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51.
勘探区地处毛乌素沙漠西南边缘,表层多为干燥疏松的沙丘和黄土;浅层为沙土、卵石、砾石层,大部分地段不含水,均为松散沉积物。区内断层和褶皱发育,煤层埋藏深度与产状变化较大。针对该区表、浅层和深层复杂的地震地质条件,通过不断优化三维地震勘探设计,最终确定了野外数据采集观测系统及激发与接收参数,并在数据处理中,选择了合适的处理技术、处理参数及处理流程,获得了信噪比与分辨率较高的三维数据体,较好的完成了地质勘探任务。 相似文献
52.
中国东部植被NDVI对气温和降水的时空响应(英文) 总被引:4,自引:4,他引:4
Temporal and spatial response characteristics of vegetation NDVI to the variation of temperature and precipitation in the whole year,spring,summer and autumn was analyzed from April 1998 to March 2008 based on the SPOT VGT-NDVI data and daily temperature and precipitation data from 205 meteorological stations in eastern China.The results indicate that as a whole,the response of vegetation NDVI to the variation of temperature is more pronounced than that of precipitation in eastern China.Vegetation NDVI maxi... 相似文献
53.
María Charco José Fernández Francisco Luzón Kristy F. Tiampo John B. Rundle 《Pure and Applied Geophysics》2007,164(4):865-878
Surface displacements and gravity changes due to volcanic sources are influenced by medium properties. We investigate topographic,
elastic and self-gravitation interaction in order to outline the major factors that are significant in data modelling. While
elastic-gravitational models can provide a suitable approximation to problems of volcanic loading in areas where topographic
relief is negligible, for prominent volcanoes the rough topography could affect deformation and gravity changes to a greater
extent than self-gravitation. This fact requires the selection, depending on local relief, of a suitable model for use in
the interpretation of surface precursors of volcanic activity. We use the three-dimensional Indirect Boundary Element Method
to examine the effects of topography on deformation and gravity changes in models of magma chamber inflation/deflation. Topography
has a significant effect on predicted surface deformation and gravity changes. Both the magnitude and pattern of the geodetic
signals are significantly different compared to half-space solutions. Thus, failure to account for topographic effects in
areas of prominent relief can bias the estimate of volcanic source parameters, since the magnitude and pattern of deformation
and gravity changes depend on such effects. 相似文献
54.
The broadband diffuse radiation method is improved to retrieve the aerosol refractive index imaginary part (AIP) and broadband (400-1000 nm mean) single scattering albedo (SSA). In this method, four sets of SSA selection criteria are proposed for quality control. The method is used to retrieve AIP, SSA and absorptive optical thickness (AbOT) from routine hourly-exposed pyrheliometer and paranometer measurements over 11 sites (meteorological observatories) in China during 1998-2003. Apart from one suburban site (Ejin Qi), the other urban sites are all located around big or medium cities. As shown in the retrieval results, annual mean SSA during 1998-2003 changes from 0.941 (Wuhan) to 0.849 (Lanzhou), and AIP from 0.0054 to 0.0203. The 11-site average annual mean SSA and AIP are 0.898 and 0.0119, respectively. SSA during winter is smaller for most sites. There is an evidently positive correlation between SSA and aerosol optical thickness (AOT) for all sites. There is also a positive correlation between SSA and relative humidity for most sites, but a negative correlation for a few sites, such as Kashi and ǚrǚmqi in Northwest China. 相似文献
55.
The climate–population relationship has long been conceived. Although the topic has been repeatedly investigated, most of
the related works are Eurocentric or qualitative. Consequently, the relationship between climate and population remains ambiguous.
