral variation of Vp/Vs ratio is in the opposite. We suggest that the NWSB might have experienced asymmetrical magma flows during sea floor spreading, which may have blurred the magnetic anomaly lineation. The comparison of S-wave velocities along the northern margin of the SCS shows that the west section is different from the east section, and the northwestern margin has a non-volcanic crust structure. The S-wave structures and P-wave velocity models along the northern margin, Macclesfield and Reed Bank show that the Macclesfield might have a conjugate relationship with the Reed Bank.  相似文献   

6.
Izvestiya, Atmospheric and Oceanic Physics - A microphysical model has been proposed to assess the scavenging of artificial aerosol particles from the atmosphere by raindrops, where the raindrops...  相似文献   

7.
The SOLAS Air-Sea Gas Exchange (SAGE) experiment was conducted in Sub-Antarctic waters off the east coast of the South Island of New Zealand in the late summer of 2004. This mesoscale iron enrichment experiment was unique in that chlorophyll a (chl a) and primary productivity were only 2× OUT stations values toward the end of the experiment and this enhancement was due to increased activity of non-diatomaceous species. In addition, this enhancement in activity appeared to occur without a significant build up of particulate organic carbon. Picoeukaryotes (<2 ??m) were the only members of the phytoplankton assemblage that showed a statistically significant increase, a doubling in biomass. To better understand the controls of phytoplankton growth and biomass, we present results from a series of on-deck perturbation experiments conducted during SAGE. Results suggest that the pico-dominated phytoplankton assemblage was only weakly inhibited by iron. Diatoms with high growth rates comprised a small (<1%) fraction of the phytoplankton assemblage, were likely iron limited, and potentially further limited by silicic acid and therefore did not significantly contribute to bloom dynamics. On deck experiments and comparison of SAGE with other iron addition experiments suggested that neither light availability nor deep mixed layers limited phytoplankton growth. Although no substantial increase in grazing rate or specific phytoplankton growth rate was detected, microzooplankton biomass doubled over SAGE as a result of an increase in cell size. The importance of microzooplankton grazing was highlighted by the fact that they were capable of consuming 15-49% of the total phytoplankton production per day. Removal was highest on eukaryotic picophytoplankton production with a mean value of 72% (29-143%). Patch dilution played an important role during SAGE; the mean patch net algal growth:dilution rate, 1.13 (0.4-2.2) was the lowest reported for a mesoscale iron enrichment experiment. Phytoplankton biomass, estimated by chlorophyll a, only accumulated when phytoplankton growth exceeded grazing and when net algal growth exceeded dilution rate. The SAGE results highlight the function of the smallest phytoplankton size fraction described by the ecumenical Iron Hypothesis. Thus, adding iron to HNLC-low silicic acid regions during certain times of the year may simply transfer more carbon through the microbial food web. A primary implication of this study is that any iron-mediated gain in fixed carbon with this set of environmental conditions has a high probability of being recycled in surface waters.  相似文献   

8.
An analysis of the 234Th method for determining the export flux of particulate organic carbon (PPOC) from the upper ocean using in situ pumps or water bottles shows that the accuracy of the method (the ratio of the experimental value of PPOC divided by the true POC flux, FPOC), defined as the p-ratio, is equal to the mean settling velocity of particulate 234Th divided by that of POC. Therefore, PPOC is equivalent to the true POC flux (FPOC) and the p-ratio is equal to unity if, and only if, POC and particulate 234Th have the same mean sinking velocities. A simple particle settling model is discussed that invokes Stokes’ Law settling velocities, volume:surface area (V:SA) fractionation of C:234Th and two assemblages of particles having different sizes and densities. The model is used to illustrate the ranges of parameter values that conform to values of the p-ratio sufficiently close to unity that the experimentally determined POC flux can be considered to be an accurate representation of the true POC flux.Despite the over-simplification of real systems implicit in the model, the results suggest that p-ratios<1, equivalent to an under-estimate of the POC flux, are representative of single particle settling regimes in which the larger particles dominate the vertical flux. This follows from the assumption that the ratio of C/234Th on particles is governed by the volume to surface area (V:SA) ratio of the particles. This results in a greater proportion of 234Th compared to C being associated with the smaller, more slowly settling particles and, as a result, normalization of the POC flux to the 234Th flux provides an under-estimate of the former quantity. However, when the smaller particle assemblage dominates the vertical flux, as could occur in open ocean regimes having high aeolian inputs of dense, rapidly settling, inorganic particles, then the p-ratio could exceed unity (p-ratio >1) resulting in an over-estimate of the POC flux using the 234Th method. High levels of flocculation associated with phytoplankton blooms in productive regions of the ocean are likely to produce p-ratios approaching unity, because flocs would tend to preserve the V:SA partitioning of the original particle size distribution and thereby minimize differences in the mean settling speeds of POC and particulate 234Th (Waite, A.W., Hill, P.S., 2006. Flocculation, phytoplankton and the accuracy of 234Th-based estimates of the vertical flux of particulate organic carbon in the sea. Marine Chemistry in press). Selective sampling of the large particle fraction using, for example, 53-μm screens can produce a more accurate estimate of the true POC flux, but may not entirely shift the p-ratio to a value of unity.  相似文献   

