On the relation between ozone storage in the residual layer and daily variation in near-surface ozone concentration — A case study

Summary Numerous tethered balloon soundings which measured meteorological parameters and ozone concentration during the POLLUMET field experiments are investigated. They give indications of the influence of ozone conservation in the nocturnal residual layer (RL) on the development of the near surface ozone concentration of the next day. Mixing down from the RL to the surface is simulated by a simple model based on transilient turbulence theory, using measured profiles as initial values or model verification. The cases investigated show that the ozone mixed down from the RL contributes 50–70% to the maximum concentration near the surface on the following day, the rest coming from chemical production and possibly advection. Various features of exchange characteristics between the RL and the nocturnal boundary layer, (NBL) are described by the analysis of the soundings. It can be shown that the vertical exchange situation during the night can have a considerable influence on the ozone concentration of the following day.     

Stratospheric ozone depletion: a key driver of recent precipitation trends in South Eastern South America

On a hemispheric scale, it is now well established that stratospheric ozone depletion has been the principal driver of externally forced atmospheric circulation changes south of the Equator in the last decades of the 20th Century. The impact of ozone depletion has been felt over the entire hemisphere, as reflected in the poleward drift of the midlatitude jet, the southward expansion of the summertime Hadley cell and accompanying precipitation trends deep into the subtropics. On a regional scale, however, surface impacts directly attributable to ozone depletion have yet to be identified. In this paper we focus on South Eastern South America (SESA), a region that has exhibited one of the largest wetting trends during the 20th Century. We study the impact of ozone depletion on SESA precipitation using output from 6 different climate models, spanning a wide range of complexity. In all cases we contrast pairs of model integrations with and without ozone depletion, but with all other forcings identically specified. This allows for unambiguous attribution of the computed precipitation trends. All 6 climate models consistently reveal that stratospheric ozone depletion results in a significant wetting of SESA over the period 1960–1999. Taken as a whole, these model results strongly suggest that the impact of ozone depletion on SESA precipitation has been as large as, and quite possibly larger than, the one caused by increasing greenhouse gases over the same period.     

A case study of the nocturnal boundary layer over a complex terrain

A case study of the structure of the nocturnal boundary layer (NBL) over complex terrain is presented. Observations were made during the third night of Project STABLE (Weber and Kurzeja, 1991), whose main goal was to study turbulence and diffusion over the complex terrain of the Savannah River Site (SRS) near Augusta, Georgia.The passage of a mesoscale phenomenon, defined as a turbulent meso-flow (TMF) with an explanation of the nomenclature used, and a composite structure of the lowest few hundred meters over complex terrain are presented. The spatial extent of the TMF was at least 30–50 km, but the forcing is not well understood. The TMF occurred without the presence of a synoptic-scale cold front, under clear conditions, and with no discernible discontinuity in a microbarograph pressure trace. The structure of the NBL over the complex terrain at SRS differed from the expected homogeneous terrain NBL. The vertical structure exhibited dual low level wind maxima, dual inversions, and a persistent elevated turbulent layer.The persistent elevated turbulent layer, with a spatial extent of at least 30 km, was observed for the entire night. The persistent adiabatic layer may have resulted from turbulence induced by shear instability.     

A case study of turbulence in the stable nocturnal boundary layer

Velocity and signal intensity data during stable conditions in the nocturnal boundary layer (NBL) were obtained with a minisodar on two consecutive nights with similar mean conditions. There was little turbulence activity during the first night, but during the second night, continuous background Kelvin-Helmholtz waves and instabilities having a 2-min period grew and penetrated above the mean NBL height at approximately 60-min intervals. Enhanced ozone concentrations at the surface occurred during the active periods even though most mean meteorological parameters were unchanged. Vertical profiles of vertical velocity standard deviation, dissipation rate, and temperature variance destruction rate in the NBL were measured and analyzed separately according to levels of turbulence activity. Well-defined differences between inactive and active periods of a factor of two to four were found for each parameter. The temperature structure parameter flux was large and in opposite directions in the upper and lower part of the NBL during active periods of turbulence, but small during other periods.     

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。     

Simulation of the influence of ion-produced NOx and HOx radicals on the antarctic ozone depletion with a one-dimensional model

A one-dimensional time-dependent photochemical model is used to simulate the influence of ion-produced NOx, and HOx radicals on the Antarctic ozone depletion in polar night and polar spring at a latitude of 73 degrees south.Vertical transport and nitrogen-oxygen (NOx), hydrogen-oxygen (HOx) production by ionic reactions have been introduced into the model.NOx and HOx produced by precipitating ions are transported into the lower stratosphere by vertical motion and have some effects in the development of the Antarctic ozone depletion.From winter through spring the calculated ozone column decreases to 269.4 DU. However, this value is significantly higher than the total ozone observed at several Antarctic ozone stations.     

