The Upper Stratospheric Ozone Budget: An Update of Calculations Based on HALOE Data

On the basis of data obtained by the Halogen Occultation Experiment (HALOE) on the Upper Atmosphere Research Satellite (UARS) box model calculations are performed to investigate the ozone budget in the upper stratosphere. The HALOE data comprise measurements of major source gases and key chemical species involved in the ozone destruction cycles. In comparison to earlier calculations using version 17 of the HALOE data, the calculated ozone destruction rate increases when the updated data version 18 is used. However, as with the previous study using version 17 of the HALOE data, no evidence for a significant model ozone deficit is found.     

运用LANDSAT ETM+和ASTER数据进行岩性分类

本文评价了运用ASTER和LANDSAT ETM+数据进行岩性制图的性能。分别利用ASTER数据不同波段区图像及其组合,以及ETM+数据进行岩性分类,并探讨了将ASTER和ETM+数据叠加在一起进行了岩性分类; 利用现有地质图对所有分类结果进行了定量评价。结果表明,ASTER数据不同波段的岩性识别能力不同,并且较ETM+数据能更准确地识别岩性。更重要的是,把ASTER与ETM+数据结合在一起进行岩性分类,可获得比用任一数据单独分类更高的分类精度,表明二者的光谱特征具有一定的互补性。     

Development and Intercomparison of Condensed Isoprene Oxidation Mechanisms for Global Atmospheric Modeling

A new condensed isoprene oxidation mechanism forglobal atmospheric modeling (MIM) was derived from ahighly detailed master chemical mechanism (MCM). In abox model intercomparison covering a wide range ofboundary layer conditions the MIM was compared withthe MCM and with five other condensed mechanisms, someof which have already been used in global modelingstudies of nonmethane hydrocarbon chemistry. Theresults of MCM and MIM were generally in goodagreement, but the other tested mechanisms exhibitedsubstantial differences relative to the MCM as well asrelative to each other. Different formation yields,reactivities and degradation pathways of organicnitrates formed in the course of isoprene oxidationwere identified as a major reason for the deviations.The relevance of the box model results for chemistrytransport models is discussed, and the need for avalidated reference mechanism and for an improvedrepresentation of isoprene chemistry in global modelsis pointed out.     

An Atmospheric Chemistry Interpretation of Mass Scans Obtained from a Proton Transfer Mass Spectrometer Flown over the Tropical Rainforest of Surinam

Data on a variety of organic gases are presented, obtained with a protontransfer mass spectrometer (PTR-MS) operated during the March 1998 LBA/CLAIREairborne measurement campaign, between 60 and 12500 m over the rainforest inSurinam (2° N–5° N, 54° W–57° W). The instrumentcan detect molecules with a proton affinity greater than water, includingalkenes, dialkenes, carbonyls, alcohols, and nitriles. Many such molecules areemitted from the rainforest (e.g., isoprene) or formed from the oxidation ofprimary emissions (e.g., methylvinylketone (MVK) and methacrolein (MACR)).From a comparison with modelled data; the variation with altitude; previouslyreported biogenic emissions and the time and location of the measurement,possible and probable identities for the significant masses encountered in therange 33–140 amu have been deduced.The main observed protonated masses, postulated identities and observedaverage boundary layer mixing ratios over the rainforest were: 33 methanol(1.1 nmol/mol); 42 acetonitrile (190 pmol/mol); 43 multiple possibilities (5.9nmol/mol), 45 acetaldehyde (1.7 nmol/mol), 47 formic acid (not quantified);59 acetone (2.9 nmol/mol), 61 acetic acid (not quantified), 63 dimethylsulphide (DMS) (289 pmol/mol), 69 isoprene (1.7 nmol/mol), 71 MVK + MACR (1.3nmol/mol), 73 methyl ethyl ketone (1.8 nmol/mol), 75 hydroxyacetone (606pmol/mol), 83 C₅ isoprene hydroxy carbonylsC₅H₈O₂, methyl furan, and cis 3-hexen-1-ol(732 pmol/mol), 87 C₅ carbonyls and methacrylic acid, 95 possibly2-vinyl furan (656 pmol/mol), 97 unknown (305 pmol/mol), 99 cis hexenal (512pmol/mol) and 101 isoprene C₅ hydroperoxides (575 pmol/mol). Somespecies agreed well with those derived from an isoprene only photochemicalmodel (e.g., mass 71 MVK + MACR) while others did not and were observed athigher than previously reported mixing ratios (e.g., mass 59 acetone, mass 63DMS). Monoterpenes were not detected above the detection limit of 300pmol/mol. Several species postulated are potentially important sources ofHO_x in the free troposphere, e.g., methanol, acetone, methyl ethylketone, methyl vinyl ketone and methacrolein.     