9.
The results of a calculation of the P-wave (V P ) velocity fields are presented on the basis of the method of the reversible wave and the TAU parameter characterizing the V P /V S ratio of seismic waves from the local volcanic earthquakes that occurred at the northern group of Kamchatka volcanoes in 2005–2007. The 3D velocity cross sections were constructed along the SW-NE-trending volcanic group from the Ploskii Tolbachik volcano in the southwest up to the Shiveluch volcano in the northeast. The change of velocity field in time and depth is found. The problems of relating these changes to volcanic activity is reviewed.  相似文献   

10.
We calculate the microphysical characteristics of stratospheric aerosol from lidar-sensing data at wavelengths of 355 and 532 nm using a priori information about the aerosol spectra obtained from balloon and aircraft measurement data. We analyze the mode structure of the spectra and its coupling with the integral microphysical characteristics of aerosol. For most implementations, it was shown that two aerosol modes (of background and volcanic natures) make commensurate contributions to integral aerosol characteristics, which makes it difficult to use the traditional method of model estimates. It is more efficient to use an optical model of a statistical character that is based on approximation dependences between the required integral aerosol characteristics and lidar-measured optical characteristics. We found that the area, volume, and effective size of particles and the lidar ratio at a wavelength of 355 nm correlated with the absolute values of backscattering coefficients at wavelengths of 355 or 532 nm and the lidar ratio at the wavelength of 532 nm correlated with the ratio of backscattering coefficients at these wavelengths. We estimate the error in the determination of integral characteristics of aerosol using the model developed. The model efficiency is demonstrated on real data of stratospheric aerosol lidar sensing.  相似文献   

11.
The influence of the aerosol component on the total transmission of sounding IR radiation is analyzed. The emissions of both industrial and natural origins into the atmosphere were regarded as the medium. It is noted that, in studying the radiative transport through gas-aerosol mixtures, it is necessary to take into account both molecular absorption and scattering from aerosol particles. It is shown that there are certain boundary values of the microphysical parameters of aerosol where it is sufficient to take into account only one of the above-mentioned factors of radiation extinction. The quantitative values of the parameters of an aerosol medium, on the basis of which the solution of the transport equation can be significantly simplified, are given.  相似文献   

12.
The distribution functions of atmospheric aerosol obtained on the basis of lidar sounding and photometric measurements over marine water areas in continental and transition zones are analyzed. Changes in the microphysical parameters of the distribution function in the continent-ocean transition zone with height are considered on the basis of data taken from three-frequency lidar sounding. Specific features of changes in the particle size distribution with height during intense dust storms and records of volcanogenic aerosol in the tropopause region in the summer of 2008 are described.  相似文献   

