Performance of various similarity functions for nondimensional wind and temperature profiles in the surface layer in stable conditions

The linear functions for non-dimensional wind and temperature profiles are commonly used to describe the surface layer fluxes in atmospheric models. However, their applicability is limited to smaller values of the stability parameter z/L (where z is the height above ground and L is the Obukhov length) i.e. z/L < 1.0. These linear functions have been modified (Webb 1970, Quart. J. Roy. Meteor. Soc. 96, 67–90; Clarke 1970, Quart. J. Roy. Meteor. Soc. 96, 91–114; Hicks 1976, Quart. J. Roy. Meteor. Soc. 102, 535–551; Beljaars and Holtslag 1991, J. Appl. Meteorol. 30, 327–341; Cheng and Brutsaert 2005, Boundary-Layer Meteorol. 114, 519–538) over the years for calculating fluxes when z/L > 1.0 under strongly stable conditions. In view of this, the objective of the present study is to analyze the performance of these similarity functions to compute surface fluxes in stable conditions.The meteorological observations from the Cooperative Atmosphere-Surface Exchange Study (CASES-99) experiment are utilized for computing the surface fluxes in stable conditions. The computed fluxes are found to be reasonably close to those observed. The ratio of observed to computed fluxes reveals that the computed fluxes are close to the observations for all the similarity functions for z/L < 1.0 whereas the computed values show relatively a large scatter from observations for z/L > 1.0. The computed values of u and heat flux do not show significant differences from those observed at 99% confidence limit. The performance of all the similarity functions considered here is found to be comparable to each other in strongly stable conditions.     

Responses of Vertical Structures in Convective and Stratiform Regions to Large-Scale Forcing during the Landfall of Severe Tropical Storm Bilis （2006）

The responses of vertical structures,in convective and stratiform regions,to the large-scale forcing during the landfall of tropical storm Bilis(2006) are investigated using the data from a two-dimensional cloud-resolving model simulation.An imposed large-scale forcing with upward motion in the mid and upper troposphere and downward motion in the lower troposphere on 15 July suppresses convective clouds,which leads to ～100% coverage of raining stratiform clouds over the entire model domain.The imposed forci...     

地表通量输送对飑线过程影响的数值模拟研究

使用水平分辨率20km的RSM-RANAL再分析资料和WRF模式,对2004年7月12日影响上海地区的一次飑线过程进行分析和数值模拟,结果表明:(1)雷暴发生区域的西北侧约300km处有一冷锋,地面风场辐合;中低层为一致西南急流,雷暴发生区域上空300hPa位于西风急流右后侧辐散区中;地面存在明显的温度梯度。(2)雷暴发生前浙皖交界山区处的CAPE增至1000J/kg,CIN减至30J/kg以下;杭州湾附近的CAPE值大于2000J/kg。这些地方之后均有强对流单体生成,并成为飑线的一部分。(3)WRF模式对这次飑线过程的主要特征模拟较好,包括地面风场和飑线的结构。(4)敏感性试验指出陆面过程对本次飑线过程的形成发展起了重要作用。一方面通过潜热通量输送增大边界层湿度;另一方面通过感热通量输送改变了边界层的层结结构,使得低层辐合(或抬升)比较容易释放不稳定。在强对流天气的预报中地表条件不可忽略。     

Gap Filling and Quality Assessment of CO2 and Water Vapour Fluxes above an Urban Area with Radial Basis Function Neural Networks

Vertical turbulent fluxes of water vapour, carbon dioxide, and sensible heat were measured from 16 August to the 28 September 2006 near the city centre of Münster in north-west Germany. In comparison to results of measurements above homogeneous ecosystem sites, the CO₂ fluxes above the urban investigation area showed more peaks and higher variances during the course of a day, probably caused by traffic and other varying, anthropogenic sources. The main goal of this study is the introduction and establishment of a new gap filling procedure using radial basis function (RBF) neural networks, which is also applicable under complex environmental conditions. We applied adapted RBF neural networks within a combined modular expert system of neural networks as an innovative approach to fill data gaps in micrometeorological flux time series. We found that RBF networks are superior to multi-layer perceptron (MLP) neural networks in the reproduction of the highly variable turbulent fluxes. In addition, we enhanced the methodology in the field of quality assessment for eddy covariance data. An RBF neural network mapping system was used to identify conditions of a turbulence regime that allows reliable quantification of turbulent fluxes through finding an acceptable minimum of the friction velocity. For the data analysed in this study, the minimum acceptable friction velocity was found to be 0.15 m s⁻¹. The obtained CO₂ fluxes, measured on a tower at 65 m a.g.l., reached average values of 12 μmol m⁻² s⁻¹ and fell to nighttime minimum values of 3 μmol m ⁻² s⁻¹. Mean daily CO₂ emissions of 21 g CO₂ m⁻²d ⁻¹ were obtained during our 6-week experiment. Hence, the city centre of Münster appeared to be a significant source of CO₂. The half-hourly average values of water vapour fluxes ranged between 0.062 and 0.989 mmol m⁻² s⁻¹and showed lower variances than the simultaneously measured fluxes of CO₂.     

