Determination of the Atmospheric Boundary Layer Height from Radiosonde and Lidar Backscatter

The height of the atmospheric boundary layer is derived with the help of two different measuring systems and methods. From radiosoundings the boundary layer height is determined by the parcel method and by temperature and humidity gradients. From lidar backscatter measurements a combination of the averaging variance method and the high-resolution gradient method is used to determine boundary layer heights. In this paper lidar-derived boundary layer heights on a 10 min basis are presented. Datasets from four experiments – two over land and two over the sea – are used to compare boundary layer heights from both methods. Only the daytime boundary layer is investigated because the height of the nighttime stable boundary layer is below the range of the lidar. In many situations the boundary layer heights from both systems coincide within ±200 m. This corresponds to the standard deviation of lidar-derived 10-min values within a 1-h interval and is due to the time and space variability of the boundary layer height. Deviations appear for certain situations and depend on which radiosonde method is applied. The parcel method fails over land surfaces in the afternoon when the boundary layer stabilizes and over the ocean when the boundary layer is slightly stable. An automatic radiosonde gradient method sometimes fails when multiple layers are present, e.g. a residual layer above the growing convective boundary layer. The lidar method has the advantage of continuous tracing and thus avoids confusion with elevated layers. On the other hand, it mostly fails in situations with boundary layer clouds     

Factor analysis for El Niño signals in sea surface temperature and precipitation

Maximum likelihood factor analysis (MLFA) is applied to investigate the variables of monthly Tropical Pacific sea surface temperatures (SST) from Niño 1+2, Niño 3, Niño 3.4, and Niño 4 and precipitation over New South Wales and Queensland of eastern Australia, Kalimantan Island of Indonesia, and California and Oregon of the west coast of the United States. The monthly data used were from 1950 to 1999. The November-February SST with time leads of 0, 1, 2, and 3 months to precipitation are considered for both El Niño warm phases and non El Niño seasons. Interpretations of the factor loadings are made to diagnose relationships between the SST and precipitation variables. For El Niño signals, the rotated FA loadings can efficiently group the SST and precipitation variables with interpretable physical meanings. When the time lag is 0 or 1 month, the November–February El Niño SST explains much of the drought signals over eastern Australia and Kalimantan. However, when the time lag is 2 or 3 months, the same SST cannot adequately explain the precipitation during January–May over the two regions. Communality results of five factors for precipitation indicate nearly 100% explanation of variances for Queensland and California, but the percentages are reduced to only about 30% for Oregon and Kalimantan. Factor scores clearly identify the strongest El Niño relevant to precipitation variations. Principal component factor analysis (PCFA) is also investigated, and its results are compared with MLFA. The comparison indicates that MLFA can better group SST data relevant to precipitation. The residuals of MLFA are always smaller than the PCFA. Thus, MLFA may become a useful tool for improving potential predictability of precipitation from SST predictors.     

使用地震波反映地球的内部结构

在地球内部产生的地震波提供了帮助我们更好地认识驱动板块运动的地幔对流方式的图案。海底扩张的发现和板块构造理论被接受以后的四十年,重要的盲点在于我们对驱动板块运动的地幔对流的方式以及导致地震、海啸和火山爆发等的原因知之甚少,目前仍然有许多激烈的争论。海洋岩石圈向下嵌入内陆板块,在板块汇聚边界处达到了地球的地幔底部了吗？细热的地幔柱上升通过板块中部“热点”火山下面的地幔了吗？     

EAF implementation in Southern Africa: Lessons learnt

The practical implementation of an ecosystem approach to fisheries (EAF) management has proved difficult to achieve. Without simple and structured guidelines for implementing an EAF, managers are grappling with the complexity of implementation and the need to prioritise resources and management actions. Ecological risk assessment has been put forward as a structured procedure. There is a need to review regularly whether progress is being made in addressing the issues and priorities identified through ecological risk assessment. Such reviews require a framework providing clear objectives for the respective fishery and delineating the steps required towards their achievement. This paper proposes a generic framework for reviewing ecological risk assessments through stakeholder workshops. This framework is aided by a fuzzy logic tool to track EAF implementation and informs the development of proactive work plans which incorporate EAF objectives. The advantages and disadvantages of a generic and participatory approach are discussed and compared with other related methods for evaluating progress in implementing an EAF.     

