Rock magnetic properties of Nihewan sediments at Xujiayao

Rock magnetic measurements of Nihewan sediments from Xujiayao section demonstrate that magnetite, hematite and maghemite are dominant remanent magnetization carriers. Monitoring the variations of magnetic susceptibility (MS) and saturating isothermal remanent magnetization (SIRM) at low temperature are the attractive ways of detecting the presence of magnetite, maghemitization and superparamagnetic grain sizes. Low-temperature MS investigations suggest that susceptibility enhancement for Xujiayao samples is mainly due to the remarkable presence of SD/MD magnetite to some degree though some magnetite grains have been partially oxidized at some depths. It is tentatively concluded that both SD/MD magnetite and hematite are of detrital origin and carry a characteristic remanent magnetization (ChRM), whereas maghemite can be attributed to be chemical origin, overprinting a reversed polarity component of Matuyama age.     

The Recent Crustal Deformation on the Sichuan-Yunnan Rhombic Block Boundaries

Based on data from an across-fault survey along the sichuan-Yunnan rhombic block boundaries,the recent deformation characteristics on each fault have been analyzed.It was found that the rate of crustal deformation is slowing down along the northern segment and increasing along the southern segment.Each fault has different features of deformation.The horizontal deformation is mainly characterized by left-lateral strike-slip.The rate of vertical deformation is less than that of the horizontal dformation.The faults have the feature of upper wall uplifting alternated with descending.The anomaly changes of crustal deformation at some sites are closely related to the seismicities near the sites.     

电离层起源的O+离子在同步高度区的分布

以卫星观测资料为基础, 应用动力论方程, 采用理论模型和数值分析方法, 研究了不同地磁活动条件下同步高度区O+离子的分布, 提出了O+离子密度和通量密度在同步高度区沿经度变化的半经验模型. 主要结果为: 在同步高度区(1) 向阳侧O+离子密度和通量密度较大, 背阳侧较小. (2) 地磁活动指数Kp越小, O+离子密度和通量密度水平及其沿经度的变化越小, Kp越大时水平及其变化越大; Kp≥6时O+离子密度和通量密度较Kp = 0时大一个量级. (3) 当Kp = 0或Kp ≥ 6时, O+离子密度在经度120°附近和240°附近最大, 在磁尾最小; 当地磁活动指数Kp = 3～5时, O+离子密度在经度0°处最大, 在磁尾最小; 无论Kp如何, O+离子通量密度都在经度120°附近和240°附近最大, 在磁尾最小.     

全新世东亚季风活动在印度尼西亚多岛海的表现

印度尼西亚多岛海位于印度洋东部 ,北印度洋和西太平洋交界处 ,由至少 8个盆地通过相对较浅的海槛相连而成 ,海盆水深一般能达 45 0 0ｍ以上。它属于表层水温大于2 8℃的西太平洋暖池范围 ,并受强烈的季风活动影响。由于风场模式差异 ,太平洋海平面较印度洋海平面有一个显著高差 ,致使海水自太平洋向印度洋流动产生印度尼西亚穿越流。 2 0 0 0ｍ深的帝汶海和位于巴厘岛和龙目岛之间的龙目海峡是印度尼西亚穿越流两个最主要的传输通道。南半球冬季 (8月 )澳大利亚上空的高压系统与亚洲上空的低压系统之间的相互作用 ,在印尼海区形成东南方向…     

Interannual and Interdecadal Variability of Winter Precipitation over China in Relation to Global Sea Level Pressure Anomalies

Based on the method of rotated principal component (RPC) analysis and wavelet transforms, the win-ter precipitation from 36 stations over China for the period 1881-1993 is examined. The results show thatthe three leading space-time modes correspond, in sequence, to winter rainfall anomalies over the reaches ofthe Yangtze River, the bend of the Yellow River, and the northeastern region of China. The three modes ex-hibit interannual oscillations with quasi-biennial and 8-year periods as well as interdecadal oscillationswith 16- and 32-year periods. The interannual oscillation (＜ 10 years) occurs in phase over the differentareas, and its maximum amplitude migrates northward considerably with prominent interdecadal variations.However, the interdecadal oscillations (10-32 years) are out of phase over the different regions, and theamplitude variations have the characteristics of stationary waves.The rainfall anomalies appear to be closely re lated to the anti-phase changes of mean sea-level pres-sure (SLP) over the Asian mainland and the North Pacific. When the SLP rises over the North Pacific anddecreases over the Asian mainland, the precipitation over East China increases noticeably. The linkage be-tween the rainfall over China and the SLP anomalies apparently results from the strength of the East Asianwinter monsoon and its associated temperature and moisture advection.     

动物行为与地震预测

生活在地震活动区的动物常常要经受强烈的地面震动，这种震动由于洞穴塌陷、蛋卵毁坏和海啸活动而使某些动物遭受灭顶之灾。尽管有关动物行为的趣闻轶事和回顾报告表明，动物的许多器官可以发觉即将来临的地震事件，但到现在为止还没有一份具有充分理由来说明动物如此行为的发展过程的详细报告。动物们逃跑响应进化机制的形成可以分为两个步骤，首先是形成一个对早期震动的触发警告系统。这个系统应该在很短的P波与S波到来之间的时间内起作用，人们对动物在地震发生前行为的描述已经表明这种反应系统的存在。如果前兆刺激也存在的话，相似的发展进程可以把这种刺激与动物对P波的触发反应感知联系起来，从而产生地震预测的反应行为。种群遗传模式表明，这种动物逃离地震区的反应系统可以不受随机突变事件的影响而得以保持，这是由于环幕选择工的结果，选择的作用时间与强震发生的时间尺度是可以相比的，这样，除地震王国本身外，对可能是地震前兆的更多理解可能要从对动物的（异常）行为，生理感觉器官和基因的研究方面得到一些有用的启示。，回顾一个我们认为可能是地震前兆的现象。如地倾斜，地下介攒 的含水程度（潮湿程度），场电和地磁感应系统。它们可能是与动物地震逃离反应系统相关联的现象，前面所提到的动物异常行为可作为地震预测手段的方法正在研究相关联的现象，前面所提到的动物异常行为可作为地震预测手段的方法正在研究之中，建议把更多的地磁，地电，地倾斜和地下介质的含水度等结合起来，对地震活动区形成一个密集地震前兆监视网。     

