An investigation of a method for predicting dew duration

Summary A method is described for the prediction of dew duration with the aid of a nomogram involving synoptic parameters. In order to enter the nomogram, knowledge of the net radiation, a characteristic dew point depression, and the wind speed near the surface is required. Methods for estimating the net radiation and the dew point depression are described.Data collected in 1954 at 18 stations representing a variety of climatic zones in the United States were analysed in nomogram form. The characteristics of the nomograms are found to be dependent on the thermal characteristics of the underlying surface. An attempt is made to relate the synoptic parameters employed to the physical processes of heat exchange at the interface. Difficulties of the forecasting problem are discussed.

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Zusammenfassung Eine Nomogramm-Methode zur Vorhersage des Auftretens und der Andauer von Tau wird beschrieben. Zur Anwendung dieser Methode werden Angaben über die Strahlungsbilanz an der Erdoberfläche, über eine charakteristische Differenz zwischen Luft- und Taupunktstemperatur sowie über die Windgeschwindigkeit in Bodennähe benötigt. Verfahren zur Abschätzung der Strahlungsbilanz und der Taupunktsdepression werden beschrieben.Die Ergebnisse umfangreicher Taubeobachtungen, welche im Sommer 1954 an 18 Stationen in verschiedenen Klimagebieten der Vereinigten Staaten gesammelt wurden, werden in Nomogrammform analysiert. Die Charakteristiken der Nomogramme erweisen sich als abhängig von den thermischen Eigenschaften der Bodenunterlage. Es wird der Versuch gemacht, die Nomogrammparameter zu den physikalischen Prozessen des Wärmeumsatzes an der Erdoberfläche in Beziehung zu setzen. Die Schwierigkeiten des Problems einer Tauvorhersage werden erörtert.

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Résumé On décrit une méthode de prévision de la durée de rosée basée sur des nomogrammes. Pour appliquer cette méthode il faut connaître le bilan radiatif à la surface du sol, une différence caractéristique entre la température de l'air et celle du point de rosée, ainsi que la vitesse du vent près du sol. On décrit également des procédés pour estimer le bilan radiatif et la dépression du point du rosée.Les résultats d'un grand nombre d'observations de rosée, qui ont été faites pendant l'été 1954 à 18 stations dans diverses régions climatiques des Etats-Unis, sont analysés à l'aide de nomogrammes. Les caractéristiques de ceux-ci ont été reconnues comme dépendantes des conditions thermiques du sol. On tente de mettre en rapport les paramètres de ces nomogrammes avec les processus physiques de l'économie thermique à la surface du sol. Pour terminer on discute les difficultés du problème de la prévision de la rosée.

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With 11 Figures     

Synchronous syntectonic granite emplacement in the south palmer river region,Hodgkinson Province,Australia

Deformation partitioning in pluton wall‐rocks during granite intrusion that is synchronous with regional tectonism potentially creates structures suggesting different timing of emplacement. This is due to variations in style and intensity of fabric development, particularly porphyroblast‐matrix microstructures. In the South Palmer River region, detailed mapping plus microstructural examination of matrix and porphyroblast‐matrix relationships assist correlation of deformation elements across variations in deformation style and intensity. The results indicate that the emplacement of each granite body occurred during the compressional Permian D₄ event. The fabrics that developed regionally and in the pluton/wall‐rock systems during D₄ show differing degrees of intensity and style, which are spatially related to the intensity of D₄ fabric development in the adjacent country rock. Granite isotopic ages support non‐diachronous formation of D₄ structures across the region.     

Continental shelf wave scattering by a semi-infinite coastline; partial removal of the “rigid lid”

Abstract

By relaxing the rigid-lid approximation in the ocean, significant improvements are made to the mathematical and physical aspects of a previously presented model. The difficulties associated with |κ| in wavenumber space are eliminated and the velocities remain bounded at the coastal tip. The method of solution has significant changes but the well-known shelf waves are essentially unaltered and the overall conclusions are similar.     

