Dynamics of upper tropospheric stationary wave anomalies induced by ENSO during the northern summer: A GCM study     

R. Krishnan  C. Venkatesan  R. N. Keshavamurty 《Journal of Earth System Science》1998,107(1):65-90

Ensemble seasonal integrations are carried out with the COLA GCM, with a view to understand the dynamical connection between warm SST anomalies in the equatorial central-eastern Pacific Ocean and the upper level stationary wave anomalies seen during drought years over the Indian summer monsoon region. In addition, experiments with and without orography are performed in order to examine the role of the Himalayas in modulating the El Niño induced stationary wave anomalies over the summer monsoon region. The GCM simulations show a statistically significant weakening of the summer monsoon activity over India in response to the SST forcing in the equatorial Pacific Ocean. This weakening of the summer monsoon appears to be largely related to modifications of the local Hadley and Walker cells over the summer monsoon region. In addition, it is seen that the anomalous ENSO divergent forcing over the tropical Pacific Ocean can act as a potential source for Rossby wave dispersion. Here one finds the possibility of meridionally propagating Rossby waves, which emanate from the ENSO forcing region, to interact with the subtropical westerlies and generate anomalous highs and lows in the subtropics and extratropics. The quasi-stationary perturbations seen over west Asia, Pakistan and northwest India during drought years, seem to be generated by the above mechanism. An alternate mechanism that could be important for the persistence of the quasi-stationary perturbations seems to be based on the dynamic excitation of middle latitude normal modes which can extract energy from the zonally varying unstable basic flow. It is seen from the GCM simulations, that the Himalayan orography plays a crucial role in anchoring the El Niño induced extratropical westerly troughs far to the west in the high latitude belt. In the absence of orography it is seen that the ENSO induced extra-tropical cyclonic anomalies tend to intrude southward into the monsoon region thereby destroying the regional scale circulations completely. Another effect due to the Himalayas is to generate lee waves on the eastern side of the topographic barrier which encircle the globe in the subtropics and midlatitudes.  相似文献   

Magma traps: Part II,application     

J. W. Elder 《Pure and Applied Geophysics》1978,117(1-2):15-33

A model of the lithostatic control of the ascent of magma, described in Part I (this volume), is tested against data from the Upper Cretaceous-Lower Tertiary sedimentary and volcanic region of central West Greeland: the thickness of sedimentary rock; the thickness of the pillow breccias; the total thickness of the lava pile; the depth of the post volcanic paleosurface. The local development is largely determined by a single parameter, the proportion of crustal thinning, and requires a magma source at 75 km depth with differentiation at 11 km depth. The model is applied in outline to the development of continental and orogenic volcanism in New Zealand.  相似文献   

1992—2007全球海平面变化     

马金周永宏  廖德春廖新浩 《中国科学院上海天文台年刊》2007,(1):37-41

引起全球海平面变化的因素是复杂多样的，大气压、风、大洋环流以及海水密度的变化，都会引起海平面在时间、空间上的变化，而海水温度的变化是海平面变化的主要原因。该文利用法国Archiving, Validation and Interpretation of Satellite Oceanographic data（AVISO）的海表面高度异常数据，计算了1992年10月至2007年1月间，全球海平面的平均上升速度，同时详细解算海平面上升速度的全球空间分布，分析全球海平面的变化趋势并将海平面变化同美国国家海洋大气署（NOAA）的Optimum Interpolation Sea Surface Temperature （OISST）海表面温度数据进行了比对和相关分析。  相似文献   

Study of temperature and precipitation variations in Italy based on surface instrumental observations   总被引：1，自引：0，他引：1  

Tiziano Colombo  Vinicio Pelino  Stefania Vergari  Paolo Cristofanelli  Paolo Bonasoni 《Global and Planetary Change》2007,57(3-4):308-318

In this paper we present a study concerning the climatic behaviour of two principal observables, temperature and precipitation as obtained from the measurements carried out at 50 Italian meteorological stations, since 1961. Analyses of WMO Climate Normals (CliNo) from 1961 to 1990 have been performed dividing the 50 Italian stations in three different classes: mountain (11 stations), continental (17) and coastal areas (21).The comparison of the CliNo 1961–1990 with the trend of temperature and precipitation for the period 1991–2000 showed a sharp significant increase of summer temperatures over Italy starting from 1980. This phenomenon was particularly evident for mountain stations, where a significant temperature increase has been recorded also during the autumn. Moreover, the analysis of precipitation data permitted to point out that, starting from 1980, mountain stations have been affected by a significant increase of precipitation events during autumn and winter, while for the rest of the Italian territory a reduction of precipitations has been recorded during early spring.  相似文献   

