江苏6—7月降水与前期澳大利亚高压及相关海温异常的关系

利用5月份澳大利亚海平面气压和中国107站的6—7月降水资料,使用SVD方法揭示了5月份澳大利亚高压(简称澳高)与江苏汛期(6—7月)降水(简称汛期降水)的联系及可能原因,研究表明:当5月澳高偏强时,汛期环流特征表现为:(1)低层风场在30°N附近存在明显的风向切变,上升气流显著,并且西太平洋副热带高压较常年偏西,这样有利于降水增多;(2)130°E附近的越赤道气流显著加强,为降水提供了很好的水汽条件。主要影响途径:当5月澳高偏强(偏弱)时,与澳高相联系的印度尼西亚附近海温持续性偏冷(偏暖),偏冷(偏暖)的海温一方面使得其区域低层风场的异常辐散(辐合),异常辐散(辐合)风场作为涡度源通过Gill型响应可引起西太平洋异常反气旋(气旋)环流,有利于副热带高压较常年偏强偏西(偏弱偏东),也增强(减弱)了自南向北的暖湿气流的输送;另一方面引起其区域下沉(上升)气流异常,进而通过类似与EAP波列,激发江淮地区的异常上升(下沉)气流,使得汛期降水偏多(偏少)。     

预报评分的框架及计算实例

评定一个预报方法或预报系统性能的最合理的量度应该是它对于用户实际或潜在的价值。但由于确定预报价值的困难性及价值随着用户决策使用方法不同而不同；因此气象学家往往用预报质量来代替预报价值。但现有的研究表明，预报的质量与价值并不总是具有线性正相关，前者并不能充分代表后者。     

粤西海域浮游植物的时空分布及其漂移特点

根据1998—1999年粤西海域4个航次浮游植物的调查资料,在GIS和SPSS的支持下对该海域浮游植物栖息密度的时空分布特征及重心位置的变化进行了初步分析。结果显示,春季、秋季和冬季浮游植物的分布趋势相似,均呈北高南低或近岸水域高、离岸水域低的分布趋势,其密集分布区均出现在电白至川山群岛一带的近岸水域,其中以冬季的分布范围最广,栖息密度最高,平均值达412.70×104cells·m-3,其次为秋季,平均值为149.75×104cells·m-3。夏季浮游植物密集分布区的范围较小,呈现出东北侧近岸水域密集程度高、西南侧水域低的分布特点,其栖息密度处于全年的最低值,平均值为15.64×104cells·m-3。偏相关分析结果表明,浮游植物栖息密度与N/P比值呈显著的正相关关系,与无机氮、磷酸盐和硅酸盐的相关性不显著。栖息密度的重心分析结果表明,春季、秋季和冬季浮游植物的重心位置彼此相近,漂移规律不明显;而夏季重心则明显向东南方向漂移,其最大漂移距离横向达24.74′,纵向达16.78′。     

Key nitrogen biogeochemical processes revealed by the nitrogen isotopic composition of dissolved nitrate in the Changjiang River estuary,China

Seasonal variations in the nitrogen isotopic composition of dissolved nitrate(δ 15 NO 3) were investigated in the surface waters of the Changjiang River estuary in 2009 and 2010. δ 15 NO 3 varied between-4.6‰ and 8.9‰ with changes in temperature, salinity, dissolved oxygen concentrations, and the composition of the dissolved inorganic nitrogen pool. In February, biological processes decreased because of low temperature, and the mean δ 15 NO 3 near the river mouth was 2.4‰. In May, δ 15 NO 3 was the highest in the surface waters among all seasons. Analysis on the conservative mixing revealed assimilation, and this fi nding is supported by positive relationship between Chl a and δ 15 NO 3. The fractionation factor of assimilation was estimated to be 2.0‰ by the Rayleigh equation. Nitrifi cation was supported based on the mixing behaviors in November 2010 and the low δ 15 NO 3 values in May and November 2009. The high ammonium concentrations in the adjacent marine area and positive relationships between total organic nitrogen and δ 15 NO 3 in November 2010 indicated that mineralization was taking place.     

Silicon and oxygen isotopic composition of igneous rocks from the eastern Manus Basin

This paper reports silicon and oxygen isotopes of 20 kinds of igneous rocks and their major elements from the eastern Manus Basin. Combining silicon and oxygen isotopic data from other studies, we suppose that both δ30Si and δ18O values increase with the increasing of SiO2 content. It means that the fractionation of silicon and oxygen isotopes are affected by the silica content. The positive correlation between CaO/Al2O3 ratios and MgO and that between Si/Al and SiO2 content indicate that clinopyroxene is the predominant mineral phase in our samples. We suppose that the fractionation of silicon and oxygen isotopes are influenced by mineral fractional crystallization. Probably, it is due to their different silicon and oxygen bridges. In this study, the δ30Simean value=-0.17‰±0.17‰ and δ18Omean value= +6.07‰±0.57‰ are higher than normal δ30Si and δ18O values of mantle, and we propose that these igneous rocks in the eastern Manus Basin are affected by hydrothermal alteration.     