基于数据窗口标准差的边界层高度反演方法——以上海市为例

大气边界层具备一个重要特性,即在边界层顶部,气溶胶浓度在垂直分布上存在显著突变.利用该特性,采用主动遥感装置经过窗口平滑去除噪点后数据,提出基于梯度法改进的大气边界层高度反演方法——窗口标准偏差法.基于激光云高仪后向散射廓线数据,利用该方法反演边界层高度,在边界层高度下大气气溶胶混合均匀时,反演结果较为理想.在此基础上...     

Divergence of turbulent fluxes in the surface layer: case of a coastal city

This study quantifies the processes that take place in the layer between the mean building height and the measurement level of an energy balance micrometeorological tower located in the dense old core of a coastal European city. The contributions of storage, vertical advection, horizontal advection and radiative divergence for heat are evaluated with the available measurements and with a three-dimensional, high-resolution meteorological simulation that had been evaluated against observations. The study focused on a summer period characterized by sea-breeze flows that affect the city. In this specific configuration, it appears that the horizontal advection is the dominant term. During the afternoon when the sea breeze is well established, correction of the sensible heat flux with horizontal heat advection increases the measured sensible heat flux up to 100 W m⁻². For latent heat flux, the horizontal moisture advection converted to equivalent latent heat flux suggests a decrease of 50 W m⁻². The simulation reproduces well the temporal evolution and magnitude of these terms.     

Accounting for flexibility against uncertain baselines: lessons from case studies in the eastern European energy sector

Abstract

The Kyoto Protocol defines two project-based flexibility mechanisms: joint implementation (JI) and the cleandevelopment mechanism (CDM). The main methodological problem associated with both these mechanisms isthe choice of an appropriate baseline: since the baseline is, by definition, counterfactual, it imposes considerable uncertainty on the accounting framework. Little work to date has been carried out on trying to estimate how largethis uncertainty might be for particular project types. This paper aims to fill this gap by proposing an approach to baseline construction which explicitly acknowledges this uncertainty. This approach is illustrated through theexamination of pilot JI projects in the energy sector in eastern Europe, and then discussed in terms of its implicationsfor climate policy. The results presented are estimates of the range of counterfactual uncertainty in greenhouse gas emission reductions based on the construction of a number of possible baselines for each project. This range is found to be about ±35% for demand side projects, ±45% for heat supply projects, ±55% for cogeneration projects, and ±60% for electricity supply projects. Estimates of uncertainty in the costs of the pilot projects are also found to be high. The paper discusses the problems arising from such large uncertainty and starts to indicate how this uncertainty may be managed.     

Accounting for flexibility against uncertain baselines: lessons from case studies in the eastern European energy sector

The Kyoto Protocol defines two project-based flexibility mechanisms: joint implementation (JI) and the clean development mechanism (CDM). The main methodological problem associated with both these mechanisms is the choice of an appropriate baseline: since the baseline is, by definition, counterfactual, it imposes considerable uncertainty on the accounting framework. Little work to date has been carried out on trying to estimate how large this uncertainty might be for particular project types. This paper aims to fill this gap by proposing an approach to baseline construction which explicitly acknowledges this uncertainty. This approach is illustrated through the examination of pilot JI projects in the energy sector in eastern Europe, and then discussed in terms of its implications for climate policy. The results presented are estimates of the range of counterfactual uncertainty in greenhouse gas emission reductions based on the construction of a number of possible baselines for each project. This range is found to be about ±35% for demand side projects, ±45% for heat supply projects, ±55% for cogeneration projects, and ±60% for electricity supply projects. Estimates of uncertainty in the costs of the pilot projects are also found to be high. The paper discusses the problems arising from such large uncertainty and starts to indicate how this uncertainty may be managed.     

Climate change and the agricultural sector in Ireland: examining farmer awareness and willingness to adopt new advisory mitigation tools

Agriculture is responsible for the bulk of Ireland’s greenhouse gas (GHG) emissions. However, the potential to mitigate some of these emissions through the adoption of more efficient farm management practices may be hampered by farmers’ awareness and attitude towards climate change and agriculture’s role in contributing to GHG emissions. This paper presents results from a survey of 746 Irish farmers in 2014, with a view to understanding farmers’ awareness of, and attitudes to, climate change and GHG emissions. Survey results show that there was a general uncertainty towards a number of questions related to agricultural GHG emissions, e.g. if tilling of land causes GHG emissions, and that farmers were reluctant to take action to reduce GHG emissions on their farm. To further explore farmers’ attitudes towards climate change, a multinomial logit model was used to examine the socio-economic factors that affect farmers’ willingness to adopt an advisory tool that would show the potential reduction in GHG emissions from the adoption of new technologies. Results show that farmers’ awareness of human-induced global climate change was positively related to the tool’s adoption.

Key policy insights

• Irish farmers are generally not sufficiently aware of the impact of their activities on climate change.

• A quarter of farmers believed that climate change will only impact on their business in the long-term; such an attitude may lead to a reluctance amongst these farmers to adopt management practices that reduce GHG emissions.

• Awareness of climate change affects positively the adoption of new tools to reduce GHG emissions on farmers’ farms.

