近40年高层温度场和高度场的时空变化特征

用4种方式对NCEP／NCAR全球再分析资料中1958－1997年300hPa月均温度、100hPa月均高度资料序列进行对比分析，发现300hPa温度资料可靠性高于100hPa高度资料；详细考察近40a高层温度场、高度场的时空变化特征，并通过Morlet小波进一步分析两要素场的周期变化发现，温度场和高度场的EOF第1模态具有很好的空间整体民生和明显的年际和年代际变化，以10a左右和3a左右的周期为主要周期。     

Water chemistry and water quality variation in the Danjiangkou Reservoir, as a function of water management for the Middle Route of South to North Water Divert Project, China

As the diversion dike of the Middle Route of the South to North Water Transfer Project （MRSNWTP）, the water quality and water quantity of Danjiangkou Reservoir is critical to the project. At present, the rates of industrial wastewater treatment and sewage discharge, which belongs to Chinese State Standard in the districts near the reservoir except Shiyan city, are less than 60% and 40% respectively. The point source pollutants will be controlled because of the project after some time, but the non-point source pollutants caused by vegetation degradation and water-soil erosion will not be controlled effectively in a long time. Water samples were collected from the Danjiangkou Reservoir during 2004 and 2005 and analyzed for trace metals, i.e., silver （Ag）, aluminum （Al）, arsenic （As）, barium （Ba）, bismuth （Bi）, calcium （Ca）, cadmium （Cd）, cobalt （Co）, chromium （Cr）, copper （Cu）, iron （Fe）, mercury （Hg）, potassium （K）, lithium （Li）, magnesium （Mg）, manganese （Mn）, molybdenum （Mo）, sodium （Na）, nickel （Ni）, lead （Pb）, antimony （Sb）, selenium （Se）, silicon （Si）, strontium （Sr）, vanadium （V）, zinc （Zn）, chemicophysical parameters and nutrients, i.e., temperature （T）, pH, dissolved oxygen （DO）, turbidity, total suspended solid （TSS）, nitrate/ammonia/ammonium-nitrogen （NO3^-/NH3/NH4^＋-N）, total nitrogen （TN）, dissolved inorganic nitrogen （DIN）, total phosphorus （TP）, potassium permanganate index （IMn）, biochemical oxygen demand （BOD）, dissolved inorganic carbon （HCO3^-）. Our results are water quality belongs to Chinese standard level II, trace metals are low, but they are accumulating, and many of which, i.e., As, Pb, will endanger reservoir water security.     

Interannual Sea Level Variations in the South China Sea Over 1950–2009

Spatial patterns of interannual sea level variations in the South China Sea (SCS) are investigated by analyzing an EOF-based 2-dimensional past sea level reconstruction from 1950 to 2009 and satellite altimetry data from 1993 to 2009. Long-term tide gauge records from 14 selected stations in this region are also used to assess the quality of reconstructed sea levels and determine the rate of sea level along the coastal area. We found that the rising rate of sea levels derived from merged satellite altimetry data during 1993–2009 and past sea level reconstruction over 1950–2009 is about 3.9 ± 0.6 mm/yr and 1.7 ± 0.1 mm/yr, respectively. For the longer period, this rate is not significantly different from the global mean rate (of 1.8 ± 0.3 mm/yr). The interannual mean sea level of the SCS region appears highly correlated with Niño 4 indices (a proxy of El Niño-Southern Oscillation/ENSO), suggesting that the interannual sea level variations over the SCS region is driven by ENSO events. Interpolation of the reconstructed sea level data for 1950–2009 at sites where tide gauge records are of poor quality (either short or gapped) show that sea level along the Chinese coastal area is rising faster than the global mean rate of 1.8 mm/yr. At some sites, the rate is up to 2.5 mm/yr.     

洞庭湖近30a水位时空演变特征及驱动因素分析

洞庭湖地处北亚热带季风湿润气候区,水情时空变化尤为明显.为了探明洞庭湖水位时空演变特征,以洞庭湖6个水位站(城陵矶、鹿角、营田、杨柳潭、南咀、小河咀)、出入湖流量("三口"总入湖流量、"四水"总入湖流量、城陵矶出湖流量)和长江干流流量(宜昌、螺山)等1985-2014年逐日数据为基础,通过构建泰森多边形计算湖泊水位,运用Morlet小波分析、层次聚类分析和地统计理论研究湖泊水位的周期性变化规律及空间分布格局和自相关性.研究结果表明:洞庭湖水位变化具有典型的季节性,且年际变化具有28和22 a的多时间尺度特征;水位空间分布格局呈现出小河咀、南咀、杨柳潭(Group 1)以及城陵矶、鹿角、营田(Group 2)两种聚类,且在不同水文季节的空间自相关性依次表现为丰水期退水期涨水期枯水期.通过建立两类水位在不同水文季节与径流量的多元逐步回归模型揭示了洞庭湖水位时空演变的驱动因素,其中Group 1水位演变主要受长江干流水文情势的影响,Group 2水位演变由出入湖径流量和长江干流径流量共同作用,并随着不同水文季节江湖关系的改变以及湖泊自身水力联系的变化而变化.研究结果对于科学认识洞庭湖水位的时空演变规律以及湖泊生态系统保护和水资源的规划、管理与调控具有重要意义.     

