This paper discusses the results of geoacoustic inversion carried out using explosive charge data from the Asian Seas International Acoustic Experiment (ASIAEX) East China Sea (ECS) Experiment. A multifrequency incoherent matched-field inversion processor and a genetic algorithm (GA) are used for the inversion. A multistep matched field inversion approach is presented, which makes use of the varying sensitivities of wave fields at various frequencies to reduce the inversion problem into a sequence of smaller inversions with fewer unknowns to estimate at each stage. Different parameters are estimated using data at different frequencies according to their sensitivities. Inversion results for different areas in the ECS region are summarized and compared with core data. 相似文献
Long-term measurement of carbon metabolism of old-growth forests is critical to predict their behaviors and to reduce the uncertainties of carbon accounting under changing climate. Eddy covariance technology was applied to investigate the long-term carbon exchange over a 200 year-old Chinese broad-leaved Korean pine mixed forest in the Changbai Mountains (128°28′E and 42°24′N, Jilin Province, P. R. China) since August 2002. On the data obtained with open-path eddy covariance system and CO2 profile measurement system from Jan. 2003 to Dec. 2004, this paper reports (i) annual and seasonal variation of FNEE, FGPP and RE; (ii) regulation of environmental factors on phase and amplitude of ecosystem CO2 uptake and release Corrections due to storage and friction velocity were applied to the eddy carbon flux.
LAI and soil temperature determined the seasonal and annual dynamics of FGPP and RE separately. VPD and air temperature regulated ecosystem photosynthesis at finer scales in growing seasons. Water condition at the root zone exerted a significant influence on ecosystem maintenance carbon metabolism of this forest in winter.
The forest was a net sink of atmospheric CO2 and sequestered −449 g C·m−2 during the study period; −278 and −171 gC·m−2 for 2003 and 2004 respectively. FGPP and FRE over 2003 and 2004 were −1332, −1294 g C·m−2. and 1054, 1124 g C·m−2 respectively. This study shows that old-growth forest can be a strong net carbon sink of atmospheric CO2.
There was significant seasonal and annual variation in carbon metabolism. In winter, there was weak photosynthesis while the ecosystem emitted CO2. Carbon exchanges were active in spring and fall but contributed little to carbon sequestration on an annual scale. The summer is the most significant season as far as ecosystem carbon balance is concerned. The 90 days of summer contributed 66.9, 68.9% of FGPP, and 60.4, 62.1% of RE of the entire year.
Analysis of Zn, Cu, Pb, Co, Cr, Li, Ni, K, Al, Fe extracted by 1 mol/L HCl or 0.5 mol/LHCl/H_2O_2, showed concentrations of Zn, Cu, Pb, Co, Cr, Fe, Ni were significantly correlated with Li, Al,K, and clay. Two methods are used to indicate the background value of the non-residual phase of elementsin sediments, and are the same as the methods used to indicate the background value of totalconcentrations in sediments. The first method uses correlograms and regression equations,the second usesthe mean element concentrations normalized with grain size. Li, Al, K can be used as reference elements to determine the background value of Zn, Cu, Pb, Co,Cr, Ni, Fe, while the clay concentration's correlation with some extractable concentrations can be used tocalculate the background value of the non-residual phase of elements as a percentage of clay concentrationin the sediments. Based on this study, the concept of using the background value of the non-residualphase of elements to compare the pollution level in differ 相似文献
Although the Songnen Plain in the northeastern China was developed relatively late in the temperate zone of the world, its eco-environment has changed greatly. This paper analyzes the changes of land cover and the rates and trends ofdesertification during the past 100 years in the Songnen Plain. According to the macroscopic analysis, we find that the eco-environment in the plain has reached to the threshold of catastrophic change since the 1950s. The Thorn Needle Catastrophic Model was used to determine and validate this conclusion. Human activities, including large-scale construction projects, such as huge dams and dikes, and excessive grazing were the primary factors contributing to regional eco-environmental catastrophe. And irrational reclamation of the wilderness also affected the eco-environmental change. The results reveal the complex human-land interactions. 相似文献
With the aim of analyzing the errors in the radial position of satellites, we give in this paper the expressions for the radial perturbation which include the complete zeroth- and first-order terms in the orbital eccentricity. A simpler and faster method of calculating the perturbation is given. 相似文献
Numerical methods are usually used for the computation of ephemerides with perturbations for the precise orbital determination of an artificial satellite. But their numerical stability will be encountered in a long arc. In this case the use the improved Encke special perturbation methods has been suggested. The results of this paper show that Encke's method does indeed have a certain effectiveness, but cannot yet completely resolve the numerical stability, and the more efficient method is to use the energy integral or its variational relation to control the growth of the along-track error in general numerical calculations so that the aim of stabilization can be achieved. 相似文献
Prediction of solar-generated disturbances and their three-dimensional propagation through interplanetary space continues
to present a vitally important operational space weather forecasting objective. This paper presents the first successful real-time
prediction of a series of major heliospheric shock waves at Earth, including the one from the 14 July 2000 (`Bastille Day')
flare. An ensemble of three models and their predictions were distributed to a world-wide group of interested scientists as
part of an informal Internet space weather forecast research program. Two of the models, STOA (Shock Time of Arrival) and
ISPM (Interplanetary Shock Propagation Model), presently in operation by the US Air Force Weather Agency, provided predictions
of shock arrival time (SAT) that were, respectively, 0.5 hours after and 3.7 hours before the observed arrival. The third
model, HAFv.2 (Hakamada–Akasofu–Fry version 2.0) predicted a time 0.3 hours after the observed shock arrival time (14:37 UT,
15 July 2000). Of primary interest to this study is the third model, firstly in terms of its capability of propagating shocks
through non-uniform solar wind conditions, and secondly, in terms of its ability to integrate multiple solar events and display
them graphically along with the background solar wind. This latter capability was brought to bear on ten real-time-reported
flares, some with CMEs (coronal mass ejections) that took place as companions to the Bastille flare during the period 7–15
July 2000. Some limited statistics are given regarding the three models' shock arrival prediction capability at Earth, as
an extension of our earlier studies with this three model ensemble in the prediction of SAT. HAFv.2, however, was able to
describe not only the ten events and their interaction as measured at Earth, but also at the spacecraft NEAR (orbiting the
asteroid, Eros, at 1.8 AU), and CASSINI (en route, at 4.0 AU, to Saturn). Several important points are noted: (1) this epoch
represents a small statistical sample that should be expanded; and (2) the three models, based on theory, empiricism, and
simulations represent the state of the art that should presage a similar community process. This paper was presented earlier
as an Invited Talk at the American Geophysical Union Fall Meeting, December 14–19, 2000, in San Francisco, CA, U.S.A.toward
space weather objectives in the Sun-Earth domain.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1014200719867 相似文献