Swift ultraviolet photometry of the Deep Impact encounter with Comet 9P/Tempel 1     

K.O. Mason  M. Chester  C. Gronwall  S. Hunsberger  S. Koch  P.T. O'Brien  P. Roming  A. Wells  R. Willingale  N. Gehrels 《Icarus》2007,187(1):123-131

We report time-resolved imaging UV photometry of Comet 9P/Tempel 1 during the interval 2005 June 29-2005 July 21, including intensive coverage of the collision with the Deep Impact probe and its immediate aftermath. The nuclear flux of the comet begins to rise within minutes of the collision, and peaks about 3 h after impact. There is no evidence for a prompt flash at the time of impact. The comet exhibits a significant re-brightening about 40 h after the initial outburst, consistent with the rotation period of the comet, with evidence for further periodic re-brightenings on subsequent rotations. Modelling of the brightness profile of the coma as a function of time suggests two distinct velocity systems in the ejecta, at de-projected expansion speeds of 190 and 550 m/s, which we suggest are due to dust and gas, respectively. There is a distinct asymmetry in the slower-moving (dust) component as a function of position angle on the sky. This is confirmed by direct imaging analysis, which reveals an expanding plume of material concentrated in the impact hemisphere. The projected expansion velocity of the leading edge of this plume, measured directly from the imaging data, is 190 m/s, consistent with the velocity of the dust component determined from the photometric analysis. From our data we determine that a total of (1.4±0.2)×¹⁰³² water molecules were ejected in the impact, together with a total scattering area of dust at 300 nm of 190±20 km².  相似文献   

Rethinking the N(H₂)/I(CO) conversion factor     

W. F. Wall 《Monthly notices of the Royal Astronomical Society》2007,379(2):674-688

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Hydrogen adsorption and diffusion on amorphous solid water ice     

A. Al-Halabi  E. F. van Dishoeck † 《Monthly notices of the Royal Astronomical Society》2007,382(4):1648-1656

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Ultraviolet dust attenuation in spiral galaxies: the role of age-dependent extinction and the initial mass function     

P. Panuzzo  G. L. Granato  V. Buat  A. K. Inoue  L. Silva  J. Iglesias-Páramo  A. Bressan 《Monthly notices of the Royal Astronomical Society》2007,375(2):640-648

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伊犁盆地北部山麓黄土粒度端元指示的粉尘堆积过程     

李越  宋友桂  宗秀兰  张治平  程良清 《地理学报》2019,74(1):162-177

中亚干旱区是全球重要的粉尘源区,是全球变化与区域响应研究的关键区域之一。中亚粉尘形成搬运沉积过程一直是全球变化研究的热点科学问题。本文选取位于伊犁盆地北部、北天山南麓不同地形和气候条件下的两处黄土剖面,对其沉积速率最高的层段进行了粒度测试分析,结合聚类分析和粒度分布曲线拟合两种方法,重建了黄土粉尘的堆积过程。伊犁盆地黄土主要由远源和近源物质组成,分别由高空西风和中尺度的区域风搬运而来。高空西风所携带的远源粘粒级矿物颗粒对盆地东部降雨较高地区有一定的贡献,而在盆地西部不容易沉降下来。中尺度区域风所搬运的近源物质组成了黄土沉积物的主体,而近源区沉积物的可用性在黄土的形成过程中扮演着重要角色。另外,非风暴过程中（沙尘暴过后）出现的浮尘在沙尘暴天气频率减少的时期对黄土的发育有重要贡献,而在沙尘暴天气频发的时期,较差的植被覆盖度能够使得已经沉降下来的浮尘组分重新被扬起至大气中。由此建立了一个粉尘堆积的概念模型。认识黄土粉尘的堆积过程对现代沙尘天气的治理和人类生存环境的改善具有重要作用。  相似文献   

Simulation of the Direct Radiative Effect of Mineral Dust and Sea Salt Aerosols in a Doubled Carbon Dioxide Climate          下载免费PDF全文

YUE Xu  LIAO Hong  TANG Jin-Ping 《大气和海洋科学快报》2013,6(5):343-348

The authors examine the equilibrium climatic response to the direct radiative effect(DRE)of mineral dust and sea salt aerosols in a doubled-CO2climate with two-way coupling of aerosol-climate interactions.In response to the drier and windier conditions,dust emissions increase by 26%in the Sahara Desert and by 18%on the global scale relative to present day.Sea salt emissions increase in high latitudes(60°)but decrease in middle latitudes(30°–60°)of both hemispheres due to the poleward shift of westerlies,leading to a 3%decrease in global emissions.The burdens of dust and sea salt increase by 31%and 7%respectively,because reductions in rainfall over the tropical oceans increase the lifetime of particles in the warmer climate.The higher aerosol loading in the doubled-CO2climate reinforces aerosol DRE by0.2 W m 2,leading to an additional cooling of 0.1°C at the surface compared with the climatic effects of aerosols in present day.The additional cooling from changes in natural aerosols compensates for up to 15%of the regional warming induced by doubled CO2.  相似文献   