Solid phase characterization and metal deportment in a mussel shell bioreactor for the treatment of AMD,Stockton Coal Mine,New Zealand

The Stockton Coal Mine, located on the West Coast of New Zealand, is evaluating the use of a mussel shell bioreactor (MSB) to treat acidic metalliferous runoff from acid forming overburden. This novel approach is similar in concept to vertical flow wetlands (VFWs) and successive alkalinity producing systems (SAPS). The MSB system is a trapezoidal pit 2 m deep, 35 m long, 3–10 m wide with 60° angle sides. During operation it contained 160 tonnes (240 m³) of mussel shell material and was saturated with a 100–200 mm water cap. Influent flowed through the reactor at a mean rate of 0.3 L s⁻¹ resulting in a hydraulic retention time (HRT) of ≈6 days. The prototype MSB was in operation for a total of 1027 days, from June 2009 through March 2012, and effectively sequestered 99.7% of Al, 99.3% of Fe, 98.8% of Ni, 98.4% Tl and 99.3% of Zn, as determined from a previous evaluation of MSB performance. The MSB also effectively neutralized acidity, which resulted in an increase in influent pH from 2.8 to 6.9 in the effluent. Based on an examination of several excavated pits, five distinct reaction zones developed within the MSB. The reaction zones consisted of an allochthonous sediment layer (0–330 mm), an oxidized iron-rich ocherous layer (at 330–350 mm depth), an aluminum layer (at 350–600 mm depth) with geochemical variations throughout (350–500 mm and 500–600 mm); and a chemically reduced bottom shell layer (at 600–1100 mm). Representative samples were collected from each layer and analyzed using a combination of geochemical and physical methods to assess the stability of the secondary minerals and trace metal deportment within the MSB. Major elements Fe, Al, Ni, Tl, and Zn where preferentially associated with particular layers within the MSB. Elevated concentrations of Fe (110,000 mg kg⁻¹) were observed in the allochthonous sediment and ocherous precipitate layers, while Al (27,816 mg kg⁻¹), Ni (55 mg kg⁻¹), and Zn (655 mg kg⁻¹) were elevated within the aluminum and lower reduced depths within the MSB. Trace Tl (21 mg kg⁻¹) showed varying concentrations throughout the MSB, but was strongly correlated to lower layers of the system. Microbial biofilms were observed within the reduced portions of the shell layers often proximal to bacterial shaped sulfides. The geochemical assessment of the MSB presented in this study is the first of its kind for a MSB, and supports the argument that this system is another viable option for passive treatment of AMD.     

Presence of LaO, ScO and VO Molecular Lines in Sunspot Umbral Spectra

High-resolution Fourier Transform Spectrometer sunspot umbral spectra of the National Solar Observatory/National Optical Astronomy Observatory at Kitt Peak were used to detect rotational lines from 19 electronic transition bands of the molecules LaO, ScO and VO, in the wavenumber range of 11 775 to 20 600 cm⁻¹. The presence of lines from the following transitions is confirmed: A ² Π _r1/2 – X ² Σ ⁺(0, 0; 0, 1), A ² Π _r3/2 – X ² Σ ⁺(1, 0), B ² Σ ⁺ – X ² Σ ⁺(0, 0; 0, 1; 1, 0) and C ² Π _r1/2 – A′²Δ _r3/2(0, 0; 1, 1) of LaO; A ² Π _r3/2 – X ² Σ ⁺(0, 0), A ² Π _r1/2 – X ² Σ ⁺(0, 0) and B ² Σ ⁺ – X ² Σ ⁺(0, 0) of ScO; and C ⁴ Σ ⁻ – X ⁴ Σ ⁻(0, 1; 1, 0; 0, 2) and (2, 0) of VO. However, the presence of A ² Π _r3/2 – X ² Σ ⁺(0, 0) and C ² Π _r3/2 – A′²Δ _r5/2(0, 0; 1, 1) of LaO and C ⁴ Σ ⁻ – X ⁴ Σ ⁻(0, 0) of VO are found to be doubtful because the lines are very weak, and detections are difficult owing to heavy blending by strong rotational lines of other molecules. Equivalent widths are measured for well-resolved lines and, thereby, the effective rotational temperatures are estimated for the systems for which the presence is confirmed.     

