基于船载太阳光度计观测的黄海海面亚洲沙尘柱总量和干沉降通量个例研究   总被引：1，自引：0，他引：1       下载免费PDF全文

YANG Dong-Xu  LIU Yi  CHEN Wen-Zhong 《大气和海洋科学快报》2010,3(2):64-69

The total dust column and the dry deposition flux were calculated based on the optical properties that were measured by a shipboard sun photometer POM-01 MKⅡ in a cloud-free and nonfrontal dust condition on 24 April 2006. The total dust column was calculated by using an integration method of the particle size distribution; the mean value was 1.42±0.30 g m-2. A linear correlation between the total dust column and the aerosol optical depth (AOD) with a linear factor of 2.7 g m-2 over the Sahara was applied to calculate the total dust column in this study; the results were lower than these calculated by the integration method. A reasonable factor of 3.2 g m-2 was achieved by minimizing the standard deviation (SD) of the two methods. The two layers model, which includes the deposition processes of turbulent transfer, Brownian diffusion, impaction and gravitational settling over the sea’s surface, was used to calculate the dry deposition flux; the mean value was 5.05±2.49 μg m-2 s-1. A correlation among the total dust column, dry deposition flux, AOD, and effective radius was discussed. The correlation between the total dust column and the AOD was better than that between the total dust column and the effective radius; however, the correlation between the dry deposition flux and the effective radius was better than that between the dry deposition flux and the AOD.  相似文献   

The Northern Path of Asian Dust Transport from the Gobi Desert to North America   总被引：1，自引：0，他引：1       下载免费PDF全文

CHEN Ke-Yi 《大气和海洋科学快报》2010,3(3):155-159

The aerosol index (AI) of the Total Ozone Mapping Spectrometer (TOMS) satellite data (1979 2001) was analyzed to reveal the climatological long-distance path of dust transport from Asia to North America. The AI in the west coast of the United States is highly correlated with that in the Gobi desert. Additionally, from the TOMS satellite images, it can be seen that very strong plumes advect from Asia to the west coast of North America in typical dust storm cases. When applying the sourcereceptor relationship to detect the northern dust transport path between the Gobi source region and the west coast of the United States receptor region, it is evident that the dust plume can be transported northward beyond 60°N from its source region and that it takes 5 to 6 days to reach the west coast of the United States. The cross correlation technique shown in this work is a useful tool that can be applied in other regions to give useful insights into relationships between major dust sources and downwind receptor locations by using remotely sensed dust observations.  相似文献   

沙尘天气产生的气候背景及物理机制     

邱明宇  王尚荣  王岩宁 《气象研究与应用》2005,26(3):30-32

沙尘天气发生频率、强度与大风、干旱过程、异常大气环流的气候背景以及人为因素有关。它的物理过程是地表上升气流把疏松地表尘粒带入空中,并且在一定层结条件下形成和加强的。利用1958~2000年内蒙古中西部70个测站的沙尘暴观测资料,对沙尘暴的地理分布、时间分布特征进行了统计分析。结果表明:内蒙古中西部有三个强沙尘暴多发中心,沙尘暴年代际变化和年际变化较明显,且沙尘暴集中出现在春季的3~5月份。  相似文献   

Seasonal variations in Dustfall and its iron content over North China   总被引：2，自引：0，他引：2  

李晋昌  董治宝  王训明  钱广强  罗万银 《大气科学进展》2008,25(3):467-473

Extensive dustfall collections were carried out from April 2001 to May 2002 in North China. The highest level of dustfall occurred in the Gobi deserts and at the margins of sandy deserts in the region. The iron content in dustfall in North China varied from 0.6% to 6.0% and there was significant seasonal variation, which indicates the dust sources differed during the year. Although the iron content in dustfall in North China is higher in the Loess Plateau and arable lands and lower in the Gobi and sandy deserts, the total iron deposition was higher in the Gobi desert regions. If the fine particles （PM10） in dustfall in North China are the major contributors of dust transport to eastern China and western parts of the North Pacific, then the annual deposition rates of iron may have been underestimated in previous studies. Our analysis indicates that iron deposition may reach 1.38 × 10^3 to 2.43 × 10^3 kg km^-2 and that most iron deposition occurs in spring and summer. If the more-coarse fractions （PM50） are considered, deposition rates may reach 2.75 × 10^3 and 6.80 × 10^3 kg km^-2, which would represent a large source of iron deposition in eastern China and the western North Pacific.  相似文献   

