共查询到20条相似文献，搜索用时 15 毫秒
1.
A one-dimensional, time-dependent cloud model with parameterized microphysics is used to investigate the processes which control the rainout and washout of soluble gases from warm, precipitating stratiform clouds. Calculations are presented simulating the distributions of soluble species within and below the cloud layer and in the precipitating raindrops as a function of time and species' solubility. Our calculations indicate that for species with low solubility, wet removal processes are relatively slow and thus do not significantly affect the species' gas-phase abundance. As a result, the removal of low-solubility species by rainout and washout is controlled by thermodynamic processes with the concentration of the species in cloud and rainwater largely determined by the species' solubility. For highly soluble species on the other hand, dissolution into cloud droplets and removal in rain is quite rapid and the abundance of highly soluble species within and below the cloud falls rapidly as soon as the precipitation begins. Because of this rapid decrease in concentration, we find that for highly soluble species: concentrations in cloud droplets near the cloud base can exceed that of raindrops by factors of 2 to 10; washout can dominate over rainout as a removal mechanism; and that, after an extended period of rainfall, the rate of removal becomes independent of the microphysical properties and rainfall rate of the cloud and is controlled by the rate of transport of material into the precipitating column by horizontal advection. 相似文献
2.
The participation of different vegetation types within the physical climate system is investigated using a coupled atmosphere-biosphere model, CCM3-IBIS. We analyze the effects that six different vegetation biomes (tropical, boreal, and temperate forests, savanna, grassland and steppe, and shrubland/tundra) have on the climate through their role in modulating the biophysical exchanges of energy, water, and momentum between the land-surface and the atmosphere. Using CCM3-IBIS we completely remove the vegetation cover of a particular biome and compare it to a control simulation where the biome is present, thereby isolating the climatic effects of each biome. Results from the tropical and boreal forest removal simulations are in agreement with previous studies while the other simulations provide new evidence as to their contribution in forcing the climate. Removal of the temperate forest vegetation exhibits behavior characteristic of both the tropical and boreal simulations with cooling during winter and spring due to an increase in the surface albedo and warming during the summer caused by a reduction in latent cooling. Removal of the savanna vegetation exhibits behavior much like the tropical forest simulation while removal of the grassland and steppe vegetation has the largest effect over the central United States with warming and drying of the atmosphere in summer. The largest climatic effect of shrubland and tundra vegetation removal occurs in DJF in Australia and central Siberia and is due to reduced latent cooling and enhanced cold air advection, respectively. Our results show that removal of the boreal forest yields the largest temperature signal globally when either including or excluding the areas of forest removal. Globally, precipitation is most affected by removal of the savanna vegetation when including the areas of vegetation removal, while removal of the tropical forest most influences the global precipitation excluding the areas of vegetation removal. 相似文献
3.
大气污染物SOx输送方程的尺度分析 总被引：5，自引：1，他引：5
文中用量纲分析方法分析了控制大气污染物输送方程的动力学特性。提出了 6种反映大气污染物输送过程中各种动力、物理和化学过程相对重要性的动力学参数。并以硫氧化物为例进行了各参数量级大小分析 ,尤其对 3种起汇作用 (去除机理 )的机理 (化学转化、干沉降和湿清除 )在不同尺度大气污染过程中的作用进行了详细分析。结果表明 :在一般情况下 ,SO2 的气相化学作用小于干沉降和湿清除的作用 ;干沉降作用很依赖于模式最底层厚度的选取 ;在有降雨时湿清除作用一般较大。文中还对大气污染物SOx 输送方程各项特征量的量级作了分析对比 ,得出了控制不同尺度大气污染物输送过程的零级近似方程和一级近似方程 ,并指出了这些方程的基本特征 相似文献
4.
