The Impact of Precipitation Scavenging on the Transport of Trace Gases: A 3-Dimensional Model Sensitivity Study   总被引：1，自引：0，他引：1  

Paul J. Crutzen  Mark G. Lawrence 《Journal of Atmospheric Chemistry》2000,37(1):81-112

With the global Chemistry-Transport model MATCHsensitivity simulations were performed to determinethe degree to which especially upward transport ofgases from the earth's surface is limited byconvective and large-scale precipitation scavenging.When only dissolution of species in the liquid phaseis taken into account, mixing ratio reductions in themiddle and upper troposphere by 10% arecalculated for gases with a Henry's Law constant H of10³ mol/l/atm. The removal increases to 50% forH = 10⁴ mol/l/atm, and to 90% for H =10⁵ mol/l/atm. We also consider scavenging by theice phase, which is generally much less efficient thanby the aqueous phase. In fact, rejection of gases fromfreezing water droplets may be a source of trace gasat higher altitudes.H₂O₂ and the strong acids (H₂SO₄,HNO₃, HCl, HBr, HI) have such large solubilitiesthat they become largely removed by precipitation.When significant concentrations of these gases andsulfate aerosol exist above the liquid water domain ofthe atmosphere, they have likely been produced thereor at higher altitudes, although some could have comefrom trace gas rejection from ice particles or fromevaporating hydrometeors. Several other gases areaffected by precipitation, but not strongly enough toprevent fractional transfer to the middle and uppertroposphere: e.g., HNO₄, HNO₂ at pH 5,CH₂O, the organic acids at pH 6,CH₃SOCH₃, HOCl, HOBr, and HOI. NH₃ islargely removed by liquid phase scavenging at pH 7 and SO₂ atpH 7. At pH less thanabout 6, upward transport of SO₂ should largelydepend on the efficiency of oxidation processes in thewater droplets by O₃ and H₂O₂.Most gases have solubilities which are too low forsignificant precipitation scavenging and aqueous phaseoxidation to occur. This holds, e.g., for O₃, CO,the hydrocarbons, NO, NO₂, HCN, CH₃CN,CH₃SCH₃, CH₃O₂H, CH₃CHOandhigher aldehydes, CH₃OH and higher alcohols,peroxyacetylnitrate (PAN), CH₃COCH₃ andother ketones (note that some of these are not listedin Table I because their solubilities are below 10mol/l/atm). Especially for the short-lived gases,transfer from the boundary layer to the middle andupper troposphere is actually promoted by the enhancedupward transport that occurs in clouds.  相似文献   

地表温度对太阳常数变化响应的数值试验研究   总被引：3，自引：0，他引：3  

张虹娇  朱伟军 《南京气象学院学报》2005,28(5):626-631

通过改变太阳常数，利用NCAR气候系统模式CSM1．4就地表温度对强外辐射强迫变化的响应及性质进行了研究。结果表明：虽然局地的增温幅度变化很大，但各试验的全球增温分布特征非常相似，并从一定程度上反映了全球增暖典型试验中的增温分布特点，即陆地比海洋增暖幅度更强，高纬度地区比低纬度地区增暖幅度更强，这一特点在太阳常数增加较大的试验中表现尤为明显。气候系统响应的性质在太阳常数分别增加2，5％、10％和15％与增加25％之间其响应方式有所改变，即气候系统对较小太阳常数变化的响应是线性的，而对较大太阳常数变化的响应则很可能是非线性的。  相似文献   

Future Projections of Precipitation Characteristics in East Asia Simulated by the MRI CGCM2   总被引：7，自引：0，他引：7  

Akio KITOH  Masahiro HOSAKA  Yukimasa ADACHI  Kenji KAMIGUCHI 《大气科学进展》2005,22(4):467-478

Projected changes in precipitation characteristics around the mid-21st century and end-of-the-century are analyzed using the daily precipitation output of the 3-member ensemble Meteorological Research Institute global ocean-atmosphere coupled general circulation model (MRI-CGCM2) simulations under the Special Report on Emissions Scenarios (SRES) A2 and B2 scenarios. It is found that both the frequency and intensity increase in about 40% of the globe, while both the frequency and intensity decrease in about 20% of the globe. These numbers differ only a few percent from decade to decade of the 21st century and between the A2 and B2 scenarios. Over the rest of the globe (about one third), the precipitation frequency decreases but its intensity increases, suggesting a shift of precipitation distribution toward more intense events by global warming. South China is such a region where the summertime wet-day frequency decreases but the precipitation intensity increases. This is related to increased atmospheric moisture content due to global warming and an intensified and more westwardly extended North Pacific subtropical anticyclone, which may be related with an E1 Nin^-o-like mean sea surface temperature change. On the other hand, a decrease in summer precipitation is noted in North China, thus augmenting a south-to-north precipitation contrast more in the future.  相似文献   

