海温异常对热带内外环流相互作用影响的对比分析

运用ECMWF的风场和高度场及TBB资料,用相关方法对比分析了热带太平洋海温分布东冷西暖（1984～1985年冬季）和东暖西冷（1982～1983年冬季）两种不同背景下,热带西太平洋对流活动与中高纬环流在季内时间尺度下相互作用的特点。结果表明,不同的海温分布其对应的大尺度环流场包括Hadley和Walker环流的位置及强弱均有较大的差别。冬季热带西太平洋对流活动与热带外大气的季内相互作用过程也有明显差异。     

利用T106数值预报产品作江西暴雨动态落区预报

首先将江西测站的降水插值到1°×1°的经纬度网格点上,然后利用1°×1°的T106数值预报产品,对江西网格点上的暴雨送行诊断分析与相关普查,最后建立了江西暴雨动态落区预报模式和动态落区预报流程。     

Post-breakup basaltic magmatism along the East Greenland Tertiary rifted margin

Mafic and ultramafic intrusions in East Greenland adjacent to the offshore Greenland–Iceland ridge were emplaced 5–9 My after continental breakup at 55 Ma [1]. Rare earth element (REE) concentrations determined by secondary ion mass spectrometry are reported for cumulus clinopyroxene from these intrusions, and the data are used to estimate REE abundance in equilibrium melts using available partitioning data. Estimated equilibrium melts from intrusions have strongly fractionated REE patterns with Nd/Dy(N) in the range 2 to 5.6 and Yb/Dy(N) 0.55 to 0.92, similar to values for coeval basalts. These melts have markedly higher Nd/Dy(N) than earlier breakup related flood basalts. The moderately low Yb/Dy(N) for the post-breakup volcanism is indicative of residual garnet in the source, while their high Nd/Dy(N) ratios can best be explained by aggregating low degree melts from a light-REE-enriched garnet- and spinel-bearing mantle source. We also report He, Sr, and Nd isotopic data for the intrusions. The highest ³He/⁴He ratios (>10 R/R_a) are found in the samples whose REE data reflect the largest proportion of melts from a garnet-bearing source, and having Sr and Nd isotopic compositions identical with the radiogenic Sr and unradiogenic Nd isotope end of the Iceland compositional field. There is no indication of a MORB-type mantle in the source of the intrusions. We postulate that post-breakup volcanism along the East Greenland coastline reflects the increasing proximity of the mantle plume to the East Greenland continental margin. The low degree of melting at high mean pressure inferred for the parental melts for the intrusions may reflect re-thickening of the lithosphere, which in turn was caused by the vigorous volcanism during breakup, with accompanying depletion of upper mantle and underplating of the crust at the continental margin.     

An effect of closure on the structure of principal components

The principal components transformation generates, from any data array, a new set of variables—the scores of the components—characterized by a total variance exactly equal to that of the initial set. It is in this sense that the transformed variables are said to contain, preserve, or account for, the variance of the original set. The scores, however, are uncorrelated. In the course of the transformation, what becomes of the strong interdependence of variance and covariance so characteristic of closed arrays? The question seems to have attracted little attention; we are aware of no study of it in the earth sciences. Experimental work reported here shows quite clearly that the overall equivalence of variance and covariance imposed by closure, though absent from the component scores,may emerge in relations between the coefficientsof each of the lower-order components; if the raw data are complete rock analyses, the sum of all the covariances of the coefficients of such a component is negative, and is very nearly equal to the sum of all the variances in absolute value. (In all cases so far examined, the absolute value of the first sum is a little less than that of the second.) The principal components transformation provides an elegant escape from closure correlation if a petrographic problem can be restated entirely in terms of component scores, but not if a physical interpretation of the component vectors is required.     

Kinetic shear resistance,fluid pressures and radiation efficiency during seismic faulting

Summary During earthquake faulting, radiation efficiency and the degree stress relief are critically dependent on the kinetic shear resistance. This is often assumed to stay constant during slip, but geological evidence suggests that for moderate or large shallow earthquakes it may decrease dramatically to near-zero values once slip is initiated, either by melt formation or by transient increases in fluid pressure on the fault plane. The latter, probably more common process may arise partly through an interaction between temperature and water pressure, and partly through dilatancy recovery as shear stress is relieved. If the fault remains undrained, stress relief should be absolute with seismic efficiency reaching high values, so that stress drops give a measure of the level of tectonic shear stress in fault zones. Supporting evidence comes from the observation that apparent stress is generally about half the stress drop.     