Carbon removal – also known as negative emissions technologies, or greenhouse gas removal – represents a core pillar of post-Paris climate policy, signaling for enhancing and constructing carbon sinks to balance emissions sources on route to ambitious temperature targets. We build on Amory Lovins’ “hard” and “soft” alternatives for energy pathways to illuminate how foundational experts, technologists, and policy entrepreneurs think about different modes of resource inputs, infrastructure and livelihoods, and decision-making, regarding ten nature-based and engineered carbon removal approaches. Based on 90 original interviews, we show that hard and soft paths reflect different conceptions of systems, spaces, and societal involvement. We highlight that pathways depend on diverging concepts of economies-of-scale (capturing carbon at the largest possible scale, versus catalyzing systemic co-benefits) and carbon management (a waste product within conventional climate governance, versus diverse end-uses and values to be diversely governed). Our analysis further emphasizes two key uncertainties: whether renewables can be upscaled to allow synergies rather than tradeoffs between carbon removal and more widespread energy demands, and whether carbon certification can expand spatially to navigate long supply chains, and conceptually to incentivize diverse co-benefits. Experts remain motivated by antecedent concerns over land-use management and extractive industries, and that exploitative systems will – without guardrails – be replicated by inertia. 相似文献
5.
Hyun-Mi Oh Kyung-Ja Ha Ki-Young Heo Kyung-Eak Kim Sang-Jong Park Jae-Seol Shim Larry Mahrt 《Asia-Pacific Journal of Atmospheric Sciences》2010,46(4):513-523
This study presents an evaluation of the atmospheric factors influencing the post-processing for fast-response data of horizontal momentum, vertical wind component, temperature, and water vapor to measure turbulent fluxes. They are observed at the Ieodo ocean research station over the Yellow Sea during the period of October 2004 to February 2008. The post process methods employed here are composed of quality control and tilt correction for turbulent flux measurement. The present result of quality control on the fast-response data shows that total removal ratio of the data generally depends on the factors such as a wind speed, relative humidity, significant wave height, visibility, and stability parameter (z/L). Especially, the removal ratio of water vapor data is significantly increased on light wind and strong stability conditions. The results show that the total removal ratio of water vapor data increases when wind speed is less than 3 m s?1 and wave height is less than 1 m. The total removal ratio of water vapor data also increases with the value of the stability parameter. Three different algorithms of tilt correction methods (double rotation, triple rotation, and planar fit) are applied to correct the tilt of the sonic anemometer used in the observation. Friction velocities in near neutral state are greater than friction velocity in other states. Drag coefficients are categorized in terms of stabilities and seasons. 相似文献
6.
Effect of Incoming Turbulent Structure on Pollutant Removal from Two-Dimensional Street Canyon 总被引：2，自引：2，他引：0
Large-eddy simulations are conducted to investigate the effects of the incoming turbulent structure of the flow on pollutant removal from an ideal canyon. The target canyon is a two-dimensional street canyon with an aspect ratio of 1.0 (building height to street width). Three turbulent flows upwind of the street canyon are generated by using different block configurations, and a tracer gas is released as a ground-level line source at the centre of the canyon floor. Mean velocity profiles for the three flows are similar, except near the roof. However, the root-mean-square values of the velocity fluctuations and the Reynolds shear stress increase with the friction velocity of the incoming turbulent flow. The spatially-averaged concentration within the canyon decreases with increasing friction velocity. Coherent structures of low-momentum fluid, generated above the upwind block configurations, contribute to pollutant removal, and the amount of pollutant removal is directly related to the size of the coherent structure. 相似文献
7.
研究了废水中不同含盐量对生化处理效果以及生物学变化规律的影响。在废水含盐量低于22g／L时,废水生化处理系统对COD的去除率可稳定在70％左右,污泥活性良好;随着进水盐浓度的增加,含盐量达到22g／L时,污泥活性开始受到抑制,COD去除率急剧下降到50％左右;当废水含盐量达到31g／L时,污泥活性明显受到抑制,污泥絮体开始部分解体,COD去除率下降到40％左右。 相似文献
8.
Large-Eddy Simulation for the Mechanism of Pollutant Removal from a Two-Dimensional Street Canyon 总被引：3，自引：3，他引：0
Takenobu Michioka Ayumu Sato Hiroshi Takimoto Manabu Kanda 《Boundary-Layer Meteorology》2011,138(2):195-213
Large-eddy simulation (LES) is conducted to investigate the mechanism of pollutant removal from a two-dimensional street canyon
with a building-height to street-width (aspect) ratio of 1. A pollutant is released as a ground-level line source at the centre
of the canyon floor. The mean velocities, turbulent fluctuations, and mean pollutant concentration estimated by LES are in
good agreement with those obtained by wind-tunnel experiments. Pollutant removal from the canyon is mainly determined by turbulent
motions, except in the adjacent area to the windward wall. The turbulent motions are composed of small vortices and small-scale
coherent structures of low-momentum fluid generated close to the plane of the roof. Although both small vortices and small-scale
coherent structures affect pollutant removal, the pollutant is largely emitted from the canyon by ejection of low-momentum
fluid when the small-scale coherent structures appear just above the canyon where the pollutant is retained. Large-scale coherent
structures also develop above the canyon, but they do not always affect pollutant removal. 相似文献
9.