13.
The microphysical characteristics of aerosol were measured in the atmospheric surface layer simultaneously over the center of Moscow and its vicinity (Zvenigorod Scientific Station, Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences) from June 15 to June 30, 2009, in order to compare the mass concentrations, particle-size distribution functions, and elemental compositions of aerosol over the megapolis and the background zone. During the fire peak of 2010, on August 8, aerosol samples were taken in the center of Moscow and their chemical composition was determined. Comparing results obtained from the simultaneous measurements of the concentrations of aerosol and its elemental composition made it possible to determine their interdiurnal variability, which suggests that the features of time variations are of a regional character and they are determined mainly by the dynamics of the synoptical processes of air-mass exchange. The chemical composition of obtained samples was determined using the method of atomic absorption spectrometry. The measurement results obtained in June 2009 revealed an increase in the content of anthropogenic elements in the atmosphere over Moscow when compared to their content in the atmosphere over the background zone. In Moscow, during the summer fires of 2010, the concentration of sulfur exceeded its concentration in June 2009 by an order of magnitude, and the concentrations of Na, Mg, Al, Si, K, Ca, and Fe increased several times. The mean mass concentration of aerosol amounted to 917 μg/m3 in August 2010 and 50–70 μg/m3 in June 2009.  相似文献   

14.
The reliability of the known models of a height profile of the wind speed V(h) in the atmospheric boundary layer (ABL) and near-surface layer (NSL) is analyzed using the data of long-term ABL measurements accumulated in Russia in the state network of meteorological and aerological stations and the data of multilevel measurements at mast wind-measuring complexes. A new multilayer semiempirical model of V(h) is proposed which is based on aerodynamic and physical representations of the ABL vertical structure and relies on the hypothesis that wind-speed profiles providing the minimum wind friction on the ground and satisfying the conditions of profile smoothness are feasible in the ABL. This model ensures the best agreement with the data of meteorological, aerological, and mast wind measurements.  相似文献   

15.
Based on mathematical simulation, quantitative estimates of the effect that coarse dust particles have on the accuracy of retrieving the optical characteristics of aerosol have been obtained from the results of ground-based measurements of the spectral fluxes of both direct and scattered solar radiations. The results of verifying a retrieval algorithm (used at the AERONET ground-based network) based on special test models showed that the aerosol characteristics retrieved with this algorithm are unsuitable for calculating integral solar fluxes and for simulating space spectrometric IR measurements when the concentration of dust particles in the atmosphere exceeds their concentration in the well-known CONT model of continental aerosol by a factor of two or more.  相似文献   

16.
Settling particles and surface sediments collected from the western region of the Sea of Okhotsk were analyzed for total organic carbon (TOC), long-chain n-alkanes and their stable carbon isotope ratio (δ13C) to investigate sources and transport of total and terrestrial organic matter in the western region of the sea. The δ13C measurements of TOC in time-series sediment traps indicate lateral transport of resuspended organic matter from the northwestern continental shelf to the area off Sakhalin via the dense shelf water (DSW) flow at intermediate depth. The n-alkanes in the surface sediments showed strong odd carbon number predominance with relatively lighter δ13C values (from −33‰ to −30‰). They fall within the typical values of C3-angiosperms, which is the main vegetation in east Russia, including the Amur River basin. On the other hand, the molecular distributions and δ13C values of n-alkanes in the settling particles clearly showed two different sources: terrestrial plant and petroleum in the Sea of Okhotsk. We reconstructed seasonal change in the fluxes of terrestrial n-alkanes in settling particles using the mixing model proposed by Lichtfouse and Eglinton [1995. 13C and 14C evidence of a soil by fossil fuel and reconstruction of the composition of the pollutant. Organic Geochemistry 23, 969–973]. Results of the terrestrial n-alkane fluxes indicate that there are two transport pathways of terrestrial plant n-alkanes to sediments off Sakhalin, the Sea of Okhotsk. One is lateral transport of resuspended particles with lithogenic material from the northwestern continental shelf by the DSW flow. Another is the vertical transport of terrestrial plant n-alkanes, which is independent of transport of lithogenic material. The latter may include dry/wet deposition of aerosol particles derived from terrestrial higher plants possibly associated with forest fires in Siberia.  相似文献   