An algorithm for the optimum distribution of a regional seismic network — II. An analysis of the accuracy of location of local earthquakes depending on the number of seismic stations

Summary Seven optimal networks consisting of 4 to 10 stations are compared for a given region, where velocity-depth profiles and the distribution of seismic intensity are known. Assuming that the standard error of arrival time is _t =0.05 s and the standard errors of the parameters of velocity-depth profiles are equal to 5% of their values, the average standard errors of the origin time and focus coordinates are estimated. The application of optimum methods to the planning of seismic networks in the Lublin Coal Basin is presented, and maps of standard errors of origin time , depth and epicenter ( _xy ) for the case of an optimum network of 6 seismic stations are given.     

Flow–duration curve integration into digital filtering algorithms for simulating climate variability based on river baseflow

ABSTRACT

A baseflow separation methodology combining the outcomes of the flow–duration curve and the digital filtering algorithms to cope with the restrictions of traditional procedures has been assessed. Using this methodology as well as the monitored and simulated hydro-climatological data, the baseflow annual variations due to climate change and human-induced activities were determined. The outcomes show that the long-term baseflow index at the upstream sub-basin is nearly half of that at the downstream from October to April, whereas they are close to each other for the remaining months. Some of the groundwater reacts to precipitation and an evident rise in the groundwater contribution was detected for the hydrological years 1998–2001 and 2006–2008. The contrary was recorded for1987. The water released from the reservoir in the dry periods led to distinctions in the detected baseflow index between the pre-damming and post-damming periods of the river.     

A Statistical Study of Rapid Sunspot Structure Change Associated with Flares

We reported recently some rapid changes of sunspot structure in white-light(WL) associated with major flares.We extend the study to smaller events and present here results of a statistical study of this phenomenon.In total,we investigate 403 events from 1998 May 9 to 2004 July 17,including 40 X-class,174 M-class,and 189 C-class flares.By monitoring the structure of the flaring active regions using the WL observations from the Transition Region and Coronal Explorer(TRACE),we find that segments in the outer sunspot structure decayed rapidly right after many flares;and that,on the other hand,the central part of sunspots near the flare-associated magnetic neutral line became darkened.These rapid and permanent changes are evidenced in the time profiles of WL mean intensity and are not likely resulted from the flare emissions.Our study further shows that the outer sunspot structure decay as well as the central structure darkening are more likely to be detected in larger solar flares.For X-class flares,over 40% events show distinct sunspot structure change.For M-and C-class flares,this percentage drops to 17% and 10%,respectively.The results of this statistical study support our previously proposed reconnection picture,i.e.,the flare-related magnetic fields evolve from a highly inclined to a more vertical configuration.     

一种可能的地震成因模型

提出了一种地震成因模型。认为不仅水库地震、矿震等是被人类工程活动诱发的，其它地震也很可能有诱发因素起作用。这种作用不仅仅是触发了地震，地震的孕育很可能也与其有关。诱发因素包括人类工程活动、地外天体的特殊位置、地球自转角速度的变化、气象异常等。这些因素对地壳产生了附加垂直力，后者引起局部地层弯曲，进而导致应力集中、构造应力作用方式的改变乃至地震发生。     

Reconstruction of fire spread within wildland fire events in Northern Eurasia from the MODIS active fire product

Russian boreal forests have been reshaped by wildland fire for millennia. While fire is a natural component of boreal ecosystems, it impacts various aspects of the environment and affects human well-being. Often fires occur over large remote areas with limited access, which makes their ground-based observation difficult. A significant progress has been made in mapping burned area from satellite imagery, which provides consistent and fairly unbiased estimates of fire impact on areas of interest at multiple scales. Although the information provided by burned area products is highly important, the spatio-temporal dynamics of individual fire events and their impact are less known. In high northern latitudes of Northern Eurasia, MODIS (Moderate Resolution Imaging Spectroradiometer) makes up to four daily observations from each of the Terra and Aqua satellites providing consistent data on fire development with high temporal frequency. Here we introduce an approach to reconstruct the development of fire events based on active fire detections from MODIS. Fire Spread Reconstruction (FSR) provides a means for characterization of fire occurrence over large territories from remotely sensed data. Individual fire detections are clustered within a GIS environment based on a set of rules determining proximity between fire observations in space and time. FSR determines the number of fire events, their approximate size, duration, and fire spread rate and allows for the analysis of fire occurrence and spread as a function of vegetation, fire season, fire weather and other parameters. FSR clusters were compared to burned scars mapped from Landsat7/ETM+ imagery over Yakutia (Russia). While some smaller burn scars were found to be formed through a continuous burning of a single fire event, large burned areas in Siberia were created by a constellation of fire events incorporating over 100 individual fire clusters. Geographic regions were found to have a stronger influence on the rates of fire activity in the area compared to vegetation zones. In addition, fire spread rates do not directly correlate with the intensity of a given fire season. FSR is also used to identify the points of ignition for individual fire events in spatio-temporal domain for fire danger and fire threat modeling. This approach presents another step towards the more complete characterization of fire events from remotely sensed data.