2010年春季北京地区强沙尘暴过程的微气象学特征   总被引：3，自引：1，他引：2  

李晓岚  张宏升 《气候与环境研究》2012,17(4):400-408

利用北京大学校园地区PM10质量浓度观测资料、中国科学院大气物理研究所325m气象塔气象要素梯度和湍流观测资料,分析了北京地区2010年3月20～22日两次强沙尘暴过程微气象学要素和沙尘参量的时空演变以及湍流输送特征,为理解北京地区强沙尘暴天气沙尘输送规律和微气象学特征提供参考。结果表明:3月20～22日强沙尘暴过程前后不同高度温度先升后降,气压和相对湿度则相反。强沙尘暴来临时,高层风速先迅速增大,低层风速增加略有滞后,风切变明显加强,PM10浓度最大值和风速极大值出现时间较吻合。强沙尘暴过境时,不同高度向下的湍流动量输送、向上的湍流热量输送和湍流动能明显加强。与3月21日非沙尘暴日相比,强沙尘暴过程湍流动量通量增加,有利于沙尘粒子的水平和垂直输送过程;由于冷锋过境,水平热通量增大;垂直热通量因白天温度垂直梯度减小而减小,夜间因逆温层被破坏而增加;水平湍流动能对湍流动能占主要贡献,垂直湍流动能仅占水平湍流动能的10%～25%。  相似文献   

Optical afterglows of gamma-ray bursts: a bimodal distribution?     

Marco Nardini  Gabriele Ghisellini  Giancarlo Ghirlanda 《Monthly notices of the Royal Astronomical Society》2008,383(3):1049-1057

The luminosities of the optical afterglows of gamma-ray bursts, 12 h (rest-frame time) after the trigger, show a surprising clustering, with a minority of events being at a significantly smaller luminosity. If real, this dichotomy would be a crucial clue to understand the nature of optically dark afterglows, i.e. bursts that are detected in the X-ray band, but not in the optical. We investigate this issue by studying bursts of the pre- Swift era, both detected and undetected in the optical. The limiting magnitudes of the undetected ones are used to construct the probability that a generic burst is observed down to a given magnitude limit. Then, by simulating a large number of bursts with pre-assigned characteristics, we can compare the properties of the observed optical luminosity distribution with the simulated one. Our results suggest that the hints of bimodality present in the observed distribution reflect a real bimodality: either the optical luminosity distribution of bursts is intrinsically bimodal, or there exists a population of bursts with a quite significant grey absorption, i.e. wavelength-independent extinction. This population of intrinsically weak or grey-absorbed events can be associated with dark bursts.  相似文献   

Galaxy evolution in the infrared: comparison of a hierarchical galaxy formation model with Spitzer data     

C. G. Lacey  C. M. Baugh  C. S. Frenk  L. Silva  G. L. Granato  A. Bressan 《Monthly notices of the Royal Astronomical Society》2008,385(3):1155-1178

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Physical, Chemical, and Mineralogical Properties of Comet 81P/Wild 2 Particles Collected by Stardust     

