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1.
It is demonstrated that the greatest influence of the variations in the groupiness of storm waves in the Baltic Sea concerns the highest waves. The variations in the height of less high waves are defined by wind speed. It is revealed that the height of 3% of the highest waves depends on their bandwidth: higher and lower waves are characterized by the larger and smaller set of frequencies, respectively. The significant wave height does not almost depend on the bandwidth. It is found that the spectrum of storm waves in the southwestern part of the Baltic Sea has a multi-peak structure which reflects the complex structure of waves consisting of several wave systems. Envelopes and individual waves of different frequency ranges superimpose, and extreme waves are generated. The probability of occurrence of extreme waves is maximum at the moments of the maximum development of wave groupiness. 相似文献
2.
The multi-channel reactions (1) CCl3CH2OH+Cl→ products and (2) CCl3CH2OH+OH→ products have been investigated by using the dual-level direct dynamics method. Two reaction channels, i.e., methylene-
and hydroxyl-hydrogen abstraction, are identified for each reaction. The optimized geometries and frequencies of the stationary
points are calculated at the B3LYP/6-311G(d,p) and MP2/6-311G(d,p) levels. Higher-level energies are obtained at the MC-QCISD
and G3(MP2) levels based on the B3LYP and MP2 geometries, respectively, as well as by the CCSD(T)/6-31G(d)+CF method using
the B3LYP geometries. Complexes with energies lower than those of the reactants are located at the entrance of each reaction
channel. The rate constants for each reaction channel are evaluated by using the canonical variational transition state theory
(CVT) incorporating the small-curvature tunneling (SCT) correction in a temperature range of 200–2000 K at the MC-QCISD//B3LYP/6-311G(d,p)
level. The agreement of the calculated rate constants and experimental values for two reactions is seen to be remarkably good.
Theoretical results indicate that in a low temperature range, the branching ratio to the hydroxyl-H-abstraction channel for
both reactions is found negligible. The reactions proceed practically via methylene-H-abstraction yielding the products of
CCl3CHOH+HCl and CCl3CHOH+H2O, respectively; while for reaction of CCl3CH2OH+Cl, hydroxyl-H-abstraction channel appears to be probable with the increase of temperature. The enthalpies of formation
for the CCl3CH2OH, CCl3CHOH, and CCl3CH2O species are evaluated via isodesmic reactions at several levels. 相似文献
3.
Experimental determination of turbulent fluxes over the heterogeneous LITFASS area: Selected results from the LITFASS-98 experiment 总被引:1,自引:0,他引:1
F. Beyrich S. H. Richter U. Weisensee W. Kohsiek H. Lohse H. A. R. de Bruin Th. Foken M. Göckede F. Berger R. Vogt E. Batchvarova 《Theoretical and Applied Climatology》2002,73(1-2):19-34
Summary ?During the LITFASS-98 experiment, local flux measurements were performed over five different types of underlying surface
(grass, barley, triticale, pine forest, water) in a heterogeneous landscape using eddy covariance and profile techniques over
a three week time period in June, 1998. Estimates of the area-integrated sensible heat flux during daytime were obtained from
continuous measurements with a large aperture scintillometer (LAS) along a 4.7 km path. The calculation of a mean diurnal
cycle of the fluxes during the experiment revealed significant differences between the main land use classes. A land-use weighted
average of the sensible heat flux was found to be in good agreement with the LAS based estimate, which in turn was supported
by other regionally integrated flux estimates from budget considerations and aircraft measurements for a few case studies.
The profiles of turbulent quantities measured along a 99 m-tower significantly deviate from “idealised” profiles measured
over homogeneous terrain. Peculiarities in the profile structure could be attributed to the heterogeneity of the terrain,
namely to the differences in the surface characteristics of the footprint areas for the different tower levels.
Received June 6, 2001; revised January 15, 2002; accepted April 4, 2002 相似文献
4.
A numerical mesoscale meteorological model has been applied over the heterogeneous terrain of central Israel in order to study wind energy characteristics of three typical synoptic situations. The supportive nature of this method for observationally oriented wind energy studies has been emphasized. Mesoscale forcing effects on the availability of wind energy and on the exponent, p, in the vertical wind power law are evaluated. 相似文献
5.
