西藏羊八井地区近地晴天大气电场周期变化   总被引：4，自引：0，他引：4       下载免费PDF全文

徐斌  张颖  贾焕玉  陈天禄  袁爱芳  孟宪茹 《高原气象》2009,28(2):314-318

基于西藏ARGO-YBJ实验,分析了2005年12月-2007年9月期间西藏羊八井地区近地晴天大气电场强度的周期变化,并重点讨论了其太阳日周期的相位变化.结果表明,晴天状态下大气电场强度存在明显的半日周期和太阳日周期变化.太阳日周期的相位变化呈现大陆复杂型(双峰、双谷),日变化曲线随季节变化,在冬季,电场强度水平较高,最大日变化幅度约30%;春、夏季电场强度水平较低,最大日变化幅度约15%.该初步研究结果对了解西藏地区晴天大气电特征具有十分重要的意义.  相似文献   

湖南夏季降水日变化特征   总被引：12，自引：2，他引：10       下载免费PDF全文

戴泽军  宇如聪  陈昊明 《高原气象》2009,28(6):1463-1470

利用湖南96个测站13年的逐时自记降水资料, 分析了夏季（6~8月）降水日变化特征。结果表明, 湖南夏季降水日变化呈现显著的区域差异。湘东南降水量、 降水频次峰值主要出现在午后到傍晚, 而其它地区的降水峰值一般出现在清晨。进一步分析显示, 降水频次峰值出现时次分布更集中, 区域特征更鲜明。湘西北、 湘东南区域平均的累积降水量、 降水频次及降水强度的日变化在清晨和午后均呈双峰型特征。湘西北主（次）峰值出现的时间大致与湘东南次（主）峰值出现的时间对应。同时, 降水日变化与降水持续时间密切相关。持续5~10 h降水事件是持续1~4 h事件与持续10 h以上事件降水量峰值出现时间发生显著变化的过渡降水事件。持续1~4 h（10 h以上）的降水事件的极值降水始发时间为午后至傍晚（夜间）。在不同持续时间的降水事件中, 持续2 h降水的累积量最大。  相似文献   

Aliphatic alkanes and polycyclic aromatic hydrocarbons in atmospheric PM₁₀ aerosols from Baoji, China: Implications for coal burning   总被引：1，自引：0，他引：1  

Mingjie Xie  Gehui Wang  Shuyuan Hu  Qingyou Han  Yajuan Xu  Zhongchao Gao 《Atmospheric Research》2009,93(4):840-848

Normal alkanes and PAHs in atmospheric PM₁₀ aerosols collected during 2008 winter and spring in Baoji, a mid-scale inland city of China, were determined on a molecular level. Concentrations of n-alkanes ranged from 232 to 3583 ng/m³ with an average of 1733 ng/m³ in winter and from 124 to 1160 ng/m³ with an average of 449 ng/m³ in spring, while PAHs in the PM₁₀ samples were 594 ± 405 and 128 ± 82 ng/m³ in the two seasons. Molecular compositions showed that CPI (odd/even) values of n-alkanes were close to unity for all the samples especially in winter, and diagnostic ratios of PAHs (e.g., Phe/(Phe + Ant), CPAH/ΣPAHs and IcdP/(IcdP + BghiP)) were found similar to those in coal burning smoke with a strong linear relationship (R² ≥ 0.85) between PAHs and fossil fuel derived n-alkanes, demonstrating that coal burning is the main source of n-alkanes and PAHs in the city, especially in winter due to house heating. Concentrations of the determined compounds in Baoji are much higher than those in Chinese mega-cities, suggesting that air pollution in small cities in the country is more serious and need more attention.  相似文献   

Model analysis of seasonal variations in tropospheric ozone and carbon monoxide over East Asia   总被引：1，自引：0，他引：1  

高丽洁  张美根  韩志伟 《大气科学进展》2009,26(2):312-318

Temporal-spatial variations in tropospheric ozone concentrations over East Asia in the period from 1 January 2000 to 31 December 2004 were simulated by using the Models-3 Community Multi-scale Air Quality (CMAQ) modeling system with meteorological fields calculated by the Regional Atmospheric Modeling System (RAMS). The simulated concentrations of ozone and carbon monoxide were compared with ground level observations at two remote sites, Ryori (39.03°N, 141.82°E) and Yonagunijima (24.47°N, 123.02°E). The co...  相似文献   

Variations in the summer monsoon rainbands across eastern China over the past 300 years     

郝志新  郑景云  葛全胜 《大气科学进展》2009,26(4):614-620

Based on reconstructions of precipitation events from the rain and snowfall archives of the Qing Dynasty (1736–1911),the drought/flood index data mainly derived from Chinese local gazettes from 1736–2000, and the observational data gathered since 1951,the spatial patterns of monsoon rainbands are analyzed at different time scales.Findings indicate that monsoon rainfall in northern China and the middle-lower reaches of the Yangtze River have significant inter-annual(e.g.,5–7-yr and 2–4-yr)as well as inter-de...  相似文献   

