Summertime Mixing Heights At Vienna, Austria, Estimated from Vertical Soundings and by a Numerical Model

Mixing heights calculated by the Danish OML meteorological pre-processor are compared to those diagnosed from radio- and tether-sonde vertical potential temperature profiles. All methods give reliable estimates of noon mixing heights deduced from radiosoundings, especially when the boundary layer is fully convective. Differences are larger during convective conditions without a well-defined capping inversion in the radiosonde potential temperature profile or when OML calculates a mechanical mixing height. The OML model is also able to calculate the daily course of the mixing height as expected. The tethersonde-derived mixing heights are especially valuable during the morning rise of the elevated inversion. Modifications to all three methods to improve mixing-height predictions are discussed.     

半球形多向波聚合波道振荡水柱气室优化设计

为了解决振动水柱式波浪能转换装置收集多向波浪问题,本文设计了半球形多向聚合波道振荡水柱气室结构,以适合远海单点波浪能采集和发电。在规则波正向入射条件下,基于流体仿真分析软件(FLUENT)、流体动力学连续性假设和粘性不可压缩流体动量守恒的运动方程(Navier-Stokes方程)建立半球形振荡气室和三维数值波浪水槽模型。仿真结果表明:增设气室后壁,合理设计波道开口角度实现多向迎波捕获波浪能,优化前壁形状可降低波浪触底反射带来的能量耗散,同时提高了气室内空气压强和出气口速度,有效提升波浪能俘获效率,为后续发电的二次能量转换提供高效的空气动力。     

漂浮通量箱法和扩散模型法测定内陆水体CH_4和N_2O排放通量的初步比较研究

采用漂浮通量箱法和扩散模型法同步地观测了模拟内陆水体在不同条件下的CH4和N2O的水-气交换通量,旨在比较两类方法取得结果的异同。结果显示:这两类方法所测得的绝大多数CH4排放通量都与水中溶解氧呈显著线性负相关(显著性系数P0.001)。同时N2O排放通量与表层水温及水中铵态氮、硝态氮、溶解碳和溶解氧的关系可用包含所有上述水环境因素的Arrhenius动力学方程来表达,这些因素可以共同解释86%~90%的N2O通量变化(P0.0001),且不同方法测定的N2O通量的表观活化能和对表层水温的敏感系数分别介于47~59 kJ mol-1和1.92~2.27之间;扩散模型法所获得的CH4和N2O通量分别是箱法测定值的13%~175%和15%~240%,差异程度因模型而异;不同模型取得通量间相差20%~1200%,平均相差2.3倍。上述结果表明:仅用一种模型方法来取得CH4或N2O排放通量易形成较大偏差;不同扩散模型法和箱法测定的通量在反映CH4和N2O排放的内在规律方面具有一致性,但它们对真实气体通量的测量是否都存在不同程度的系统误差,尚需进一步研究。     

新型扩散云室搭建及其对黄山地区大气冰核的观测研究

本研究利用自行搭建的大气冰核高压静电采样器和静力真空水汽扩散云室,并结合其他大气冰核及气象要素观测仪器,于2011年5～9月及2012年9～10月在黄山三层不同高度上同时进行大气冰核及相关气象要素的连续观测。结果显示:黄山地区总冰核数浓度平均为18.74 L-1,凝结冻结核化冰核数浓度平均为0.79 L-1,凝华核化冰核数浓度平均为0.19 L-1。黄山地区冰核数浓度,随着高度的增加而减小;且存在春季较高、秋季居中、夏季较少的季节变化规律;下午达到一天中的最高值,夜晚达到一天中的最低值;总冰核数浓度较北方少。黄山山顶冰核数浓度随活化温度的升高而减小,随过饱和度的升高而增大,随风速的增强而增大,长期主要由西南风向山顶的输送,且其主要由大粒子来充当。     

Evaluation of oceanic transport parameters using transient tracers from observations and model output