Spatiotemporal Changes of Vegetation Cover in Response to Climate Change on the Tibetan Plateau

The Tibetan Plateau is one of the most important ecological barriers in China.Resolving the internal relations and dynamics ruling the association between regional vegetation and climate change is important to understand and protect the regional ecosystems.Based on vegetation,temperature and precipitation data of the Tibetan Plateau from 2001 to 2010,we analyze the spatial and temporal variations of vegetation cover over the past 10 years and discuss the vegetation response to climate change using empirical orthogonal function and singular value decomposition.Our results reveal the following：（1） vegetation cover gradually decreases from the southeast to the northwest of the Tibetan Plateau; （2） vegetation cover has increased on the Tibetan Plateau over the past 10 years,mainly in the central and eastern zones; and （3） a significant positive relationship was suggested between vegetation cover during growing season and the temperature in the entire region and with precipitation in the central and southern zones.     

试论大厂生物礁灰岩中硫化物矿床金、银的分布特征

本文着重讨论大厂锡矿田生物礁灰岩硫化物矿床中金、银的分布特点。金与毒砂、黄铁矿、磁黄铁矿共生;银有独立矿物,与脆硫锑铅矿关系密切。并进一步阐明了同为100号矿体,同为脆硫锑铅矿,而其中银含量向低标高增加的原因。过去总结大厂长坡矿床中银赋存规律为银含量向低标高降低,这次整理中得到证实的是向低标高银降低的原因,即Mn、Pb,Sb品位降低之故,但仍服从于大厂地区每1％Pb+Sb含Ag为15—17g/T的规律。 生物礁礁灰岩硫化物矿床中Pb,Sb品位是逐步向深处增加,故银含量也逐步增加。经单矿物挑选分析,同为“脆硫锑铅矿”,但其银的含量向深部增加,其原因就是向深处逐步有含锰脆硫锑铅矿出现之故,从而证实了Mn~(2+)—Mn~(4+)时,有助于将Ag~+还原到自然状态,因而提高银的成色,是银在同一矿物中向深处品位逐步升高的原因,这是过去未曾论证过的。     

Maximum flux density of the gyrosynchrotron spectrum in a nonuniform source

The maximum flux density of a gyrosynchrotron radiation spectrum in a mag- netic dip|oe model with self absorption and gyroresonance is calculated. Our calculations show that the maximum flux density of the gyrosynchrotron spectrum increases with in- creasing low-energy cutoff, number density, input depth of energetic electrons, magnetic field strength and viewing angle, and with decreasing energy spectral index of energetic electrons, number density and temperature of thermal electrons. It is found that there are linear correlations between the logarithms of the maximum flux density and the above eight parameters with correlation coefficients higher than 0.91 and fit accuracies better than 10%. The maximum flux density could be a good indicator of the changes of these source parameters. In addition, we find that there are very good positive linear correla- tions between the logarithms of the maximum flux density and peak frequency when the above former five parameters vary respectively. Their linear correlation coefficients are higher than 0.90 and the fit accuracies are better than 0.5%.     

陕西黄龙树轮年表的建立及其2-3月降水记录

通过两组油松树轮宽度的研究,建立了陕西黄龙地区过去近200 a来的树轮STD、RES、ARS年表,树轮宽度在20世纪20年代有过明显的下降,1929年前后达到年轮宽度最低值,与历史记载的自民国11年以来连续干旱时期相吻合(1922-1932年).经过相关函数、响应函数分析,发现树轮宽度与生长季当年2-3月降水显著正相关,在此基础上设计了转换方程,重建了过去200 年来黄龙地区早春2-3月降水历史,重建序列的解释方差为44.3%(F=16.298,p<0.001).功率谱分析检测到2-3月降水存在7.69、6.90、6.06、5.13、5.00、4.88、4.65、2.02、2.00 年的周期.     

秦岭-黄淮平原交界带地表径流与其时间变化的关系分析

根据秦岭-黄淮平原交界带及其邻近地区42个径流站1962~1999年的观测资料,分析了地表径流量及其时间变化(年内分配和年际变化)的空间分布规律,得出二者之间存在正相关关系的结论,并探讨了这种反常现象的成因。