SEASONAL VARIATIONS OF CONVECTIVE ACTIVITIES OVER THE SOUTH CHINA SEA AND ITS NEIGHBORHOOD AND THEIR COMPARATIVE ANALYSES IN THE STRONG AND WEAK CONVECTION YEARS^*          下载免费PDF全文

ZHANG Weiqing  QIAN Yongfu 《Acta Meteorologica Sinica》2001,15(2):205-217

The seasonal variations of convective activities over the South China Sea(SCS) and its neighborhood.as well as the similarities and differences of convection in the different key regions during the strong and weak convection years are analyzed by using the pentad data of TBB from 1980 to 1993.The results show that in winter and summer the seasonal variations of the convective activities are synchronous over the SCS and its neighborhood,the anomalous convection amplitudes are obviously different in different regions.The significant extents of convective activities have somewhat seasonal differences in the strong and weak convection years.In the strong convection years,it is in winter,spring and autumn that the convection anomaly is more evident than that in the normal years,however,after the summer monsoon onset the convection is sustained.stable and similar to that in the normal years.In the weak convection years.the convection weakens greatly in each season.but the primary weakening occurs in spring.summer and autumn.No matter in the strong or the weak convection years.the convective activities are somewhat of difference in the Bay of Bengal.the Indochina Peninsula.the SCS and the Philippines.In addition.the convective activities are also different over the south and the north parts of the SCS.the convection variation in the strong year is similar to that in the weak year over the north part of the SCS.but over the south part there are great differences.  相似文献   

1988～1998年北半球积雪时空变化特征分析   总被引：17，自引：0，他引：17  

杨修群  张琳娜 《大气科学》2001,25(6):757-766

利用NOAA提供的北半球近10年(1988～1998)逐周雪盖观测资料，通过引入年或季节累积雪盖周数作为对雪量累积情况的定量衡量，对北半球雪盖变化时空特征进行了分析。结果表明:近10年来，北半球积雪年际变化的关键区位于青藏高原、蒙古高原、欧洲阿尔卑斯山脉及北美中西部，其中青藏高原是北半球积雪异常变化最强烈的区域。青藏高原和欧亚大陆其他地区积雪变化的关联表现为两种不同的时空变化型，第一种型表现为青藏高原地区和其他地区(如欧洲、俄罗斯远东地区)积雪的同位相趋势性增多；第二种型表现为青藏高原地区和中亚地区积雪变化同位相，而和蒙古高原－我国东北地区积雪变化反位相的年际振荡。  相似文献   

On the anomalous features of the geomagnetic quiet-day field variations at Nagpur, India     

E. Chandrasekhar  S. Alex 《Geophysical Journal International》1996,127(3):703-707

The quiet-day geomagnetic field variation data from the recently commissioned Nagpur geomagnetic observatory, which has augmented the currently active latitudinal chain of Indian magnetic observatories, are analysed for the year 1993- The variations for diurnal frequencies (Sq) recorded at Nagpur do not follow the expected trend with latitude. This is most conspicuous in the northward horizontal ( X ) component. The anomalous behaviour at Nagpur is also seen in the diurnal harmonic amplitudes when compared with those of the neighbouring stations Alibag (south of Nagpur) and Ujjain (north of Nagpur). This behaviour is attributed to the presence of electrically conducting anomalous sources in the vicinity of Nagpur. The anomalous internal source is inferred to be located at relatively shallower depths and is highly localized.  相似文献   

Morphological aspects of a new type of counter electrojet event     

R. G. Rastogi 《Annales Geophysicae》1999,17(2):210-219

The study describes the time and space morphologies of a rather new type of counter electrojet event on the basis of data from the excellent chain of magnetic and ionospheric observatories along the Indo-Russian longitude sector. Abnormally large westward currents are observed during almost the whole of the daytime hours on a series of days. These events do not form any vortices in the current system and do not apparently seem to be associated with tidal effects or any solar magnetosphere events or geomagnetic disturbances. The existence of a westward electric field over the equatorial ionosphere has been confirmed by the absence of an equatorial type of sporadic E in the ionograms at Thumba precisely during the periods when H at Trivandrum minus H at Alibag is negative. The equatorial F region anomaly was also absent on the counter electrojet day. Such counter electrojet events during the northern winter months of low solar activity years are suggested to be the result of the modified wind system in the ionosphere associated with stratospheric warming events.  相似文献   

Mathematical simulation of stable and equilibrium river bed profiles and slopes     

A. M. Trofimov  V. M. Moskovkin 《地球表面变化过程与地形》1983,8(4):383-390

Two approaches to the simulation of stable and equilibrium longitudinal profiles and slopes are considered. The first one deals with a solution to the equation of solid matter (sediment) continuity in the equilibrium case and the second approach deals with the application of variational principles. The approaches considered and results obtained can be used in hydroengineering construction for designing stable and equilibrium longitudinal profiles of water streams and slopes.  相似文献