A method is presented to find the age distribution of ocean waters, the transit-time distribution (TTD), by combining an eddying global ocean model’s estimate of the TTD with hydrographic observations of CFC-11, temperature, and salinity. The method uses a mixture model of an assumed form of the TTD, an inverse Gaussian (IG), and an established Bayesian statistical method. All known significant sources of uncertainty are propagated to arrive at estimates of two oceanic transport parameters associated with the IG TTD, the mean age (Γ) and either the half-variance (${\mathrm{\Delta }}^2$) or the Peclet number ($\mathit{Pe}={\mathrm{\Gamma }}^2/{\mathrm{\Delta }}^2$). It is found that the uncertainties on Γ do not overlap zero in most locations using only CFC-11, temperature, and salinity. However, the uncertainty on the other IG parameter does not overlap zero in only a few locations. With the inclusion of another transient tracer (³He/³H), the uncertainty on this other IG parameter does not overlap zero in just a few additional locations in the deep North Atlantic Ocean. Neither a single- nor mixture-IG representation is adequate for representing the full TTD in the ocean, particularly in the Southern Ocean.Differences between the IG parameters estimated using the model’s tracers as data (BayesPOP) and those estimated using tracer observations as data (BayesObs) provide information about the sources of model biases, and give a more nuanced picture than can be found by comparing the simulated CFCs with observed CFCs. Using the differences between each of the oceanic transport parameters from BayesObs and those from BayesPOP with and without a constant Pe assumption along each of the hydrographic cross-sections considered here, it is found that the model’s eddy mixing biases often lead to larger model errors than the model’s mean advection time biases. It is also found that mean advection time biases in the model can be statistically significant at the 95% level where mode water is found in the Southern Ocean.     

The Characteristics of Atmospheric Ice Nuclei Measured at Different Altitudes in the Huangshan Mountains in Southeast China简

The concentration of ice nuclei （IN） and the relationship with aerosol particles were measured and analyzed using three 5-L mixing cloud chambers and a static diffusion cloud chamber at three altitudes in the Huangshan Mountains in Southeast China from May to September 2011.The results showed that the mean total number concentration of IN on the highest peak of the Huangshan Mountains at an activation temperature （Ta） of-20℃C was 16.6 L-1.When the supersaturation with respect to water （Sw） and with respect to ice （Si） were set to 5％,the average number concentrations of IN measured at an activation temperature of-20℃C by the static diffusion cloud chamber were 0.89 and 0.105 L-1,respectively.A comparison of the concentrations of IN at three different altitudes showed that the concentration of IN at the foot of the mountains was higher than at the peak.A further calculation of the correlation between IN and the concentrations of aerosol particles of different size ranges showed that the IN concentration was well correlated with the concentration of aerosol particles in the size range of 1.2-20 μtm.It was also found that the IN concentration varied with meteorological conditions,such as wind speed,with higher IN concentrations often observed on days with strong wind.An analysis of the backward trajectories of air masses showed that low IN concentrations were often related to air masses travelling along southwest pathways,while higher IN concentrations were usually related to those transported along northeast pathways.     

Impact of climate change on wetland ecosystems: A critical review of experimental wetlands

