The influence of isoprene peroxy radical isomerization mechanisms on ozone simulation with the presence of NOx

Isoprene peroxy radical isomerizations (1,5- and 1,6-H shifts) have recently been proposed as important pathways regenerating and recycling HO_x (OH?+?HO₂) in the atmosphere under low-NO_x conditions (Peeters et al. Phys. Chem. Chem. Phys. 28: 5935?C5939 2009; da Silva et al. Environ. Sci. Technol. 44:250?C256 2010). Evaluation and comparison of the isoprene peroxy radical isomerization mechanisms from recent studies have been performed against isoprene-NO_x experiments conducted in the UNC dual outdoor smog chambers. Five different kinetic mechanisms were tested in this study, including the original Master Chemical Mechanism (MCM) v3.1; two modified MCM mechanisms both implementing isoprene peroxy radical isomerization reactions but with different rate coefficients; the Carbon Bond 6 (CB6) mechanism; and the ISO-UNC mechanism. Sensitivity analyses of the unsaturated hydroxyperoxy aldehydes (HPALDs) reaction mechanisms under fast isomerization have also been performed. The results indicate that the fast isomerization mechanism and the mechanisms with high OH yields from HPALDs photolysis both significantly enhance HO_x estimates with increasing isoprene/NO_x ratios. However, O₃ predictions, as well the isoprene decay rates are substantially overestimated. Our results suggest that given the current state of our knowledge, it is difficult to improve both HO_x levels and maintain reasonable O₃ simulations using the Peeters et al. (Peeters et al. Phys. Chem. Chem. Phys. 28: 5935?C5939 2009) mechanism.     

Analytical studies on the variations of the antarctic ozone layer

The Antarctic ozone hole which was discovered in the mid 1980s has caused much attention from the scientists and politicians throughout the world.For the formation of the Antarctic ozone hole, most scientists believe that the man-made chemical materials such as CFCs etc. are main cause. On the other hand, the electrochemistry-dynamics theory presented by Wei (Guang Ming Daily Dec. 11, 1990) two years ago has also caused some attention.In the paper the data of ozone, solar activity meteorology over Antarctica have been used for statistical analyti-cal studies. Our results present some new evidence to support Wei's theory. However the influence of the human activ-ities can never be slighted.     

南极臭氧洞的研究

南极臭氧总量在晚冬和早春减少了30—40％,形成一个“臭氧洞”。本文概述了一些作者对这一观测事实给出的解释,以期使读者对此问题有一个全面的认识。无论是从光化学角度还是从动力学角度,给出臭氧变化的机制都是初步的,但这是认识这种现象的第一步。作者认为将光化学和动力学两种观点结合起来,做全面的分析,是问题完满解决的途径。     

南极臭氧洞计算机模拟

一维时空光化学模式引进垂直运动及离子反应生成的氮氧(NOx)、氢氧(HOx)化合物。模式中采用1978到1983年期间的太阳紫外辐射通量及南极73度的纬向八月份平均温度。 计算结果表明:春季南极出现臭氧洞,主要是第21太阳黑子周峰值期太阳紫外辐射减少造成的。其次,在太阳黑子周峰值期伴随多次大的太阳质子事件,产生大量氮氧、氢氧化合物。在极区太阳质子事件产生的化合物催化破坏平流层臭氧可持续几天至几年。 南极冬春季节强大的下降垂直运动是南极臭氧洞形成发展极其重要的局部动力条件,特别是在极夜期间。太阳升起后,垂直运动的影响不明显。 南极臭氧洞的形成主要是通过光化变化过程,动力过程是其局部的充要条件,人为活动产生的含氯化合物对低层大气臭氧的直接破坏不可忽视。基于上述论点,可以预期进入第22太阳黑子周期,南极及全球大气臭氧的分布状态将会改变,大自然本身自复。     

Responses of the tropospheric ozone and odd hydrogen radicals to column ozone change

The response of tropospheric ozone to a change in solar UV penetration due to perturbation on column ozone depends critically on the tropospheric NO _x (NO+NO₂) concentration. At high NO _x or a polluted area where there is net ozone production, a decrease in column ozone will increase the solar UV penetration to the troposphere and thus increase the tropospheric ozone concentration. However, the opposite will occur, for example, at a remote oceanic area where NO _x is so low that there is net ozone destruction. This finding may have important implication on the interpretation of the long term trend of tropospheric ozone. A change in column ozone will also induce change in tropospheric OH, HO₂, and H₂O₂ concentrations which are major oxidants in the troposphere. Thus, the oxidation capacity and, in turn, the abundances of many reduced gases will be perturbed. Our model calculations show that the change in OH, HO₂, and H₂O₂ concentrations are essentially independent of the NO _x concentration.     

