CONDITIONAL SAMPLING AND SCALE ANALYSIS OF THE MARINE ATMOSPHERIC MIXED LAYER -- SOFIA EXPERIMENT

During the SOFIA experiment, performed in the Azores region in June1992, airborne missions were conducted in the atmospheric boundary layerwith two aircraft instrumented for turbulence measurements. We show howthe conditional sampling technique, applied to the velocity, temperatureand moisture fluctuations, is able to describe the various parcels whichconstitute the turbulent field. Each parcel, so identified, is characterized byits fractional area and by its contribution to the transfers of sensible heat andlatent heat. On the other hand, a scale analysis is conducted by filteringthe turbulent signals in five non-overlapping frequency bands, definedaccording to the characteristic turbulent scales. The contribution of eachband to the turbulent energy and to the transfers is thus presented. Theimportance of the lowest frequencies, which are generally removed fromthe signals by high-pass filtering before computing turbulent fluxes, isshown. In the final section, the conditional sampling technique is applied tothe signals filtered in the various bands. Despite a slight deformation of theeddies due to the filtering technique, the contribution of each parcel can beestimated at the various scales analysed.     

关于我国华北沙尘天气的成因与治理对策

２０００年春季,我国华北沙尘天气次数陡增,影响广泛,损失明显增加。利用长期气象观测数据,结合遥感和ＧＩＳ技术,对今年华北沙尘天气的成因进行分析,提出造成沙尘天气的原因在于：①北方地区大风日数的增减是气候周期性变化的反映,今年强沙尘天气陡增是因为处于反厄尔尼诺事件的高峰期所致;②我国北方地表覆被状况局部改善、整体恶化也是今年强沙尘天气产生的另一重要原因。影响华北地区的沙尘天气主要必源于内蒙古中西部和     

UNCERTAINTY AND SENSITIVITY ANALYSES OF SEDIMENT TRANSPORT FORMULAS

ＵＮＣＥＲＴＡＩＮＴＹＡＮＤＳＥＮＳＩＴＩＶＩＴＹＡＮＡＬＹＳＥＳＯＦＳＥＤＩＭＥＮＴＴＲＡＮＳＰＯＲＴＦＯＲＭＵＬＡＳＫｅｈＣｈｉａＹＥＨ１ａｎｄＳｅｎＬｏｎｇＤＥＮＧ２ＡＢＳＴＲＡＣＴＩｎｖｉｅｗｏｆｔｈｅｒａｎｄｏｍｃｈａｒａｃｔｅｒｉｓｔ...     

关税变化对中国贸易碳排放的影响研究北大核心CSCD

为了适应气候变化,中国作为世界上产生碳排放最多的国家,正在从多方面制定减少碳排放的计划,并提出了2060年实现碳中和的目标。随着贸易全球化,全球其他国家消费的排放越来越多地在中国生产。国家间的贸易条件受政策影响很大,关税的高低会导致商品的贸易出现变化,进而导致进出口商品包含排放的变化。本文结合中美两国的贸易冲突,对中美两国加征关税后的贸易变化进行模拟,结合全球贸易分析模型的结果与投入产出分析法,定量地研究了关税变动后中国进出口隐含排放的变化。研究发现,在中美加征关税后,中美两国的贸易量大幅减少,并导致两国贸易涉及的排放变少,而中国向世界出口的排放反而有所增加。另外,由于进口市场被冲击,中国从全世界进口的排放明显变少,进而导致中国净出口的碳排放在加征关税后变多,且集中于能源密集型产业。从结果看,中国在贸易受限的情况下依旧向世界出口了大量排放,通过贸易合作来促进新能源产业的进步或许可以更好地解决减排需求。     

Investigation of the impacts of vegetation distribution and evaporative cooling on synthetic urban daytime climate using a coupled LES—LSM model

