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101.
This article focused on the research progress in the gravity wave analysis based on satellite measurements including MODIS, AIRS, AMSU, MLS, DNB, COSMIC,HIRDLS and SOFIE. Besides, a few ground-based observation results and numerical models were briefly introduced and some cases of joint applications of satellite observations with ground-based observations and numerical models in the gravity waves were listed. In general, the satellite remote sensing data play an important role in the study of the characteristics in near-space environment, which can be applied to analyze the scales of gravity waves induced by different sources, correlations between the instabilities and waves as well as their patterns, the impacts in the climate process, wave-wave interactions and wave-flow interactions with other data. 相似文献
102.
103.
东北地震活动性短期预报方法研究 总被引:1,自引:1,他引:1
研究了1970年以来东北地区发生的MS≥5·0浅源地震孕育过程中地震活动性参数和地震活动图像的变化特征,并对地震活动性参数进行了比较系统地综合预报效能评价,结果显示:东北9次(组)浅震地震前,所研究的5项地震活动性参数中,88·9%出现了持续3个月以上的短期异常变化,且5项参数R值评分结果都满足97·5%的置信水平;88·9%地震前震源区附近出现了孕震空区,有87·5%孕震空区在空区边缘或空区内部出现了ML≥4·0逼近地震,逼近地震以单个或成对的形式出现。66·7%的地震在震源区附近出现了地震条带异常。最后给出东北地区中强震的短期预报方法,这对未来东北地区的地震预报工作将起着一定的参考意义。 相似文献
104.
105.
Xuan Ding LianFeng Gao NianQiao Fang WenJun Qu Jian Liu JiangShan Li 《中国科学D辑(英文版)》2009,52(8):1091-1103
Base on the Os isotope stratigraphy together with the empirical growth rate models using Co concentrations, the growth ages
of the ferromanganese crusts MHD79 and MP3D10 distributed in the seamount of Pacific are confirmed. Through the contrast and
research on the previous achievements including ODP Leg 144 and the crusts CD29-2, N5E-06 and N1–15 of the seamount of the
Central Pacific, the uniform five growth and growth hiatus periods of them are found, and closely related to the Cenozoic
ocean evolvement process. In the Paleocene Carbon Isotope Maximum (PCIM), the rise of the global ocean productivity promoted
the growth of the seamount crust; the first growth hiatus (I) of the ferromanganese crust finished. In the Paleocene-Eocene
Thermal Maximum (PETM), though the vertical exchange of seawater was weakened, the strong terrestrial chemical weathering
led to the input of a great amount of the terrigenous nutrients, which made the bioproductivity rise, so there were no crust
hiatuses. During 52–50 Ma, the Early Eocene Optimum Climate (EECO), the two poles were warm, the latitudinal temperature gradient
was small, the wind-driven sea circulation and upwelling activity were weak, the terrestrial weathering was also weakened,
the open ocean bioproductivity decreased, and the ferromanganese crust had growth hiatus again (II). From early Middle Eocene-Late
Eocene, Oligocene, it was a long-term gradually cooling process, the strengthening of the sea circulation and upwelling led
to a rise of bioproductivity, and increase of the content of the hydrogenous element Fe, Mn and Co and the biogenous element
Cu, Zn, so that was the most favorable stage for the growth of ferromanganese crust (growth periods III and IV) in the studied
area. The hiatus III corresponded with the Eocene- Oligocene boundary, is inferred to relate with the global climate transformation,
celestial body impact event in the Eocene-Oligocene transition. From the early to the middle Miocene, a large-scale growth
hiatus (hiatus period IV) of the ferromanganese crust in the studied area is inferred to relate with temporary warm up climate
and ephemeral withdrawal of Antarctic bottom water in the early Miocene. After that, the Antarctic ice sheets extended, the
bottom water circumfluence strengthened, the ocean fertility increased, and the once interrupted crust continued to grow in
the late Miocene (growth period V).
Supported by China Ocean Mineral Resources Research and Development Association “10th Five Year” Topic (Grant No. DY105-01-04-14) 相似文献
106.