Numerical experiments with a one-dimensional higher order turbulence model: Simulation of the Wangara Day 33 case

A one-dimensional stratocumulus model is developed and incorporated into a cloud/mesoscale model to simulate the evolution of the marine stratocumulus-capped mixed layer. This paper describes the formulation of the higher-order turbulence model. In a companion paper (Chen and Cotton, 1983), the formulation of the atmospheric radiation model, the partial condensation and the cloud fractional parameterization are described. The second-order moments of this model are partially diagnosed. In order to close the system, the parameterization for the third-order moments given by Zeman and Lumley (1976) is adopted and is generalized to include total water and cloud water. A new scheme to parameterize the skewness terms is proposed in order to satisfy the enforced realizability. Those skewness terms are used to close the third-order moments. In this paper, experiments are carried out to test the turbulence model by using the Wangara Day 33 data, which represents a ‘dry’ case study. Sensitivity experiments using the turbulence length scale parameterizations formulated by Andréet al. (1978) and Sun and Ogura (1980) are reformed and are compared.     

南极大陆沿岸地面臭氧损耗事件的研究

利用南极大陆沿岸中山站2008-2013年的地面臭氧连续观测数据和相关资料,对地面臭氧损耗事件（ODE）进行研究。结果显示,春季南极中山站常发生臭氧损耗事件。在该事件发生期间,气象要素有明显的突变过程,包括气温明显下降,风向由偏东风转变为偏北风,风速随之下降。来自海冰区的偏北风增多,风速很小,使臭氧浓度维持在较低水平。地面臭氧损耗事件主要与南极沿岸海冰区的活性溴（BrO）浓度有关。春季南极大陆沿岸海冰冻融过程中形成的冰间水道和冰间湖,在低温的作用下会再次冻结,形成薄冰和霜花。卫星资料能够观测到薄冰区释放的活化海盐溴高浓度区,活性溴与臭氧发生化学反应形成地面臭氧损耗事件。臭氧损耗现象是在未受到人为影响的自然状态下发生的,与中高纬度地区光化学反应导致臭氧消耗有所不同。      

Scenarios of possible changes in atmospheric temperatures and ozone concentrations due to man's activities,estimated with a one-dimensional coupled photochemical climate model

A one-dimensional coupled climate and chemistry model has been developed to estimate past and possible future changes in atmospheric temperatures and chemical composition due to human activities. The model takes into account heat flux into the oceans and uses a new tropospheric temperature lapse rate formulation. As found in other studies, we estimate that the combined greenhouse effect of CH₄, O₃, CF₂Cl₂, CFCl₃ and N₂O in the future will be about as large as that of CO₂. Our model calculates an increase in average global surface temperatures by about 0.6°C since the start of the industrial era and predicts for A.D. 2050 a twice as large additional rise. Substantial depletions of ozone in the upper stratosphere by between 25% and 55% are calculated, depending on scenario. Accompanying temperature changes are between 15°C and 25°C. Bromine compounds are found to be important, if no rigid international regulations on CFC emissions are effective. Our model may, however, concivably underestimate possible effects of CFCl₃, CF₂Cl₂, C₂F₃Cl₃ and other CFC and organic bromine emissions on lower stratospheric ozone, because it can not simulate the rapid breakdown of ozone which is now being observed worldwide. An uncertainty study regarding the photochemistry of stratospheric ozone, especially in the region below about 25 km, is included. We propose a reaction, involving excited molecular oxygen formation from ozone photolysis, as a possible solution to the problem of ozone concentrations calculated to be too low above 45 km. We also estimate that tropospheric ozone concentrations have grown strongly in the northern hemisphere since pre-industrial times and that further large increases may take place, especially if global emissions of NO_x from fossil fuel and biomass burning were to continue to increase. Growing NO_x emissions from aircraft may play an important role in ozone concentrations in the upper troposphere and low stratosphere.     