Climate change is identified as a major threat to wetlands. Altered hydrology and rising temperature can change the biogeochemistry and function of a wetland to the degree that some important services might be turned into disservices. This means that they will, for example, no longer provide a water purification service and adversely they may start to decompose and release nutrients to the surface water. Moreover, a higher rate of decomposition than primary production (photosynthesis) may lead to a shift of their function from being a sink of carbon to a source. This review paper assesses the potential response of natural wetlands (peatlands) and constructed wetlands to climate change in terms of gas emission and nutrients release. In addition, the impact of key climatic factors such as temperature and water availability on wetlands has been reviewed. The authors identified the methodological gaps and weaknesses in the literature and then introduced a new framework for conducting a comprehensive mesocosm experiment to address the existing gaps in literature to support future climate change research on wetland ecosystems. In the future, higher temperatures resulting in drought might shift the role of both constructed wetland and peatland from a sink to a source of carbon. However, higher temperatures accompanied by more precipitation can promote photosynthesis to a degree that might exceed the respiration and maintain the carbon sink role of the wetland. There might be a critical water level at which the wetland can preserve most of its services. In order to find that level, a study of the key factors of climate change and their interactions using an appropriate experimental method is necessary. Some contradictory results of past experiments can be associated with different methodologies, designs, time periods, climates, and natural variability. Hence a long-term simulation of climate change for wetlands according to the proposed framework is recommended. This framework provides relatively more accurate and realistic simulations, valid comparative results, comprehensive understanding and supports coordination between researchers. This can help to find a sustainable management strategy for wetlands to be resilient to climate change.     

Shallow and deep reservoirs involved in magma supply of the 1944 eruption of Vesuvius

 During the 1944 eruption of Vesuvius a sudden change occurred in the dynamics of the eruptive events, linked to variations in magma composition. K-phonotephritic magmas were erupted during the effusive phase and the first lava fountain, whereas the emission of strongly porphyritic K-tephrites took place during the more intense fountain. Melt inclusion compositions (major and volatile elements) highlight that the magmas feeding the eruption underwent differentiation at different pressures. The K-tephritic volatile-rich melts (up to 3 wt.% H₂O, 3000 ppm CO₂, and 0.55 wt.% Cl) evolved to reach K-phonotephritic compositions by crystallization of diopside and forsteritic olivine at total fluid pressure higher than 300 MPa. These magmas fed a very shallow reservoir. The low-pressure differentiation of the volatile-poor K-phonotephritic magmas (H₂O<1 wt.%) involved mixing, open-system degassing, and crystallization of leucite, salite, and plagioclase. The eruption was triggered by intrusion of a volatile-rich magma batch that rose from a depth of 11–22 km into the shallow magma chamber. The first phase of the eruption represents the partial emptying of the shallow reservoir, the top of which is within the volcanic edifice. The newly arrived magma mixed with that resident in the shallow reservoir and forced the transition from the effusive to the lava fountain phase of the eruption. Received: 14 September 1998 / Accepted: 10 January 1999     

环境同位素在北京平谷盆地山前侧向补给研究中的应用

利用地下水水化学和同位素测试分析成果,结合区域地质、水文地质条件研究了平谷北山山区侧向补给情况和中桥水源地地区第四系松散孔隙水和下伏岩溶水关系。结果表明：研究区第四系松散孔隙水和基岩岩溶地下水均来源于大气降水,地下水化学类型均为HCO-3-Ca2+?Mg2+ 型;平谷北山山前基岩岩溶水侧向补给平原区第四系松散孔隙水和下伏岩溶地下水;通过D值估算得到中桥水源地第四系浅层地下水的山区岩溶水侧向补给和垂向降水入渗补给比例为57：43;中桥水源地基岩岩溶水接受山区岩溶水侧向补给和第四系孔隙水垂向越流补给比例为87：13。研究成果为平谷地区地下水资源量评价和地下水动力场数值模型的建设提供了关键参数,为区域地下水的合理开采和有序回补涵养提供了科学依据。     

A pair production telescope for medium-energy gamma-ray polarimetry

We describe the science motivation and development of a pair production telescope for medium-energy (∼5–200 MeV) gamma-ray polarimetry. Our instrument concept, the Advanced Energetic Pair Telescope (AdEPT), takes advantage of the Three-Dimensional Track Imager, a low-density gaseous time projection chamber, to achieve angular resolution within a factor of two of the pair production kinematics limit (∼0.6° at 70 MeV), continuum sensitivity comparable with the Fermi-LAT front detector (<3 × 10⁻⁶ MeV cm⁻² s⁻¹ at 70 MeV), and minimum detectable polarization less than 10% for a 10 mCrab source in 10⁶ s.