中国利用星载激光雷达开展沙尘和污染研究的综述   总被引：1，自引：0，他引：1       下载免费PDF全文

王天河  孙梦仙  黄建平 《大气科学学报》2020,43(1):144-158

激光雷达作为一种新兴的主动遥感探测工具,被广泛应用于大气遥感、环境监测等领域。星载激光雷达由于其较广的探测范围、较高的时空分辨率、可获得连续的廓线数据等优势,已经成为全球及区域气溶胶和云特性观测研究的强有力工具。本文总结了自2006年CALIPSO卫星发射以来,中国科学家在利用其开展沙尘气溶胶及污染研究方面的工作,重点阐述了沙尘气溶胶的时空分布、远距离传输、分类识别、光学特性、沙尘释放、辐射与气候效应,以及灰霾和烟尘特性等方面的最新研究成果。对以上研究成果的梳理,有助于深入理解中国在利用星载激光雷达开展沙尘与污染研究的水平,也为未来开拓中国自主研发星载激光雷达的遥感应用领域奠定了基础。  相似文献   

阿拉善高原干涸湖床沉积物与华北地区沙尘暴   总被引：16，自引：3，他引：13  

岳乐平  杨利荣  李智佩  王珉  张维吉  聂浩刚  张睿  武力超 《第四纪研究》2004,24(3):311-317

文章通过内蒙古阿拉善高原古居延泽干涸湖床沉积物、周缘活动沙丘、沙质草原地表土壤及古代弃荒土地的粒度组成分析,论述干涸湖床沉积物对沙尘天气的影响。古居延泽湖床沉积粒度分析结果表明,干涸湖床的地表湖相沉积物粒径小于10μm的颗粒占64%以上,可以在一般风暴条件下在大气中搬运几千公里,这意味着西北地区干涸湖床产生的粉尘在风暴作用下可以横扫整个东亚北部地区。中国西北地区冬、春季多西北风造成沙尘暴或扬沙天气,西部沙漠、沙地或沙质草场遭遇强风时沙尘被席卷进气流,但其中粗砂粒扬起的高度、搬运的距离有限,当风力稍稍减弱,粗颗粒砂粒沉降,而粉尘继续悬浮运移。当强风途径下一个沙区时新的沙尘加入,沙尘暴呈“接力方式”继续向东南部移动。  相似文献   

A global satellite view of the seasonal distribution of mineral dust and its correlation with atmospheric circulation     

《Dynamics of Atmospheres and Oceans》2014

Aerosols make a considerable contribution to the climate system through their radiative and cloud condensation nuclei effects, which underlines the need for understanding the origin of aerosols and their transport pathways. Seasonal distribution of mineral dust around the globe and its correlation with atmospheric circulation is investigated using satellite data, and meteorological data from ECMWF. The most important sources of dust are located in North Africa, the Middle East and Southwest Asia with an observed summer maximum, and East Asia with a spring peak. Maximum dust activity over North Africa and the Middle East in summer is attributed to dry convection associated with the summertime low-pressure system, while unstable weather and dry conditions are responsible for the spring peak in dust emission in East Asia. Intercontinental transport of mineral dust by atmospheric circulation has been observed, including trans-Atlantic transport of North African dust, trans-Pacific transport of Asian dust, and transport of dust from the Middle East across the Indian Ocean. The extent of African dust over the Atlantic Ocean and its latitudinal variation with season is related to the large-scale atmospheric circulation, including seasonal changes in the position of the intertropical convergence zone (ITCZ) and variation of wind patterns. North African aerosols extend over longer distances across the North Atlantic in summer because of greater dust emission, an intensified easterly low level jet (LLJ) and strengthening of the Azores-Bermuda anticyclonic circulation. Transport of East Asian aerosol is facilitated by the existence of a LLJ that extends from East Asia to the west coast of North America.  相似文献   

2014年4月大气环流和天气分析   总被引：2，自引：1，他引：1  

樊利强  张涛  孙瑾 《气象》2014,40(7):898-904

2014年4月大气环流特征为,北半球极涡呈单极型分布,中心位于喀拉海北端附近;亚洲大陆东部高压脊强度偏强,导致4月我国气温较常年同期(11.0℃)偏高1.1℃,为1961年同期以来第五高值。东亚大槽强度和位置、南支系统和西北太平洋副热带高压接近常年平均状况。4月全国平均降水量为43.7 mm,比常年同期略偏少。月内,江南南部和华南等地出现短时强降水、雷雨大风等强对流天气;北方地区出现多次沙尘天气过程;此外,部分站次出现极端高温、极端降温事件。  相似文献