闪电产生的氮氧化物对青藏高原臭氧低值区的可能影响

为进一步认识闪电放电对夏季青藏高原地区臭氧低值区形成的可能影响,本文利用2005年-2013年星载光学瞬变探测器O TD和闪电成像仪LIS资料合成的LIS/OTD2.3版本再分析格点资料与荷兰皇家气象研究所TIMES提供的由OMI卫星得到的对流层NO_2垂直浓度月均值资料(NO2VCD)以及臭氧总浓度柱月均值资料(TOC)分析了中国地区臭氧(O_3)的空间分布特征,确定了青藏高原臭氧低值区范围。分析了所选范围内夏季闪电、NO_2VCD的空间分布以及年际变化关系。基于上述分析结果,进一步计算分析了NO_2VCD与O_3逐年夏季间浓度的差值关系。结果表明:青藏高原臭氧低值区范围为25°-43°N、72°-107°E。闪电产生的氮氧化物(LNOX)会明显导致夏季青藏高原臭氧的降低。     

中国对流层NOx垂直柱总量分布特征及其与闪电活动的相关性分析

闪电放电过程发出很强的光辐射,促进了光化学反应的进行,加快了NO_x向上的垂直输送,造成对流层上部NO_x的增加。闪电生成氮氧化物(LNO_x)是对流层上部NO_x(NO和NO_2)的主要来源,影响了对流层和平流层大气成分的垂直分布。本文利用2005—2013年TRMM卫星LIS传感器闪电密度和Aura卫星OMI传感器对流层NO_2垂直柱总量遥感观测数据,分析了中国地区对流层NO_2柱总量时空分布特征及其与闪电活动的相关性。发现,青藏高原地区对流层NO_2柱总量与闪电密度变化特征一致,表现为夏季高,冬季低,该地区LNO_x估算值约为339mol/次。基于LNO_x估算值分析中国不同地区LNO_x/NO_x百分比分布特征,发现,青藏高原地区春季和夏季LNO_x/NO_x较高,约为20%~60%,秋季和冬季低于20%;与之相比,NO_x排放较为严重的四川盆地、长江三角洲和珠江三角洲等地区普遍低于20%,中国地区LNO_x/NO_x百分比平均值低于10%。由此得出结论,LNO_x是青藏高原地区NO_x的主要排放源,人口密集和工业程度较高的四川盆地、长江三角洲和珠江三角洲地区NO_x主要来自于其它排放源。研究结果揭示了中国地区对流层NO_x柱总量分布特征及其与闪电活动的关系,对于研究闪电过程对于氮氧化物生成量的影响有重要意义。     

闪电产生氮氧化物(LNOx)全球特征计算

利用(美国)国家航空和宇宙航行局(NASA)通过卫星上的光学瞬态探测器(OTD)观测到的闪电资料,从计算闪电能量入手,对闪电产生氮氧化物量(NOx)的时空分布进行了计算分析。结果表明,全球LNOx大部分集中在南北半球低纬地区,约占65％,南北基本对称,但中高纬地区南北不对称,北半球产N量远大于南半球,呈现很大的不对称性。全球有6大雷暴群,其中非洲中南部的雷暴群产N量比例最大,占全球总量的近四分之一;其次是北美和南美。中国LNOx量较大的区域主要集中在长江以南的地区,年平均LNOx量占全球的7．8％,青藏高原占中国地区的9．1％～12．2％,5年平均为10．2％。全球各季节的平均产N量分别为42．5kt(春)、67kt(夏)、51．4kt(秋)、37．4kt(冬),全年全球平均闪电产N量估计为200kt。     

