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171.
Abstract The effects of condensational heating on the semi‐geostrophic dynamics of frontogenesis are studied using a two‐dimensional deformation model. The model includes water vapour and allows the formation of stratiform clouds. Analysis and numerical results show that heating due to stratiform clouds has the effect of reducing stability to slantwise convection, as found in previous studies (Thorpe and Emanuel, 1985). In addition, heating‐induced potential vorticity and temperature anomalies play a very important role in the frontal circulation. The ageostrophic flow induced by these anomalies tends to reinforce the effect of heating and increases the strength of frontal cloud. The model is also able to produce the low‐level jet maximum ahead of a cold front at an elevated level, in agreement with observations, owing to the explicit condensation scheme used in the model. 相似文献
172.
Summary Theory for the transmission of electromagnetic waves in a non-uniform troposphere is presented. The atmospheric refractive index is allowed to vary both with height and range. The formulation is facilitated by the fact that the field within a piecewise (laterally) uniform section can be represented by a discrete sum of modes that are orthogonal in the transverse plane. Using the appropriate radial wave functions, mode conversion at a junction between two laterally uniform sections is considered. The analysis is then extended to multi-section structures. A few typical profiles of refractive index are examined numerically for both uniform and non-uniform models. One of the important findings is that the lateral non-uniformities in an elevated duct will enhance the overall transmission for ground-based transmitting and receiving antennas. 相似文献
173.
Surface wave dispersion is studied to obtain the 1-D average velocity structure of the crust in the Korean Peninsula by inverting
group- and phase-velocities jointly. Group velocities of short-period Rayleigh and Love waves are obtained from cross-correlations
of seismic noise. Multiple-filter analysis is used to extract the group velocities at periods between 0.5 and 20 s. Phase
velocities of Rayleigh waves in 10- and 50-s periods are obtained by applying the two-station method to teleseismic data.
Dispersion curves of all group and phase velocities are jointly inverted for the 1-D average model of the Korean Peninsula.
The resultant model from surface wave analysis can be used as an initial model for numerical modeling of observations of North
Korean events for a velocity model appropriated to the Korean Peninsula. The iterative process is focused especially on the
surface sedimentary layer in the numerical modeling. The final model, modified by numerical modeling from the initial model,
indicates that the crust shear wave velocity increases with depth from 2.16 km/s for a 2-km-thick surface sedimentary layer
to 3.79 km/s at a Moho depth of 33 km, and the upper mantle has a velocity of 4.70 km/s. 相似文献
174.
Minkyu Moon Taekyu Kim Juhan Park Sungsik Cho Daun Ryu Sanguk Suh Hyun Seok Kim 《山地科学学报》2016,13(6):1024-1034
It is difficult to scale up measurements of the sap flux density (Js) for the characterization of tree or stand transpiration (E) due to spatial variations in JS and their temporal changes. To assess spatial variations in the sap flux density of Korean pine (Pinus koraiensis) and their effects on E estimates, we measured the Js using Granier-type sensors. Within trees, the Js decreased exponentially with the radial depth, and the Js of the east aspects were higher than those of the west aspects. Among trees, there was a positive relationship between Js and the tree diameter at breast height, and this positive relationship became stronger as the transpiration demand increased. The spatial variations that caused large errors in E estimates (i.e., up to 110.8 % when radial variation was ignored) had varied systematically with environmental factors systematic characteristics in relation to environmental factors. However, changes in these variations did not generate substantial errors in the E estimates. For our study periods, the differences in the daily E (E D) calculated by ignoring radial, azimuthal and tree-to-tree variations and the measured E D were fairly constant, especially when the daily vapor pressure deficit (D_D) was higher than 0.6 kPa. These results imply that the effect of spatial variations changes on sap flow can be a minor source of error compared with spatial variations (radial, azimuthal and tree-to-tree variations) when considering E estimates. 相似文献
175.