• IT literacy affects willingness to adopt new tools to address GHG emissions.

• Reception of agri-environmental advice can have a positive influence on farmers’ willingness to adopt new GHG emission abatement tools.

• Farmers in receipt of environmental subsidies are more likely to adopt new abatement tools, either because they are more environmentally conscious or because the subsidy raised their environmentally consciousness.

• Willingness to adopt differs between different farm enterprises; operating dairy enterprise increases the willingness to adopt new advisory mitigation tools.

     

Global social and environmental change drives the management and delivery of ecosystem services from urban gardens: A case study from Central Coast,California

Urban community gardens are vital green spaces threatened by global social and environmental change factors. Population growth has reduced the amount of space available in cities, and climate change challenges plant growth thresholds. Urban community gardens provide dynamic socio-ecological systems to study how such social and environmental change factors affect the management and delivery of ecosystem services. They provide spaces where urban citizens purposefully interact with nature and receive multiple benefits. In this paper, we synthesize the results of three years of research in a case study of urban community gardens across the Central Coast of California and present a framework showing how both social and environmental change factors at the regional scale affect the ecological make-up of urban community gardens, which in turn affect the ecosystem services coming from such systems. Our study reveals that global environmental change felt at the regional level (e.g., increased built environment, climate change) interact with social change and policy (e.g., population growth, urbanization, water use policy), thus affecting regulations over garden resources (e.g., water availability) and management decisions by gardeners (e.g., soil management, crop planting decisions). These management decisions at the plot-scale, determine the ecological complexity and quality of the gardens and affect the resulting ecosystem services that come from these systems, such as food provision for both humans and urban animals. A greater understanding of how environmental and social change factors drive the management processes of urban community gardens is necessary to design policy support systems that encourage the continued use and benefits arising from such green spaces. Policies that can support urban community gardens to maintain ecological complexity and increase biodiversity through active management of soil quality and plant diversity have the potential to increase social and environmental outcomes that feedback to the larger environmental and social system.     

Convective boundary layer in the region of the Monsoon Trough—A case study

A case study of the convectively driven monsoon boundary layer has been carried out using the aerological ob-servations at four stations in the region of monsoon trough during Monsoon Trough Boundary Layer Experiment (MONTBLEX) 1988. The Convective Boundary Layer (CBL) in the region of monsoon trough did not show double mixing line structure. A single mixing line representing the CBL with different stabilities with respect to the convective activities was observed.     

The conductance of a maize crop and the underlying soil to ozone under various environmental conditions

Flux measurements of ozone and water vapour employing the eddy correlation technique were used to determine the surface conductance and canopy conductance to ozone. In the surface conductance to ozone, all surfaces at which ozone is destroyed and the transport process to these surfaces are included. The canopy conductance to ozone represents the ozone uptake of transpiring plant parts. The surface conductance to ozone of the maize crop and the underlying soil was generally larger than the canopy conductance to ozone. This means that beside the uptake by stomata, there was another important ozone sink. Under wet soil surface conditions, the surface conductance and the canopy conductance to ozone coincided. This indicates that the resistance of wet soil and the remaining plant parts (cuticle) to ozone was much larger than the stomatal or soil resistance. On the other hand, under dry soil conditions the conductances differ, largely caused by a variation in the transport process to the soil. The transport of ozone to soil increased with increasing friction velocity (u _*) and decreased with increasing atmospheric stability, leaf area index (LAI) or crop height (h). These effects for midday (unstable) conditions were parameterized with an in-crop aerodynamic resistance,r _inc in a very straightforward way;r _inc=13.9 LAIh/u _*+67 (cc.=0.77). If the ozone flux in air pollution models is described with a simple resistance model (Big Leaf model), the extra destruction at the soil should be modelled using an in-crop aerodynamic resistance. For these measurements the ozone flux to the soil was 0–65% of the total ozone flux measured above the crop. Under wet soil conditions, this was less than 20%; under dry soil conditions, this was 30–65%.     

对流边界层湍流通量及逆梯度输送参数化分析

"K"理论是众多气象预报模式中运用最广泛的湍流参数化方案之一,但无法解释"逆梯度"的输送,必须进行修正。最具代表性的修正方案有三种:方案Ⅰ(Deardroff方案)、方案Ⅱ(Holtslag和Moeng方案)和方案Ⅲ(刘烽方案)。本文利用香河的边界层观测资料对上述三种方案进行验证和比较,发现方案Ⅰ的结果在整个对流边界层(Convective Boundary Layer,CBL)呈系统性偏低,与观测不符;方案Ⅱ在CBL中上部能够再现逆梯度输送现象,基本能给出合理的湍流通量垂直分布,但在CBL的下部和上部与观测不符;方案Ⅲ的逆梯度项与高度有关,并在CBL中部达到最大,而其他两个方案中逆梯度项随高度不变。该方案不但在CBL中上部与方案Ⅱ的结果一致,并能合理表达整个CBL内的湍流通量分布,更接近观测结果。