Uncertainty analysis of CO_2 flux components in subtropical evergreen coniferous plantation

We present an uncertainty analysis of ecological process parameters and CO2 flux components (Reco, NEE and gross ecosystem exchange (GEE)) derived from 3 years’ continuous eddy covariance meas-urements of CO2 fluxes at subtropical evergreen coniferous plantation, Qianyanzhou of ChinaFlux. Daily-differencing approach was used to analyze the random error of CO2 fluxes measurements and bootstrapping method was used to quantify the uncertainties of three CO2 flux components. In addition, we evaluated different ...     

MELTWATER FLUXES AT AN ARCTIC FOREST-TUNDRA SITE

Models of surface energy balance and snow metamorphism are utilized to predict the energy and meltwater fluxes at an Arctic site in the forest–tundra transition zone of north-western Canada. The surface energy balance during the melt period is modelled using an hourly bulk aerodynamic approach. Once a snowcover becomes patchy, advection from the bare patches to the snow-covered areas results in a large spatial variation in basin snowmelt. In order to illustrate the importance of small-scale, horizontal advection, a simple parameterization scheme using sensible heat fluxes from snow free areas was tested. This scheme estimates the maximum horizontal advection of sensible heat from the bare patches to the snow-covered areas. Calculated melt was routed through the measured snowcover in each landscape type using a variable flow path, meltwater percolation model. This allowed the determination of the spatial variability in the timing and magnitude of meltwater release for runoff. Model results indicate that the initial release of meltwater first occurred on the shallow upland tundra sites, but meltwater release did not occur until nearly two weeks later on the deep drift snowcovers. During these early periods of melt, not all meltwater is available for runoff. Instead, there is a period when some snowpacks are only partially contributing to runoff, and the spatial variation of runoff contribution corresponds to landscape type. Comparisons of melt with and without advection suggests that advection is an important process controlling the timing of basin snowmelt.     

青藏高原东部表层土壤色度的空间变化特征及其环境意义

认识青藏高原东部现代表土的色度特征及其空间分布,理解其与现代气候因子之间的联系,对于高原地区黄土-古环境重建和揭示第四纪环境变化历史具有重要意义。通过对研究区表层土壤色度的详细分析,对比现代气候资料,探讨了青藏高原东部表层土壤色度的空间变化特征及其环境意义。结果表明：① 高原东部表土色度参数空间变化特征差异显著,表现为随纬度升高,土壤亮度呈先减小后增大的趋势,而红度和黄度则逐步减小;随经度的升高,黄度先增大后减小,而红度值逐步减小;红度和黄度整体随着海拔上升而呈先减小后升高的特征。这些变化特征和差异是表土色度对高原东部复杂地理环境和水热条件变化响应的结果。② 在高原的干旱-半湿润区,土壤亮度对降水的响应敏感;红度和黄度对大尺度的温度变化响应较敏感,而较冷的环境下,红度对温度响应复杂,但与降水存在一定的联系。红度/黄度比值主要指示了气候控制下的赤铁矿和针铁矿的变化和竞争,对干旱-半湿润区域的降水变化响应较为敏感。青藏高原东部现代表土色度与气候密切相关,其空间变化特征一定程度上反映了该地区现代气候因子的空间变化;另一方面由于该区地形和气候复杂多变,部分色度指标与气候关系复杂,在重建青藏高原东部黄土古环境变化历史时需要谨慎。     

Anisotropy beneath Hawaii from surface wave particle motion observations

Observed polarization ellipses for fundamental-mode surface waves observed at a digital station in Hawaii deviate from those expected for isotropic models of crust and mantle structure for that region. The anomalous motion occurs as rotations of the ellipse about all three axes in a cartesian corrdinate system. The largest and most consistent deviations occur as anomalous slopes of the ellipse about the horizontal axis transverse to the direction of propagation.The observed orientations and magnitudes of these angles can be explained by models of the upper mantle which contain olivine for which thea-axis dips significantly from the horizontal and which includes a sufficiently thick sedimentary layer (1 km) and a thicker than normal oceanic crust (15 km). The ellipses are also generally inclined from great circle paths about the vertical axis and are tilted about the axis aligned with the propagation direction. Both angles are small and difficult to measure, but the inclination angles are consistent with a model of the upper mantle in which thea-axis of olivine is preferentially oriented in an east-west direction.     

地球磁尾中不同类型磁结构的磁螺度演化特征

在二维三分量MHD数值模拟的基础上 ,对地球磁尾不同类型磁结构的形成作磁螺度分析 .研究表明 ,对于由晨昏电场产生的磁尾驱动重联过程 ,通过系统边界输运的磁螺度通量是引起系统总磁螺度变化的直接原因 .不同的初始磁螺度密度分布和磁螺度通量输运 ,可以引起中性片区域磁螺度密度分布的不同演化 ,从而导致具有不同拓扑位形磁结构的形成 .     