Yu Qin 《Journal of Atmospheric Chemistry》1992,14(1-4):143-151
The acidification of precipitation and the wet removal of pollutants in South China in spring are evaluated by using a one dimensional, time-dependent, physico-chemical model of stratiform clouds. The results are consistent with the mean field data. In the typical condition, the in-cloud scavenging of gases and aerosols is the major removal process at the begining of rainfall, then fractions of below-cloud scavenging of S(VI) from S(IV) oxidation, NH3, HNO3 and particles increase gradually. It can be treated as an irreversible process. Numerical tests show that the concentration of oxidants, H2O2 can affect wet removal of SO2, as well as the formation and deposition amount of S(VI). The convergence of airflow can compensate partially the depletion of pollutants by wet removal. 相似文献
10.
Alan L. Dick 《Journal of Atmospheric Chemistry》1990,11(1-2):179-196
A model has been set up to investigate the wet and dry aerosol removal processes which occur in clean air over the Antarctic Peninsula. Input for the model was obtained from bulk chemical analysis and scanning electron microscopy of aerosol and snow samples collected simultaneously at remote sites around the Peninsula. The model predicts that sulphate and sea-salt aerosol will be removed mainly in-cloud by riming of falling snow and ice crystals. Crustal aerosol is principally removed by acting as nuclei for these crystals and by impaction on falling snow. For the largest, locally-generated aerosol dry deposition is indicated as the major removal process. These findings suggest a possible mechanism for the observed air/snow fractionation. 相似文献
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12.
“麦莎”远距离台风暴雨的排熵指数分析 总被引：5，自引：0，他引：5
对2005年8月5日山东省一次远距离台风暴雨过程进行了诊断分析。从引起远距离台风暴雨的几个因素,分析此次山东地区强降水过程与台风“麦莎”及中纬度西风带系统的关系,判别台风暴雨的类型;应用耗散结构理论,分析了排熵指数与远距离台风暴雨区的关系。结果表明：该次暴雨过程是在远距离台风（0509号“麦莎”台风）和西风槽相互作用下产生的;非纬向的高、低空急流对本次暴雨过程起着重要作用;负熵变区（IRE〈0）对应着暴雨区,负熵变区的汇合反映远距离台风暴雨的落区,排熵指数对远距离台风暴雨分析预报有一定的指示作用。 相似文献
13.
通过UASB反应器处理猪粪废水试验,研究了UASB处理猪粪废水的启动过程。在水浴35℃时,接种处理啤酒废水的厌氧颗粒污泥,通过控制较低的表面水力负荷,经逐步驯化66 d,完成了启动过程。结果表明:UASB反应器对COD的去除率为88.5%,其容积负荷达到10.9 kg/(m3.d),SS去除率为90.0%或以上。试验可为农村地区资源化技术提供一定的科学依据和借鉴。 相似文献
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15.
湖北省高速公路道路结冰预警模型 总被引：3，自引：0，他引：3
利用2013年以来建立的湖北省高速公路沿线的87个交通气象观测站每10分钟一次的气温及路面温度等实况资料,对各个高速路段的路面结冰频率随气温的变化规律进行了分析,发现均满足Logistic回归模型,但不同高速路段结冰对应的环境气温有差异。通过研究各个高速路段道路结冰的气温条件概率,计算得到湖北高速各个路段拐点气温,再结合路段降水情况,可以对湖北省高速公路结冰进行预警,从而为高速公路是否开展消冰措施、何时开展消冰措施提供建议。 相似文献
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17.