Interannual sea level variability in the South China Sea and its response to ENSO   总被引：18，自引：0，他引：18  

Zengrui Rong  Yuguang Liu  Haibo Zong  Yongcun Cheng   《Global and Planetary Change》2007,55(4):257-272

Sea level observed by altimeter during the 1993–2004 period, thermosteric sea level from 1945 through 2004, and tide gauge records are analyzed to investigate the interannual variability of sea level in the South China Sea (SCS) and its relationship with ENSO (El Niño and Southern Oscillation). Both the interannual variations of the observed sea level and the thermosteric sea level are closely related to ENSO. An ‘enigma’ that the SST and sea level in the SCS have inverse response to ENSO is revealed. It is found that the thermosteric sea level has an excellent correspondence to seawater temperature at 100 m depth, and their variations are unsynchronized to SST. Detailed analysis denotes that the warming of seawater occurs only in the upper 75 m during and after the mature phase of El Niño, while the cooling appears in the layers deeper than 75 m during El Niño years. The volume transports between the SCS and the adjacent oceans and the anomalous Ekman pumping contribute a lot for the sea level fall in the developing stage of El Niño, while the mass exchange, which is dominated by precipitation, plays a more significant role in the following continuous negative sea level anomalies.  相似文献   

IMPACT OF SSTA OF SOUTHERN HEMISPHERE ON FLOOD SEASON PRECIPITATION ANOMALIES IN YUNNAN     

杨竹云  杨素雨  严华生  张瑾文 《热带气象学报(英文版)》2015,21(3):255-264

Based on the reanalysis data of monthly mean global SST and wind from the NCEP/NCAR and the observation data of rain seasons in 124 stations of Yunnan province from 1961 to 2006, we applied the analytical methods of correlation analysis and composite analysis and a significance testing method to two sets of samples of average differences. The goal is to investigate into the influence of the Southern Hemispheric (SH) SST on the summer precipitation in Yunnan from January to May so as to identify the key time and marine regions. Physical mechanisms are obtained by analyzing the influence of sea level wind and the key marine regions on the precipitation during Yunnan’s rain season. Results show that there is indeed significant relationship between the SST in SH and summer precipitation in Yunnan. The key areas for influencing the summer precipitation are mainly distributed in a region called “West Wind Drift” in the SH, including the Southeast Indian, southern Australia, west coast of eastern Pacific off Chile, Peru and the southwest Atlantic Magellan. Besides, the most significant marine region is the west coast of Chile and Peru (cold-current areas of the eastern Pacific). Diagnostic analysis results also showed that monsoons in the Bay of Bengal, a cross-equatorial flow in the Indian Ocean near the equator and southwest monsoon in India weaken during the warm phase of the Peruvian cold current in the eastern Pacific. Otherwise, they strengthen.  相似文献   

A DIAGNOSTIC ANALYSIS OF AIR TEMPERATURE ANOMALY MODE OVER CHINA IN 2009/2010 WINTER BASED ON GENERALIZED EQUILIBRIUM FEEDBACK ASSESSMENT (GEFA) METHOD     

江志红  吴燕珠  刘征宇  温娜  赵灿 《热带气象学报(英文版)》2015,21(2):121-130

By using the observed monthly mean data over 160 stations of China and NCAR/NCEP reanalysis data, the generalized equilibrium feedback assessment(GEFA) method, combined with the methods of EOF analysis, correlation and composite analysis, is used to explore the influence of different SST modes on a wintertime air temperature pattern in which it is cold in the northeast and warm in the southwest in China. The results show that the 2009/2010 winter air temperature oscillation mode between the northern and southern part of China is closely related to the corresponding sea surface temperature anomalies(SSTA) and its associated atmospheric circulation anomalies. Exhibiting warming in Northeast China and cooling in Southwest China, the mode is significantly forced by the El Nio mode and the North Atlantic SSTA mode, which have three poles. Under the influence of SSTA modes, the surface northerly flow transported cold air to North and Northeast China, resulting in low temperatures in the regions. Meanwhile, the mid-latitude westerlies intensify and the polar cold air stays in high latitudes and cannot affect the Southwest China, resulting in the warming there.  相似文献   

