BECAPEX科学试验城市建筑群落边界层大气环境特征及其影响   总被引：9，自引：1，他引：9  

徐祥德  丁国安  卞林根  谢立安 《气象学报》2004,62(5):663-671

20 0 1～ 2 0 0 3年在北京实施了大气边界层动力、热力、化学综合观测试验 (BECAPEX ,BeijingCityAtmosphericPollutionObservationFieldExperiment) ,获取了北京城市大气动力和大气化学三维结构图像。综合观测试验分析研究发现 ,城市区域呈非均匀次生尺度热岛分布 ,并伴随着城市次生尺度环流 ,影响了局地空气污染物分布特征。MODIS卫星遥感 地面观测资料经过变分分析 ,可发现北京城市空气污染与周边区域影响源有密切关系 ,并影响城市群落环境气候特征 ,导致该区域日照、雾日、低云量和能见度呈显著年代际变化趋势。  相似文献   

“雪龙号”2003北极航次气相多环芳烃纬度分布观测          下载免费PDF全文

丁翔  谢周清  向彩红  麦碧娴  王新明  孙立广  盛国英  傅家谟 《极地研究》2005,17(4):272-278

2003年“雪龙号”北极科学考察期间,对沿途海洋大气进行采样,分析其中气相多环芳烃的空间分布。结果显示,气相中主要是2-4环的多环芳烃,其中菲为主要的化合物,平均占到总多环芳烃的55.1%。在整个航程的广泛区域尺度内,气相总多环芳烃浓度在1043.9-92993.1pg/m3。空间分布上,远东亚的海面>北太平洋海面>北极圈以内海面;总多环芳烃的浓度随纬度升高呈现显著降低的趋势。通过Clausius-Clapeyron方程对浓度和温度相互关系的分析表明,温度是控制气相多环芳烃长距离传输的主要因素。  相似文献   

The effect of terrain factors on rice production: A case study in Hunan Province     

Wang  Chenzhi  Zhang  Zhao  Zhang  Jing  Tao  Fulu  Chen  Yi  Ding  Hu 《地理学报(英文版)》2019,29(2):287-305

Journal of Geographical Sciences - Rice (Oryza sativa L.) is the most important staple crop of China, and its production is related to both natural condition and human activities. It is fundamental...  相似文献   

Vertical vibration of a rigid strip footing on viscoelastic half-space     

Changjie Zheng  Lubao Luan  George Kouretzis  Xuanming Ding 《国际地质力学数值与分析法杂志》2020,44(14):1983-1995

This paper presents an analytical method for modeling the dynamic response of a rigid strip footing subjected to vertical-only loads. The footing is assumed to rest on the surface of a viscoelastic half-space; therefore, effects of hysteretic soil damping on the impedance of the foundation and the generated ground vibrations are considered in the solution. To solve the mixed boundary value problem, we use the Fourier transform to cast a pair of dual integral equations providing contact stresses, which are solved by means of Jacobi orthogonal polynomials. The resulting soil and footing displacements and stresses are obtained by means of the Fourier inverse transform. The solution provides more realistic estimates of footing impedance, compared to existing solutions for elastic soil, as well as of the attenuation of ground vibrations with distance of the footing. The latter is important for the estimation of machine vibration effects on nearby structures and installations.  相似文献   

Remote estimation of terrestrial evapotranspiration by Landsat 5 TM and the SEBAL model in cold and high‐altitude regions: a case study of the upper reach of the Shule River Basin,China          下载免费PDF全文

Yaping Chang  Yongjian Ding  Qiudong Zhao  Shiqiang Zhang 《水文研究》2017,31(3):514-524