In this study, fine-grained temperature reconstructions and historical population data sets have been employed to statistically
test a hypothesized relationship between temperature change and population growth (i.e., cooling associated with below average
population growth) in China over the past millennium. The important results were: (1) Long-term temperature change significantly
determined the population growth dynamics of China. However, spatial variation existed, whilst population growth in Central
China was shown to be responsive to both long- and short-term temperature changes; in marginal areas, population growth was
only sensitive to short-term temperature fluctuations. (2) Temporally, the temperature–population relationship was obscured
in some periods, which was attributable to the factors of drought and social buffers. In summary, a temperature–population
relationship was mediated by geographic factors, the aridity threshold, and social factors. Given the upcoming threat posed
by climate change to human societies, this study seeks to improve our knowledge and understanding of the climate–society relationship. 相似文献
56.
X. Yin 《Theoretical and Applied Climatology》1999,63(3-4):183-194
Summary A lack of information for surface water vapor pressure (WVP) represents a major impediment to model-assisted ecosystem analysis
for understanding plant-environment interactions or for projecting biospheric responses to global climate change. This paper
reports on a generic algorithm that captures global variation in monthly WVP. The algorithm solves WVP in terms of reduction
from saturation WVP as a negative exponential function of potential evapotranspiration; the reduction rate per unit potential
evapotranspiration in turn varies with monthly precipitation and a series of variables that distinguish local climate regimes.
Data input to the algorithm is limited to monthly air temperature and precipitation, plus latitude, longitude and elevation.
The algorithm is specified through regression fitting to monthly climate normal data from 852 stations around the world. It
accounts for 96% of the variance in the WVP data, with a root mean square error of 0.17 kPa, or 12% of the data mean. The
algorithm closely reproduces five-year sequential monthly WVP data for each of five selected United States locations representitative
of diverse climate regimes: the average error generally falls within ±12% of the data mean, and the absolute error within
±0.2 kPa. Its projections also compare favorably against the WVP output from the General Circulation Models for temperature
and precipitation conditions under the scenario of a doubled atmospheric carbon-dioxide concentration: the two fall within
±10% of each other for 75% of a total 264 data cases, or within ±20% for 94% of the cases. These statistics suggest that the
spatially-based algorithm is useful for projecting temporal variation in WVP, and for extrapolative applications beyond the
fluctuation range of present climate.
Received March 4, 1999 相似文献
57.
UV attenuation in the cloudy atmosphere 总被引:1,自引:0,他引:1
Jianhui Bai 《Journal of Atmospheric Chemistry》2009,62(3):211-228
Ultraviolet (UV) energy absorption plays a very important role in the Earth–atmosphere system. Based on observational data
for Beijing, we suggest that some atmospheric constituents utilize or transfer UV energy in chemical and photochemical (C&P) reactions, in addition to those which absorb UV energy directly. These constituents are primarily volatile organic compounds
(VOCs) emitted from both vegetative and anthropogenic sources. The total UV energy loss in the cloudy atmosphere for Beijing
in 1990 was 78.9 Wm−2. This attenuation was caused by ozone (48.3 Wm−2), other compounds in the atmosphere (26.6 Wm−2) and a scattering factor (4.0 Wm−2). Our results for a cloudy atmosphere in the Beijing area show that the absorption due to these other compounds occurs largely
through the mediation of water vapor. This fraction of energy loss has not been fully accounted for in previous models. Observations
and previous models results suggest that 1) a cloudy atmosphere absorbs 25∼30 Wm−2 more solar shortwave radiation than models predict; and 2) aerosols can significantly decrease the downward mean UV-visible
radiation and the absorbed solar radiation at the surface by up to 28 and 23 Wm−2, respectively. Thus, quantitative study of UV and visible absorption by atmospheric constituents involved in homogeneous
and heterogeneous C&P reactions is important for atmospheric models. 相似文献
58.