Possible mechanism of ozone depletion on ice crystals in the polar stratosphere

Developed is a new mechanism of photochemical reactions taking account of the dipole interaction between the molecules and the ??sharp?? inhomogeneities of electrified ice crystals in polar stratospheric clouds. This mechanism enables to explain the ozone depression formation during the winter-spring period in the polar stratosphere.     

Impact of increasing stratospheric water vapor on ozone depletion and temperature change

Using a detailed, fully coupled chemistry climate model (CCM), the effect of increasing stratospheric H_{2O on ozone and temperature is investigated. Different CCM time-slice runs have been performed to investigate the chemical and radiative impacts of an assumed 2 ppmv increase in H2O. The chemical effects of this H2O increase lead to an overall decrease of the total column ozone (TCO) by ～1% in the tropics and by a maximum of 12% at southern high latitudes. At northern high latitudes, the TCO is increased by only up to 5% due to stronger transport in the Arctic. A 2-ppmv H2O increase in the model's radiation scheme causes a cooling of the tropical stratosphere of no more than 2 K, but a cooling of more than 4 K at high latitudes. Consequently, the TCO is increased by about 2%--6%. Increasing stratospheric H2O, therefore, cools the stratosphere both directly and indirectly, except in the polar regions where the temperature responds differently due to feedbacks between ozone and H2O changes. The combined chemical and radiative effects of increasing H2O may give rise to more cooling in the tropics and middle latitudes but less cooling in the polar stratosphere. The combined effects of H2O increases on ozone tend to offset each other, except in the Arctic stratosphere where both the radiative and chemical impacts give rise to increased ozone. The chemical and radiative effects of increasing H2O cause dynamical responses in the stratosphere with an evident hemispheric asymmetry. In terms of ozone recovery, increasing the stratospheric H2O is likely to accelerate the recovery in the northern high latitudes and delay it in the southern high latitudes. The modeled ozone recovery is more significant between 2000--2050 than between 2050--2100, driven mainly by the larger relative change in chlorine in the earlier period.}     

Simulation and causes of eastern Antarctica surface cooling related to ozone depletion during austral summer in FGOALS-s2

Two parallel sets of numerical experiments （an ozone-hole simulation and a non-ozone-hole simulation） were performed to investigate the effect of ozone depletion on surface temperature change using the second spectral version of the Flexible Global Ocean-Atmosphere-Land System model （FGOALS-s2）, focusing on the eastern Antarctica （EA） continent in austral summer. First, we evaluated the ability of the model to simulate the EA surface cooling, and found the model can successfully reproduce the cooling trend of the EA surface, as well as the circulation change circling the South Pole in the past 30 years. Second, we compared the two experiments and discovered that the ozone depletion causes the cooling trend and strengthens the circumpolar westerly flow. We further investigated the causes of the EA surface cooling associated with the ozone hole and found two major contributors. The first is the ozone-hole direct radiation effect （DRE） upon the surface that happens because the decrease of the downward longwave （LW） radiation overcomes the increase of the downward shortwave （SW） radiation under clear sky. The second is the cloud radiation effect （CRE） induced by ozone depletion, which happens because the decreased downward SW radiation overcomes the increased downward LW radiation in the case of increased cloud. Although the CRE is theoretically opposite to the DRE, their final net effect makes comparable contributions to the EA surface cooling. Compared with the surface radiation budget, the surface heat flux budgets have a much smaller contribution. We additionally note that the CRE is basically ascribed to the circulation change.     

The ozone,aerosol depletion and condensation nuclei events in the stratosphere

Recently, the depletion in ozone and aerosol extinctions inside Antarctic Spring westerly vortex and condensa-tion nuclei enhancement events in the mid latitudes stratosphere were related to downward transport of aerosols by subsidence and sedimentation. However, the problems associated with such hypothesis would keep a constraint on photochemical theories on ozone hole and stratospheric condensation nuclei (CN) events. Alternately, the gross fea-tures of aerosol hole are better explicable assuming a reversed residual circulation. This opens a path for combined operation on ozone by both photochemistry and dynamics in the same space domain.Independently, we relate the CN events to the growth and transport of negative ion complexes above the Peak of Junge Layer (PJL) without invoking photochemistry in order to be consistant with the observed interhemispheric dif-ferences in the planetary wave activity and CN concentration.     