Evapotranspiration (ET) is an important expenditure in water and energy balances, especially on cold and high‐altitude land surfaces. Daily ET of the upper reach of the Shule River Basin was estimated using Landsat 5 TM data and the Surface Energy Balance Algorithm for Land (SEBAL) model. Based on observations made at the Suli station, the algorithms of land surface temperature and soil heat flux in SEBAL were modified. Land surface temperature was retrieved and compared with ground truth via three methods: the radiative transfer equation method, the mono‐window algorithm, and the single‐channel method. We selected the best of these methods, mono‐window algorithm, for estimating ET. The average error of daily ET estimated by the modified SEBAL model and measured by the eddy covariance system was 16.4%, with a root‐mean‐square error of 0.52 mm d^?1. The estimated ET means were 3.09, 2.48, and 1.48 mm d^?1 on June 9 (DOY 160), June 25 (DOY 176), and July 27 (DOY 208) of the year 2010, respectively. The average estimated ET on the glacier surface of all days was more than 3 mm d^?1, a measurement that is difficult to capture in‐situ and has rarely been reported. This study will improve the understanding of water balance in cold, high‐altitude regions. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Torsional dynamic response of a large‐diameter pipe pile in viscoelastic saturated soil     

Changjie Zheng  Hanlong Liu  Xuanming Ding  Yaru Lv 《国际地质力学数值与分析法杂志》2014,38(16):1724-1743

An analytical solution is developed in this paper to investigate the dynamic response of a large‐diameter end‐bearing pipe pile subjected to torsional loading in viscoelastic saturated soil. The wave propagation in saturated soil and pile are simulated by Biot's two‐phased linear theory and one‐dimensional elastic theory, respectively. The dynamic equilibrium equations of the outer soil, inner soil, and pile are established. The solutions for the outer and inner soils in frequency domain are obtained by Laplace transform technique and the separation of variables method. Then, the dynamic response of the pile is obtained on the basis of the perfect contacts between the pile and the outer soil as well as the inner soil. The results in this paper are compared with that of a solid pile in elastic saturated soil to verify the validity of the solution. Furthermore, the solution in this paper is compared with the classic plane strain solution to verify the solution further and check the accuracy of the plane strain solution. Numerical results are presented to analyze the vibration characteristics and illustrate the effect of the soil parameters and the geometry size of the pile on the complex impedance and velocity admittance of the pile head. Finally, the displacement of the soil at different depth and frequency is analyzed. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Exploring the interaction of surface roughness and slope gradient in controlling rates of soil loss from sloping farmland on the Loess Plateau of China     

Taotao Li  Longshan Zhao  Hongteng Duan  Yifan Yang  Yu Wang  Faqi Wu 《水文研究》2020,34(2):339-354

Surface roughness and slope gradient are two important factors influencing soil erosion. The objective of this study was to investigate the interaction of surface roughness and slope gradient in controlling soil loss from sloping farmland due to water erosion on the Loess Plateau, China. Following the surface features of sloping farmland in the plateau region, we manually prepared rough surfaces using four tillage practices (contour drilling, artificial digging, manual hoeing, and contour plowing), with a smooth surface as the control measure. Five slope gradients (3°, 5°, 10°, 15°, and 20°) and two rainfall intensities (60 and 90 mm/hr) were considered in the artificial rainfall simulation experiment. The results showed that the runoff volume and sediment yield increased with increasing slope gradient under the same tillage treatment. At gentle slope gradients (e.g., 3° and 5°), the increase in surface roughness prevented the runoff and sediment production, that is, the surface roughness reduced the positive effect of slope gradient on the runoff volume and sediment yield to a certain extent. At steep slope gradients, however, the enhancing effect of slope gradient on soil erosion gradually increased and surpassed the reduction effect of surface roughness. This study reveals the existence of a critical slope gradient that influences the interaction of surface roughness and slope gradient in controlling soil erosion on sloping farmland. If the slope gradient is equal to or less than the critical value, an increase in surface roughness would decrease soil erosion. Otherwise, the increase in surface roughness would be ineffective for preventing soil erosion. The critical slope gradient would be smaller under higher rainfall intensity. These findings are helpful for us to understand the process of soil erosion and relevant for supporting soil and water conservation in the Loess Plateau region of China.  相似文献   

Nitrogen fixation driven by mesoscale eddies and the Kuroshio Current in the northern South China Sea and the East China Sea     