A. Shanmugaraju Y.-J. Moon K.-S. Cho Y.-H. Kim M. Dryer S. Umapathy 《Solar physics》2005,232(1-2):87-103
We report on the detailed analysis of a set of 38 multiple type II radio bursts observed by Culgoora radio spectrograph from
January 1997 to July 2003. These events were selected on the basis of the following criteria: (i) more than one type II were
reported within 30 min interval, (ii) both fundamental and harmonic were identified for each of them. The X-ray flares and
CMEs associated with these events are identified using GOES, Yohkoh SXT, SOHO/EIT, and SOHO/LASCO data. From the analysis
of these events, the following physical characteristics are obtained: (i) In many cases, two type IIs with fundamental and
harmonic were reported, and the time interval between the two type IIs is within 15 min; (ii) The mean values of starting
frequency, drift rate, and shock speed of the first type II are significantly higher than those of the second type II; (iii)
More than 90% of the events are associated with both X-ray flares and CMEs; (iv) Nearly 75% of the flares are stronger than
M1 X-ray class and 50% of CMEs have their widths larger than 200^∘ or they are halo CMEs; (v) While most of the first type
IIs started within the flare impulsive phase, 22 out of 38 second type IIs started after the flare impulsive phase. Weak correlations
are found between the starting and ending frequencies of these type II events. On the other hand, there was no correlation
between two shock speeds between the first and the second type II. Since most of the events are associated with both the flares
and CMEs, and there are no events which are only associated with multiple impulsive flares or multiple mass ejections, we
suggest that the flares and CMEs (front or flank) both be sources of multiple type IIs. Other possibilities on the origin
of multiple type IIs are also discussed. 相似文献
176.
Michiyo Sawai Ikuo Katayama Arisa Hamada Makoto Maeda Satoru Nakashima 《Physics and Chemistry of Minerals》2013,40(4):319-330
The dehydration kinetics of serpentine was investigated using in situ high-temperature infrared microspectroscopy. The analyzed antigorite samples at room temperature show relatively sharp bands at around 3,655–3,660 cm?1 (band 1), 3,570–3,595 cm?1 (band 2), and 3,450–3,510 cm?1 (band 3). Band 1 corresponds to the Mg–OH bond, and bands 2 and 3 correspond to OH associated with the substitution of Al for Si. Isothermal kinetic heating experiments at temperatures ranging from 625 to 700 °C showed a systematic decrease of the OH band absorbance with heating duration. The one-dimensional diffusion was found to provide the best fit to the experimental data, and diffusion coefficients were determined with activation energies of 219 ± 37 kJ mol?1 for the total water band area, 245 ± 46 kJ mol?1 for band 1, 243 ± 57 kJ mol?1 for band 2, and 256 ± 53 kJ mol?1 for band 3. The results indicate that the dehydration process is controlled by one-dimensional diffusion through the tetrahedral geometry of serpentine. Fluid production rates during antigorite dehydration were calculated from kinetic data and range from 3 × 10?4 to 3 × 10?5 $ {\text{m}}_{\text{fluid}}^{ 3} \,{\text{m}}_{\text{rock}}^{ - 3} \,{\text{s}}^{ - 1} $ . The rates are high enough to provoke hydraulic rupture, since the relaxation rates of rocks are much lower than these values. The results suggest that the rapid dehydration of antigorite can trigger an intermediate-depth earthquake associated with a subducting slab. 相似文献
177.
Tae Keun Rho Stephen Coverly Eun-Soo Kim Dong-Jin Kang Sung-Hyun Kahng Tae-Hee Na Sung-Rok Cho Jung-Moo Lee Cho-Rong Moon 《Ocean Science Journal》2015,50(4):709-720
In this study we describe measures taken in our laboratory to improve the long-term precision of nitrate and ammonia analysis in seawater using a microflow segmented-flow analyzer. To improve the nitrate reduction efficiency using a flow-through open tube cadmium reactor (OTCR), we compared alternative buffer formulations and regeneration procedures for an OTCR. We improved long-term stability for nitrate with a modified flow scheme and color reagent formulation and for ammonia by isolating samples from the ambient air and purifying the air used for bubble segmentation. We demonstrate the importance of taking into consideration the residual nutrient content of the artificial seawater used for the preparation of calibration standards. We describe how an operating procedure to eliminate errors from that source as well as from the refractive index of the matrix itself can be modified to include the minimization of dynamic refractive index effects resulting from differences between the matrix of the samples, the calibrants, and the wash solution. We compare the data for long-term measurements of certified reference material under two different conditions, using ultrapure water (UPW) and artificial seawater (ASW) for the sampler wash. 相似文献
178.
