Reduced Horizontal Sea Surface Temperature Gradients Under Conditions of Clear Skies and Weak Winds

Consideration of the dependence of various components of the sea-surface heat and momentum fluxes on sea surface temperature (SST) leads to an explanation for the observed reduction in the horizontal temperature gradients in the uppermost layer of the ocean (a few to 10 m in depth). Horizontal temperature gradients within the mixed layer can be masked by a near-surface layer of warm water. This camouflage of horizontal temperature gradients has importance for the remote sensing of SST used by the fishing industry, for the estimation of acoustic transmission, and for the forecasting of hurricane development, among many uses of SST data. Diurnal warming conditions in the Straits of Florida are examined by a simulation calculation and by analysis of observations obtained on moorings deployed on the south-east Florida shelf. When there is net heating (i.e., the solar input is stronger than the combined latent, sensible and longwave radiative heat losses) the originally warmer water experiences less heating than the colder water, leading to a weakening of the horizontal SST gradients as seen by surface buoys or satellites. The warmer water also experiences more mixing and therefore less increase in temperature. The strongest effect of the diurnal heating on wind stress occurs when the SST starts out cooler than the air temperature and the atmosphere is stably stratified. Diurnal warming can then rapidly increase the SST above the air temperature because of reduced wind stress and reduced upper-ocean mixing. After that the wind stress increases as convectively driven turbulence contributes to the atmospheric exchange.     

Fluorite Deposits at Voznesenka in the Khanka Massif, Russia: Geology and Age of Mineralization

Abstract. A huge fluorite deposit at Voznesenka in the Khanka massif, Far East Russia is concluded to have formed at ca. 450 Ma in Late Ordovician time based on the K‐Ar ages for Li‐micas in the fluorite ore and greisenized leucogranite within the deposit. This conclusion is inconsistent with the current view of Devonian mineralization that stemmed from widely scattered whole‐rock Rb‐Sr isotope data for the heterogeneous leucogranite stocks influenced by strong alteration. The Voznesenka and neighboring fluorite deposits may have formed in Cambrian limestone in relation to the intrusion of the Li‐F‐rich felsic magma which has a similar chemistry to representative Li‐F‐rich felsic rocks including topaz granite and ongonite or topaz rhyolite; these rocks may be classified as a specific group of highly fractionated felsic magmas. Biotite granite plutons exposed in the Voznesenka district are divided in age into two groups based on the CHIME age data for zircon, monazite and xenotime: Ordovician and Permian. The Ordovician plutons seem to be coeval to the fluorite deposits and are characterized by F‐rich chemistry, reduced nature and association of tin mineralization with the deposition of fluorite and tourmaline. The biotite granite magmas of initially enhanced F contents could have been highly fractionated to form Li‐F‐rich leucogranite cupolas that provided fluorite deposits within the host limestone. Future prospecting for similar fluorite deposits is to be focused on areas of intersection between Ordovician Li‐F‐rich granite and Cambrian carbonate sequences. The Permian granite of southeastern margin of the Grodekovo batholith is characterized by lesser F content, oxidized nature and the lack of tin and fluorite mineralization in contrast to the Ordovician granite. The result of Permian age does not support the current view of Silurian age for the batholith and requires overall chronological reinvestigation in connection with the tectonic history of the Khanka massif because the Grodekovo is a representative of Paleozoic batholiths in Primorie.     

Supply limited sediment transport in a high-discharge event of the tropical Burdekin River, North Queensland, Australia

Interactions between catchment variables and sediment transport processes in rivers are complex, and sediment transport behaviour during high‐flow events is not well documented. This paper presents an investigation into sediment transport processes in a short‐duration, high‐discharge event in the Burdekin River, a large sand‐ and gravel‐bed river in the monsoon‐ and cyclone‐influenced, semi‐arid tropics of north Queensland. The Burdekin's discharge is highly variable and strongly seasonal, with a recorded maximum of 40 400 m³ s^?1. Sediment was sampled systematically across an 800 m wide, 12 m deep and straight reach using Helley‐Smith bedload and US P‐61 suspended sediment samplers over 16 days of a 29‐day discharge event in February and March 2000 (peak 11 155 m³ s^?1). About 3·7 × 10⁶ tonnes of suspended sediment and 3 × 10⁵ tonnes of bedload are estimated to have been transported past the sample site during the flow event. The sediment load was predominantly supply limited. Wash load included clay, silt and very fine sand. The concentration of suspended bed material (including very coarse sand) varied with bedload transport rate, discharge and height above the bed. Bedload transport rate and changes in channel shape were greatest several days after peak discharge. Comparison between these data and sparse published data from other events on this river shows that the control on sediment load varies between supply limited and hydraulically limited transport, and that antecedent weather is an important control on suspended sediment concentration. Neither the empirical relationships widely used to estimate suspended sediment concentrations and bedload (e.g. Ackers & White, 1973) nor observations of sediment transport characteristics in ephemeral streams (e.g. Reid & Frostick, 1987) are directly applicable to this river.     