17.
This paper deals with a laboratory investigation on measuring suspended sediment volume and mass concentration (SSC) and particle size distribution (PSD) by a portable submersible laser diffractometer (LISST-100X) focusing on effects of particle shape and inversion modes on the results. Experiments were carried out in a mixing tank using suspensions of glass beads, fine quartz sand, feldspar and mica powder particles of spherical, rounded, angular and flaky shapes respectively, at various SSCs. SSCs and PSDs measured by LISST were compared to SSCs from gravimetric analysis and to PSDs obtained from image analysis of dry particles and from a non-portable laser diffractometer. Experiments using spherical and rounded particles showed that LISST with the corresponding inversion modes, i.e. spherical and ‘random shaped’, provides PSD and SSC values similar to reference methods. For angular and flaky particles, however, SSCs were found to be overestimated by factors of 1.5 and 8 respectively. Measurements in a mixture of 70% feldspar and 30% mica powders showed that the SSC overestimation factor for mixed particle-type suspensions can be predicted as the weighted sum of the SSC factors of the components and their mixing ratio. For known highly non-spherical particle types, LISST SSCs can be corrected by a gravimetrically determined or predicted overestimation factor. Moreover, correction of overestimated contributions of lower size bins, the range of measureable SSC and time averaging of LISST measurements are addressed. Further investigations are necessary to assess effects of non-spherical particles and mixtures of various particle types on LISST SSC and PSD estimates.  相似文献   

18.
Monitoring data on the ion composition of aerosols and gas admixtures in the background and polluted atmosphere of the Lake Baikal region are presented. The ion composition and morphology of aerosols are affected by heterogeneous chemical reactions and variations in relative humidity. Two types of aerosol particles are revealed over this region. The fraction of solid particles recorded in most episodes includes primarily carbonates of alkaline and alkaline-earth metals. With increased atmospheric humidity, these particles are engaged in heterogeneous chemical reactions with gas-phase NH3 and H2SO4, proceeding through the phase of watering. As a result, the composition of these aerosols is changed, and a fraction of aqueous H2O/H2SO4/(NH4)2SO4 aerosol particles of a different composition is formed. On the basis of a physical and chemical analysis of monitoring data on the aerosol composition and concentrations of gas admixtures, the average aerosol-size distribution of different types is estimated. For the first time, the mean acidity of aqueous aerosol particles is estimated.  相似文献   

19.
Gas hydrate has been recognized as a potential energy resource in South China Sea (SCS). Understanding the acoustic response of gas hydrate formation in the SCS sediments is essential for regional gas hydrate investigation and quantification. The sediments were obtained from gravity core sampling at E 115°12.52363′ N 19°48.40299′. Gas hydrate was formed within a “gas + water-saturated SCS sediments” system. Combination of a new bender element technique and coated time domain reflectometry (TDR) was carried out to study the acoustic response of hydrate occurrence in SCS sediments. The results show the acoustic signal becomes weak when hydrate saturation (Sh) is lower than 14%. The acoustic velocities (Vp, Vs) of the sediments increase with Sh during hydrate formation, and Vs increases relatively faster when Sh is higher than 14%. These results indicate that tiny hydrate particles may firstly float in the pore fluid, which causes a significant acoustic attenuation, but has little influence on shear modulus. As time lapses and Sh approaches 14%, numerous particles coalesce together and contact with sediment particles. As a result, Vs has a sharp increase when hydrate saturation exceeds 14%. Several velocity models were validated with the experimental data, which suggests a combination of the BGTL (Biot–Gassmann Theory modified by Lee) model and the Weighted Equation is suitable to estimate Sh in SCS.  相似文献   

20.
为准确模拟台风路径和强度,采用WRF模式比较不同微物理过程和积云对流过程参数化方案对台风路径和强度模拟的影响,并基于集合预报方法考虑对台风预报系统误差进行优化。选用4种微物理过程方案和3种积云对流参数化方案,针对1213号台风“启德”进行模拟,结果表明不同的参数化方案对台风路径和强度的预报结果有明显影响,积云对流过程参数化方案相对于微物理过程参数化方案更加敏感。基于不同参数化方案扰动成员的集合平均预报方法,对于台风路径和强度的模拟误差均有明显改善,台风路径误差随时间增幅较小,其结果优于全部12个单方案试验的模拟结果;从台风强度方面来看,基于集合预报方法模拟得到的台风强度变化趋势与实况结果一致,且误差较小,优于大多数试验方案。结果表明:采用不同微物理过程和积云对流过程参数化方案的组合构建的集合预报模型,对于台风路径和强度的模拟均有一定程度改善,减小了采用不同参数化方案产生的路径不确定性,使其在台风“启德”的路径模拟上与实况更为接近,可为提升台风预报能力提供科学参考。  相似文献   

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