IMPROVEMENTS OF A DISTRIBUTED HYDROLOGY MODEL DHSVM AND ITS CLIMATOLOGICAL-HYDROLOGICAL OFF-LINE SIMULATIONAL EXPERIMENTS

The advanced distributed hydrology-soil-vegetation model DHSVM,developed by Wigmostaet al.(1994)is introduced from US Pacific Northwest National Laboratory.To apply DHSVM inChina for the first time some improvements have been made in terms of the basin characteristics:1)to change evapotranspiration model,using the improved Penman-Monteith approach in place ofthe original one;2)to change the model structure,inserting datasets from 4 stations to grid cellsfor each river basin,instead of datasets from one or two stations;3)to develop new hydrology,vegetation and soil parameterization schemes for improving the simulated results,with focus oncalculation and adjustment of 11 parameters,such as soil porosity (?),field capacity θ_(fc),leaf areaindex LAI,stochastic resistance γ_s,among the total 33 parameters.Then the improved DHSVM isdriven by observed datasets for Luanhe River Basin and Sanggan River Basin,respectively.Thesimulated evapotranspiration(ET),runoff,snow water equivalent,water table,soil moisture andpercolation are then gained as DHSVM outputs.The simulated ET shows that the highest peakappears in May or June instead of July or August.This is consistent with the real situations,owing to the improvement of ET model.The simulated runoff process and flood peak are quiteconsistent with the observed ones.The model efficiency values for Luanhe River and SangganRiver Basins are 0.89 and 0.82,respectively,which shows high simulating ability of the modelsystem for both relatively humid and dry basins.     

NUMERICAL SIMULATION EXPERIMENTS BY NESTING HYDROLOGY MODEL DHSVM WITH REGIONAL CLIMATE MODEL RegCM2/CHINA

Based on improvement of a distributed hydrology-soil-vegetation model (DHSVM for short)and its application to North China,a nested regional climatic-hydrologic model system is developedby connecting DHSVM with RegCM2/China.The simulated climate scenarios,including controland 2×CO_2 outputs,are downscaled to 8 stations in Luanhe River and Sanggan River Basins todrive the hydrology model.According to simulation results,under double CO_2 scenarios,annualmean temperature and evapotranspiration will increase 2.8C and 29 mm,respectively;precipitation also increase but with different value for each basin,6 mm for Luanhe River Basinwhile 46 mm for Sanggan River Basin;runoff change for the two basins is different too,27 mmdecrease for Luanhe River Basin while 26 mm increase for Sanggan River Basin.As a result,therunoff in future for Luanhe River Basin and Sanggan River Basin will be 74 mm and 71 mm,respectively,which is approximately a quarter of annual mean runoff(284 mm)of the wholecountry.Total streamflow for the two basins will decrease about 2.5×10~8m~3.All these indicatethat the warm and dry trend will continue in the two river basins under double CO_2 scenarios.Thenested model system,with both climatic and hydrologic prediction ability,could also be applied toother basins in China by parameter adjustment.     

Larch growth across thermal and moisture gradients in the Siberian Mountains

Climate-driven changes in the thermal and moisture regimes may variously influence different tree species growth and ranges. We hypothesize that drought resistant Siberian larch(Larix sibirica Ledeb.) and precipitation-sensitive Siberian pine(Pinus sibirica Du Tour) responded differently to climate change along the elevational thermal and precipitation gradients. We studied the influence of air temperature, precipitation, soil moisture, and atmospheric drought(indicated by the drought index SPEI...     

Influence of Turbulence Intensity and Turbulence Length Scale on the Drag, Lift and Heat Transfer of A Circular Cylinder

Influence of the turbulence intensity and turbulence length scale on the hydrodynamic characteristics and heat transfer of a circular cylinder, streamlined by a viscous fluid flow, is numerically studied. We take the Reynolds number of the oncoming flow equal to 4×10⁴, the turbulence intensity Tu_f and the dimensionless turbulence length scale L_f varying from 1.0% to 40% and from 0.25 to 4.0, respectively. We confirmed that the increase of Tu_f leads to the suppression of the periodic vortex shedding from the cylinder surface, and as a result the stationary mode of streamlining is formed. Consequently, with the increasing turbulence intensity directly in front of the cylinder Tu^*, the amplitude of the lift coefficient decreases monotonically. Nevertheless, the time-averaged drag coefficient of the streamlined cylinder decreases at Tu^*<6.0%, and increases at Tu^*>9.0%. The dependence of the average Nusselt number on Tu^* is near-linear, and with the increasing turbulence intensity, the Nusselt number rises. However, the change of the average Nusselt number depending on L_f is non-monotonic and at L_f=1.0, the value reaches its maximum.