中国区域闪电特征分析及闪电产生NOx量的估算

利用中国2008-2010年的闪电定位数据,分析了闪电次数的空间分布和时间变化,结合Price理论,估算了闪电产生的氮氧化物（LNOx）量,初步分析了LNOx的时空分布特征。结果表明：闪电的高发期为7、8月,广州、武汉为闪电高发区;LNOx主要分布在（105～125°E,25～40°N）地区,其中武汉、广州、成都、重庆、长沙、南京和南昌地区量值较大;7月和8月LNOx的产量明显高于其他几个月,8月产量最高;此外,LNOx的分布具有明显的季节特征,春夏秋冬四季产量分别占总产量的4．8％、89．4％、5．3％以及0．5％,春季的LNOx主要出现在广州地区,夏季LNOx高值区分布北移,分布范围较广;秋季分布范围减小,最大值出现在广州地区,冬季产量明显变小,最大值出现在武汉的西南方向。     

中国地区闪电和对流层上部NOx的时空分布特征及其相关性分析

为了解闪电对对流层上部NO_x的贡献,本文利用美国全球水资源和气候中心（GHRC）提供的1995年4月~2005年12月的闪电卫星格点资料及高层大气研究卫星 (UARS) 上的卤素掩星试验装置 (HALOE) 1991年10 月~2005 年11月的观测资料,分析了中国地区闪电与对流层上部NO_x体积混合比的时空分布特征及两者的相关性.结果表明:中国地区闪电和对流层上部的NO_x在季节分布、年际分布和空间分布上保持很好的一致性,闪电是对流层上部NO_x的重要来源;NO极值高度在350 hPa左右,云闪直接产生的NO是极值产生的主要原因,NO₂的极值高度在250 hPa左右,因为闪电产生的NO在传输过程中会被氧化成NO₂并通过雷暴的垂直输送作用抬升到更高高度;强对流活动有利于NO_x的传输,而人类活动产生的NO_x一般较难输送到对流层上部,因此闪电多发区的NO_x极值较大,所在的高度也较高.     

闪电产生氮氧化物对青藏高原臭氧低谷形成的影响

为了进一步了解青藏高原闪电的产生氮氧化物（LNO_x）经由光化学反应对O₃浓度变化及夏季O₃低谷形成的可能影响,本文利用2005~2013年由OMI卫星得到的对流层NO₂垂直浓度柱（NO₂ VCD）、O₃总浓度柱（TOC）和O₃廓线以及星载光学瞬变探测器OTD和闪电成像仪LIS获取的总闪电数资料,对青藏高原和同纬度长江中下游地区的TOC和NO₂ VCD月均值时空分布特征、闪电与NO₂ VCD的相关性和O₃的垂直分布特征及其与LNO_x的关系进行了对比分析。结果表明,青藏高原的O₃低谷主要出现在夏季和秋季,其TOC值比同纬度长江中下游地区低约10~15 DU（Dobson unit）。青藏高原NO₂VCD总体较小,表现为夏高冬低的分布特征。青藏高原夏季O₃浓度受南亚高压的影响总体呈减小趋势,但因强雷暴天气导致对流层中上部LNO_x浓度升高,并随强上升气流向对流层顶输送,同时通过光化学反应使O₃浓度增加,缩小了青藏高原和同纬度地区的O₃浓度差,减缓了O₃总浓度的下降,抑制了夏季O₃低谷的进一步深化。     

OMI遥感珠三角城市群NO2的时空分布特征及人类活动影响分析

基于2005—2013年臭氧监测仪(OMI)遥感反演对流层NO2垂直柱浓度资料,分析珠江三角洲地区(简称珠三角)城市群及其相邻区域NO2的时空分布特征及变化趋势,并探究人类活动对NO2的影响。与地面观测数据对比检验显示,OMI遥感NO2资料可靠性较高。研究发现,珠三角城市地区由于工业生产活跃、汽车拥有量高、能源和电力消费量大,相应的化石能源消耗量大,这导致该地区对流层NO2柱浓度平均值(7.4×1015 molec/cm2)约为相邻地区的3倍。与此同时,珠三角地区NO2高污染区域连成一片,城市群效应显著。正弦模型能较好地拟合珠三角及相邻地区NO2的周期性变化特征,NO2浓度高值均出现在冬季,低值出现在夏季。近9年珠三角地区NO2浓度呈下降趋势,与其第二产业产值和汽车拥有量呈较显著的负相关,这表明珠三角地区对氮氧化物排放的治理初见成效。粤东和粤北地区NO2浓度增长趋势显著,与第二产业产值和汽车拥有量存在较好的正相关性,可见工业排放和汽车尾气是这些地区NO2的重要污染源。粤西地区NO2浓度基本不变。      

