东亚经向型气压异常偶极模与冬季北太平洋关键区域海温的关系及其数值模拟试验     

赵巧莲  李崇银  李琳 《气候与环境研究》2013,18(2):232-242

进一步从资料分析和大气环流模式的敏感性试验, 对西北太平洋海温异常与亚太中高纬度地区冬季海平面气压异常经向偶极模的关系及影响进行了研究。资料分析表明, 对应冬季亚太地区海平面气压的经向(ME)型偶极模, 西北太平洋中高纬度海温异常的影响存在两个重要关键区。尤其是(40°N～55°N, 150°E～160°W)海区的海温异常与冬季东亚经向型气压偶极模指数I_ME有明显正相关, (20°N～35°N, 125°E～170°W)海区的海温异常与指数I_ME有明显负相关。而上述两个关键海区的SSTA对经向型振荡模的影响, 主要是通过热通量异常的作用。敏感性模拟试验清楚表明, 西北太平洋关键区的海温异常对亚洲—太平洋地区冬季海平面气压场的经向偶极模有一定影响。区域1(42°N～62°N, 145°E～165°W)的负异常相对于其自身的正异常来说, 对亚太地区海平面气压场的负经向偶极模贡献更大, 而区域2 [(22°N～42°N, 135°E～175°E)和(26°N～42°N, 175°E～170°W)]的正异常相对区域1的负异常来说对负经向偶极模的贡献更大一些。但是, 单独区域1的负异常海温和单独区域2的正异常海温影响下的海平面气压场响应的负经向偶极模都会有不同程度的位置偏移。当存在区域1的负异常海温和区域2的正异常海温相互匹配的情况下, 亚洲—太平洋地区冬季海平面气压场的负经向偶极模特征更为显著。  相似文献   

Thirty-Element Active Antenna Array as a Prototype of a Huge Low-Frequency Radio Telescope     

Alexander?Alexandrovich?KonovalenkoEmail author  Igor?Savelievich?Falkovich  Nikolay?Nikolaevich?Kalinichenko  Alexander?Alexandrovich?Gridin  Igor?Nikolaevich?Bubnov  Alain?Lecacheux  Carlo?Rosolen  Helmut?O.?Rucker 《Experimental Astronomy》2003,16(3):149-164

An effective wide-band (10 to 60 MHz) active antenna element has been developed. The cost of one short (3 m), thin dipole with built-in amplifier and metal construction is less than 45 euro. It was shown both theoretically and experimentally that the upper limiting frequency is at least 60 MHz, the dynamic range is 90 dB/V and the share of the amplifier noise to the background antenna temperature is about 10%. The developed active dipole was tested by building a 30-element antenna array and comparing its parameters with one of the subpart of the UTR-2 radio telescope having passive dipoles of 8.6 m in length and 1.8 m in diameter. The 3C461 ionospheric scintillation spectra observed in the experiments show that the sensitivities and noise-immunities of both antennas are close. This proves the availability using of a short cheap active dipole in new generation giant radio telescopes.  相似文献   

Dipole electrode sounding in earthquake prone region     

Youfa Chen  Yunsheng Kang  Xuebin Du  Baozhi Chen  Gesu Liang  Yongde Dong 《地震学报(英文版)》1992,5(4):797-806

This paper aims to analyse the geoelectrical resistivityρ _s data on the dipole electrode sounding, which were firstly accumulated from the earthquake prone region in China. The analyses on the one order difference value of the geoelectrical resistivity indicated that, firstly, more than 4 percent of theρ _s data reveals the precursors by 3 to 76 days ahead the earthquakes occurring, with the magnitude range of 4 ≤M ≤ 6. 4, in a region of 100 km around the station, and secondly, the results revealed that the seasonal variation ofρ _s data were slight. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 211–219, 1992.  相似文献   