松辽盆地营城组中基性火山岩成岩作用:矿物晶出序列、杏仁体充填和储层效应

利用露头和钻井资料,通过显微镜观测、化学分析和电子探针分析,研究营城组中基性火山岩的矿物晶出系列和杏仁体充填及其储层效应。本区中基性火山岩包括玄武岩、安山岩、玄武安山岩、粗面玄武岩、玄武粗安岩和粗安岩。斑晶矿物的晶出顺序为:橄榄石最早并几乎全部蚀变为蛇纹石、伊丁石和磁铁矿,仅保留橄榄石假象;辉石被斜长石包含或与之交生,说明辉石晶出有的略早于斜长石、有的与之同时。基质呈间隐间粒结构,为比斑晶偏酸性/碱性的板条状微晶长石堆积搭成格架、内充填玻璃质及微晶粒状矿物(橄榄石、辉石和磁铁矿)。基质结晶晚于斑晶,晶出序列为微晶粒状矿物→微晶长石→玻璃质。有单成分和复成分两种杏仁体。单成分者主要见硅质和钙质,具结晶世代性,为后生流体沉淀充填形成,可作为储层变差或非储层的标志。复成分杏仁体是原生火山玻璃固态下水合与蚀变作用的结果:包括蛇纹石/绿泥石-火山玻璃、石英-方解石-皂石/方解石和石英-绿泥石-方解石等组合类型,通常可作为储层改善或有效性增加的标志。中基性火山玻璃蚀变分为四个阶段:新鲜火山玻璃(折光率1.57)→水合火山玻璃(折光率降至1.53)→橙玄玻璃(铁镁质微晶矿物集合体)→新生矿物(石英、方解石、蛇纹石、绿泥石、皂石);由火山玻璃变为新生矿物的体积减小或孔隙增加效应为7%～10%。     

Impact of Non-Methane Hydrocarbons on Tropospheric Chemistry and the Oxidizing Power of the Global Troposphere: 3-Dimensional Modelling Results