Simulation of stratospheric ozone in global forecast model using linear photochemistry parameterization

The two types of ozone, the simulation with interactive (prognostic) ozone using linear photochemistry parameterization (LPP) (INTR) and the simulation with non-interactive ozone using ozone climatology (CLIM), were used in the global forecast model. These two types of ozone were compared with ozone observations from the Aura Microwave Lim Sounder (MLS) and ozonesondes from 16-30 September 2008. The INTR is sensitive to LPP schemes while less sensitive to the time average of initial ozone data. Among three LPP schemes, CARIOLLE, COPCAT, and LINOZ, the COPCAT produces ozone profiles with least differences from MLS and ozonesondes. CLIM overestimates MLS at 200-20 hPa while INTR with COPCAT scheme underestimates MLS ozone above 5 hPa. Over the Antarctic in the lower stratosphere CLIM overestimates MLS and ozonesondes whereas INTR underestimates MLS but overestimates the ozonesonde data. Thus, COPCAT agrees better with ozonesonde data than any other LPP schemes and CLIM. Changing the ozone distribution from CLIM to INTR affects temperature profiles mainly through the modification of differential radiative fluxes. The correlations between ozone, differential radiative fluxes, and temperature are distinguished by altitude (or pressure levels). The correlations are strong or moderate between 3-1000 hPa (lower atmosphere) and weak above 3 hPa (upper atmosphere). This study demonstrates that the simulation of ozone using an appropriate LPP scheme is excellent in overcoming the drawbacks of using climatological ozone profiles that poorly agree with observations in extreme ozone hole events.     

Simulation of the influence of solar radiation variations on the global climate with an ocean-atmosphere general circulation model

 Two simulations with a global coupled ocean-atmosphere circulation model have been carried out to study the potential impact of solar variability on climate. The Hoyt and Schatten estimate of solar variability from 1700 to 1992 has been used to force the model. Results indicate that the near-surface temperature simulated by the model is dominated by the long periodic solar fluctuations (Gleissberg cycle), with global mean temperatures varying by about 0.5 K. Further results indicate that solar variability and an increase in greenhouse gases both induce to a first approximation a comparable pattern of surface temperature change, i.e., an increase of the land-sea contrast. However, the solar-induced warming pattern in annual means and summer is more centered over the subtropics, compared to a more uniform warming associated with the increase in greenhouse gases. The observed temperature rise over the most recent 30 and 100 years is larger than the trend in the solar forcing simulation during the same period, indicating a strong likelihood that, if the model forcing and response is realistic, other factors have contributed to the observed warming. Since the pattern of the recent observed warming agrees better with the greenhouse warming pattern than with the solar variability response, it is likely that one of these factors is the increase of the atmospheric greenhouse gas concentration. Received: 14 October 1996 / Accepted: 9 May 1997     

Variations in surface ozone and NOx at Kannur: a tropical, coastal site in India

Continuous measurements of surface ozone (O₃), NOx (NO + NO₂) and meteorological parameters have been made in Kannur (11.9?°N, 75.4?°E, 5?m asl), India from November 2009 to October 2010. It was observed that O₃ and NOx showed distinct diurnal and seasonal variabilities at this site. The annual average diurnal profile of O₃ showed a peak of (30.3?±?10.4) ppbv in the late afternoon and a minimum of (3.2?±?0.7) ppbv in the early morning. The maximum value of O₃ mixing ratio was observed in winter (44?±?3.1) ppbv and minimum during monsoon (18.46?±?3.5) ppbv. The rate of production of O₃ was found to be higher in December (10.1?ppbv/h) and lower in July (1.8?ppbv/h) during the time interval 0800?C1000?h. A correlation coefficient of 0.52 for the relationship between O₃ and [NO₂]/[NO] reveals the role of NO₂ photolysis that generates O₃ at this site. The correlation between O₃ and meteorological parameters indicate the influence of seasonal changes on O₃ production. Investigations were further extended to explore the week day weekend variations in O₃ mixing ratio at an urban site reveals the enhancement of O₃. The variations of O₃ mixing ratio with seasonal air mass flows were elucidated with the aid of backward air trajectories. This study also indicates how vapor phase organic species present in the ambient air at this location may influence the complex chemistry involving (VOCs) that enhances the production of O₃ at this location.     

