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981.
A clamped square-plate is subjected to a uniform state of stress in the x-direction. The present study deals with the basic question of determining the variation of the lower natural frequencies of transverse vibration of a plate as a small diameter, central hole is made in it, introducing a stress concentration field. 相似文献
982.
M.E. vinogradov E.A. Shushkina V.I. Vedernikov N.P. Nezlin V.I. Gagarin 《Deep Sea Research Part II: Topical Studies in Oceanography》1997,44(9-10)
Data collected from 20 years of observations by the P. P. Shirshov Institute of Oceanology (about 250 comprehensive ecosystem stations) are summarized to evaluate the primary production and biomass of the principal groups of plankton in the Pacific Ocean. The stations were classified into geographical regions according to satellite determined criteria. The areas of these regions were evaluated according to CZCS data from 1978 to 1986. The total value of primary production was evaluated as 26·9 Gt C year−1. Taking the “bottle effect” correction into account, this value may be as high as 45.6 Gt C year−1. Total biomass values of phytoplankton (134 Mt C), bacteria (86 Mt C), protozoa (26 Mt C) and mesoplankton (184 Mt C) were also calculated. Seasonal variabilities of all these values were remarkably insignificant. 相似文献
983.
Seasonal evolution of surface mixed layer in the Northern Arabian Sea (NAS) between 17° N–20.5° N and 59° E-69° E was observed
by using Argo float daily data for about 9 months, from April 2002 through December 2002. Results showed that during April
- May mixed layer shoaled due to light winds, clear sky and intense solar insolation. Sea surface temperature (SST) rose by
2.3 °C and ocean gained an average of 99.8 Wm−2. Mixed layer reached maximum depth of about 71 m during June - September owing to strong winds and cloudy skies. Ocean gained
abnormally low ∼18 Wm−2 and SST dropped by 3.4 °C. During the inter monsoon period, October, mixed layer shoaled and maintained a depth of 20 to
30 m. November - December was accompanied by moderate winds, dropping of SST by 1.5 °C and ocean lost an average of 52.5 Wm−2. Mixed layer deepened gradually reaching a maximum of 62 m in December. Analysis of surface fluxes and winds suggested that
winds and fluxes are the dominating factors causing deepening of mixed layer during summer and winter monsoon periods respectively.
Relatively high correlation between MLD, net heat flux and wind speed revealed that short term variability of MLD coincided
well with short term variability of surface forcing. 相似文献
984.
I. N. Mordvintsev N. G. Platonov I. V. Alpatsky 《Izvestiya Atmospheric and Oceanic Physics》2011,47(9):1127-1134
The main results of processing the long-term satellite data in different spectral ranges and with different spatial resolutions
used to map Arctic sea ice parameters are presented. The advantages of the methods developed in order to estimate these parameters
on the basis of microwave sensor measurements are indicated. The specific features of the long-term dynamics of the main sea
ice geophysical parameters (the sea ice area and distribution during the summer minimum, ice age structure and thickness,
multiyear ice concentration, times of ice melt and freeze onset, etc.) are presented. The effect of changes in sheet ice on
the status of large Arctic mammals is estimated. 相似文献
985.
V. V. Zuev S. L. Bondarenko N. E. Zueva 《Izvestiya Atmospheric and Oceanic Physics》2011,47(9):1032-1038
The response of the total ozone (TO) at subarctic latitudes to volcanic eruptions, products of which were injected into the
stratosphere, is analyzed. It is established that the behavior of the series of average annual TO values according to the
TOMS, SCIAMACHY, and GOME space equipment data averaged for 55°–65° N latitudes agrees with the activity of explosive volcanic
eruptions. The series of the TO satellite monitoring instrumental data are extended by 200 years into the past using a reconstruction
from the dendro-chronologic data. An analysis of the series of TO reconstructed values indicates that volcanogenic perturbations
of the subarctic ozonosphere initiate long-term negative TO deviations. In this case, the TO negative deviation depth depends
on the frequency of the ozonosphere volcanogenic perturbations and the phase of quasiperiodic oscillation cycles rather than
on the strength of a single volcanic explosion. 相似文献
986.
M. B. Gokhberg G. M. Steblov S. L. Shalimov V. A. Veis E. A. Grekhova 《Izvestiya Atmospheric and Oceanic Physics》2011,47(8):929-940
Using available Russian and international Global Positioning System (GPS) network data, we studied the ionospheric response
to the M = 8.9 submarine earthquake of March 11, 2011, on the northeastern coast of Honshu Island, Japan, both near and far (about
2000 km away) from the epicenter. In the region over the epicenter, 8.7 min after the event, we detected a characteristic
signal of the total electron content (TEC) variations consisting of compression and rarefaction phases and a linear transition
zone in between, i.e., in the form of an N-type wave with a steep leading front indicating a rapid uplift of the water surface and, correspondingly, the bottom of the
ocean. The shape of the signal can be used for early tsunami warning; i.e., it may indicate the tsunamigenic character of
a submarine earthquake. We monitored the subsequent evolution of the ionospheric response as far as 2000 km from the epicenter.
It was shown that, besides the wellknown ionospheric N-type wave response to the earthquake, there is also a response in the form of an inverted N-wave, both nearby and far from the epicenter. We detected two more types of ionospheric responses far from the epicenter:
a solitary-like wave and an internal gravity wave (IGW). The detected signals have been interpreted. 相似文献
987.
988.
989.
990.
Determining the age of water and long-term transport timescale of the Chesapeake Bay 总被引:5,自引:0,他引:5
The concept of age of water (AW) is applied to the Chesapeake Bay to investigate the long-term transport properties for dissolved substances. A real-time calibrated hydrodynamic Chesapeake Bay model in 3 Dimensions (CH3D), employing a boundary-fitted curvilinear grid, is used for the study. The long-term transport properties, represented by AW, are investigated under the conditions of low river inflow of 1995 and high river inflow of 1996, as well as for constant mean inflows. The influences of freshwater, density-induced circulation, and wind-induced transport on age distribution have been investigated. Model results show that river inflows, wind stress, and density-induced circulation play important roles in controlling the long-term transport in the Bay. The model results shows that it requires 120–300 days for a marked change in the characteristics of the pollutant source discharged into the Bay from the Susquehanna River to affect significantly the conditions near the mouth under different hydrodynamic conditions. An increase of river discharge results in increases of downstream residual current and gravitational circulation, and thus reduces AW. The density-induced circulation contributes to the transport substantially. The dissolved substances discharged into the Bay are transported out of the Bay more rapidly when the estuary becomes more stratified. Southeasterly and southwesterly winds have strong impacts on the transport compared to the northeasterly and northwesterly winds. The former increases lateral and vertical mixing significantly. Consequently, the gravitational circulation is reduced and the transport time is increased by 50%. The model results provide useful information for understanding the long-term transport processes in the Bay. 相似文献