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111.
利用欧洲中心全球客观分析的7层月平均位势高度距平资料,分别计算了相同格点上12-2月和6-8月各层高度距平之间的同时相关分布。结果表明:全球月平均位势高度距平场的正压、斜压性随地理区域变化很大,并有较明显的季节变化。其中12-2月对流层下部大气环流距平场在海洋上空有较好的相当正压性,在大陆上空正压性较差;对流层上部大气环流异常的正、斜压性分布与下部不同,赤道附近地区是相关系数的高值区,副热带地区主要是低值区;在对流层下部与上部大气环流距平场的相关系数分布图上,海洋上空并不总是高值区,在热带东太平洋区域就出现最强的负相关中心。与6-8月的相关系数分布型比较发现:特别明显的季节变化在非洲大陆和热带印度洋区域,12-2月为强正压区,6-8月为强斜压区。 相似文献
112.
Zhang Qin Ni Yunqi Lin Wuyin Wang Zhaomin D. D. Houghton 《Acta Meteorologica Sinica》1991,5(4):411-425
In this paper, five-year simulated data from a low-resolution global spectral model with triangular trunca-lion at wavenumber 10 are analyzed in order to study dynamical features and propagation characteristics ofintraseasonal oxillations over the mid-latitudes and the tropical atmosphere. The simulations show that thereis the 30-50 day periodic oscillation in the low-resolution spectral model without non-seasonal external forcing,and spatial scale of the intraseasonal oscihations is of the globe .Further analysis finds that propagation charac-ters of intraseasonal oscillations over the mid-latitudes and the tropics are different. The 30-50 day oscillationover the tropics exhibits structure of the velocity potential wave with wavenumber 1 in the latitudinal and thecharacter of the traveling wave eastward at speed of 8 longitudes/day. However, the 30-50 day oscillationsin mid-latitude atmosphere exhibit phase and amplitude oscillation of the standing planetary waves and theyare related to transform of teleconnection patterns over the mid-latitudes. The energy is not only transferredbetween the tropics and the middle-high latitudes, but also between different regions over the tropics. Based on the analysis of 5-year band pass filtered data from a 5-layer global spectral model of Jow-ordetwith truncated wavenumber l0,investigation is done of the source of intraseasonal oscillations in the extratropicalmodel atmosphere and its mechanism. Results show that (1) the convective heat transferred eastward alongthe equator serves as the source of the intraseasonal oxillation both in the tropical and the extratropical atmos--phere; (2) the velocity-potential wave of a zonal structure of wavenumber 1 gives rise to oxillation in divergentand convergent wind fields of a dipole-form as seen from the equatorial Indian Ocean to the western Pacificduring its eastward propagation, thus indicating the oscillation in the dipole-form heat soure:e/sink pattertl; (3)the tropical heat-source oscillation is responsible for the variation in phase and intensity of the extratropicalstationary wave train, and the interaction between the oscillating low-frequency inertial gravity and stationaryRossby modes that are probably mechanisms for the oscillations ip the middle-high latitudes. 相似文献
113.
1993年第三季度,全球地震活动水平为中等偏高,明显高于上半年平均水平。日本北海道西南近海发生7.6级浅源地震,但不属于日本海沟地震。埃及西奈半岛发生5.7级地震,为今年亚欧带西段之最大地震。马里亚纳群岛发生8.1级中深震,使西北太平洋地区地震水平达到全球第一。兴都库什地区接连发生三次较大中深震,可能对我国西部地区地震活动有影响。墨西哥恰帕斯州近海发生7.3级地震,美洲带新的地震活动轮回正式开始。印度南部发生6.3级中强震,属于板内地震。 相似文献
114.
Field measurements of NO and NO2 emissions from soils have been performed in Finthen near Mainz (F.R.G.) and in Utrera near Seville (Spain). The applied method employed a flow box coupled with a chemiluminescent NO
x
detector allowing the determination of minimum flux rates of 2 g N m-2 h-1 for NO and 3 g m-2 h-1 for NO2.The NO and NO2 flux rates were found to be strongly dependent on soil surface temperatures and showed strong daily variations with maximum values during the early afternoon and minimum values during the early morning. Between the daily variation patterns of NO and NO2, there was a time lag of about 2 h which seem to be due to the different physico-chemical properties of NO and NO2. The apparent activation energy of NO emission calculated from the Arrhenius equation ranged between 44 and 103 kJ per mole. The NO and NO2 emission rates were positively correlated with soil moisture in the upper soil layer.The measurements carried out in August in Finthen clearly indicate the establishment of NO and NO2 equilibrium mixing ratios which appeared to be on the order of 20 ppbv for NO and 10 ppbv for NO2. The soil acted as a net sink for ambient air NO and NO2 mixing ratios higher than the equilibrium values and a net source for NO and NO2 mixing ratios lower than the equilibrium values. This behaviour as well as the observation of equilibrium mixing ratios clearly indicate that NO and NO2 are formed and destroyed concurrently in the soil.Average flux rates measured on bare unfertilized soils were about 10 g N m-2 h-1 for NO2 and 8 g N m-2 h-1 for NO. The NO and NO2 flux rates were significantly reduced on plant covered soil plots. In some cases, the flux rates of both gases became negative indicating that the vegetation may act as a sink for atmospheric NO and NO2.Application of mineral fertilizers increased the NO and NO2 emission rates. Highest emission rates were observed for urea followed by NH4Cl, NH4NO3 and NaNO3. The fertilizer loss rates ranged from 0.1% for NaNO3 to 5.4% for urea. Vegetation cover substantially reduced the fertilizer loss rate.The total NO
x
emission from soil is estimated to be 11 Tg N yr-1. This figure is an upper limit and includes the emission of 7 Tg N yr-1 from natural unfertilized soils, 2 Tg N yr-1 from fertilized soils as well as 2 Tg N yr-1 from animal excreta. Despite its speculative character, this estimation indicates that NO
x
emission by soil is important for tropospheric chemistry especially in remote areas where the NO
x
production by other sources is comparatively small. 相似文献
115.