赤道印度洋偶极子对重庆夏季降水的影响分析          下载免费PDF全文

唐红玉  吴遥  董新宁  刘晓冉  魏麟骁  张驰 《山东气象》2020,40(2):52-61

利用重庆34个气象台站1961—2017年夏季降水量、NCEP/NCAR的再分析月平均高度场资料和海面温度资料，分析发现，上年秋季尤其是11月的赤道（热带）印度洋偶极子（tropical Indian Ocean dipole, TIOD）模态与重庆夏季降水存在正相关关系。通过前期海面温度对大气环流的影响分析，结果表明：上年11月TIOD和夏季500 hPa高度场的相关与重庆夏季降水和高度场的相关一致，显示出从高纬度到低纬度“+、-、+”的相关分布，反映出当上年11月TIOD正位相（负位相）时，次年夏季环流场表现出乌拉尔山阻塞高压明显（不明显）、中纬度30°～37°N低值系统活跃（不活跃），西太平洋副热带高压偏强（弱）、位置偏南（北）的重庆夏季典型的降水偏多环流特征；前期赤道太平洋ENSO暖事件和前期TIOD事件同时发生时，两个事件的作用相互叠加，使得西太平洋副热带高压加强西伸并且位置偏南，造成重庆夏季降水的异常偏多。  相似文献   

Shallow bias in Mediterranean paleomagnetic directions caused by inclination error     

Wout Krijgsman  Lisa Tauxe 《Earth and Planetary Science Letters》2004,222(2):685-695

A variety of paleomagnetic data from the Mediterranean region show a strong bias toward shallow inclinations. This pattern of shallow inclinations has been interpreted to be the result of (1) major northward terrane displacement, (2) large nondipole components in the Earth's magnetic field, and (3) systematic inclination flattening of the paleomagnetic directions. Here, we use the observation that, in addition to the well-known variation of magnetic inclination with latitude, the N-S elongation of directional dispersion also varies, being most elongate at the equator and nearly symmetric at the poles. Assuming that inclination shallowing follows the relationship long known from experiment, we invert the inclinations using a range of “flattening factors” to find the elongation/inclination pair consistent with a statistical model for the paleosecular variation. We apply the so-called “elongation/inclination” method to the extensive paleomagnetic data sets from the Miocene sediments of the Calatayud basin (Spain) and the island of Crete (Greece). After correction, the Spanish data are in good agreement with the expected middle Miocene latitude of the region. The data from Crete suggest that it occupied a position in the late Miocene about 275 km north of the predicted location. This is in agreement with the geological and geodynamical models for the east Mediterranean region, which indicate that slab rollback processes in combination with Anatolian push generated southward migration of Crete. The 7.5 million year average displacement rate of Crete estimated by the E/I method is 37 mm/yr to the south, which closely coincides with present-day rates based on global positioning system (GPS) and model measurements. We also show that inappropriate tilt corrections lead to a shallow inclination bias as well, explaining that observed in studies of lava flows of the region. We conclude that the east Mediterranean inclination anomaly is caused by sedimentary inclination error and not by a persistent octupolar contribution to the geomagnetic field, or northward transport.  相似文献   

Is 600 Myr long enough for the random palaeogeographic test of the geomagnetic axial dipole assumption?     

P. L. McFadden 《Geophysical Journal International》2004,158(2):443-445

  相似文献   

WINTER QINGHAI-XIZANG T_(BB) FEATURES IN RELATION TO ATMOSPHERIC CIRCULATION PATTERN AND ASIAN-AUSTRALIAN MONSOONS     

朱乾根  白虎志 《Acta Meteorologica Sinica》1997,(3)

Predominantly in the context of Japan GMS-derived T_(BB) data,study is undertaken of therelationship between the winter thermal conditions of the Qinghai-Xizang Plateau(QXP)andanomaly in Asian-Australian monsoons during northern summer.Evidence suggests that anti-correlation of cold air activity of East Asia with that of Mid Asia is responsible for the counterpartof the ground thermal characteristics anomaly on an interannual basis between the SW and NEQXP;the winter thermal pattern bears a closer correlativity with the subsequent summertimeAsian-Australian monsoons anomaly;as the thermal distribution is reversed,so are the convectionfeatures over North and South China,maritime continent,the NW and SW Pacific at tropical andequatorial latitudes,resulting in vast difference between East-Asian summer and Indonesian-NorthAustralian winter monsoons;the subtropical monsoon-associated rainbelt over the mid-lowerChangjiang basins exhibits the discrepancy in vigor and northerly shift timing.Besides,part of theresults has been further borne out through analysis of temperature and precipitation records of theeastern portion of the country in monsoon climate.  相似文献   

