Palaeovariations in the East-Asian Monsoon Regime Geochemically Recorded in Varved Sediments of Lake Sihailongwan (Northeast China, Jilin Province). Part 2: a 200-Year Record of Atmospheric Lead-210 Flux Variations and its Palaeoclimatic Implications

Palaeovariations of the atmospheric ²¹⁰Pb flux in Northeast China (Long Gang area, Jilin province), quantified by high resolution ²¹⁰Pb measurements on seasonally laminated sediments of Lake Sihailongwan are presented on decadal scale. The mean flux of unsupported ²¹⁰Pb between 1790 and 1970 for the centre of the lake basin is 517 Bq m⁻² yr⁻¹ with maximum deviations between −23% and +27% of this value. Flux rates above this average were found between 1783 and 1813, around 1836, and between 1860 and 1901. The mean ²¹⁰Pb^exc flux rates derived were clearly lower around 1821, 1908, 1930, and 1953. The ²¹⁰Pb^exc flux reached its minimum of 344 Bq m⁻² yr⁻¹ during the period 1977–1982. The atmospheric flux of unsupported ²¹⁰Pb is correlated with the precipitation frequency during the summer monsoon and shows coinciding variability with geochemical proxies that document the groundwater inflow into the lake. Al₂O₃-rich dust of remote provenance scavenged by wet-deposition in the rainy season is the major carrier of the atmospheric ²¹⁰Pb^exc flux.     

Palaeovariations in the East-Asian Monsoon Regime Geochemically Recorded in Varved Sediments of Lake Sihailongwan (Northeast China, Jilin Province). Part 1: Hydrological Conditions and Dust Flux

The varved sediments of the dimictic Lake Sihailongwan (Long Gang mountain area, Jilin Province, Northeast China) represent a palaeoclimatic archive which documents the local precipitation frequency during the summer monsoon, and variations in the aeolian flux of dust with their remote sources in the arid and semi-arid regions of inner Asia. Based on a detailed discussion of sediment genesis in Lake SHL, dust flux rates and palaeohydrological conditions were reconstructed on a decadal scale over the past 220 years. The aeolian influx by dry and wet deposition was quantified and characterised in its chemical composition. Photosynthetic production in the lake is positively correlated with the inflow of nutrient-rich groundwater. The groundwater discharge largely reflects the strength of the summer monsoon. Net accumulation rates for biogenic silica were determined for annually laminated sediments from the centre of the U-shaped lake basin based on sediment data. In a Si-balance model of the modern lake, the depositional flux of biogenic silica could be independently quantified on the base of hydrochemical monitoring data. Comparison of the both estimates allowed to asses the focussing of the particle flux in the lake. Though water retention in Lake SHL is rather high (ca. 30 years), changes in the hydrological conditions are sensitively recorded in the sediments because (i) nutrient-rich groundwater discharges into the productive zone of the lake, (ii) a substantial proportion of the total dissolved Si-inventory of the mixed lake (ca. 30%) is annually consumed by diatom growth, and (3) sediment accumulation is substantially focussed towards the flat bottom of the lake basin. The bulk siliciclastic sediment fraction (ca. 75 wt.%) largely originates from influx of dust of remote provenance. In sediment thin-sections, the dry-deposited dust fraction is microscopically identifiable as seasonal silt layer. Aeolian input by wet-deposition shows a distinctly higher variability than the influx of dust by dry-deposition. As diatom production, wet-deposition of dust is positively correlated with the rainfall during the summer monsoon. The inferred positive correlation between rainfall and dust flux during the summer monsoon implies that dust deposition is determined by the out-wash efficiency of mineral particles for a permanent high atmospheric dust concentration over Northeast China in the last 220 years.     

Application of membrane technology for water treatment： Ultrasound-associated cleaning of fouled microfiltration membranes

The use of membranes is a widely employed, versatile, and effective separation process. One of the limiting aspects in applying microfiltration （MF） for wastewater treatment is that of problems with membrane fouling and consequent flux reduction. Membrane fouling occurs by the irreversible deposition of retained particles, colloids, macromolecules, salts, etc. at the membrane surface and/or inside the membrane. The predominant fouling mechanisms observed with MF membranes are classified as three categories： the build-up of a cake layer on the membrane surface, blocking of membrane pores, and adsorption of fouling material on the membrane surface or in the pore walls. Although many techniques have been developed to overcome fouling, studies on membrane cleaning still seem to be insufficient for practical membrane filtration systems. Current membrane cleaning technologies include hydraulic, chemical, and mechanical methods. Ultrasound （US） has been widely used as a method of cleaning materials because of the cavitation phenomenon. In this study, US cleaning technique was applied to removing the fouling of polyvinglidenefluoride （PVDF） MF membrane, which was used to treat yeast cell and isolated soybean protein （ISP） solution, respectively. The US employed 40 kHz frequency and the output power of 1.43-2.85 W/cm^2. The evolution of the cleaning effect is followed by the measurements of the flux recovery rate （FRstat） and the cleaning time cycle. Results showed that the membrane property, which was fouled by yeast cell solution, could be recovered by water cleaning with US irradiation. And the cleaning time with the same FRstat decreased with the increase of US intensity.     