Liuyang Li  Chao Wu  Jun Sun  Shuqun Song  Changling Ding  Danyue Huang  Laxman Pujari 《海洋学报(英文版)》2020,39(12):30-41

N₂ fixation rates (NFR, in terms of N) in the northern South China Sea (nSCS) and the East China Sea (ECS) were measured using the acetylene reduction assay in summer and winter, 2009. NFR of the surface water ranged from 1.14 nmol/(L·d) to 10.40 nmol/(L·d) (average at (4.89±3.46) nmol/(L·d), n=11) in summer and 0.74 nmol/(L·d) to 29.45 nmol/(L·d) (average at (7.81±8.50) nmol/(L·d), n=15) in winter. Significant spatio-temporal heterogeneity emerged in our study: the anticyclonic eddies (AE) (P<0.01) and the Kuroshio Current (KC) (P<0.05) performed significantly higher NFR than that in the cyclonic eddies or no-eddy area (CEONE), indicating NFR was profoundly influenced by the physical process of the Kuroshio and mesoscale eddies. The depth-integrated N₂ fixation rates (INF, in terms of N) ranged from 52.4 μmol/(m2·d) to 905.2 μmol/(m2·d) (average at (428.9±305.5) μmol/(m2·d), n=15) in the winter. The contribution of surface NFR to primary production (PP) ranged from 1.7% to 18.5% in the summer, and the mean contribution of INF to new primary production (NPP) in the nSCS and ECS were estimated to be 11.0% and 36.7% in the winter. The contribution of INF to NPP (3.0%–93.9%) also decreased from oligotrophic sea toward the eutrophic waters affected by runoffs or the CEONE. Furthermore, we observed higher contributions compared to previous studies, revealing the vital roles of nitrogen fixation in sustaining the carbon pump of the nSCS and ECS.  相似文献   

Estimation of instantaneous peak flow from maximum mean daily flow by regionalization of catchment model parameters          下载免费PDF全文

Jie Ding  Uwe Haberlandt 《水文研究》2017,31(3):612-626

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Shallow sediment deformation styles in north-western Campeche Knolls,Gulf of Mexico and their controls on the occurrence of hydrocarbon seepage     

Feng Ding  Volkhard Spiess  Ian R. MacDonald  Markus Brüning  Noemi Fekete  Gerhard Bohrmann 《Marine and Petroleum Geology》2010,27(4):959-972

During German R/V Meteor M67/2 expedition to Campeche Knolls, southern Gulf of Mexico, a set of 2D high resolution seismic data was acquired to study the near-surface sediment structure and its relationship with hydrocarbon seepages in this salt province. The comprehensive survey covered 20 individual bathymetric highs or ridges and identified three principle structural types: Passive Type, Chaopopte Type, and Asymmetric Flap Type. The first type is the result of passive diapirism, whereas the latter two were initialized by a regional compressional event in the Miocene, but are later differently modified by salt tectonism. Chapopote Type structures appear as symmetrical domes, with uplifted coarse-grained Miocene sediments in their cores and rather thin syn-kinematic sediments covering the crests. Asymmetric Flap Type structures are also first folded as domes or ridges, but one flap later subsided together with salt evacuation, resulting in single uplifted monoclines. With the coarse-grained pre-kinematic sediments as reservoir units, both structural types can focus and accumulate hydrocarbons. The geometries of the structures suggest that hydrocarbons are accumulated in the center of the Chapopote Type structures and in the subsided flaps of the Asymmetric Flap Type structures. Hydrocarbon leakage from these thinly sealed reservoirs is regarded as the principle mechanism for the seepage in the study area, and accordingly the most seepage-prone positions are above these reservoirs. The seep locations suggested by analysis of sea-surface oil slick images of SAR satellite data are also examined in this study. These independently derived seep locations confirm the seepage-prone positions to be above the shallow buried reservoirs. This study suggest that the shallow sediment structures control the distribution of the hydrocarbon seeps of the north-western Campeche Knolls, although the hydrocarbons are sourced from the greater depth.  相似文献