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Based on the land surface temperature (LST), the land cover classification map,vegetation coverage, and surface evapotranspiration derived from EOS-MODIS satellite data, and by the use of GIS spatial analytic technique and multivariate statistical analysis method, the urban heat island (UHI) spatial distribution of the diurnal and seasonal variabilities and its driving forces are studied in Beijing city and surrounding areas in 2001. The relationships among UHI distribution and landcover categories, topographic factor, vegetation greenness, and surface evapotranspiration are analyzed. The results indicate that: (i) The significant UHI occur in Beijing city areas in the four seasons due to high heat capacity and multi-reflection of compression building, as well as with special topographic features of its three sides surrounded by mountains,especially in the summer. The UHI spatial distribution is corresponding with the urban geometry structure profile. The LST difference is approximately 4-6℃ between Beijing city and suburb areas, comparatively is 8- 10℃ between Beijing city area and outer suburb area in northwestern regions. (ii) The UHI distribution and intensity in daytime are different from nighttime in Beijing city area, the nighttime UHI is obvious. However, in the daytime, the significant UHI mainly appears in the summer, the autumn takes second place, and the UHI in the winter and the spring seem not obvious. The surface evapotranspiration in suburb areas is larger than that in urban areas in the summer, and high latent heat exchange is evident, which leads to LST difference between city area and suburb area. (iii) The reflection of surface landcover categories is sensitive to the UHI, the correlation between vegetation greenness and UHI shows obviously negative.The scatterplot shows that there is the negative correlation between NDVI and LST (R2 = 0.6481).The results demonstrate that the vegetation greenness is an important factor for reducing the UHI,and large-scale construction of greenbelts can considerably reduce the UHI effect. 相似文献
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Zhaochong ZHANG Houmin LI Jianwei LI Xie-Yan SONG Hao HU Lixing LI Fengmei CHAI Tong HOU Deru XU 《中国科学:地球科学(英文版)》2021,(5):691-715
The predominant types of high-grade iron deposits in China include skarn, sedimentary metamorphic(banded ironformation, BIF-type), continental/submarine volcanic-hosted and magmatic Fe-Ti-Voxide deposits. Based on a comprehensive review of current studies on these deposits, this paper suggests that the oxygen concentration in atmosphere played an important role for the formation of BIFs, whereas the tectonic setting and deep magmatic differentiation processes are more important for the other types. Notably, both high temperature and high pressure experiments and melt inclusion studies indicate that during the differentiation, high temperature magmas could develop iron-rich magma via liquid immiscibility but not pure oxide melt("iron ore magma"). Fe-P melt could be generated directly by liquid immiscibility under hydrous and oxidized condition. The formation of high-grade iron deposits is mostly associated with the processes related to multiple stages of superimposition, e.g., desiliconization and iron enrichment, removal of impurity, and remobilization and re-precipitation of iron. According to the temporal evolution, the high-grade iron deposit could be divided into multi-episode superimposition type(temporally discontinuous mineralization) and multi-stage superimposition type(temporally continuous mineralization). The former is represented by the sedimentary metamorphic iron deposit, and the latter includes those related to magmatic-hydrothermal fluids(e.g., skarn,volcanic-hosted and magmatic types). 相似文献
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Polycyclic aromatic hydrocarbons (PAHs) contamination of topsoil in Benxi City, Northeast China was investigated in this study,
and sampling sites were located in industrial area and residential area. Results demonstrate that there is high variability
in the total PAHs concentrations, ranging from 783.00 ng/g to 729 076.29 ng/g dry weight in the topsoil of Benxi City and
the pollution in industrial area is the most serious. The results also present that higher molecular weight PAHs (4–6 rings)
contribute substantially (79.03%) to the overall content of PAHs. The PAHs sources were determined with factor analysis by
nonnegative constraints, and the results show that PAHs originating from traffic tunnel, power plant, coke oven and residential
emission sources, account for 27.10%, 40.81%, 20.11% and 11.98%, respectively, of the total. The PAHs pollution is the most