长江三角洲地区水和热通量的时空变化特征及影响因子

文中利用改进的K B模式和牛顿扩散方法及 196 1年以来的长江三角洲 (2 8～ 33°N ,118～ 12 3°E)地区的 4 8个测站的常规气象资料 ,估计了该地区近 4 0a来的蒸散量和感热通量。结合该地区的气温、太阳辐射等气候资料和 196 0年以来该区域土地资源利用变化等有关信息对该地区的潜热通量和感热通量的时 空间变化特征及其可能成因进行了综合分析。结果认为该地区自 2 0世纪 70年代开始平均蒸散量有逐渐减小的趋势 ,与 1980年相比 ,1998年区域年平均蒸散量减小了 2 4mm。区域平均感热通量与蒸散量相比在此期间变化并不明显。通过对该地区的云量、太阳辐射及土地利用变化资料分析认为 ,造成该地区平均蒸散量减少趋势的的原因之一是用于蒸发的能量即太阳辐射的减少 ,而造成太阳辐射减少的可能原因为云量及大气透明度的变化所至 ;原因之二是该地区地表覆盖条件的改变。近 2 0a来 ,该地区的水田、旱地及水域面积占总面积的比率分别减少 1.35 3% ,4 .4 4 2 %和2 .5 97% ,而城镇建设、工矿及其它建设用地面积则增加 3.345 %。耕地及水面的减小和城镇及建设用地面积的增加从整体上使区域平均蒸发量减少。     

乾安地区盐碱地显热通量的测量

文中给出了用大孔径闪烁仪在 2 0 0 0年生长季观测到的盐碱地区显热通量的主要结果 ,并初步计算了当地的水热平衡状况。结果表明 :乾安盐碱地区显热通量占净辐射量的百分比在干旱、非生长季达到 6 5 % ,在多雨、植被生长季仅为 11% ;显热通量因降水而明显降低 ,幅度与降水强度有关 ,反映了当地的气候和土壤特征。文中还把LAS的测量结果与传统的梯度法作了比较 ,结果基本一致。     

T106产品中700hPa垂直速度和水汽能量与塔城大降水关系的探讨

对塔城盆地1998－1999年15个大降水个例进行了诊断分析，发现了T106产品700hPa垂直速度和水汽通量与塔城盆地大降水量级呈正相关，并给出了定量预报指标。     

中尺度模式中的边界层特征量分析

在中尺度数值天气预报模式MM4中，用level3及E-ε-l两种湍流闭合方法对原总体边界层参数化方案进行改进，使得中尺度模式中可以直接输出有关湍流量，并对地表通量参数化方案进行改进，进而对不同下势需如沙漠，植被上的有关湍流量和边界层特征量进行分析。研究中尺度系统中边界层结构的特征，本文主要从地表通量，湍流交换系数，湍流动能（q^2)，温度脉动方差（θ^2)及风温廓线等几个方面进行研究，结果表明，新方案能更好地反映边界层特征。     

东南极Lambert冰川-Amery冰架系统平衡通量分布的计算

通过对Lambert冰川盆地(LGB)考察路线上约1 700 km长的LGB剖面和距冰架末端约50 km、长150 km的A剖面, 分别利用GPS冰流速值及雷达测厚值进行冰通量的计算得出:每年流过LGB剖面的冰通量为43.95 Gta-1, 而通过A剖面的冰通量仅为26. 42 Gt*a-1, Amery冰架底部净融化量为7.8 Gt*a-1. 整个Lambert冰川-Amery冰架系统(LAS)地区的表面净物质平衡总量约为90 Gt*a-1; LGB地区的表面净物质平衡总量为46 Gt*a-1. 通过分析得出, 整个LAS地区及LGB地区均处于物质正平衡状态, 而LAS流域的上游区域S'则处于物质负平衡状态.     

MODIFIED MASS FLUX CUMULUS CONVECTIVE PARAMETERIZATION SCHEME AND ITS SIMULATION EXPERIMENT—PART Ⅰ:MASS FLUX SCHEME AND ITS SIMULATION OF THE 1991 FLOOD EVENT*

Based on the existing cumulus convective parameterization schemes,a mass flux scheme (MFS) for cumulus convective parameterization has been successfully developed by reference to the work of Chen et al. (1996).The MFS is a comprehensive scheme.In MFS,not only the importance of the large-scale moisture convergence is taken into account,but also it includes the cumulus updrafts and downdrafts,cumulus-induced subsidence in the environmental air.entrainment,detrainment and evaporation.The interaction between the cumulus and the environment is described by using a one-dimensional bulk model.At the same time the scheme includes the penetrative and shallow convections.The MFS has been successfully incorporated into the regional climate model RegCM2 developed by NCAR.The new model has been applied to simulate summer monsoon characteristics and their variations of heavy rainfall process in the Changjiang-Huaihe River Basins for three months from May to July 1991.The results show that the new model can successfully simulate this rainfall prolonged process.By comparising the model outputs of RegCM2.using the Kuo scheme and the MFS.it is found that the MFS is better in simulating the surface temperature,rainfall position and amount,and rainfall duration.