The global distribution of methane in the troposphere 总被引:6,自引:0,他引:6
L. P. Steele P. J. Fraser R. A. Rasmussen M. A. K. Khalil T. J. Conway A. J. Crawford R. H. Gammon K. A. Masarie K. W. Thoning 《Journal of Atmospheric Chemistry》1987,5(2):125-171
Methane has been measured in air samples collected at approximately weekly intervals at 23 globally distributed sites in the NOAA/GMCC cooperative flask sampling network. Sites range in latitude from 90° S to 76° N, and at most of these we report 2 years of data beginning in early 1983. All measurements have been made by gas chromatography with a flame ionization detector at the NOAA/GMCC laboratory in Boulder, Colorado. All air samples have been referenced to a single secondary standard of methane-in-air, ensuring a high degree of internal consistency in the data. The precision of measurements is estimated from replicate determinations on each sample as 0.2%. The latitudinal distribution of methane and the seasonal variation of this distribution in the marine boundary layer has been defined in great detail, including a remarkable uniformity in background levels of methane in the Southern Hemisphere. We report for the first time the observation of a complete seasonal cycle of methane at the South Pole. A significant vertical gradient is observed between a sea level and a high altitude site in Hawaii. Globally averaged background concentrations in the marine boundary layer have been calculated for the 2 year-period May 1983–April 1985 inclusive, from which we find an average increase of 12.8 ppb per year, or 0.78% per year when referenced to the globally averaged concentration (1625 ppb) at the mid-point of this period. We present evidence that there has been a slowing down in the methane growth rate.Presented at the Conference on the Scientific Application of Baseline Observations of Atmospheric Composition (SABOAC), Aspendale, Australia, 7–9 November 1984. 相似文献
116.
P. J. Fraser R. A. Rasmussen J. W. Creffield J. R. French M. A. K. Khalil 《Journal of Atmospheric Chemistry》1986,4(3):295-310
New CH4 emission data from a number of Northern and Southern Hemispheric, tropical and temperate termites, are reported, which indicate that the annual global CH4 source due to termites is probably less than 15 Tg. The major uncertainties in this estimate are identified and found to be substantial. Nevertheless, our results suggest that termites probably account for less than 5% of global CH4 emissions. 相似文献
117.
Renjie Zhao Quanshu Yan Haitao Zhang Yili Guan Zhenmin Ge Long Yuan Shishuai Yan 《地球科学进展》1986,35(8):789-803
Subducted sediments play an important role in crust-mantle interaction and deep mantle processes, especially for subduction zone magmatism and mantle geochemistry. The current rate of Global Subducting Sediments (GLOSS) is 0.5~0.7 km3/a. The GLOSS are composed of terrigenous material(76 wt.%), calcium carbonate(7 wt.%), opal(10 wt.%) and mineral-bound H2O+(7 wt.%). The chemical compositions of GLOSS are similar to those of upper continental crust which is mainly controlled by the terrigenous materials, and yet the materials formed by marine processes will dilute the terrigenous materials. The components of subducted sediments are different among trenches. In the accretionary margin, the components of subducted sediments are similar to those of the upper crust, while in the non-accretionary margin the components are terrigenous materials plus those produced by marine processes. During subduction, subducted sediments will released fluids, melt or supercritical fluid to affect island arc/back-arc basin magmatism by means of aqueous fluid or sediment melt. In addition, a part of subducted sediments, together with underlying altered oceanic crust/lithosphere, recycle into the mantle and contribute to the mantle heterogeneity. Geochemical tracers indicate that subducted sediments play variable contributions to the magmatic processes in different tectonic setting. Thus, subducted sediments play an important role in two relatively independent dynamics systems (plate tectonics and mantle plume), as well as related mantle evolution models. As a result, by accurately calculating the compositions of subduction sediments and using various geochemical indicators, we can further limit the input and output fluxes of various elements or isotopes, and then obtain more accurately residual subducted components, which can provide us some important clues for geodynamic process. 相似文献
118.
119.
120.
深海钻探揭示的古新统—始新统界线上许多全球性变化引起了地质学家的普遍关注。这些变化包括:岩性上从海绿石石英砂岩变化到粘土岩、粘土矿物组合从伊利石/蒙脱石为主变化为高岭石为主、大陆植物群的绝灭和迁移、钙质超微化石物种更新速度加快、底栖有孔虫绝灭和分异度降低、碳氧同位素强烈负异常、大陆哺乳动物演化发生变化、大气环流强度减弱、海洋环流模式改变、海平面上升、海底热液活动呈1~2个数量级加强。通过对古新世—始新世的地层沉积学、古生物学、古气候学和古海洋学研究,确认古新统—始新统地层界线是全球构造事件的结果,表现为全球板块边界重组、扩张中心和转换断层模式改变、海底热液活动呈1~2个数量级加强。 相似文献