José Luís Argaín Miguel A. C. Teixeira Pedro M. A. Miranda 《Boundary-Layer Meteorology》2017,165(1):145-160
A method is proposed for estimating the surface-layer depth \((z_s)\) and the friction velocity \((u_*)\) as a function of stability (here quantified by the Obukhov length, L) over the complete range of unstable flow regimes. This method extends that developed previously for stable conditions by Argaín et al. (Boundary-Layer Meteorol 130:15–28, 2009), but uses a qualitatively different approach. The method is specifically used to calculate the fractional speed-up \((\varDelta S)\) in flow over a ridge, although it is suitable for more general boundary-layer applications. The behaviour of \(z_s \left( L\right) \) and \(u_*\left( L\right) \) as a function of L is indirectly assessed via calculation of \(\varDelta S\left( L\right) \) using the linear model of Hunt et al. (Q J R Meteorol Soc 29:16–26, 1988) and its comparison with the field measurements reported in Coppin et al. (Boundary-Layer Meteorol 69:173–199, 1994) and with numerical simulations carried out using a non-linear numerical model, FLEX. The behaviour of \(\varDelta S\) estimated from the linear model is clearly improved when \(u_*\) is calculated using the method proposed here, confirming the importance of accounting for the dependences of \(z_s\left( L \right) \) and \(u_*\left( L \right) \) on L to better represent processes in the unstable boundary layer. 相似文献
59.
Juan Huang Yanli Feng Jian Li Bin Xiong Jialiang Feng Sheng Wen Guoying Sheng Jiamo Fu Minghong Wu 《Journal of Atmospheric Chemistry》2008,61(1):1-20
The levels of carbonyl compounds in Shanghai ambient air were measured in five periods from January 2007 to October 2007 (covering
winter, high-air-pollution days, spring, summer and autumn). A total of 114 samples were collected and eighteen carbonyls
were identified. Formaldehyde, acetaldehyde and acetone were the most abundant carbonyls and their mean concentrations of
19.40 ± 12.00, 15.92 ± 12.07 and 11.86 ± 7.04 μg m−3 respectively, in the daytime for five sampling periods. Formaldehyde and acetaldehyde showed similar diurnal profiles with
peak mixing ratios in the morning and early afternoon during the daytime. Their mean concentrations were highest in summer
and lowest in winter. Acetone showed reversed seasonal variation. The high molecular weight (HMW, ≥C5) carbonyls also showed
obvious diurnal variations with higher concentrations in the daytime in summer and autumn, while they were all not detected
in winter. Formaldehyde and acetaldehyde played an important role in removing OH radicals in the atmosphere, but the contribution
of acetone was below 1%. The carbonyls levels in high-air-pollution days were reported. More carbonyl species with higher
concentrations were found in high-air-pollution days than in spring. These carbonyls were transported with other pollutants
from north and northwest in March 27 to April 2, 2007 and then mixed with local sources. Comparing with Beijing and Guangzhou,
the concentrations of formaldehyde and acetaldehyde in Shanghai were the highest, which indicated that the air pollution in
Shanghai was even worse than expected. 相似文献
60.
General purpose Computational Fluid Dynamics (CFD) solvers are frequently used in small-scale urban pollution dispersion simulations
without a large extent of ver- tical flow. Vertical flow, however, plays an important role in the formation of local breezes,
such as urban heat island induced breezes that have great significance in the ventilation of large cities. The effects of
atmospheric stratification, anelasticity and Coriolis force must be taken into account in such simulations. We introduce a
general method for adapting pressure based CFD solvers to atmospheric flow simulations in order to take advantage of their
high flexibility in geometrical modelling and meshing. Compressibility and thermal stratification effects are taken into account
by utilizing a novel system of transformations of the field variables and by adding consequential source terms to the model
equations of incompressible flow. Phenomena involving mesoscale to microscale coupled effects can be analyzed without model
nesting, applying only local grid refinement of an arbitrary level. Elements of the method are validated against an analytical
solution, results of a reference calculation, and a laboratory scale urban heat island circulation experiment. The new approach
can be applied with benefits to several areas of application. Inclusion of the moisture transport phenomena and the surface
energy balance are important further steps towards the practical application of the method. 相似文献