LNAPL Recovery Endpoints: Lessons Learnt Through Modeling,Experiments, and Field Trials

It is important to estimate what light nonaqueous phase liquid (LNAPL) recovery can be practicably achieved from subsurface environments. Over the last decade, research to address this included a broad field program, laboratory measurements and experimentation, and modeling approaches. Here, we consolidate key findings from the research in the context of current literature and understanding, with a focus on a well-validated, multiphase multicomponent modeling approach to achieve estimates of reasonable endpoints for LNAPL recovery. Simple analytical models can provide approximate saturation distributions and estimates of LNAPL recoverability via transmissivity approximation, but are insufficient to predict LNAPL saturation- and composition-based recovery endpoints for various recovery technologies. This is because they cannot account for multiphase, multicomponent fate and transport and key processes such as hysteresis. Recent advances to improve estimates of the fraction of recoverable LNAPL and its transmissivity are summarized. These advances include further development and application of a well-validated model to characterize active LNAPL recovery endpoints. We present key factors that affect the determination of LNAPL recovery endpoints, and outline how recovery endpoints are affected by natural source zone depletion (NSZD—currently gaining acceptance as a LNAPL remediation option). Major factors include geo-physical characteristics of the formation, magnitude of an LNAPL release and partitioning properties of the key LNAPL constituents of concern. Based on the capabilities of the validated model, the paper also provides a basis to optimize LNAPL recovery efforts.     

Chemical composition of HAL,an isotopically-unusual Allende inclusion

Thirty-seven major, minor and trace elements were determined by INAA and RNAA in samples of hibonite, black rim and portions of friable rim from an unusual Allende inclusion, HAL. The peculiar isotopic, mineralogical and textural properties of HAL are accompanied by very unusual trace element abundances. The most striking feature of the chemistry is the virtual absence of Ce from an inclusion otherwise highly enriched in REE compared to Cl chondrites. HAL is also depleted in Sr, Ba, U, V, Ru, Os and Ir, relative to other refractory elements. Of the lithophile elements determined which are normally considered to be refractory in a gas of solar composition, Sr, Ba, Ce, U and V are the most volatile in oxidizing gases. The distribution of REE between hibonite and rims seems to have been established when hibonite and other refractory minerals were removed at slightly different temperatures from a hot, oxidizing gas in which they previously coexisted as separate grains. On the basis of HAL's chemical and isotopic composition, possible locations for the chemical and mass dependent isotopic fractionation are in ejecta from the low temperature helium-burning zone of a supernova and in the locally oxidizing environment generated by evaporation of interstellar grains of near-chondritic chemical composition.     

水泥材料碳汇研究综述

本文从水泥材料碳汇发生原理、碳化影响因素、混凝土水泥碳汇、砂浆水泥碳汇与水泥窑灰碳汇等方面,综述水泥材料整个生命周期碳汇的相关研究。众多研究表明,水泥材料的碳化过程受水泥的材料因素和环境因素影响较大;混凝土在在建筑使用阶段的碳汇量核算方法主要通过碳化深度定量表达,而在拆毁和回收利用阶段的碳汇核算方法缺乏;砂浆水泥和水泥窑灰的碳化速度要高于混凝土,但其碳汇核算方法仍未建立。今后的研究应侧重以下几个方面:继续加强水泥材料碳汇影响因素及相应碳化参数的研究,从生命周期角度系统建立完整的水泥材料碳汇核算方法体系;精确核算中国乃至全球水泥材料年碳吸收量、碳汇累积量,并分析水泥材料碳汇在碳失汇中的贡献比例;从生态学和气候变化视角阐述水泥材料碳汇对城市碳循环的影响。     

Airborne measurements of dimethylsulfide,sulfur dioxide,and aerosol ions over the Southern Ocean South of Australia

Vertical distributions of dimethylsulfide (DMS), sulfur dioxide (SO₂), aerosol methane-sulfonate (MSA), non-sea-salt sulfate (nss-SO₄ ^2-), and other aerosol ions were measured in maritime air west of Tasmania (Australia) during December 1986. A few cloudwater and rainwater samples were also collected and analyzed for major anions and cations. DMS concentrations in the mixed layer (ML) were typically between 15–60 ppt (parts per trillion, 10^–12; 24 ppt=1 nmol m^–3 (20°C, 1013 hPa)) and decreased in the free troposphere (FT) to about <1–2.4 ppt at 3 km. One profile study showed elevated DMS concentrations at cloud level consistent with turbulent transport (cloud pumping) of air below convective cloud cells. In another case, a diel variation of DMS was observed in the ML. Our data suggest that meteorological rather than photochemical processes were responsible for this behavior. Based on model calculations we estimate a DMS lifetime in the ML of 0.9 days and a DMS sea-to-air flux of 2–3 mol m^–2 d^–1. These estimates pertain to early austral summer conditions and southern mid-ocean latitudes. Typical MSA concentrations were 11 ppt in the ML and 4.7–6.8 ppt in the FT. Sulfur-dioxide values were almost constant in the ML and the lower FT within a range of 4–22 ppt between individual flight days. A strong increase of the SO₂ concentration in the middle FT (5.3 km) was observed. We estimate the residence time of SO₂ in the ML to be about 1 day. Aqueous-phase oxidation in clouds is probably the major removal process for SO₂. The corresponding removal rate is estimated to be a factor of 3 larger than the rate of homogeneous oxidation of SO₂ by OH. Model calculations suggest that roughly two-thirds of DMS in the ML are converted to SO₂ and one-third to MSA. On the other hand, MSA/nss-SO₄ ^2- mole ratios were significantly higher compared to values previously reported for other ocean areas suggesting a relatively higher production of MSA from DMS oxidation over the Southern Ocean. Nss-SO₄ ^2- profiles were mostly parallel to those of MSA, except when air was advected partially from continental areas (Africa, Australia). In contrast to SO₂, nss-SO₄ ^2- values decreased significantly in the middle FT. NH₄ ⁺/nss-SO₄ ^2- mole ratios indicate that most non-sea-salt sulfate particles in the ML were neutralized by ammonium.     