Wang Mingxing 《大气科学进展》1984,1(1):76-94
The acidity of precipitation in both clean and polluted areas was calculated for atmospheric CO2 and SO2 in equilibrium with water. pH values of 5 and 4.5 were obtained. In Beijing the pH value is increased due to paniculate chlorine reactivity and rainout of CaO in the atmosphere. The increase of pH value is related to liquid water content in cloud and the elemental concentrations of paniculate Cl and Ca in the atmosphere. This mechanism may help to explain the nonacid rain observed in Beijing where the air pollution problem is serious, as viewed by SO2 concentration and paniculate burden in the atmosphere. 相似文献
6.
Numerical study on the impacts of heterogeneous reactions on ozone formation in the Beijing urban area 总被引:2,自引:0,他引:2
The air quality model CMAQ-MADRID (Community Multiscale Air Quality-Model of Aerosol Dynamics, Reaction, Ionization and Dissolution) was employed to simulate summer O3 formation in Beijing China, in order to explore the impacts of four heterogeneous reactions on O3 formation in an urban area. The results showed that the impacts were obvious and exhibited the characteristics of a typical response of a VOC-limited regime in the urban area. For the four heterogeneous reactions considered, the NO2 and HO2 heterogeneous reactions have the most severe impacts on O3 formation. During the O3 formation period, the NO2 heterogeneous reaction increased new radical creation by 30%, raising the atmospheric activity as more NO→NO2 conversion occurred, thus causing the O3 to rise. The increase of O3 peak concentration reached a maximum value of 67 ppb in the urban area. In the morning hours, high NO titration reduced the effect of the photolysis of HONO, which was produced heterogeneously at night in the surface layer. The NO2 heterogeneous reaction in the daytime is likely one of the major reasons causing the O3 increase in the Beijing urban area. The HO2 heterogeneous reaction accelerated radical termination, resulting in a decrease of the radical concentration by 44% at the most. O3 peak concentration decreased by a maximum amount of 24 ppb in the urban area. The simulation results were improved when the heterogeneous reactions were included, with the O3 and HONO model results close to the observations. 相似文献
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A model study of ATMOS observations and the heterogeneous loss of N2O5 by the sulphate aerosol layer
The heterogeneous removal of N2O5 by sulphuric acid aerosols as been invoked to explain the decline of mid-latitude ozone in the last decade. We have used a photochemical model to study measurements of odd-nitrogen made by Spacelab 3. The gas-phase photochemical model overestimates the amount of N2O5 present. The loss of N2O5 by aerosols does reduce N2O5, but is likely to be slower than assumed in WMO (1992). The sunset measurements at 25.5 km cannot be explained by heterogeneous loss of N2O5 and is more likely to be due to a faster photolysis than assumed. New absorption cross-sections of HNO3 reduce the photolysis of HNO3 so that the model with gas-phase chemistry only gives better agreement at 19 km, than a model including heterogeneous chemistry. 相似文献
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D. P. Renouard F. J. Seabra Santos A. M. Temperville 《Dynamics of Atmospheres and Oceans》1985,9(4):341-358
In a (36 m × 0.55 m × 1.30 m) channel we did numerous experiments to study the generation, propagation, damping and reflexion along a wall of a solitary wave. The data are compared with the available analytical or numerical results. From a given paddle movement, the Inverse Scattering Method is proved to provide with great accuracy the number and amplitude of the generated solitary waves. Then, studying the damping of the wave due to dispersion and viscosity, we find that the formula proposed by Keulegan describes the phenomenon well. This last result enables us to modify the KdV equation with the second term used by Kakutani and Matsuuchi, to compute the solitary wave and tail generated by a given intumescence or a given paddle movement. We notice that the computations fit well with the experimental measurements. Finally, we study the reflexion of a solitary wave from a plane vertical wall. To obtain good experimental data requires great care, but the results agree with the analytical prediction. The reflexion appears to be a rather complex phenomenon and needs further theoretical developments. We present here some experimetal data which confirm recent numerical observations (Mirie and Su, Fenton and Rienecker). 相似文献
12.