1997年和2011年春季北极臭氧损耗事件的对比分析

采用SLIMCAT化学传输模式以及再分析资料,对比分析了1997和2011年北极地区平流层臭氧异常偏低事件及其成因。结果表明,1997和2011年3月北极地区大气臭氧柱总量（TCO）异常值都达到了约-80 DU,并且在30-200 hPa（中下平流层）区域的大气臭氧柱总量异常约占整层大气臭氧柱总量异常的80%。分析表明发生在这两年的极端臭氧偏低事件均可能是由于上一年冬季的拉尼娜事件导致上传的行星波减少,使得北极极涡加强,平流层温度异常偏低,生成了更多极地云,引起更强的臭氧化学损耗导致的。对比这两年的大气臭氧柱总量变化发现,2011年的柱总量减少得更快。2011年北极地区上对流层下平流层（UTLS）区域臭氧下降要明显强于1997年,其主要原因应该是2010-2011冬季的拉尼娜活动更强,北太平洋海温更高,进一步减弱阿留申低压和平流层波活动。这导致2011年极涡温度异常偏低更强烈,形成了更多的极地平流层云甚至出现了第二类极地平流层云,最终加速该年春季的臭氧化学损耗引起的。     

A one-dimensional photochemical model of the troposphere with planetary boundary-layer parameterization

The results from a one-dimensional photochemical model of the troposphere representative of summertime conditions at Northern Hemisphere mid-latitudes are presented. A parameterization of mixing processes within the planetary boundary layer (PBL) has been incorporated into the model for both the daytime convective PBL and the formation of the nocturnal PBL. One result of the parameterized PBL is that the concentrations of some trace species in the free troposphere are 20–30% higher than when mixing processes are described by a vertical eddy diffusion coefficient which is held constant with respect to height and time.The calculations indicate that the lifetime of the oxides of nitrogen (NO _x =NO+NO₂) against photochemical conversion to nitric acid (HNO₃) during summertime conditions is on the order of 6 h. This lifetime is short enough to deplete most of the NO _x in the PBL, resulting in the finding that other reactive nitrogen species (HNO₃ and peroxyacetyl nitrate) are more abundant than NO _x throughout the free troposphere, even though NO _x is the most abundant reactive nitrogen species at the surface. The effects of the inclusion of anthropogenic nonmethane hydrocarbon (NMHC) chemistry are also discussed. The inclusion of NMHC chemistry has a pronounced effect on the photochemistry of tropospheric oxone and increases thein situ column production by more than 30%.     

青藏高原气温变化趋势与同纬度带其他地区的差异以及臭氧的可能作用

利用台站探空观测资料和卫星观测资料,分析了1979—2002年青藏高原上空温度的变化趋势。结果表明：高原地区上空平流层低层和对流层上层的温度与对流层中低层具有反相变化趋势。平流层低层和对流层上层降温,温度出现降低趋势,降温幅度无论是年平均还是季节平均都比全球平均降温幅度更大。高原上空对流层中低层增温,温度显示出增加的趋势,并且比同纬度中国东部非高原地区有更强的增温趋势。对1979—2002年卫星臭氧资料的分析表明,青藏高原上空臭氧总量在每个季节都呈现出明显的下降趋势,并且比同纬度带其他地区下降得更快。由于青藏高原上空臭氧有更大幅度的减少,造成高原平流层对太阳紫外辐射吸收比其他地区更少,使进入对流层的辐射更多,从而导致高原上空平流层低层和对流层上层降温比其他地区更强,而对流层中低层增温更大。因此,高原上空比其他地区更大幅度的臭氧总量减少可能是造成青藏高原上空与同纬度其他地区温度变化趋势差异的一个重要原因。