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41.
Transition of Tidal Waves from the East to South China Seas over the Taiwan Strait: Influence of the Abrupt Step in the Topography 总被引:7,自引:0,他引:7
Observations of tidal waves between the East and South China Seas (ECS and SCS) over the Taiwan Strait (TS) suggest that the
diurnal tides simply appear as one southward-propagating wave from the ECS to the SCS through the TS. The semidiurnal tides,
however, behave differently in that they appear as a southward-propagating Kelvin wave in the western TS and a nearly standing
wave in the eastern TS, and then diminish rapidly over the shallow shoal in the southern TS. A smaller-domain model, with
sea-level boundary conditions derived from a larger-domain tidal model, was first used to simulate tides in the TS to an overall
percentage of accuracy of about 90%. Subsequent numerical experiments and theoretical analysis revealed that the southward-propagating
semidiurnal tides to be impeded and then reflected as they arrive at an abrupt, deepened step in the topography of the southern
TS. This reflection enhances the amplitudes of the incident semidiurnal tides and contributes to the formation of a nearly
standing wave in the eastern TS. The southward-propagating diurnal tides in the TS are connected by the diurnal tides in the
northern SCS when the amplitudes of the two tide systems are comparable and their phases nearly equal at the step.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
42.
A three-component decomposition is applied to global analysis data to show the existence of a beta
gyre, which causes Tropical Cyclone (TC) to drift from a large-scale environmental steering current. Analyses
from the Global Data Assimilation and Prediction System (GDAPS) of the Korea Meteorological Administration (KMA),
the Global Forecast System (GFS) of NCEP, and the Navy Operational Global Atmospheric Prediction System (NOGAPS)
are used in this study.
The structure of the beta gyre obtained in our analyses is in good agreement with the theoretical structure,
with a cyclonic circulation to the southwest of the TC center, an anticyclonic circulation to the northeast,
and a ventilation flow directed northwestward near the center. The circulation of the beta gyre is strongest
at the 850-hPa level where the cyclonically swirling primary circulation is strongest, and decreases with
height, in a pyramid shape similar to the primary circulation. The individual structure of the beta gyre is
case- and model-dependent. At a certain analysis time, one model may clearly reveal a well-defined beta gyre,
but the other models may not. Within one model, the beta gyre may be well defined at some analysis times,
but not at other times. The structure of the beta gyre in the analysis field is determined by the nature of
the vortex initialization scheme and the model behavior during the 6-h forecast in the operational data
assimilation cycle. 相似文献
43.
Joe Kidston Christian Brümmer T. Andrew Black Kai Morgenstern Zoran Nesic J. Harry McCaughey Alan G. Barr 《Boundary-Layer Meteorology》2010,136(2):193-218
Components of the surface energy balance of a mature boreal jack pine forest and a jack pine clearcut were analysed to determine
the causes of the imbalance that is commonly observed in micrometeorological measurements. At the clearcut site (HJP02), a
significant portion of the imbalance was caused by: (i) the overestimation of net radiation (R
n
) due to the inclusion of the tower in the field of view of the downward facing radiometers, and (ii) the underestimation
of the latent heat flux (λE) due to the damping of high frequency fluctuations in the water vapour mixing ratio by the sample tube of the closed-path
infrared gas analyzer. Loss of low-frequency covariance induced by insufficient averaging time as well as systematic advection
of fluxes away from the eddy-covariance (EC) tower were discounted as significant issues. Spatial and temporal distributions
of the total surface-layer heat flux (T), i.e. the sum of sensible heat flux (H) and λE, were well behaved and differences between the relative magnitudes of the turbulent fluxes for several investigated energy
balance closure (C) classes were observed. Therefore, it can be assumed that micrometeorological processes that affected all turbulent fluxes
similarly did not cause the variation in C. Turbulent fluxes measured at the clearcut site should not be forced to close the energy balance. However, at the mature
forest site (OJP), loss of low-frequency covariance contributed significantly to the systematic imbalance when a 30-min averaging
time was used, but the application of averaging times that were long enough to capture all of the low-frequency covariance
was inadequate to resolve all of the high-frequency covariance. Although we found qualitative similarity between T and the net ecosystem exchange (NEE) of carbon dioxide (CO2), forcing T to closure while retaining the Bowen ratio and applying the same factor to CO2 fluxes (F
C
) cannot be generally recommended since it remains uncertain to what extent long wavelength contributions affect the relationship
between T, F
C
and C. 相似文献
44.