非均匀地表条件下区域平均径流率的一种参数化方法及其模拟试验 总被引:6,自引:0,他引:6
从陆面水文过程的物理机制出发,引进概率统计分布理论,推导出一种由非均匀土壤含水量及降水气候强迫所形成的次网格尺度非均匀径流率的解析表达式,从而将通常的次网格尺度地表径流的参数化方案(mosaic方法)改进为考虑网格区整体非均匀性的统计-动力参数化方案。文中用仿真模拟资料验证了该方案的可靠性与可行性,并作数值试验。结果表明,该方案切实可行。 相似文献
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Experimental study of the imbalance of water budget over the Loess Plateau of China 总被引:1,自引:0,他引:1 下载免费PDF全文
The imbalance of land-surface water budget was discovered in past studies, but there have been few further investigations
on the relevant causes. To probe into the problem, annual variations of precipitation and land-surface evapotranspiration
were analyzed by using the historical observation data from a comprehensive land-surface observation base of LOPEX (Loess
Plateau Experiment). A remarkable imbalance in the land-surface water budget was found, and the total annual imbalance reached
20.6%. Then, the impact factors related to additional water budget components and observational methods were studied. The
total annual imbalance could be reduced to 3.8% by using a combination of compensated land-surface water budget components
and the surface evapotranspiration values obtained from the large-scale weighing lysimeter rather than from the eddy correlation
method. 相似文献
17.
Using the three-layer variable infiltration capacity (VIC-3L) hydrological model and the successive interpolation approach (SIA) of climate factors, the authors studied the effect of different land cover types on the surface hydrological cycle. Daily climate data from 1992 to 2001 and remotely-sensed leaf area index (LAI) are used in the model. The model is applied to the Baohe River basin, a subbasin of the Yangtze River basin, China, with an area of 2500 km2. The vegetation cover types in the Baohe River basin consist mostly of the mixed forest type (85%). Comparison of the modeled results with the observed discharge data suggests that: (1) Daily discharges over the period of 1992–2001 simulated with inputs of remotely-sensed land cover data and LAI data can generally produce observed discharge variations, and the modeled annual total discharge agrees with observations with a mean difference of 1.4%. The use of remote sensing images also makes the modeled spatial distributions of evapotranspiration physically meaningful. (2) The relative computing error (RCE) of the annual average discharge is ?24.8% when the homogeneous broadleaf deciduous forestry cover is assumed for the watershed. The error is 21.8% when a homogeneous cropland cover is assumed and ?14.32% when an REDC (Resource and Environment Database of China) land cover map is used. The error is reduced to 1.4% when a remotely-sensed land cover at 1000-m resolution is used. 相似文献
18.
Many studies show that, within a certain distance (ca. 700–800 n mi), two typhoons forming a binary typhoon (BT) system would
rotate as a whole and attract each other, which is known as “Fuji-whara Effect” (FE). This paper indicates that only 30.3%
of BTs has experienced remarkable cyclonic rotation with a 12-hr angle ≥+10° when two components are less than 20° lat apart,
and that the probability is much higher with the eastern component in the NE than in the SE quadrant for the western one,
implying the steering effect of the environmental flow field (EFF) on them.
47 observations from 13 BTs are separately used for calculating the angular velocity due to FE and EFF and the results are
compared. The conclusion can be stated as follows: FE is dominant with the centers of two elements below 7° lat apart; the
EFF steering current plays a major role when they are in the range of 7–15° and for a distance above 15° the principle of
FE holds no longer. 相似文献
19.
利用江苏省6部S波段全相参多普勒天气雷达测得的2007-2011年28个阵风锋观测实例,检验多普勒天气雷达的阵风锋自动识别算法的效果。该算法主要包括熵函数模板的反射率强度边界识别、风切变算法,并综合依据径向速度及谱宽进行阵风锋识别。在阵风锋的识别中,多普勒速度的径向切变有利于判别雷达波束垂直于阵风锋边界的辐合,旋转切变可更好地显示平行于波束的阵风锋边界。在参与检测的28个个例中,成功检测出的有13个;因雷达资料质量影响,7个个例检测出部分阵风锋;8个个例未检测到阵风锋。经过检验,该算法的识别效果较好,但仍存在一些不足,需要进一步完善雷达资料的质量控制,和对低层弱切变特征的提取研究。 相似文献