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Search Results: 1 - 10 of 280186 matches for " <br>陆日宇 "
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Separation of Interannual and Interdecadal Variations of Rainfall in North China

Lu Riyu,<br>
大气科学 , 2002,
Abstract: The precipitations in North China in rainy seasons (July and August, or JA) show variation characteristics both on interannual and interdecadal scales. In this study, these two time scales are separated by: considering five-year running mean of JA precipitations as interdecadal variations, and considering the difference between JA precipitations and the interdecadal variations as interannual variations. After the separation, analyses are performed by use of NCAR/NCEP reanalysis data on respective atmospheric circulation anomalies associated with these two time scales. The great differences between these two kinds of asociations suggest the different physical mechanisms for interannual and interdecadal variations of JA rainfall in North China. The atmospheric circulation associations on interdecadal scale include the remarkable anomalies of the meridional velocity over the eastern part of China and geopotential heights over the Asian continent. The associations on the interannual scale by a routine composite method without the separation exhibit the mixed characteristics of two types of atmospheric circulation anomalies associated with the separated time scales. The atmospheric circulation associations on the interannual scale, after removing the interdecadal scale, include the anomalies of geopotential heights and zonal velocities over East Asia, indicating the poleward displacement of the upper-level jet during flood summers.
Eddies during the Blocking Maintenance over the Northeastern Asia in Summer

Lu Riyu,<br>
大气科学 , 2001,
Abstract: Using the NCEP/ NCAR daily data, the intensity and propagation of band-pass eddies (2.5 to 6 days) during a blocking episode over the northeastern Asia in summer (from June 27 to July 16, 1999) are examined. The analyzed results show that the intensity of band-pass eddies are stronger considerably than climatology over the upstream of the blocking high (or over the Barents Sea). The band-pass eddies continually propagate eastward from the Barents Sea and a climatological storm track region of the Northeast Atlantic, and decayed sharply over the northeastern Asia. It is inferred that eddies transfer their energy to the blocking high over the northeastern Asia during the blocking maintenance. The analysis by use of vector Eu also confirms such an energy propagation of the band-pass eddies. The forcing role of the band-pass eddies on the time-mean zonal and meridional flows is also examined by use of vectors Eu and Ev. It is shown that the forcing of band-pass eddies is acting to decelerate the time-mean westorlies around the splitting point. The forcing of band-pass eddies, in addition, clearly results in the splitting and confluence of the mean flows at the up- and down-stream regions of the blocking high, respectively. Finally, the meridional heat transport by highand low-frequency components is analyzed. The analyzed result clearly shows that the heat is fluxed northward (i.e., southward transport of colder air or northward transport of warmer air) by high- frequency component around the tropopause over East Asia. The transport by low-frequency component (that can be referred as the role of blocking flow pattern), however, appears in the middle and lower troposphere, and is relatively obscure.
Cold Vortex over Northeast China and Its Climate Effect

Hu Kaixi,Lu Riyu,Wang Donghai,<br>胡开喜,,王东海
大气科学 , 2011,
Abstract: Based on the long-term dataset of cold vortex over Northeast China derived from automatic method of detection and track, interannual variability of cold vortex over Northeast China, the effect of its persistent activities on regional climate, and the associated large-scale circulation anomalies are investigated. The results show that the cold vortex has a considerable interannual variability, but no significant long-term trends. Persistent activities of cold vortex have a major oscillation with a period of about 2.5 a. Frequent occurrences of cold vortex can cause a significant negative air temperature anomaly over Northeast China for all seasons and lead to more local rainfall in spring and summer seasons. There are likely more rainfalls over the Yangtze River basin when the summer cold vortex is more frequent. In winter when the cold vortex occurs more frequently, most of China experiences lower air temperature and less rainfall, which is highly related to strong East Asian winter monsoon. In the summer of more cold vortices, deep dipole-like geopotential height anomaly maintains over East Asia, the upper-level jet stream shifts southward and is strengthened slightly, and the lower-tropospheric anticyclonic anomaly over the western North Pacific and the easterly anomaly over high latitudes facilitate the water vapor flux to be convergent over the Yangtze River basin and Northeast China, respectively.
Energetics Examination of the Blocking Episodes in the Northern Hemisphere