Near‐surface hydraulic conductivity of northern hemisphere glaciers

The hydrology of near‐surface glacier ice remains a neglected aspect of glacier hydrology despite its role in modulating meltwater delivery to downstream environments. To elucidate the hydrological characteristics of this near‐surface glacial weathering crust, we describe the design and operation of a capacitance‐based piezometer that enables rapid, economical deployment across multiple sites and provides an accurate, high‐resolution record of near‐surface water‐level fluctuations. Piezometers were employed at 10 northern hemisphere glaciers, and through the application of standard bail–recharge techniques, we derive hydraulic conductivity (K) values from 0.003 to 3.519 m day^?1, with a mean of 0.185 ± 0.019 m day^?1. These results are comparable to those obtained in other discrete studies of glacier near‐surface ice, and for firn, and indicate that the weathering crust represents a hydrologically inefficient aquifer. Hydraulic conductivity correlated positively with water table height but negatively with altitude and cumulative short‐wave radiation since the last synoptic period of either negative air temperatures or turbulent energy flux dominance. The large range of K observed suggests complex interactions between meteorological influences and differences arising from variability in ice structure and crystallography. Our data demonstrate a greater complexity of near‐surface ice hydrology than hitherto appreciated and support the notion that the weathering crust can regulate the supraglacial discharge response to melt production. The conductivities reported here, coupled with typical supraglacial channel spacing, suggest that meltwater can be retained within the weathering crust for at least several days. Not only does this have implications for the accuracy of predictive meltwater run‐off models, but we also argue for biogeochemical processes and transfers that are strongly conditioned by water residence time and the efficacy of the cascade of sediments, impurities, microbes, and nutrients to downstream ecosystems. Because continued atmospheric warming will incur rising snowline elevations and glacier thinning, the supraglacial hydrological system may assume greater importance in many mountainous regions, and consequently, detailing weathering crust hydraulics represents a research priority because the flow path it represents remains poorly constrained.     

寒潮过程中风浪对黄海海气热量通量和动量通量影响研究

采用2009—2013年CFSR(Climate Forecast System Reanalysis)大气和海洋再分析资料对黄海海气间热量通量和动量通量的特征进行统计分析,并通过FVCOMSWAVE浪流耦合模式对典型寒潮过程中风浪的影响效果进行模拟研究与对比分析。统计结果显示,通量受海表大风、海气温差及海洋环流等因子影响,秋冬季节强烈,春夏季节相对较弱,在寒潮活跃的冷季该海域的海流处于弱流期,风浪对海面通量的作用明显增强。海温特征也显示冷季的不稳定性显著强于暖季,因此该海域冷季具有更强的海气热量通量。沿岸站点的比较显示,南部吕泗站面向更开阔的东海海域,其平均波高高出北部20%左右。这与沿海南部通量强于北部特征对应。数值模拟显示,在寒潮过程中,海气界面热量通量和动量通量输送比多年月平均状态显著增强,动量通量增大1~5倍,热量通量增大1~6倍。寒潮过程入海冷锋走向、强度、移动方向显著影响海面热量通量和动量通量大值区的分布。偏北路寒潮纬向型冷锋入海,其强度东部大于西部,造成通量大值区形成在黄海东北部,而偏西路寒潮经向型冷锋入海,其强度南部大于北部,造成通量大值区形成在黄海南部。同时偏北路径寒潮强度大于偏西路径,海气动量通量响应较偏西路径强约25%,热量通量强约50%。耦合风浪作用的模拟显示,海气间热量通量和动量通量明显增大,对不同强度风浪,浪高增加1.5倍,动量通量最大值增大约2倍,热量通量增大10~160 W/m2;浪高减弱至0.5倍,动量通量最大值则减弱约40%,热量通量减小10~55 W/m2。冷锋及其驱动的风浪强烈影响区域海气通量时空特征。     

The Effect of Macrofauna on Porewater Profiles and Nutrient Fluxes in the Intertidal Zone of the Humber Estuary

Macrofauna, nutrient fluxes, porewater chemistry and sediment characteristics were measured at six intertidal mudflat sites in the Humber Estuary, U.K., during the different seasons. Nereis diversicolor , Macoma balthica and Corophium volutator were found to be the dominant macrofauna. Salinity was the baseline control on macrofauna distribution but this was overprinted by periodic impoverishment due to sediment mobilization. High resolution gel probe porewater samplers provided direct evidence for the impact of burrows on porewater chemistry. The macrofauna modified nutrient fluxes during periods of mud flat stability. Nereis caused a decrease in silicate and phosphate effluxes but enhanced ammonia release and nitrate uptake. Macoma enhanced ammonia and nitrite release. The impact of Corophium was not possible to discern. The Humber is a large, highly dynamic macrotidal estuary in which sediment resuspension has a large impact on porewater profiles, nutrient fluxes and macrofaunal communities. Simple patterns and inter-relationships which are seen in small sheltered estuaries are not observed in the Humber.     

Characteristics of metals in atmosphere over the western Taiwan Strait Ⅱ. Sources and fluxes

I~IOWDuceetal.(1980)calculatedthattheair-seaexchangeprocesscouldsupply80%--90%ofthediforedironinputtothephotcrzoneoftheSargassoAsfromairand16%--76%tothecentralNorthPacific.CuisessentialtotheTnarineorganisms,butexcessiveCuistoxictOtheOrganisms.CdandPh...