Correcting the errors from variable sea salt retention and water of hydration in loss on ignition analysis: Implications for studies of estuarine and coastal waters

The standard technique of determining the concentrations of total suspended solids (TSSs), particulate inorganic matter (PIM), and particulate organic matter (POM) by filtration with glass fiber filters is subject to an error or bias from sea salt plus water of hydration retention, when applied to saline waters. The sea salt plus water of hydration retention by the filters occurs even after washing the filter with 300 ml of deionized water, a greater volume than any wash recommended in the literature. We determined that the mass retention on a glass fiber filter, at a given salinity, is essentially constant, no matter the volume of seawater passed through the filter. We also determined that the sea salt plus water of hydration retention on glass fiber filters is directly proportional to the salinity of the seawater filtered. Sea salt plus water of hydration retention causes an overestimate of TSS; sea salt retention causes an overestimate of PIM; volatilization of water of hydration causes an overestimate of POM. Thus a correction curve is required for sea salt and water of hydration errors in the determination of TSS and PIM. Corrected POM comes from the difference between the two. Also, filter blanks (procedural control filters), run with deionized (DI) water rather than the seawater sample, are required to correct for possible filter mass loss during the analysis. We demonstrate correction curves for sea salt plus water of hydration retention for Whatman GF/F filters, 47 mm diameter, utilizing the methods of the APHA Manual, Standard Methods for the Examination of Water and Wastewater. Application of other glass fiber filter types or an analytical technique differing significantly from that employed here requires a different correction curve for retention of sea salt and water of hydration. These methods can be used to reanalyze older data on PIM, POM, and TSS.We apply these corrections to PIM and POM data from the northern Gulf of Mexico and examine the interactions of these filter corrections with corrections for structural water volatilization from suspended clay minerals in the determinations of PIM and POM. We analyze published data on PIM and POM determinations and their application to remote sensing. We conclude that sea salt and water of hydration retention on filters has an adverse effect on remote-sensing algorithms inverting radiance reflectance to estimate concentrations of suspended matter.     

Temperature and precipitation extremes in the second half of the twentieth century from numerical modeling results and observational data

The procedure and results of an objective comparison of climatologies and historical trends of temperature and precipitation extremes are considered using observations and numerical experiments of 20th-century climate simulations. The experimental climatic realizations of five coupled atmosphere-ocean models represented in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change are used. The effect of using ensembles of climatic realizations (including multimodel ensembles) in the problems of simulating climatology and climate changes in annual meteorological extremes is estimated. The positive effect of the ensemble approach is evident when individual ensemble members show significant success.     

A simplified method for unified buckling and free vibration analysis of pile-supported structures in seismically liquefiable soils

In seismic-prone zones with liquefiable deposit piles are routinely used to support structures (buildings/bridges). In this paper, a unified buckling and dynamic approach is taken to characterize this vibration. The pile–soil system is modelled as Euler–Bernoulli beam resting against an elastic support with axial load and a pile head mass with rotary inertia. The emphasis here is to obtain a simple expression that can be used by practicing engineers to obtain the fundamental frequency of the structure–pile–soil system. An approximate method based on an equivalent single-degree-of-freedom model has been proposed. Natural frequencies obtained from the exact analytical method are compared with approximate results. Proposed expressions are general as they are functions of non-dimensional parameters. It is shown that this simplified method captures the essential design features such as: (a) the continuous reduction of the first natural frequency of the structure–pile–soil system due to progressive reduction of soil stiffness due to liquefaction; (b) the reduction in the axial load-carrying capacity of the pile due to instability caused by liquefaction. The results derived in this paper have the potential to be directly applied in practice due to their simple yet general nature. An example problem has been taken to demonstrate the application of the method.     