澳大利亚植被覆盖对亚澳季风影响的数值模拟(Ⅰ): 对澳洲气候及冬季风的影响     

鲍艳  吕世华  刘海辉 《高原气象》2006,25(5):763-771

通过澳大利亚植被绿化和沙漠化的数值试验,对植被覆盖变化引起的地方性气候变化及对半球尺度环流的影响进行了探讨.结果表明,澳洲大陆植被覆盖变化可显著影响地方性温湿和降水,大陆中西部绿化可使大陆东部显著降温,局地水汽增加对温度变化影响显著.绿化引起的中东部降水增加与地表粗糙度增加引发的水汽辐合增强,垂直上升运动增强引发的对流旺盛有关系.局地温湿和环流的变化通过大气定长波的经向传播影响了越赤道气流的强弱,进而对亚澳冬季季风系统降水产生了影响.研究表明, 绿化使低层南北半球越赤道气流略微增强,增加了北半球冬季寒潮深入南半球内部的几率,并引起了澳洲大陆北部沿岸的气流明显增强,季风槽南移,降雨带区域性的南移,增加了气旋干扰深入内陆的几率,降水发生的频率增多; 沙漠化则引起澳洲大陆增温显著,由于局地下沉运动抑制了对流,造成了陆上降水的减少,通过波的外传,引起了100°～110°E和120°～130°E的低层越赤道气流的变弱和澳大利亚季风槽降水的减少.  相似文献   

澳大利亚植被覆盖对亚澳季风影响的数值模拟(I):对澳洲气候及冬季风的影响   总被引：2，自引：0，他引：2  

鲍艳  吕世华  刘海辉 《高原气象》2006,(5)

通过澳大利亚植被绿化和沙漠化的数值试验,对植被覆盖变化引起的地方性气候变化及对半球尺度环流的影响进行了探讨。结果表明,澳洲大陆植被覆盖变化可显著影响地方性温湿和降水,大陆中西部绿化可使大陆东部显著降温,局地水汽增加对温度变化影响显著。绿化引起的中东部降水增加与地表粗糙度增加引发的水汽辐合增强,垂直上升运动增强引发的对流旺盛有关系。局地温湿和环流的变化通过大气定长波的经向传播影响了越赤道气流的强弱,进而对亚澳冬季季风系统降水产生了影响。研究表明,绿化使低层南北半球越赤道气流略微增强,增加了北半球冬季寒潮深入南半球内部的几率,并引起了澳洲大陆北部沿岸的气流明显增强,季风槽南移,降雨带区域性的南移,增加了气旋干扰深入内陆的几率,降水发生的频率增多;沙漠化则引起澳洲大陆增温显著,由于局地下沉运动抑制了对流,造成了陆上降水的减少,通过波的外传,引起了100°~110°E和120°~130°E的低层越赤道气流的变弱和澳大利亚季风槽降水的减少。  相似文献   

瞬变电磁法偶极装置模型实验研究     

刘长胜  林君  嵇艳鞠  吴国强 《物探与化探》2006,30(5):430-434

通过室内大量的模型实验,分析了偶极装置下导电球体、柱体及球柱组合体的瞬变响应特征,研究了偶极装置的探测分辨能力,讨论了极距大小和测点定位问题,最后归纳出偶极装置的一些工作特点。偶极装置下异常曲线形态较为复杂,解释难度较大,但受一次场影响较小,浅层探测分辨能力强,而且野外工作方便灵活,这些特点为偶极装置在诸如海底等特殊环境中进行瞬变电磁探测奠定了基础。  相似文献