A one-dimensional cloud model with size-resolved microphysics and size-resolved aqueous-phase chemistry, driven by prescribed
dynamics, has been used to study gas scavenging by weak precipitation developed from low-level, warm stratiform clouds. The
dependence of the gas removal rate on the physical and chemical properties of precipitation has been explored under controlled
initial conditions. It is found that the removal of four gaseous species (SO2, NH3, H2O2 and HNO3) strongly depends on the total droplet surface area, regardless the mean size of droplets. The removal rates also correlate
positively with the precipitation rate, especially for precipitation having a mean radius larger than 20 μm. The dependence
of the scavenging coefficients on the total droplet surface area is stronger than on the precipitation rate.
The removal rates of SO2, NH3 and H2O2 by precipitation strongly depend on the others' initial concentrations. When NH3 (or H2O2) concentration is much lower than that of SO2, the removal rate of SO2 is then controlled by the concentration of H2O2 (or NH3). The removal of NH3 (or H2O2) also directly depends on the concentration of SO2. NH3 and H2O2 can also indirectly affect each other's removal rate through interaction with SO2. The scavenging coefficient of SO2 increases with the concentration ratio of NH3 to SO2 if the ratio is larger than 0.5, while the scavenging coefficient of NH3 increases with the concentration ratio of SO2 to NH3 when the ratio is smaller than 1. The scavenging coefficient of H2O2 generally increases with the concentration ratio of SO2 to H2O2. Although the Henry's law equilibrium approach seems to be able to simulate gas scavenging by cloud droplets, it causes large
errors when used for simulating the scavenging of soluble gas species by droplets of precipitating sizes. 相似文献
18.
Carbon dioxide removal (CDR) is the only geoengineering technique that allows negative emissions and the reduction of anthropogenic carbon in the atmosphere. Since the time scales of the global carbon cycle are largely driven by the exchanges with the natural oceanic stocks, the implementation of CDR actions is anticipated to create outgassing from the ocean that may reduce their efficiency. The adjustment of the natural carbon cycle to CDR was studied with a numerical Earth System Model, focusing on the oceanic component and considering two idealized families of CDR policies, one based on a target atmospheric concentration and one based on planned negative emissions. Results show that both actions are anticipated to release the anthropogenic carbon stored in the surface ocean, effectively increasing the required removal effort. The additional negative emissions are expected to be lower when the CDR policy is driven by planned removal rates without prescribing a target atmospheric CO2 concentration. 相似文献
19.
A review of climate geoengineering proposals 总被引：2，自引：0，他引：2
Climate geoengineering proposals seek to rectify the current radiative imbalance via either (1) reducing incoming solar radiation (solar radiation management) or (2) removing CO2 from the atmosphere and transferring it to long-lived reservoirs (carbon dioxide removal). For each option, we discuss its effectiveness and potential side effects, also considering lifetime of effect, development and deployment timescale, reversibility, and failure risks. We present a detailed review that builds on earlier work by including the most recent literature, and is more extensive than previous comparative frameworks. Solar radiation management propsals are most effective but short-lived, whilst carbon dioxide removal measures gain effectiveness the longer they are pursued. Solar radiation management could restore the global radiative balance, but must be maintained to avoid abrupt warming, meanwhile ocean acidification and residual regional climate changes would still occur. Carbon dioxide removal involves less risk, and offers a way to return to a pre-industrial CO2 level and climate on a millennial timescale, but is potentially limited by the CO2 storage capacity of geological reservoirs. Geoengineering could complement mitigation, but it is not an alternative to it. We expand on the possible combinations of mitigation, carbon dioxide removal and solar radiation management that might be used to avoid dangerous climate change. 相似文献
20.
涡旋相关法测定湍流通量偏低的研究 总被引：15，自引：3，他引：12
针对野外实验所发现的不同观测法测定地表能通量不平衡问题,进行了均匀加热大气边界层的大涡模拟实验.用模拟的湍流风、温度和湿度涨落的时间序列证实,对流边界层低频涡普遍存在,并经常以一簇一簇热泡的形式出现.风速较小时,有限时长的取样不足以捕捉低频涡的贡献,可造成涡旋相关法测量的统计量异常偏低.仿照涡旋相关法的步骤进行数据处理发现,经去除平均或趋势计算的温度和湿度通量偏低程度在边界层下部随观测高度的增高而显著,其中尤以湿度通量为甚.其结果在一定程度上可以解释低风速条件下地表能通量测量的不闭合问题,但是尚不能完全解释诸如青藏高原实验出现的严重不闭合.文中对此作了探讨性的讨论. 相似文献