Local flow properties and regional weather or climate are strongly affected by land‐atmosphere interactions of momentum and scalars within the daytime convective boundary layer (CBL). In this study, we investigate the impact of green space scale on the daytime atmospheric boundary layer (ABL) over a synthetic urban domain using a recently developed large‐eddy simulation‐land surface model (LES–LSM) framework. With the use of realistic soundings as initial conditions, a series of numerical experiments over synthetic urban surfaces with varied scale of vegetated area is performed. Simulated micrometeorological properties, surface fluxes, basic CBL characteristics, and cloud distribution are analysed. The results show reference‐level air potential temperature and specific humidity as well as surface fluxes over green space are significantly affected by the scale of green space in the urban domain. The surface organization due to vegetated area scale also has impacts on horizontally averaged scalar and momentum profiles; however, the magnitude in this study is smaller than the results of a previous study using a set of offline surface fluxes as the lower boundary condition for LES. In addition, even though this study only performs a daytime diurnal cycle, the impact of green space scale on cloud distribution in simulations is significant. The cases with more organized green space yield lower‐elevated cumulus cloud and larger‐cloud cover fraction, which impacts the energy budget at the top of boundary layer and, in turn, could lead to additional surface cooling with respect to longer‐term weather and climate. Copyright © 2010 John Wiley & Sons, Ltd.     

A New Method for Determining Fluid Compositions in the H20-NaCl-CaCl2 System with Cryogenic Raman Spectroscopy

Raman peaks of various hydrates in the H20-NaCl-CaCl2 system have been previously identified, but a quantitative relationship between the Raman peaks and XNaCl （i.e.,NaCl/ （NaCl＋CaCl2）） has not been established, mainly due to the difficulty to freeze the solutions. This problem was solved by adding alumina powder to the solutions to facilitate nucleation of crystals. Cryogenic （-185℃） Raman spectroscopic studies of alumina-spiced solutions indicate that XNaCl is linearly correlated with the total peak area fraction of hydrohalite. Capsules of solutions made from silica capillary were prepared to simulate fluid inclusions. Most of these artificial fluid inclusions could not be totally frozen even at temperatures as low as -185℃, and the total peak area fraction of hydrohalite is not correlated linearly with XNaCI. However, the degree of deviation （△XNaCl） from the linear correlation established earlier is related to the amount of residual solution, which is reflected by the ratio （r） of the baseline ＂bump＂ area, resulting from the interstitial unfrozen brine near 3435 cm^-1, and the total hydrate peak area between 3350 and 3600 cm^-1. A linear correlation between △XNaCl and r is established to estimate XNaCl from cryogenic Raman spectroscopic analysis for fluid inclusions.     

GIS支持下基于DEM的中等流域的划分——以富县为例

以陕西富县为例,探讨在GIS环境下从数字高程模型(DEM)中提取流域特征并进行中等流域的划分的详细过程,包括DEM的预处理、流水方向的确定、汇流累积量分析、河网的提取和子流域的划分,通过设定不同的汇流累积量的阈值,通过实验,富县地区的阈值设为20 000,得到中等流域的划分结果较为合理。     

Analysis of solute transport in a divergent flow tracer test with scale‐dependent dispersion

It has been known for many years that dispersivities increase with solute displacement distance in a subsurface. The increase of dispersivities with solute travel distance results from significant variation in hydraulic properties of porous media and was identified in the literature as scale‐dependent dispersion. In this study, Laplace‐transformed analytical solutions to advection‐dispersion equations in cylindrical coordinates are derived for interpreting a divergent flow tracer test with a constant dispersivity and with a linear scale‐dependent dispersivity. Breakthrough curves obtained using the scale‐dependent dispersivity model are compared to breakthrough curves obtained from the constant dispersivity model to illustrate the salient features of scale‐dependent dispersion in a divergent flow tracer test. The analytical results reveal that the breakthrough curves at the specific location for the constant dispersivity model can produce the same shape as those from the scale‐dependent dispersivity model. This correspondence in curve shape between these two models occurs when the local dispersivity at an observation well in the scale‐dependent dispersivity model is 1·3 times greater than the constant dispersivity in the constant dispersivity model. To confirm this finding, a set of previously reported data is interpreted using both the scale‐dependent dispersivity model and the constant dispersivity model to distinguish the differences in scale dependence of estimated dispersivity from these two models. The analytical result reveals that previously reported dispersivity/distance ratios from the constant dispersivity model should be revised by multiplying these values by a factor of 1·3 for the scale‐dependent dispersion model if the dispersion process is more accurately characterized by scale‐dependent dispersion. Copyright © 2007 John Wiley & Sons, Ltd.