serious around Benxi Iron and Steel Group Corporation, and the PAHs mainly originate from coke oven and traffic tunnel, with
the average contribution rate of 57.40% and 42.60%, respectively. The source apportionment results are basically consistent
with the industry distribution, and the geographical and climatic characteristics of the study area. 相似文献
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Rivers in the Liaohe River Estuary area have been seriously polluted by discharges of wastewater containing petroleum pollutants and nutrients. In this paper, The Enhanced Stream Water Quality Model (QUAL2K) and its revised model as well as One-dimensional Tide Mean Model (1D model) were applied to predict and assess the water quality of the tidal river reach of the Liaohe River Estuary. Dissolved oxygen (DO), biochemical oxygen demand (BOD5), ammonia nitrogen (NH3-N) and total phosphorus (TP) were chosen as water quality indices in the two model simulations. The modelled results show that the major reasons for degraded rivers remain petroleum and non-point source pollution. Tidal water also has a critical effect on the variation of water quality. The sensitivity analysis identifies that flow rate, point load and diffuse load are the most sensitive parameters for the four water quality indices in the revised QUAL2K simulation. Uncertainty analysis based on a Monte Carlo simulation gives the probability distribution of the four water quality indices at two locations (6.50 km and 44.84 km from the river mouth). The statistical outcomes indicate that the observed data fall within the 90% confidence intervals at all sites measured, and show that the revised QUAL2K gives better results in simulating the water quality of a tidal river. 相似文献
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A multi-proxy reconstruction of spatial and temporal variations in Asian summer temperatures over the last millennium 总被引:1,自引:0,他引:1
Feng?Shi Quansheng?GeEmail author Bao?Yang Jianping?Li Fengmei?Yang Fredrik?Charpentier?Ljungqvist Olga?Solomina Takeshi?Nakatsuka Ninglian?Wang Sen?Zhao Chenxi?Xu Keyan?Fang Masaki?Sano Guoqiang?Chu Zexin?Fan Narayan?P.?Gaire Muhammad?Usama?Zafar 《Climatic change》2015,131(4):663-676
To investigate climate variability in Asia during the last millennium, the spatial and temporal evolution of summer (June–July–August; JJA) temperature in eastern and south-central Asia is reconstructed using multi-proxy records and the regularized expectation maximization (RegEM) algorithm with truncated total least squares (TTLS), under a point-by-point regression (PPR) framework. The temperature index reconstructions show that the late 20th century was the warmest period in Asia over the past millennium. The temperature field reconstructions illustrate that temperatures in central, eastern, and southern China during the 11th and 13th centuries, and in western Asia during the 12th century, were significantly higher than those in other regions, and comparable to levels in the 20th century. Except for the most recent warming, all identified warm events showed distinct regional expressions and none were uniform over the entire reconstruction area. The main finding of the study is that spatial temperature patterns have, on centennial time-scales, varied greatly over the last millennium. Moreover, seven climate model simulations, from the Coupled Model Intercomparison Project Phase 5 (CMIP5), over the same region of Asia, are all consistent with the temperature index reconstruction at the 99 % confidence level. Only spatial temperature patterns extracted as the first empirical orthogonal function (EOF) from the GISS-E2-R and MPI-ESM-P model simulations are significant and consistent with the temperature field reconstruction over the past millennium in Asia at the 90 % confidence level. This indicates that both the reconstruction and the simulations depict the temporal climate variability well over the past millennium. However, the spatial simulation or reconstruction capability of climate variability over the past millennium could be still limited. For reconstruction, some grid points do not pass validation tests and reveal the need for more proxies with high temporal resolution, accurate dating, and sensitive temperature signals, especially in central Asia and before AD 1400. 相似文献
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随着《地面气象观测新规范》和《OSSMO-HY2002》软件的正式启用,笔者就此软件与AHDM4.1在实际应用方面略作归纳整理。 相似文献
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东海陆架盆地位于欧亚板块的东南缘和西太平洋活动大陆边缘,本文选取了东海陆架盆地主要凹陷的17条地震剖面,采用平衡剖面技术,计算了主要凹陷新生代不同演化阶段的伸展率和压缩率。分析表明,东海陆架盆地构造演化总体由西向东跃迁。晚白垩世至晚古新世东海陆架盆地裂陷中心在西部坳陷带,始新世东迁至东部坳陷带,上新世东迁至东海陆架盆地东侧的冲绳海槽盆地。古新世中后期东海陆架盆地西部坳陷带北侧昆山凹陷反转;中新世东部坳陷带的西湖凹陷反转。东海陆架盆地西部坳陷带与东部坳陷带构造演化不同,证明了东海陆架盆地的东西分带。西部坳陷带北部的长江坳陷和南部的台北坳陷构造演化不同,东部坳陷带北部的西湖凹陷和南部的钓北凹陷构造演化不同,证明了东海陆架盆地的南北分块。 相似文献