The impact of natural and anthropogenicnon-methane hydrocarbons (NMHC) on troposphericchemistry is investigated with the global,three-dimensional chemistry-transport model MOGUNTIA.This meteorologically simplified model allows theinclusion of a rather detailed scheme to describeNMHC oxidation chemistry. Comparing model resultscalculated with and without NMHC oxidation chemistryindicates that NMHC oxidation adds 40–60% to surfacecarbon monoxide (CO) levels over the continents andslightly less over the oceans. Free tropospheric COlevels increase by 30–60%. The overall yield of COfrom the NMHC mixture considered is calculated to beabout 0.4 CO per C atom. Organic nitrate formationduring NMHC oxidation, and their transport anddecomposition affect the global distribution of NO _x and thereby O₃ production. The impact of theshort-lived NMHC extends over the entire tropospheredue to the formation of longer-lived intermediateslike CO, and various carbonyl and carboxyl compounds.NMHC oxidation almost doubles the net photochemicalproduction of O₃ in the troposphere and leads to20–80% higher O₃ concentration inNO _x -rich boundarylayers, with highest increases over and downwind ofthe industrial and biomass burning regions. Anincrease by 20–30% is calculated for the remotemarine atmosphere. At higher altitudes, smaller, butstill significant increases, in O₃ concentrationsbetween 10 and 60% are calculated, maximizing in thetropics. NO from lightning also enhances the netchemical production of O₃ by about 30%, leading to asimilar increase in the global mean OH radicalconcentration. NMHC oxidation decreases the OH radicalconcentrations in the continental boundary layer withlarge NMHC emissions by up to 20–60%. In the marineboundary layer (MBL) OH levels can increase in someregions by 10–20% depending on season and NO _x levels.However, in most of the MBL OH will decrease by10–20% due to the increase in CO levels by NMHCoxidation chemistry. The large decreases especiallyover the continents strongly reduce the markedcontrasts in OHconcentrations between land and oceanwhich are calculated when only the backgroundchemistry is considered. In the middle troposphere, OHconcentrations are reduced by about 15%, although dueto the growth in CO. The overall effect of thesechanges on the tropospheric lifetime of CH₄ is a 15%increase from 6.5 to 7.4 years. Biogenic hydrocarbonsdominate the impact of NMHC on global troposphericchemistry. Convection of hydrocarbon oxidationproducts: hydrogen peroxides and carbonyl compounds,especially acetone, is the main source of HO _x in theupper troposphere. Convective transport and additionof NO from lightning are important for the O₃ budgetin the free troposphere.     

Ground Based Gas Phase Measurements in Surinam during the LBA-Claire 98 Experiment

As part of the LBA-CLAIRE-98 experiment, ground level atmosphericconcentrations of O₃, CO, hydroperoxides and organic acids weremeasured in the rainforest region in Surinam. Measurements of CO andO₃ were also made at a coastal site.The results suggest that a significant consumption of `boundary layer' ozoneoccurs over the forested region of Surinam, with an estimated net ozoneconsumption of about 5% hr^–1 during daytime. Thiswould be mainly explained by a low photochemical production and high drydeposition to the forest vegetation. Compared to other tropical sites, lowerlevels of H₂O₂ were observed at the rainforest site,with an average boundary layer concentration of 0.55± 0.2 nmolmol^–1. Also acetic and formic acids showed relatively lowaverage boundary layer mixing ratios; 1.1± 0.4 nmolmol^–1 and 1.4± 0.5 nmol mol^–1,respectively. Significant correlations were found between both acids andbetween the acids and hydrogen peroxide, suggesting an atmospheric source forthe acids.From the available observations we discuss possible implications of ourmeasurements for the O₃, HO₂, and NO_x budgetsand concentrations in the boundary layer. We conclude that, despite the highsolar irradiation, relatively low levels of O₃,H₂O₂, HCOOH and CH₃COOH are observed in theboundary layer of the rainforest of Surinam, probably due to low levels ofNO_x and high levels of VOCs, which leads to loss of OH andHO₂ radicals. Additionally, high deposition rates of these gasesoccur to the forest vegetation.     

A discussion of the chemistry of some minor constituents in the stratosphere and troposphere

A discussion is given of atmospheric reactions in the H₂O–CH₄–O₂–O₃–NO _x system. In the lower troposphere such reactions may lead to significant production of ozone. Their role in the odd hydrogen balance, especially of the troposphere and lower stratosphere, is discussed. CH₃OH may be an intermediate in the oxidation cycle of methane, especially in the cold stratosphere. Its photodissociation into H₂ and CH₂O may consequently provide an important source for stratospheric H₂. Catalytic photochemical chains of reactions involving NO _x and HO _x may also lead to tropospheric destruction of ozone. Due to lack of knowledge it is not possible at present to evaluate the importance of the before-mentioned reactions.With the aid of model calculations it is indicated that stratospheric ozone is most sensitive to changes in the adopted lower boundary values of N₂O and that an increase in water vapour concentrations in the lower stratosphere will indeed cause some increase in ozone as predicted.Fluctuations in the flux of solar radiation near 190 nm may cause significant variations in stratospheric ozone concentrations.