INTEX-B NO_2排放源在中国地区的应用与检验

将INTEX-B排放源应用到空气质量模型Model3-CMAQ中,对中国地区对流层NO2的浓度分布进行了数值模拟,并与OMI卫星对流层NO2资料进行了对比和验证。结果表明：将INTEX-B排放源应用到Model3-CMAQ模式,模拟的NO2浓度在中国地区的分布、季节变化规律与卫星资料所得结果一致。敏感性试验表明,工业及电厂排放对NO2的浓度贡献最大,而交通排放的贡献相对较小,两种排放均主要集中在京津、长江三角洲等经济发达地区。     

华北地区香河站对流层NO_2的MAX-DOAS光谱仪观测及变化特征分析

利用中国科学院大气物理研究所香河大气探测综合试验站2010年3月至2012年2月(2年)的多轴差分吸收光谱仪(MAX-DOAS)观测数据和32 m高塔常规气象资料,反演了华北地区香河站对流层NO2柱浓度,分析了该区域NO2柱浓度的季节变化特征。研究表明:可见光455~485 nm、紫外330~370 nm都可以作为MAX-DOAS工作波段很好地反演NO2;香河地区NO2柱浓度夏季最低,几乎保持在2×1016 cm–2以下,春、秋季次之,在3×1016 cm–2上下小范围浮动,冬季最高,可达4.5×1016 cm–2;月平均最低值出现在7月,最高值出现在11月。NO2柱浓度与风速、风向密切相关:来自东边唐山方向的风,风速越大时NO2浓度越高,因为唐山是NO2的高值区之一;其它方向风速越大,浓度越低。春、夏两季NO2柱浓度日变化趋势比较平缓,秋、冬两季日变化明显,秋季正午偏高,冬季早晚偏高。     

近51年我国对流层顶高度的变化特征

利用NCEP/NCAR的对流层顶气压多年月平均和逐月平均再分析资料,运用EOF和REOF方法对近51年中国对流层顶高度的空间分布和时间演变特征进行了详细分析。结果表明,中国地区热带对流层顶(第二对流层顶)和极地对流层顶(第一对流层顶)的边界线,2月最南,8月最北,较高的热带对流层顶从2月开始,逐渐北进,8月到达最北界(44°N附近),然后开始南退,2月其北界处于最南端,在29°～30°N附近;我国29°～44°N之间的中纬度地区,对流层顶高度的年变化幅度较大;对流层顶高度场有三种主要的模态:第一种为全区一致的偏高(偏低)型;第二种为南高(低)北低(高)的南北相反分布型;第三种为南北地区-中部地区相反分布型。对对流层顶高度场进行REOF分解可将中国地区分为6个气候分区,即华南区、新疆区、东北区、华北区、长江流域区和青藏高原区,各区对流层顶高度最大值一般都出现在夏季,最小值出现在冬季,只有华南区的最大值出现在春季,最小值出现在夏季。中国地区对流层顶高度的年际变化和长期趋势具有十分明显的区域性。     

Estimation of Lightning-Generated NOx in the Mainland of China Based on Cloud-to-Ground Lightning Location Data

Lightning-generated nitrogen oxides(LNO_x) have a major influence on the atmosphere and global climate change.Therefore, it is of great importance to obtain a more accurate estimation of LNO_x. The aim of this study is to provide a reference for the accurate estimation of the total LNO_x in the mainland of China based on cloud-to-ground lightning(CG)location data from 2014 to 2018. The energy of each CG flash was based on the number of return strokes per CG flash, t...     