Hyun-Sil Kang Hyun-Ki Hong Kyung-Il Park Moonjae Cho Seok-Hyun Youn Kwang-Sik Choi 《Ocean Science Journal》2017,52(1):139-146
Manila clam Ruditapes philippinarum is one of the most important benthic animals in the coastal north Pacific region, where clam populations have been mixed genetically through trade and aquaculture activities. Accordingly, identification of the genetically different clam populations has become one of the most important issues to manage interbreeding of the local and introduced clam populations. To identify genetically different populations of clam populations, we developed 11 expressed sequence tag (EST)-microsatellite loci (i.e., simple sequence repeat, SSR) from 1,128 clam hemocyte cDNA clones challenged by the protozoan parasite Perkinsus olseni. Genotype analysis using the markers developed in this study demonstrated that clams from a tidal flat on the west coast contained 6 to 19 alleles per locus, and a population from Jeju Island had 4 to 20 alleles per locus. The expected heterozygosity of the 2 clam populations ranged from 0.472 to 0.919 for clams from the west coast, and 0.494 to 0.919 for clams from Jeju Island, respectively. Among the 11 loci discovered in this study, 7 loci significantly deviated from the Hardy-Weinberg equilibrium after Bonferroni correction. The 5 loci developed in this study also successfully amplified the SSRs of R. variegatus, a clam species taxonomically very close to R. philippinarum, from Hong Kong and Jeju Island. We believe that the 11 novel polymorphic SSR developed in this study can be utilized successfully in Manila clam genetic diversity analysis, as well as in genetic discrimination of different clam populations. 相似文献
179.
This study provides a practical guide to the use of classical tidal prediction algorithms in coastal numerical forecasting models such as tide and tide-storm-surge models. Understanding tidal prediction parameter formulas and their limitations is key to successfully modifying and upgrading tidal prediction modules in order to increase the accuracy of perpetual interannual simulations and, in particular, storm-surge modeling studies for tide-dominated coastal environments. The algorithms for the fundamental prediction parameters, the five astronomical variables, used in tidal prediction are collated and tested. Comparisons between their estimation using different parameterizations shows that these methods yield essentially the same results for the period 1900–2099, revealing all are applicable for tidal forecasting simulation. Through experiments using a numerical model and a harmonic prediction program, the effects of nodal modulation correction and its update period on prediction accuracy and sensitivity are examined and discussed using a case study of the tidally-dominated coastal regime off the west coast of Korea. Results indicate that this correction needs updating within <30 days for accurate perpetual interannual tidal and mean sea-level predictions, and storm-surge model predictions requiring centimeter accuracy, for tidally-dominated coastal regimes. Otherwise, unacceptable systematic errors occur. 相似文献
180.
Summary This study shows that precipitation over the United States has two time scales of intraseasonal variation at about 37 days
and 24 days. The results are derived from the application of a combination of statistical methods including principal component
analysis (PCA), singular spectrum analysis (SSA), and multi-channel singular spectrum analysis (MSSA) to over 10 years of
gridded daily precipitation records. Both oscillations have largest amplitude during the cold season. The 37-day oscillation
has larger interannual variability. Intraseasonal oscillations are most significant in the Pacific Northwest. The 37-day oscillation
has opposite phases between the western and eastern United States, while the 24-day oscillation has the same phases. These
intraseasonal time scale precipitation variations may be associated with previously revealed mid-tropospheric circulation
anomalies that oscillate at similar time scales.
Received February 7, 2000 Revised October 20, 2000 相似文献