青藏高原热力异常与华北汛期降水关系的研究   总被引：24，自引：3，他引：24  

赵声蓉  宋正山  纪立人 《大气科学》2003,27(5):881-893

利用1980～1994年NCEP/NCAR再分析资料,以及我国336个测站1956～1994年月降水量资料,通过诊断分析和数值实验,研究了夏季高原上热力异常与华北汛期降水的关系.结果表明:华北汛期干旱年,青藏高压及西太平洋副热带高压偏南、偏东,华北汛期降水偏多年则相反;华北汛期旱年时,高原上升、高原东侧邻近地区下沉的垂直环流明显加强,而降水偏多年时,垂直环流减弱,华北地区为上升气流控制;夏季高原为热源和水汽汇区,它们的异常对华北地区降水有很大影响,当热源和水汽汇增强(减弱)时,华北地区降水偏少(偏多).数值试验表明,高原上潜热加热异常引起青藏高压、西太平洋副热带高压、亚洲季风以及欧亚中高纬地区环流的变化,进而影响到华北地区的降水.  相似文献   

Day-side ionospheric conductivities at Mars     

H.J. Opgenoorth  R.S. Dhillon  M. Lester  S.E. Milan  D. Brain 《Planetary and Space Science》2010,58(10):1139-1151

We present estimates of the day-side ionospheric conductivities at Mars based on magnetic field measurements by Mars Global Surveyor (MGS) at altitudes down to ∼100 km during aerobraking orbits early in the mission. At Mars, the so-called ionospheric dynamo region, where plasma/neutral collisions permit electric currents perpendicular to the magnetic field, lies between 100 and 250 km altitude. We find that the ionosphere is highly conductive in this region, as expected, with peak Pedersen and Hall conductivities of 0.1-1.5 S/m depending on the solar illumination and induced magnetospheric conditions. Furthermore, we find a consistent double peak pattern in the altitude profile of the day-side Pedersen conductivity, similar to that on Titan found by Rosenqvist et al. (2009). A high altitude peak, located between 180 and 200 km, is equivalent to the terrestrial peak in the lower F-layer. A second and typically much stronger layer of Pedersen conductivity is observed between 120 and 130 km, which is below the Hall conductivity peak at about 130-140 km. In this altitude region, MGS finds a sharp decrease in induced magnetic field strength at the inner magnetospheric boundary, while the day-side electron density is known to remain high as far down as 100 km. We find that such Titan-like behaviour of the Pedersen conductivity is only observed under regions of strongly draped magnetospheric field-lines, and negligible crustal magnetic anomalies below the spacecraft. Above regions of strong crustal magnetic anomalies, the Pedersen conductivity profile becomes more Earth-like with one strong Pedersen peak above the Hall conductivity peak. Here, both conductivities are 1-2 orders of magnitude smaller than the above only weakly magnetised crustal regions, depending on the strength of the crustal anomaly field at ionospheric altitudes. This nature of the Pedersen conductivity together with the structured distribution of crustal anomalies all over the planet should give rise to strong conductivity gradients around such anomalies. Day-side ionospheric conductivities on Mars (in regions away from the crustal magnetic anomalies) and Titan seem to behave in a very similar manner when horizontally draped magnetic field-lines partially magnetise a sunlit ionosphere. Therefore, it appears that a similar double peak structure of strong Pedersen conductivity could be a more general feature of non-magnetised bodies with ionised upper atmospheres, and thus should be expected to occur also at other non-magnetised terrestrial planets like Venus or other planetary bodies within the host planet magnetospheres.  相似文献   

卫星热红外遥感技术在火山区地热探测中的应用——以内蒙古锡林郭勒火山区为例   总被引：1，自引：0，他引：1       下载免费PDF全文

彭芬  黄少鹏  时庆金  程玉祥  荆勇河 《地质科学》2014,(3):899-914

能源的全球性短缺以及全球环境问题的日益加剧,使得绿色新能源的研究与开发成为当今世界许多国家的一项重要任务。地热资源作为其中一员其重要性日益凸显。在地热资源的勘查中,传统的地质和地球物理勘探投入高、难度大,而遥感技术具有经济、高效、覆盖范围广等优势,已逐渐成为地热资源探测与调查的一种新技术手段。地热能开发的首选地区往往是新生代火山活动区,因其在相对较小的深度内就能获得很高的温度。本文综述了国内外利用遥感技术探测火山地热的发展历史和研究现状,介绍了这项技术在美国黄石公园、日本阿苏火山以及我国长白山火山和腾冲火山的应用。同时选取内蒙古锡林郭勒盟新生代火山活动构造区作为实例,利用美国NASA陆地卫星Landsat-7 ETM+第6波段的红外遥感数据反演了研究区的地表温度,结合ETM+7-4-1波段组合影像的地质构造解译结果以及其它相关资料对研究区地表温度分布进行了分析。结果表明,区内红外遥感地表温度异常区多位于北东东与北西向构造的交汇处或与环形构造密切相关。本文圈定了7个地表温度异常区作为这一地区下一步地热资源勘查的远景区。  相似文献