Global NOx Production by Lightning

Lightning is thought to represent an important source of tropospheric reactive nitrogen species NO_x (NO + NO₂),but estimates of global production of NO_x by lightning varyconsiderably. We evaluate the production of NO_x by lightning using a global chemical/transport model, satellite lightning observations, and airborne NO_x measurements. Various model calculations are conducted toassess the global NO_x production rate of lightning by comparing the model calculations with airborne measurements. The results show that the simulated NO_x in the tropical middle and upper troposphere are very sensitiveto the amount and altitude of the lightning NO_x used in the model. A global lightning NO_x production of 7 Tg N yr^–1uniformly distributed in convective clouds or 3.5 Tg N yr^–1 distributedin the upper cloud regions produces good agreement between calculated and measured NO_x concentrations in the tropics.     

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.     

A model investigation of the impact of increases in anthropogenic NO x emissions between 1967 and 1980 on tropospheric ozone

Recent observations suggest that the abundance of ozone between 2 and 8 km in the Northern Hemisphere mid-latitudes has increased by about 12% during the period from 1970 to 1981. Earlier estimates were somewhat more conservative suggesting increases at the rate of 7% per decade since the start of regular observations in 1967. Previous photochemical model studies have indicated that tropospheric ozone concentrations would increase with increases in emissions of CO, CH₄ and NO _x . This paper presents an analysis of tropospheric ozone which suggests that a significant portion of its increase may be attributed to the increase in global anthropogenic NO _x emissions during this period while the contribution of CH₄ to the increase is quite small. Two statistical models are presented for estimating annual global anthropogenic emissions of NO _x and are used to derive the trend in the emissions for the years 1966–1980. These show steady increase in the emissions during this interval except for brief periods of leveling off after 1973 and 1978. The impact of this increase in emissions on ozone is estimated by calculations with a onedimensional (latitudinal) model which includes coupled tropospheric photochemistry and diffusive meridional transport. Steady-state photochemical calculations with prescribed NO _x emissions appropriate for 1966 and 1980 indicate an ozone increase of 8–11% in the Northern Hemisphere, a result which is compatible with the rise in ozone suggested by the observations.     

Subsonic aircraft and ozone trends

Growth in subsonic air traffic over the past 20 years has been dramatic, with an annual increase of }6.1% over the decade between 1978 and 1988. Furthermore, aircraft activities in the year 2000 are predicted to be double those of 1990, with a shift towards more high-flying, longhaul subsonics. Aircraft exhaust gases increase the amount of nitrogen oxides (NO _x ) in the upper troposphere/lower stratosphere through injection at cruise altitudes. Given that NO _x is instrumental in tropospheric ozone production and stratospheric ozone destruction, it is important to determine the influence of subsonic aircraft NO _x emissions on levels of atmospheric ozone. This paper describes calculations designed to investigate the impact that subsonic aircraft may already have had on the atmosphere during the 1980s, run in a 2-D chemical-radiative-transport model. The results indicate a significant increase in upper tropospheric ozone over the decade arising from aircraft emissions. However, when comparing model results with observational data, certain discrepancies appear. Lower stratospheric ozone loss over the 1980s does not appear to be greatly altered by the inclusion of aircraft emissions in the model. However, given the trend in greater numbers of long-haul subsonic aircraft, this factor must be considered in any further calculations.     

Impacts of Global Emissions of CO, NOx, and CH4 on China Tropospheric Hydroxyl Free Radicals

Using the global chemistry and transport model MOZART,the simulated distributions of tropospheric hydroxyl free radicals(OH) over China and its sensitivities to global emissions of carbon monoxide(CO),nitrogen oxide(NO x),and methane(CH 4) were investigated in this study.Due to various distributions of OH sources and sinks,the concentrations of tropospheric OH in east China are much greater than in west China.The contribution of NO + perhydroxyl radical(HO 2) reaction to OH production in east China is more pronounced than that in west China,and because of the higher reaction activity of non-methane volatile organic compounds(NMVOCs),the contributions to OH loss by NMVOCs exceed those of CO and take the dominant position in summer.The results of the sensitivity runs show a significant increase of tropospheric OH in east China from 1990 to 2000,and the trend continues.The positive effect of double emissions of NO x on OH is partly offset by the contrary effect of increased CO and CH 4 emissions:the double emissions of NO x will cause an increase of OH of 18.1%-30.1%,while the increases of CO and CH 4 will cause a decrease of OH of 12.2%-20.8% and 0.3%-3.0%,respectively.In turn,the lifetimes of CH 4,CO,and NO x will increase by 0.3%-3.1% with regard to double emissions of CH 4,13.9%-26.3% to double emissions of CO and decrease by 15.3%-23.2% to double emissions of NO x.     