A Case Study on the Effects of Heterogeneous Soil Moisture on Mesoscale Boundary-Layer Structure in the Southern Great Plains, U.S.A. Part I: Simple Prognostic Model

The atmospheric boundary-layer (ABL) depth was observed by airborne lidar and balloon soundings during the Southern Great Plains 1997 field study (SGP97). This paper is Part I of a two-part case study examining the relationship of surface heterogeneity to observed ABL structure. Part I focuses on observations. During two days (12–13 July 1997) following rain, midday convective ABL depth varied by as much as 1.5 km across 400 km, even with moderate winds. Variability in ABL depth was driven primarily by the spatial variation in surface buoyancy flux as measured from short towers and aircraft within the SGP97 domain. Strong correlation was found between time-integrated buoyancy flux and airborne remotely sensed surface soil moisture for the two case-study days, but only a weak correlation was found between surface energy fluxes and vegetation greenness as measured by satellite. A simple prognostic one-dimensional ABL model was applied to test to what extent the soil moisture spatial heterogeneity explained the variation in north–south ABL depth across the SGP97 domain. The model was able to better predict mean ABL depth and variations on horizontal scales of approximately 100 km using observed soil moisture instead of constant soil moisture. Subsidence, advection, convergence/divergence and spatial variability of temperature inversion strength also contributed to ABL depth variations. In Part II, assimilation of high-resolution soil moisture into a three-dimensional mesoscale model (MM5) is discussed and shown to improve predictions of ABL structure. These results have implications for ABL models and the influence of soil moisture on mesoscale meteorology     

Assessing the additive risks of PSII herbicide exposure to the Great Barrier Reef

Herbicide residues have been measured in the Great Barrier Reef lagoon at concentrations which have the potential to harm marine plant communities. Monitoring on the Great Barrier Reef lagoon following wet season discharge show that 80% of the time when herbicides are detected, more than one are present. These herbicides have been shown to act in an additive manner with regards to photosystem-II inhibition. In this study, the area of the Great Barrier Reef considered to be at risk from herbicides is compared when exposures are considered for each herbicide individually and also for herbicide mixtures. Two normalisation indices for herbicide mixtures were calculated based on current guidelines and PSII inhibition thresholds. The results show that the area of risk for most regions is greatly increased under the proposed additive PSII inhibition threshold and that the resilience of this important ecosystem could be reduced by exposure to these herbicides.     

Dynamics of herbicide transport and partitioning under event flow conditions in the lower Burdekin region, Australia

This study examined the temporal variability in herbicide delivery to the Great Barrier Reef (GBR) lagoon (Australia) from one of the GBR catchment's major sugarcane growing regions. Annual loads of measured herbicides were consistently in the order of 200+kg. Atrazine, it's degradate desethylatrazine, and diuron contributed approximately 90% of annual herbicide load, with early 'first-flush' events accounting for the majority of herbicide loads leaving the catchment. Assessment of herbicide water-sediment partitioning in flood runoff highlighted the majority of herbicides were transported in predominantly dissolved form, although a considerable fraction of diuron was transported in particulate-bound form (ca. 33%). Diuron was also the herbicide demonstrating the highest concentrations and frequency of detection in sediments collected from catchment waterways and adjacent estuarine-marine environments, an outcome aligning with previous research. Herbicide physico-chemical properties appear to play a crucial role in partitioning between water column and sediment habitat types in GBR receiving ecosystems.