George James Flynn 《Earth, Moon, and Planets》2008,102(1-4):447-459

NASA’s Stardust spacecraft collected dust from the coma of Comet 81P/Wild 2 by impact into aerogel capture cells or into Al-foils. The first direct, laboratory measurement of the physical, chemical, and mineralogical properties of cometary dust grains ranging from <10⁻¹⁵ to ∼10⁻⁴ g were made on this dust. Deposition of material along the entry tracks in aerogel and the presence of compound craters in the Al-foils both indicate that many of the Wild 2 particles in the size range sampled by Stardust are weakly bound aggregates of a diverse range of minerals. Mineralogical characterization of fragments extracted from tracks indicates that most tracks were dominated by olivine, low-Ca pyroxene, or Fe-sulfides, although one track was dominated by refractory minerals similar to Ca–Al inclusions in primitive meteorites. Minor mineral phases, including Cu–Fe-sulfide, Fe–Zn-sulfide, carbonate and metal oxides, were found along some tracks. The high degree of variability of the element/Fe ratios for S, Ca, Ti, Cr, Mn, Ni, Cu, Zn, and Ga among the 23 tracks from aerogel capture cells analyzed during Stardust Preliminary Examination is consistent with the mineralogical variability. This indicates Wild 2 particles have widely varying compositions at the largest size analyzed (>10 μm). Because Stardust collected particles from several jets, sampling material from different regions of the interior of Wild 2, these particles are expected to be representative of the non-volatile component of the comet over the size range sampled. Thus, the stream of particles associated with Comet Wild 2 contains individual grains of diverse elemental and mineralogical compositions, some rich in Fe and S, some in Mg, and others in Ca and Al. The mean refractory element abundance pattern in the Wild 2 particles that were examined is consistent with the CI meteorite pattern for Mg, Si, Cr, Fe, and Ni to 35%, and for Ca, Ti and Mn to 60%, but S/Si and Fe/Si both show a statistically significant depletion from the CI values and the moderately volatile elements Cu, Zn, Ga are enriched relative to CI. This elemental abundance pattern is similar to that in anhydrous, porous interplanetary dust particles (IDPs), suggesting that, if Wild 2 dust preserves the original composition of the Solar Nebula, the anhydrous, porous IDPs, not the CI meteorites, may best reflect the Solar Nebula abundances. This might be tested by elemental composition measurements on cometary meteors.  相似文献   

The Meteors, Meteoroids and Interplanetary Dust Program of the International Heliophysical Year 2007/9     

Svitlana V. Kolomiyets  Mykola I. Slipchenko 《Earth, Moon, and Planets》2008,102(1-4):305-307

Under the title ‘Meteors, Meteoroids and Interplanetary Dust’, meteor research is included in the program of the International Heliophysical Year 2007/9.We list issues for coordinated meteor research within the framework of this global international program.  相似文献   

Contributions of sandy lands and stony deserts to long-distance dust emission in China and Mongolia during 2000–2006   总被引：2，自引：0，他引：2  

Baolin Zhang  Atsushi Tsunekawa  Mitsuru Tsubo 《Global and Planetary Change》2008,60(3-4):487-504

More than 400 Moderate Resolution Imaging Spectroradiometer (MODIS) images of dust storm events were collected and analyzed, and individual events were tracked back to their origins. Dust tracks were determined from color composite images, brightness temperature difference (BTD) and the NOAA Hybrid Single-Particle Lagrangian Integrated Trajectory model. The results showed that five regions (sandy lands in central Inner Mongolia and the adjacent area of Mongolia; the Gobi Desert in Xinjiang and Gansu provinces, western Inner Mongolia, and the adjacent southwestern area of Mongolia; the Gobi Desert in southern Mongolia and the adjoining area of northern Inner Mongolia; sandy lands and deserts around the middle reaches of the Yellow River; and the area rimming the Taklimakan Desert) were the main contributors to long-lived mineral dusts in northern China and Mongolia. Of these dust production areas, sandy lands and stony deserts, rather than the sandy deserts of Inner Mongolia and Mongolia, were found to be the dominant dust sources, accounting for more than 75% of regional dust emission events. Dust events in the Taklimakan Desert were often local phenomena, although they could also be transported eastward if they were uplifted high enough to escape the enclosing topographic highs. Dust sources in northwestern China are mainly alluvial fans and dry lake and river beds. Success in identifying the sources and trajectories of Asian dust storms would guide future ground-based research and steppe degradation countermeasures and help reduce the uncertainties in modern modeling of Asian dust.  相似文献