Cropland cover change in Northeast China during the past 300 years 总被引:15,自引:0,他引:15
Land use/cover change induced by human activities has emerged as a “global” phenomenon with Earth system consequences. Northeast
China is an area where the largest land cultivation activities by migrants have happened in China during the past 300 years.
In this paper, methods including documentary data calibration and multi-sourced data conversion model are used to reconstruct
historical cropland cover change in Northeast China during the past 300 years. It is concluded that human beings have remarkably
changed the natural landscape of the region by land cultivation in the past 300 years. Cropland area has increased almost
exponentially during the past 300 years, especially during the past 100 years when the ratio of cropland cover changed from
10% to 20%. Until the middle of the 19th century, the agricultural area was still mainly restricted in Liaoning Province.
From the late 19th century to the early 20th century, dramatic changes took place when the northern boundary of cultivation
had extended to the middle of Heilongjiang Province. During the 20th century, three agricultural regions with high ratio of
cropland cover were formed after the two phases of spatial expansion of cropland area in 1900s–1930s and 1950s–1980s. Since
1930s–1940s, the expansion of new cultivated area have invaded the forest lands especially in Jilin and Heilongjiang Provinces.
Supported by National Natural Science Foundation of China (Grant No. 40571165) and Innovation Foundation of Chinese Academy
of Sciences (Grant No. KZCX2-YW-315) 相似文献
107.
108.
邱忠坊 《CT理论与应用研究》1994,3(3):27-32
本文是文献[8]的继续,文中提出了地震勘探的带阻尼波动方程反演的新方法,应用此反演算法可以通过微机识别地层的波阻抗,这里把地层分成100层,地震数据含有10%的误差,且反演计算时间仅仅是正演计算时间的三倍.文献[1]-[4]的计算方法是基于波动方程的混合问题,而文献[8]所提出的反演算法是基于波动方程的哥西问题,许多例子充分说明后者更有效. 相似文献
109.
为解决EDAS?24GN6数据采集器对策克台井下宽频带地震计GL?S120B进行正弦标定的过程中产生的响应波形限幅问题,分析了数据采集器?地震计这一系统的标定过程及原理,结合GL?S120B的幅频响应特征,推导出正弦标定频点参数中的频率f、衰减因子λ与标定响应波形限幅之间的关系。分析表明,在GL?S120B平坦响应频带内,为避免出现标定波形响应限幅,频率f与衰减因子λ的乘积应至少大于限幅下限50.93;而在其衰减响应频带内,由于地震计电压灵敏度的衰减,频率f与衰减因子λ的乘积最小取值也相应减小。据此,对衰减因子λ进行校正,并再次对GL?S120B进行正弦标定。标定及计算结果显示:标定波形未限幅,GL?S120B三分向幅频响应特征较为一致;灵敏度对出厂值的变化率保持在5%范围内。本研究结论可为采用EDAS?24GN6和GL?S120B地震观测系统的台站进行正弦波标定提供频点参数,并为其他台站解决正弦标定波形限幅问题提供分析依据。 相似文献
110.
噪声源的空间分布和季节变化会对噪声互相关函数中的信号产生一定影响.本文选取了ChinArrry二期台阵南部的322个宽频带地震台,利用其2013年9月至2016年6月的垂直分量连续记录计算了台站间的互相关函数,进而通过背景噪声能量流的方法,分析了周期频段4~8 s,8~12 s和12~20 s的噪声能量随时间的演化规律.结果表明,在不同频段,背景噪声的强度及优势来源方向均具明显的季节变化,且不同周期频段的噪声能量变化规律有所差异.总体而言,噪声能量在北半球冬季较强,夏季较弱,与全球海洋活动的季节性变化一致,能量优势来源方向也与全球海浪波高分布相符.同时,在10~20 s频段范围内,噪声互相关函数中存在较强的异常信号.该信号在环形台阵路径上的到时呈现随方位角的规律变化,且冬季较强,夏季较弱.基于走时的分析表明,该信号是由大西洋北部的一个强噪声源激发产生的.在特定路径上,该信号可能对频散提取产生干扰.研究表明,噪声源分布的不均匀性以及季节变化会对噪声互相关函数中信号的细节形态产生影响,进而影响格林函数的收敛程度,相关精细化研究应对噪声源的特性予以关注.
相似文献