An easy approach to assess the susceptibility of a landslide by utilizing simple raster overlay methods: A case study on Huangtupo landslide (P.R. China)

Semi qualitative index based methods using rankings and ratings are commonly used in susceptibility estimations over a wide area. However, generalized ranking and ratings are not applicable for one single landslide. This paper gives an easy and transferable approach to a susceptibility assessment of Huangtupo landslide (P.R. China), using raster addition without taking account for ranking and ratings. Slope, aspect, curvature, location and drainage buffer distance raster data sets have been obtained out of open source digital elevation models using ESRI’s ArcGIS. These conditioning factor raster data sets have been translated into raster data sets including simple yes or no criteria, referring to triggering or not. Subsequently they have been added by raster math to acquire a simple raster overlay map. After that this map is compared to initial displacement measurements, obtained by using a ground based synthetic aperture radar device. Acquired data is recalculated to a raster data set using the same spatial extent, to provide the possibility of comparison of the two raster data sets. The results reveal, that 76.35% of all measured movements occur in areas where raster cells include three or more conditioning factors, indicating that easy raster math operations can lead to satisfying results in local scale.     

Toward Improved Solar Irradiance Forecasts: a Simulation of Deep Planetary Boundary Layer with Scattered Clouds Using the Weather Research and Forecasting Model

Accurate forecasts of solar irradiance are required for electric utilities to economically integrate substantial amounts of solar power into their power generation portfolios. A common failing of numerical weather models is the prediction of scattered clouds at the top of deep PBL which are generally difficult to be resolved due to complicated processes in the planetary boundary layer. We improved turbulence parameterization for better predicting solar irradiance during the scattered clouds’ events using the Weather Research and Forecasting model. Sensitivity tests show that increasing the exchange coefficient leads to enhanced vertical mixing and a deeper mixed layer. At the top of mixed layer, an adiabatically ascending air parcel achieved the water vapor saturation and finally scattered cloud is generated.     

Land cover dynamics monitoring with Landsat data in Kunming,China: a cost-effective sampling and modelling scheme using Google Earth imagery and random forests

Changes in forest composition impact ecological services, and are considered important factors driving global climate change. A hybrid sampling method along with a modelling approach to map current and past land cover in Kunming, China is reported. MODIS land cover (2001–2011) data-sets were used to detect pixels with no apparent change. Around 3000 ‘no change points’ were systematically selected and sampled using Google Earth’s high-resolution imagery. Thirty-five per cent of these points were verified and used for training and validation. We used Random forests to classify multi-temporal Landsat imagery. Results show that forest cover has had a net decrease of 14385?ha (1.3% of forest area), which was primary converted to shrublands (11%), urban and barren land (2.7%) and agriculture (2.5%). Our validation indicates an overall accuracy (Kappa) of 82%. Our methodology can be used to consistently map the dynamics of land cover change in similar areas with minimum costs.     

圣彼得堡土地利用格局现状特征及形成机制

以圣彼得堡市为例,依据1948、1987和2016年土地利用数据计算居住、工业和商业用地的区位熵值并分析其变化,基于统计小区、圈层式及扇形分布3个视角,运用GIS分析计划与市场经济影响下的城市用地空间分布特征。研究结果表明,居住、工业和商业用地的空间分布规律不同：① 3类用地在城市整体空间分布中均表现出一定的分散特征,其中,居住用地空间分布表现最为分散,工业用地呈现出分区域性布局特征,相比而言商业用地空间聚集程度最高;② 商业用地在核心圈层处于主导地位,工业用地在老城区圈层为主导地位,居住用地在近郊区圈层为主导地位,远郊区圈层仍处于初步发展阶段,城市景观发展尚未成熟;③ 对比圈层式和象限式结构各类用地区位熵值分布结果,提出圣彼得堡市3类用地空间分布扇形结构特征明显,说明沿主要交通线路是现代城市用地空间扩展主要方式,其中工业用地在城市空间分布中占据更为有利的交通区位优势,居住用地次之,商业用地在城市中心区域中分布不足。圣彼得堡城市用地空间分布形成主要机制总结为以下5个方面：前苏联时期城市用地空间结构主要框架的保持;行政区划调整为城市用地结构改善提供了路径;市场经济下住房体制改革推进了城市居住郊区化;土地市场对土地功能置换进程作用较弱;产业转型缓慢导致老城区仍主要为生产中心。