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861.
LIU Shixiang ZHANG Cunjie ZHAO Jianhu WANG Suichan HUANG Yuxia 《Acta Meteorologica Sinica》2006,20(5):108-121
The water vapor in the air over the Hexi Corridor on the northeastern side of the Qilian Mountains and adjacent regions and its transport characteristics were studied using the upper-air and surface data observed in many years. The sources of water vapor and its transport pathways were explored. The results show that: (1) The Qinghai-Tibetan Plateau is a source area of water vapor directly supplied to the Hexi region and the westerly airflow is the main transport of water vapor to the region. (2) The center of the transport intensity of water vapor over the Hexi region occurs near the height of 500 hPa and the maximum daily change of water vapor occurs between 700 and 600 hPa, which is quite different from the changes of water vapor transport and the maximum daily changes of water vapor over the eastern China. (3) During the mid-1960s to the mid-1980s, the moisture content in the air over the Hexi region exhibited a significant decrease trend, but from the mid-1980s to the late 1990s, it tended to increase. Such a variation trend
appears to be consistent in winter and spring and is particularly evident in the transition period between winter and spring. 相似文献
862.
We derive general results on the existence of stationary configurations for N co-orbital satellites with small but otherwise arbitrary masses m
i
, revolving on circular and planar orbits around a massive primary. The existence of stationary configurations depends on
the parity of N. If N is odd, then for any arbitrary angular separation between the satellites, there always exists a set of masses (positive or
negative) which achieves stationarity. However, physically acceptable solutions (m
i
> 0 for all i) restrict this existence to sub-domains of angular separations. If N is even, then for given angular separations of the satellites, there is in general no set of masses which achieves stationarity. The case N=3 is treated completely for small arbitrary satellite masses, giving all the possible solutions and their stability, to within
our approximations. 相似文献
863.
The contrast between the eastern and central responses of zonal and vertical circulation in the Pacific (EP- and CP-) E1 Nino is observed in the different tropics. To measure the different responses of the atmo- spheric circulation to the two types of E1 Nino, an eastern and a central Pacific southern oscillation index (EP- and CP-SOI) are defined based on the air-sea coupled relationship between eddy sea level pressure and sea surface temperature. Analyses suggest that while the EP-SOI exhibits variability on an interannual (2- 7-yr) time scale, decadal (10-15-yr) variations in the CP-SOI are more dominant; both are strongly coupled with their respective EP- and CP-E1 Nino patterns. Composite analysis suggests that, during EP-ENSO, the Walker circulation exhibits a dipole structure in the lower-level (850 hPa) and upper-level (200 hPa) velocity potential anomalies and exhibits a signal cell over the Pacific. In the case of CP-ENSO, however, the Walker circulation shows a tripole structure and exhibits double cells over the Pacific. In addition, the two types of ENSO events show opposite impacts on global land precipitation in the boreal winter and spring seasons. For example, seasonal precipitation across mainland China exhibits an opposite relationship with the EP- and CP-ENSO during winter and spring, but the rainfall over the lower reaches of the Yangtze River and South China shows an opposite relationship during the rest of the seasons. Therefore, the different relationships between rainfall and EP- and CP-ENSO should be carefully considered when predicting seasonal rainfall in the East Asian monsoon regions. 相似文献
864.
865.
根据新的调查和综合研究,南楼山组早期于建组剖面附近的四方顶子和玉兴屯获流纹岩全岩K-Ar同位素年龄176.1Ma和176.7Ma,近期又在建组剖面的北大湖二道沟和南大岭分别获得流纹岩和辉石安山岩的锆石U-Pb高精度年龄(174.0±3.4)Ma和(179.4±1.1)Ma,故南楼山组的时代可确认为早侏罗世晚期土阿辛期(Toarcian)。双丫子东山火山岩全岩K-Ar同位素年龄(195.0±5.01)Ma;官马金矿区火山岩全岩Rb-Sr等时线年龄(222±10)Ma,不应划入南楼山组或将其时代修定为晚三叠世。 相似文献
866.
867.
868.
869.
南海中部晚更新世以来沉积物常量元素组分含量分布特征及其影响因素 总被引:1,自引:0,他引:1
为研究南海中部沉积物中常量元素组分含量的分布特征及其影响因素,对南海中部中沙以南陆坡一深海盆区的表层沉积物和2根柱状样进行了Si02、A1:O。、Fe:03、TiO:、K:O、MnO、P:O,、CaCO,等常量元素组分及生物硅(BSi)含量的分析.结果显示,南海中部表层沉积物中SiO:、A1:03、Fe:O3、TiO小K:O等与陆源碎屑矿物有关的常量元素组分含量的变化主要受生源CaCO,含量的控制,而CaCO,的含量,则受水深的控制.CaCO,含量与水深的关系表明,研究区CaCO。临界补偿深度约为3800m.受底层洋流的控制,研究区海山附近硅质生物碎屑局部富集,并稀释其他元素含量.研究区表层沉积物中的MnO和P:O,含量的分布规律不同于其他常量元素组分,其中,Mn可能部分交代CaCO,中的Ca,P,O,部分可能为海底超基性岩海解来源的.2根柱样的地球化学变化特征显示,晚更新世以来,南海中部CaCO,临界补偿深度以浅海底沉积物中除Mn和P以外的其他各常量元素含量受生源CaCO,含量的影响,而在CaCO。临界补偿深度以深的海域,则受BSi含量的影响.南海中部沉积物柱样中的CaCO,和BSi含量变化与全球变化有关,可作为古气候环境变化研究的代用指标.摘要:为研究南海中部沉积物中常量元素组分含量的分布特征及其影响因素,对南海中部中沙以南陆坡一深海盆区的表层沉积物和2根柱状样进行了Si02、A120。、Fe20。、TiO:、K20、MnO、P20,、CaCO,等常量元素组分及生物硅(BSi)含量的分析.结果显示,南海中部表层沉积物中SiO:、A1:03、Fe20¨TiO小K:O等与陆源碎屑矿物有关的常量元素组分含量的变化主要受生源CaCO,含量的控制,而CaCO,的含量,则受水深的控制.CaCO,含量与水深的关系表明,研究区CaCO,临界补偿深度约为3800m.受底层洋流的控制,研究区海山附近硅质生物碎屑局部富集,并稀释其他元素含量.研究区表层沉积物中的MnO和P:O,含量的分布规律不同于其他常量元素组分,其中,Mn可能部分交代CaCO,中的Ca,P,O,部分可能为海底超基性岩海解来源的.2根柱样的地球化学变化特征显示,晚更新世以来,南海中部CaCO,临界补偿深度以浅海底沉积物中除Mn和P以外的其他各常量元素含量受生源CaCO,含量的影响,而在CaCO,临界补偿深度以深的海域,则受BSi含量的影响.南海中部沉积物柱样中的CaCO,和BSi含量变化与全球变化有关,可作为古气候环境变化研究的代用指标. 相似文献
870.
调查了鄱阳湖荷溪区域湿地鸟类资源,并对164种鸟类的种类组成、区系特点、珍稀濒危性、鸟类季节性、生态分布进行了分析,针对湿地鸟类保护中存在的问题,提出了保护对策。 相似文献