Towards global earth tomography using the spectral element method: a technique based on source stacking     

Y. Capdeville  Y. Gung  B. Romanowicz 《Geophysical Journal International》2005,162(2):541-554

  相似文献   

近景摄影测量限差的特殊性   总被引：1，自引：0，他引：1  

冯文灏 《武汉大学学报(信息科学版)》2000,25(6):542-547

在近景摄影测量的全过程中 ,包括摄影机检校、实地控制测量以及摄影测量处理各阶段 ,其操作限差存在特殊的理论 ,系统说明这些理论并详尽推导了一系列相应的关系式。  相似文献   

非规则采矿工作面积分区间确定方法   总被引：2，自引：0，他引：2  

李永树  韩丽萍 《测绘学报》2000,29(2):166-171

针对工作面形状多种多样的特点,本文采用二次曲线描述工作面水平投影边界,并且利用分段积分的方法处理更加复杂的工作面形状,合理地解决了非规则采矿工作面积分区间的划分问题;同时,给出了工作面形状系数的计算公式,整个计算过程利用计算机技术实现自动解算,避免了对任意曲边形工作面采用矩形分割的近似处理方法,提高了地面沉陷预计精度。最后,用实例说明了本文提供的对非规则采矿工作面的处理方法比现行处理方法具有更高的  相似文献   

近百余年北京气候变化的小波特征   总被引：60，自引：0，他引：60  

谢庄  曹鸿兴  李慧  张雷刚  陈道东 《气象学报》2000,58(3):362-369

文中对1870～1994年北京年、季平均气温,以及1841～1994年北京年、季降水序列进行了分析和小波变换计算,对所得结果进行了宏观分析。结果表明,温度增暖期和低温期与小波波幅中心间的周期增长、波幅加强相关联。降水距平绝对值越大,相应的小波周期越长和波幅越强。即小波分析在气候变化研究中显现了年与年之间、波长与波长之间的波幅变化形态与特征,从而为了解气温和降水随着年代的变化展示了一个视窗。  相似文献   

Adding Local Accuracy to Direct Sequential Simulation   总被引：3，自引：0，他引：3  

Jef Caers 《Mathematical Geology》2000,32(7):815-850

Geostatistical simulations are globally accurate in the sense that they reproduce global statistics such as variograms and histograms. Kriging is locally accurate in the minimum local error variance sense. Building on the concept of direct sequential simulation, we propose a fast simulation method that can share these opposing objectives. It is shown that the multiple-point entropy of the resulting simulation is related to the univariate entropy of the local conditional distributions used to draw simulated values. Adding local accuracy to conditional simulations does not detract much from variogram reproduction and can be used to increase multiple-point entropy. The methods developed are illustrated using a case study.  相似文献   

Local music policies within a global music industry: cultural quarters in Manchester and Sheffield   总被引：4，自引：0，他引：4  

Adam Brown  Justin O'Connor  Sara Cohen 《Geoforum》2000,31(4):437-451

This paper will explore the relationship between the local and the global in the music industry through the lens of place-based cultural policies.The first part of the paper will outline current debates around the complex interaction of the local and the global in culture in general and the popular music industry in particular. Alongside the continuous expansion of globalisation has been a reassertion of ‘place', of ‘locality'. Whilst this has been investigated to some extent at the level of local music scenes it has never been fully addressed in terms of music industry policy as part of an economic development strategy. Yet it is here that the particular values of ‘place' are asserted in the face of some ‘global' music industry with a view to developing (or at least retaining some of the benefits of) a local music industry.Whilst situating itself within these debates about the relationship of local and global musical production and consumption, the paper explores the different strategies of two northern English cities and their attempts to promote culture, and music, within each cities ‘cultural quarter': Sheffield's Cultural Industries Quarter and Manchester's Northern Quarter. The paper analyses the role and appropriateness of local authority policy intervention, the importance of ‘soft' networks within local music scenes and the different ways in which authorities in each example have tried to overcome dichotomies of art and industry, cultural and economy.  相似文献   

掺气减蚀设施体型优化研究   总被引：14，自引：0，他引：14       下载免费PDF全文

杨永森  杨永全 《水科学进展》2000,11(2):144-147

建立了计算掺气设施水力特性的数学模型和挑坎掺气槽坎高的优化目标函数,对原型掺气槽的体型优化进行了研究.研究表明,掺气设施的优化坎高主要与来流Fr数有关,来流Fr数愈大,所需坎高愈小;来流Fr数愈小,所需坎高愈大.  相似文献