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911.
Analyses of aerosol optical properties and direct radiative forcing over urban and industrial regions in Northeast China 总被引:1,自引:0,他引:1
912.
913.
Performance of the seasonal forecasting of the Asian summer monsoon by BCC_CSM1.1(m) 总被引:1,自引:0,他引:1
Xiangwen Liu Tongwen Wu Song Yang Weihua Jie Suping Nie Qiaoping Li Yanjie Cheng Xiaoyun Liang 《大气科学进展》2015,32(8):1156-1172
This paper provides a comprehensive assessment of Asian summer monsoon prediction skill as a function of lead time and its relationship to sea surface temperature prediction using the seasonal hindcasts of the Beijing Climate Center Climate System Model, BCC_CSM1.1(m). For the South and Southeast Asian summer monsoon, reasonable skill is found in the model's forecasting of certain aspects of monsoon climatology and spatiotemporal variability. Nevertheless, deficiencies such as significant forecast errors over the tropical western North Pacific and the eastern equatorial Indian Ocean are also found. In particular, overestimation of the connections of some dynamical monsoon indices with large-scale circulation and precipitation patterns exists in most ensemble mean forecasts, even for short lead-time forecasts. Variations of SST, measured by the first mode over the tropical Pacific and Indian oceans, as well as the spatiotemporal features over the Niño3.4 region, are overall well predicted. However, this does not necessarily translate into successful forecasts of the Asian summer monsoon by the model. Diagnostics of the relationships between monsoon and SST show that difficulties in predicting the South Asian monsoon can be mainly attributed to the limited regional response of monsoon in observations but the extensive and exaggerated response in predictions due partially to the application of ensemble average forecasting methods. In contrast, in spite of a similar deficiency, the Southeast Asian monsoon can still be forecasted reasonably, probably because of its closer relationship with large-scale circulation patterns and El Niño-Southern Oscillation. 相似文献
914.
This study explores the characteristics of high temperature anomalies over eastern China and associated influencing factors using observations and model outputs. Results show that more long-duration (over 8 days) high temperature events occur over the middle and lower reaches of the Yangtze River Valley (YRV) than over the surrounding regions, and control most of the interannual variation of summer mean temperature in situ. The synergistic effect of summer precipitation over the South China Sea (SCS) region (18°-27°N, 115°-124°E) and the northwestern India and Arabian Sea (IAS) region (18°-27°N, 60°-80°E) contributes more significantly to the variation of summer YRV temperature, relative to the respective SCS or IAS precipitation anomaly. More precipitation (enhanced condensational heating) over the SCS region strengthens the western Pacific subtropical high (WPSH) and simultaneously weakens the westerly trough over the east coast of Asia, and accordingly results in associated high temperature anomalies over the YRV region through stimulating an East Asia-Pacific (EAP) pattern. More precipitation over the IAS region further adjusts the variations of the WPSH and westerly trough, and eventually reinforces high temperature anomalies over the YRV region. Furthermore, the condensational heating related to more IAS precipitation can adjust upper-tropospheric easterly anomalies over the YRV region by exciting a circumglobal teleconnection, inducing cold horizontal temperature advection and related anomalous descent, which is also conducive to the YRV high temperature anomalies. The reproduction of the above association in the model results indicates that the above results can be explained both statistically and dynamically. 相似文献
915.
H. J. Peng Q. Gao Z. G. Wu W. X. Zhong 《Celestial Mechanics and Dynamical Astronomy》2011,110(4):319-342
In this paper, from a Hamiltonian point of view, the nonlinear optimal control problems are transformed into nonlinear two-point
boundary value problems, and a symplectic adaptive algorithm based on the dual variational principle is proposed for solving
the nonlinear two-point boundary value problem. The state and the costate variables within a time interval are approximated
by using the Lagrange polynomial and the costate variables at two ends of the time interval are taken as independent variables.
Then, based on the dual variational principle, the nonlinear two-point boundary value problems are replaced by a system of
nonlinear equations which can preserve the symplectic structure of the nonlinear optimal control problem. Furthermore, the
computational efficiency of the proposed symplectic algorithm is improved by using the adaptive multi-level iteration idea.
The performance of the proposed algorithm is tested by the problems of Astrodynamics, such as the optimal orbital rendezvous
problem and the optimal orbit transfer between halo orbits. 相似文献
916.
917.
918.
Y.‐C. Wei C.‐M. Zhang Y.‐H. Zhao Q.‐H. Peng X.‐J. Wu J. Wang Y.‐Y. Pan H.‐X. Yin Y. Yan T.‐S. Yan H.‐J. Tian A. Esamdin A.L. Luo Y. Cai A. Taani 《Astronomische Nachrichten》2010,331(8):817-831
Under the two initial 1‐D one parameter velocity distribution forms (one is normal, the other is exponential), the z direction scale height evolution of normal neutron stars in the Galaxy is studied by numerical simulation. We do statistics for the cases at different time segments, also do statistics for the cumulative cases made of each time segment. The results show in the cumulative cases the evolution curves of the scale heights are smoother than in the each time segment, i.e., the cumulation improve the signal‐to‐noise ratio. Certainly the evolution cases are different at different Galactic disk locations, which also have very large difference from the average cases in the whole disk. In the initial stages of z evolution of normal neutron stars, after the beginning transient states, the cumulative scale heights increase linearly with time, and the cumulative scale height increasing rates have linear relationship with the initial velocity distribution parameters, which have larger fluctuation in the vicinity of the Sun than in the whole disk. We utilize the linear relationship of the cumulative scale height increasing rates vs. the initial velocity distribution parameters in the vicinity of the Sun to make comparison with the observation near the Sun. The results show if there is no magnetic decay, then the deserved initial velocity parameters are obvious lower than the present well known results from some authors; whereas if introducing magnetic decay, for the 1‐D normal case we can make consistence among concerning results using magnetic decay time values which are supported by some authors, while for the 1‐D exponential case the results show the lackness of young pulsar samples in the larger z in the vicinity of the Sun (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
919.
To investigate the dependence of the Holmberg effect of paired galaxies on three-dimensional separations, we have constructed
four subsamples characterized by three-dimensional separations s ≤ 50 kpc, 50 kpc < s ≤ 100 kpc , 100kpc < s ≤150kpc , and
150 kpc < s ≤ 200 kpc , respectively. In this study, linear correlation coefficients and surplus standard deviations of color
indices, luminosity, and size between two components of paired galaxies are calculated. It is found that there is a weak tendency
for correlation coefficients of color indices to increase with decreasing three-dimensional separations, but such a tendency
does not exist for ones of luminosity and size. We also note that there is no tendency for surplus standard deviations to
decrease with decreasing three-dimensional separations. This suggests that it is still very difficult to clearly affirm the
dependence of the Holmberg Effect of paired galaxies on three-dimensional separations. 相似文献
920.
Xin Wu 《中国天文和天体物理学报》2010,10(3)
A global relation ship between cosmological time and Belinskii-Khalatnikov-Lifshitz(BKL)time during the entire evolution of the Mixmaster Bianchi Ⅸ universe is used to explain why all the Lyapunov exponents are zero at the BKL time.The actual reason is that the domain of the cosmological time is finite as the BKL time runs from minus infinity to infinity. 相似文献