Remotely sensed rivers in the Anthropocene: state of the art and prospects

The rivers of the world are undergoing accelerated change in the Anthropocene, and need to be managed at much broader spatial and temporal scales than before. Fluvial remote sensing now offers a technical and methodological framework that can be deployed to monitor the processes at work and to assess the trajectories of rivers in the Anthropocene. In this paper, we review research investigating past, present and future fluvial corridor conditions and processes using remote sensing and we consider emerging challenges facing fluvial and riparian research. We introduce a suite of remote sensing methods designed to diagnose river changes at reach to regional scales. We then focus on identification of channel patterns and acting processes from satellite, airborne or ground acquisitions. These techniques range from grain scales to landform scales, and from real time scales to inter-annual scales. We discuss how remote sensing data can now be coupled to catchment scale models that simulate sediment transfer within connected river networks. We also consider future opportunities in terms of datasets and other resources which are likely to impact river management and monitoring at the global scale. We conclude with a summary of challenges and prospects for remotely sensed rivers in the Anthropocene. © 2019 John Wiley & Sons, Ltd.     

The source of raw materials for Roman pottery from Leptiminus,Tunisia

Leptiminus, a Roman port city on the west coast of Tunisia, North Africa, exported olive oil and a garum fish paste to Rome. Excavations have uncovered many facilities including kilns and a potter's workshop, indicating an extensive ceramic industry. The vessels, manufactured at Leptiminus, included African red‐slip fineware, coarseware, and amphorae. A petrographic study of pottery sherds showed them to contain very similar temper, rounded aeolian sand grains and limestone, but varying in proportions to produce different textures. An investigation of the source of raw materials for the pottery found three distinct types of clay within a 50 km radius of Leptiminus: grey Miocene, brown Pliocene, and green Late Pliocene clay. Statistical analysis of trace element compositions, using induced neutron activation, of clays and sherds showed that the Pliocene brown clay was used to create all types of pottery. The specific clay horizon, used in Roman times, has apparently been removed by quarrying. However, a lateral continuation of this bed was found 7 m beneath the Leptiminus site 290. © 2002 Wiley Periodicals, Inc.     

Sampling Method for the Determination of Total Inorganic Carbon (TIC) in Strongly Acidic Waters

Samples from extremely acidic waters should be taken using the introduced syringe technique avoiding atmospheric contact to minimize CO2 evaporation from the samples. The syringe technique inclusive manual injection enables the determination of TIC in acid waters with high precision and accuracy. If a TOC analyser with a small sample volume is used, the vials should be filled directly inside the water sampler without air bubbles, covered with aluminium foil and transported at ambient water temperatures. If an autosampler is used, partial selection of the vials increases the stability of the results. Care should be taken that samples can be analysed within a short time.     

Vertical accretion rates in fluvial systems: ­a comparison of volumetric and depth‐based estimates

A wide range of approaches has been adopted for collecting and reporting vertical accretion rates, hence evaluation of results from different catchments, or even from different reaches within the same basin, is difficult as they may not be directly comparable. The present study compares depth‐ and volume‐based estimates of sediment accumulation for well‐dated vertical accretion sequences at Broomhaugh Island in the Tyne basin, northern England. High resolution dating control (based on heavy metal stratigraphy and cartography) coupled with detailed reconstruction of channel geometry allows accumulation rates to be calculated for the last 300–400 years. The results show a marked disparity in the magnitude and pattern of vertical accretion rates between the two approaches. The average annual thickness of sediment increases progressively, with a six‐fold difference between the seventeenth and twentieth centuries. The volume figures are more consistent, with a two‐fold difference between the highest and lowest rates, both of which occurred in the twentieth century. A major control on vertical accretion is found to be changing channel shape and capacity. Enlargement of the channel by 76 per cent since the seventeenth century, associated with channel bed incision, has resulted in fewer overbank flows. Hence floods, with their associated suspended sediment loads, which once inundated the floodplain are now confined within the channel. The reduced areal extent of surfaces available for deposition has resulted in greater annual thickness of sediment accumulated, despite an overall reduction in volume. This study emphasizes that caution is needed when attempting to identify causal linkages between changes in sedimentation rates and catchment land use and/or climatic factors and the geomorphological setting of the site must be taken into account. Copyright © 2000 John Wiley & Sons, Ltd.