Global financial crisis making a V-shaped fluctuation in NO<Subscript>2</Subscript> pollution over the Yangtze River Delta

The Yangtze River Delta (YRD), China’s main cultural and economic center, has become one of the most seriously polluted areas in the world with respect to nitrogen oxides (NO_x), owing to its rapid industrialization and urbanization, as well as substantial coal consumption. On the basis of nitrogen dioxide (NO₂) density data from ozone monitoring instrument (OMI) and ground-based observations, the effects of industrial fluctuations due to the financial crisis on local NO₂ pollution were quantitatively assessed. The results were as follows. (1) A distinct V-shaped fluctuation of major industrial products, thermal generating capacity, electricity consumption, and tropospheric NO₂ densities was associated with the global financial crisis from May 2007 to December 2009, with the largest anomalies 1.5 times more than standard deviations at the height of the crisis period from November 2008 to February 2009. (2) Among all industrial sectors, thermal power plants were mainly responsible for fluctuations in local NO₂ pollution during the crisis period. Thermal generating capacity had its greatest decrease of 12.10% at the height of the crisis compared with that during November 2007–February 2008, leading to local tropospheric NO₂ density decreasing by 16.97%. As the crisis appeased, thermal generating capacity increased by 29.63% from November 2009 to February 2010, and tropospheric NO₂ densities correspondingly increased by 30.07%. (3) Among all industrial sectors in the YRD, the thermal power sector has the greatest coal consumption of about 65.96%. A decline in thermal power of about 10% can induce a decrease of about 30% in NO_x emissions and NO₂ densities, meaning that a relative small fluctuation in industrial production can lead to a large decrease in tropospheric NO₂ densities over industrially developed areas like the YRD region. Since electricity is mainly obtained from local coal-burning thermal plants without NO_x-processing equipment, installing NO_x-removal devices for all thermal power plants is an important and feasible way of controlling local NO_x pollution at present.     

Satellite Measurements of Tropospheric Column O<Subscript>3</Subscript> and NO<Subscript>2</Subscript> in Eastern and Southeastern Asia: Comparison with a Global Model (MOZART-2)

Satellite measurements of tropospheric column O₃ and NO₂ in eastern and southeastern Asia are analyzed to study the spatial and seasonal characteristics of pollution in these regions. Tropospheric column O₃ is derived from differential measurements of total column ozone from Total Ozone Mapping Spectrometer (TOMS), and stratospheric column ozone from the Microwave Limb Sounder (MLS) instrument on the Upper Atmosphere Research Satellite (UARS). The tropospheric column NO₂ is measured by Global Ozone Monitoring Experiment (GOME). A global chemical and transport model (Model of Ozone and Related Chemical Tracers, version 2; MOZART-2) is applied to analyze and interpret the satellite measurements. The study, which is based on spring, summer, and fall months of 1997 shows generally good agreement between the model and satellite data with respect to seasonal and spatial characteristics of O₃ and NO₂ fields. The analysis of the model results show that the industrial emission of NO_x (NO + NO₂) contributes about 50%–80% to tropospheric column NO₂ in eastern Asia and about 20%–50% in southeastern Asia. The contribution of industrial emission of NO_x to tropospheric column O₃ ranges from 10% to 30% in eastern Asia. Biomass burning and lightning NO_x emissions have a small effect on tropospheric O₃ in central and eastern Asia, but they have a significant impact in southeastern Asia. The varying effects of NO_x on tropospheric column ozone are attributed to differences in relative abundance of volatile organic compounds (VOCs) with respect to total nitrogen in the two regions.