Lu Riyu,Huang,Ronghui,<br>,黄荣辉
大气科学 , 1996,
Abstract: In this paper, the variation of zonal mean flow before the formation of three blocking episodes in the Northern Hemisphere which maintained for a long time and the energetics of these three blocking episodes are analysed diagnostically. The analysed results show that before the occurrence of the blocking situation, the zonal wind decreases through the wave--mean flow interaction, and the interaction has different characters over the Pacific and Atlantic. The analysed results also show that the planetary waves are amplified by the wave--wave interaction at the stage of the maintaince of the blocking, and are weakened at the stage of the collapse also mainly by the wave--wave interaction.
Comparison between the Results on Seasonal Evolution of Summer Precipitation over Eastern China Simulated by a Regional Climate Model and the Driving GCM

XU Xuan,LU Riyu,SHI Ying,<br>徐璇,,石英
大气科学 , 2011,
Abstract: The authors compared the simulations of seasonal evolution of rainfall over eastern China and the associated large-scale circulation during summer by a coupled general circulation model (CGCM, MIROC3.2_hires) and the nested regional climate model (RegCM3). Results show that both the MIROC3.2_hires and RegCM3 can reproduce the basic features of summer mean atmospheric circulation, and the spatial distribution of precipitation in China characterized by a decrease from the southeast to northwest of China. Comp...
Variability of the East Asian Upper-Tropospheric Jet in Summer and Its Impacts on the East Asian Monsoon

LU Riyu,LIN Zhongda,ZHANG Yaocun,<br>,林中达,张耀存
大气科学 , 2013,
Abstract: 东亚高空急流是东亚夏季风系统的一个重要组成部分,对东亚地区的天气和气候有着重要影响。近十年来,对东亚高空的变异规律及其相关机理、急流对东亚气候的影响等方面做了大量的观测资料分析和数值模拟研究。本文从夏季东亚高空急流的变化特征及其与东亚气候的关联、东亚高空急流的变异机理以及当前的气候模式对东亚高空急流的模拟能力评估和未来预估等几个方面,对这些研究结果进行了综述。
Simulation Study of Robust Control System for Optical Phase-Shifting Interferometer Vibration Isolation System

光子学报 , 2007,
Abstract: The hybrid control technology of the active vibration isolation and the passive vibration isolation is presented to solve the uncertainty of the optical phase-shifting interferometer vibration isolation system.The active vibration isolation exploits the theory of Robust Control,which overcome the uncertainty of model and the disturbance,and make the control system restrain the uncertainty of the model and the disturbance of the vibration.The simulation results prove that this method has good robustness and control precision in the vibration isolation of the optical phase-shifting interferometer.
Effects of the SSTA in the Tropical Western Pacific on the Blocking Highs over Northeastern Asia

Lu Riyu,Huang Ronghui,<br>,黄荣辉
气候与环境研究 , 1996,
Abstract: The effects of the observed sea surface temperature anomalies (SSTA) and the idealized SSTA in the tropical western Pacific on the atmospheric circulation anomaly during summer over East Asia were simulated by the IAP-AGCM. By comparing the simulated results to the observed results, we studied indirectly the influence of SSTA on the blocking situations over northeastern Asia. At first, by the use of the observed SSTA in 1980, we simulated the atmospheric circulation anomaly in the July and August of the year, through three anomalous runs (Global SSTA run, Tropical SSTA run, and Extratropical SSTA run). It was shown that the SSTA influence greatly the formation and maintenance of the blocking highs over northeastern Asia. It was also shown that the tropical SSTA play a more important role in influencing the atmospheric circulation anomaly than the extratropical SSTA. We also simulated the effects of the idealized SSTA in the tropical western Pacific on the atmospheric circulation anomaly over East Asia. The simulated results showed that the negative SSTA in the tropical western Pacific are beneficial to the formation and maintenance of the blocking highs over northeastern Asia.

科学通报 , 2003,
Abstract: 华北地区汛期(7月和8月)降水量的变化具有明显的年代际和年际两种时间尺度。在年代际时间尺度上,华北降水在20世纪70年代末发生突然减少,研究了降水突然减少对应的大气环流变化以及对降水年际变化产生的影响,发现年代际变化所提供的背景对华北降水年际变化的规律和物理机制没有影响,华北汛期降水年代际和年际变化之间的关系是线性的。

科学通报 , 2005,
Abstract: 华北地区汛期(7和8月)降水量具有明显的年际变化特征.本文分析了华北汛期降水量的年际变化对应的环流和海温异常,发现海温异常在赤道东太平洋有显著的信号,而且华北汛期降水和赤道东太平洋海温对应的东亚高空急流变化具有明显的相似性,进而给出了赤道东太平洋海温异常影响华北汛期降水年际变化的可能物理机制.
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