High resolution remote sensing observations for missions to the Jovian system: Io as a case study 总被引:1,自引:0,他引:1
We present modeled images of Io at a variety of distances from the surface as a function of imager aperture size and wavelength. We consider the science objectives that could be achieved from missions engaged in long range remote-sensing of Io during the approach to the Jovian system and subsequently from orbit around Europa or Ganymede, in both the visible and near infrared wavelength ranges. We find that basic global mapping objectives in the visible can be met with a traditional 0.5 m telescope design. A more ambitious 1.5 m telescope could accomplish much more detailed objectives such as topographical measurements, and determination of flow patterns and thermal sources for individual active regions on Io. 相似文献
45.
On shear-wave triplication in transversely isotropic media 总被引:1,自引:0,他引:1
The exact solution to the problem of qSV triplication in homogenous transversely isotropic media has been long known, but the result is algebraically complex and is seldom applied in practice. We present an appropriate approximation (not assuming weak qSV-anisotropy) that simplifies the conditions for the onset of off-axis triplication as anisotropy is increased, identifying the anisotropy parameter σ as the controlling parameter. It follows that commonly reported surface-seismic P-wave move-out measurements imply that many formations in the earth's sedimentary crust support off-axis qSV triplications. For typical Vp/Vs velocity ratios and a horizontally stratified earth, however, off-axis qSV triplications appear to only occur for shear-wave incidence angles too far from the vertical to be sampled by surface-seismic converted-wave survey geometries. 相似文献
46.
47.
Ultraviolet Imaging Telescope (UVIT) is one of the payloads onboard AstroSat, India’s first multi-wavelength Astronomy mission. UVIT is primarily designed to make high resolution images in wide field, in three wavelength channels simultaneously: FUV (130–180 nm), NUV (200–300 nm) and VIS (320–550 nm). The intensified imagers used in UVIT suffer from distortions, and a correction is necessary for these to achieve good astrometry. In this article we describe the methodology and calculations used to estimate the distortions in ground calibrations. 相似文献
48.
Among others, one commonly identified negative consequence of urban sprawl is an increase in the length of the journey to work. However, there has been more discussion of this than serious scrutiny, hence the relationship between urban sprawl and commuting patterns, especially at the intraurban level, remains unclear. Using the 2000 Census Transportation Planning Package (CTPP) data for two Southeastern metropolitan areas, this research investigates the extent to which workers living in sprawl areas commute farther to work than those living in higher density areas. The analysis of variance confirms that workers commuting from sprawl areas to urban areas experience a longer commute in terms of time as well as mileage, though this varies when workplace and home locations are taken into account. However, multivariate statistical results suggest that there are limits to the utility of sprawl as a predictor of travel behavior compared to workers' socioeconomic characteristics, as other factors appear to be equally or more important. 相似文献
49.
Estimating groundwater storage changes in the Mississippi River basin (USA) using GRACE 总被引:7,自引:0,他引:7
Matthew Rodell Jianli Chen Hiroko Kato James S. Famiglietti Joe Nigro Clark R. Wilson 《Hydrogeology Journal》2007,15(1):159-166
Based on satellite observations of Earth’s time variable gravity field from the Gravity Recovery and Climate Experiment (GRACE), it is possible to derive variations in terrestrial water storage, which includes groundwater, soil moisture, and snow. Given auxiliary information on the latter two, one can estimate groundwater storage variations. GRACE may be the only hope for groundwater depletion assessments in data-poor regions of the world. In this study, soil moisture and snow were simulated by the Global Land Data Assimilation System (GLDAS) and used to isolate groundwater storage anomalies from GRACE water storage data for the Mississippi River basin and its four major sub-basins. Results were evaluated using water level records from 58 wells set in the unconfined aquifers of the basin. Uncertainty in the technique was also assessed. The GRACE-GLDAS estimates compared favorably with the well based time series for the Mississippi River basin and the two sub-basins that are larger than 900,000 km2. The technique performed poorly for the two sub-basins that have areas of approximately 500,000 km2. Continuing enhancement of the GRACE processing methods is likely to improve the skill of the technique in the future, while also increasing the temporal resolution. 相似文献
50.