A DIAGNOSTIC ANALYSIS OF AIR TEMPERATURE ANOMALY MODE OVER CHINA IN 2009/2010 WINTER BASED ON GENERALIZED EQUILIBRIUM FEEDBACK ASSESSMENT (GEFA) METHOD

By using the observed monthly mean data over 160 stations of China and NCAR/NCEP reanalysis data, the generalized equilibrium feedback assessment(GEFA) method, combined with the methods of EOF analysis, correlation and composite analysis, is used to explore the influence of different SST modes on a wintertime air temperature pattern in which it is cold in the northeast and warm in the southwest in China. The results show that the 2009/2010 winter air temperature oscillation mode between the northern and southern part of China is closely related to the corresponding sea surface temperature anomalies(SSTA) and its associated atmospheric circulation anomalies. Exhibiting warming in Northeast China and cooling in Southwest China, the mode is significantly forced by the El Nio mode and the North Atlantic SSTA mode, which have three poles. Under the influence of SSTA modes, the surface northerly flow transported cold air to North and Northeast China, resulting in low temperatures in the regions. Meanwhile, the mid-latitude westerlies intensify and the polar cold air stays in high latitudes and cannot affect the Southwest China, resulting in the warming there.     

Observational estimation of heat budgets on drifting ice and open water over the Arctic Ocean

It is of major scientific interests to determine the parameters of momentum, heat and vapor exchange in the planetary boundary layer in order to study the effects of ocean-ice-atmosphere interactions and their feedback mechanisms on global climate[1]. Lin…     

风沙流中沙粒浓度分布的实验研究

利用粒子图像测速技术（PIV）,在风洞内对与天然沙接近的石英沙风沙流沙颗粒浓度沿高度分布进行了研究。对 3种不同轴线风速研究结果表明,风沙流中沙粒浓度沿水平方向基本不变,而随高度呈指数衰减,而且其衰减速率与风速密切相关。风速越大,衰减速率越慢;风速越小,衰减速率越快。风沙运动一旦发生时,靠近沙床表面的沙粒浓度随风速变化很小,可以认为趋于稳定,达到最大值。     

ANNUAL VARIATIONS OF TEMPERATURE ON FOUR URBAN UNDERLYING SURFACES AND FITTING ANALYSIS

Based on the observed 2-year temperature data for four kinds of typical urban underlying surfaces, including asphalt, cement, bare land and grass land, the annual variations and influencing factors of land surface temperature are analyzed. Then fitting equations for surface temperature are established. It is shown that the annual variation of daily average, maximum and minimum temperature and daily temperature range on the four urban underlying surfaces is consistent with the change in air temperature. The difference of temperature on different underlying surfaces in the summer half year (May to October) is much more evident than that in the winter half year (December to the following April). The daily average and maximum temperatures of asphalt, cement, bare land and grass land are higher than air temperature due to the atmospheric heating in the daytime, with that of asphalt being the highest, followed in turn by cement, bare land and grass land. Moreover, the daily average, maximum and minimum temperature on the four urban underlying surfaces are strongly impacted by total cloud amount, daily average relative humidity and sunshine hours. The land surface can be cooled (warmed) by increased total cloud amount (relative humidity). The changes in temperature on bare land and grass land are influenced by both the total cloud amount and the daily average relative humidity. The temperature parameters of the four land surfaces are significantly correlated with daily average, maximum and minimum temperature, sunshine hours, daily average relative humidity and total cloud amount, respectively. The analysis also indicates that the range of fitting parameter of a linear regression equation between the surface temperature of the four kinds of typical land surface and the air temperature is from 0.809 to 0.971, passing the F-test with a confidence level of 0.99.     

A Note on Reviving the Goddard Satellite-Based Surface Turbulent Fluxes （GSSTF） Dataset

Accurate sea surface flux measurements are crucial for understanding the global water and energy cycles. The oceanic evaporation, which is a major component of the global oceanic fresh water flux, is useful for predicting oceanic circulation and transport. The global Goddard Satellite-based Surface Turbulent Fluxes Version-2 (GSSTF2; July 1987--December 2000) dateset that was officially released in 2001 has been widely used by scientific community for global energy and water cycle research, and regional and short period data analyses. We have recently been funded by NASA to resume processing the GSSTF dataset with an objective of continually producing a uniform dataset of sea surface turbulent fluxes, derived from remote sensing data. The dataset is to be reprocessed and brought up-to-date (GSSTF2b) using improved input datasets such as a recently upgraded NCEP/DOE sea surface temperature reanalysis, and an upgraded surface wind and microwave brightness temperature V6 dataset (Version 6) from the Special Sensor Microwave Imager (SSM/I) produced by Remote Sensing Systems (RSS). A second new product (GSSTF3) is further proposed with a finer temporal (12-h) and spatial (0.25^ox0.25^o) resolution. GSSTF2b (July 1987--December 2008) and GSSTF3 (July 1999--December 2009) will be released for the research community to use by late 2009 and early 2011, respectively.