Modeling long term lake variations by physically based stochastic dynamic models

Several physically based stochastic dynamic models (SDM) are described including year-to-year variations of water volume in terminal and non-terminal lakes, streamflow of lake-fed rivers, and salinity of an inland sea (the Sea of Azov). All of these models are based upon the SDM of water volume of terminal lakes developed by Kritzky and Menkel in 1946 in co-operation with Kolomogorov. Explicit formulae are derived for second order statistical moments of the output processes, including variance, correlation function, spectra, etc., under the assumption that the forcing functions from stationary random sequences. The least-squares prediction problem is solved for both stationary and non-stationary cases. Some of the processes are shown to possess high statistical predictability. Actual predictions are compared with independent observations. Problems for further study are stated.     

Tide-induced variability in beach surface moisture: Observations and modelling

The moisture content w_s of a beach surface strongly controls the availability of sand for aeolian transport. Our predictive capability of the spatiotemporal variability in w_s, which depends to a large extent on water table depth, is, however, limited. Here we show that water table fluctuations and surface moisture content observed during a 10-day period on a medium-grained (365μm) planar (1:30) beach can be predicted well with the nonlinear Boussinesq equation extended to include run-up infiltration and a soil–water retention curve under the assumption of hydrostatic equilibrium. On the intertidal part of the beach the water table is observed and predicted to continuously fall from the moment the beach surface emerges from the falling tide to just before it is submerged by the incoming tide. We find that on the lower 30% of the intertidal beach the water table remains within 0.1–0.2 m from the surface and that the sand is always saturated (w_s≈20%, by mass). Higher up on the intertidal beach, the surface can dry to about 5% when the water table has fallen to 0.4–0.5 m beneath the surface. Above the high-tide level the water table is always too deep (>0.5 m) to affect surface moisture and, without precipitation, the sand is dry (w_s < 5 − 8%). Because the water table depth on the emerged part of the intertidal beach increases with time irrespective of whether the (ocean) tide falls or rises, we find no need to include hysteresis (wetting and drying) effects in the surface-moisture modelling. Model simulations suggest that at the present planar beach only the part well above mean sea level can dry sufficiently (w_s < 10%) for sand to become available for aeolian transport. ©2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

Statistical analysis of surface hydrography and circulation variations in northern South China Sea

1 INTRODUCTIONThe South China Sea (SCS) is a semi-enclosedmarginal sea in western North Pacific Ocean withvery complex topography and is the important pas-sage connecting the Pacific and Indian Oceans. Ithas great impact to the global climate and a greatinterest of many oceanography researchers. Twodominant surface hydrographic and circulation fea-tures in the northern SCS are a strong fresh waterexpansion and a warm and high-salinity seawaterintrusion such as the SCS Diluted Water…     

Spatiotemporal variations of maximum seasonal freeze depth in 1950s–2007 over the Heihe River Basin, Northwest China

Investigation on spatiotemporal variations of maximum seasonal freeze depth （MSFD） over the Heihe River Basin is of great importance for systematic understanding of regional climate and environmental change, ecological-hydrological processes, water resources assessment, construction and resource development. Based on soil and air temperatures at the meteorological stations of the China Meteorological Administration （CMA） over the Heihe River Basin, MSFDs time series are structured into a composite time series over the 1960-2007 period. Evaluating the averaged MSFD time series for 1960 2007 reveals a statistically significant trend of 4.0 cm/decade or a net change of-19.2 cm for the 48-year period over the basin. The MSFD had significantly negative correlation with mean annual air temperature （MAAT）, winter air temperature, mean annual ground surface temperature （MAGST）, degree days of thawing for the air （DDTa） as well as for the surface （DDTs）, and degree days of freezing for the surface （DDFs）. While there was significantly positive correlation between DDF,. and MSFD time series, MSFD was deeper and changed greatly in the Heihe River source area. It was shallower in the east-central basin and gradually deepened in other sections of the basin. The MSFD distribution pattern in 2003-2005 is consistent with that of averaged degree days of freezing for air （DDFa） in 1960-2007. However, the maximum of MSFD may not be accurate, because there is no long term observation data in the deep seasonally frozen ground regions near the lower boundary of permafrost. With increasing elevation, averaged DDFa increased at a rate of 51.6 ℃-day/100m, therefore, the MSFG and the date reaching MSFG became deeper and later, respectively.