排序方式: 共有37条查询结果,搜索用时 15 毫秒
1.
2.
GRACE重力卫星任务即将结束,后续GRACE Follow-On卫星计划于2017年发射,在此期间,迫切需要一个新的卫星计划继续对全球时变重力场进行连续监测,以保证时变重力场信息时间序列的连贯性.SWARM计划包括三颗轨道高为300~500 km的近极轨卫星星座,类似于三颗CHAMP卫星,具有接替时变重力场探测的潜力.本文首先分析SWARM(模拟)、CHAMP、GRACE反演至60阶时变重力场球谐系数的误差特性及不同高斯平滑半径对高频误差的抑制效果,然后分别利用SWARM、CHAMP、GRACE的时变重力场模型恢复全球质量变化,结果表明,SWARM模拟观测数据的高频误差低于CHAMP观测数据,探测时变重力场的整体精度优于CHAMP,略低于GRACE探测精度;其次,对比2003年1月—2009年12月期间CHAMP(hl-SST)和GRACE(ll-SST)时变重力场模型反演格陵兰岛冰盖质量变化趋势,结果显示,CHAMP数据得到格陵兰岛冰盖质量变化趋势为-50.2±2.0 Gt/a,GRACE所得结果为-41.2±1.6 Gt/a,两者相差21.8%;最后,对比2000年1月—2004年12月间SWARM模拟数据和"真实"模型数据反演的格陵兰岛冰盖质量变化趋势,结果表明,两者相差19.2%.本文研究表明,利用SWARM hl-SST数据探测时变重力场可以达到20%相对精度水平,有潜力用于填补GRACE和GRACE Follow-On期间探测地球时变重力场的空白. 相似文献
3.
4.
The flow patterns of Euro-Atlantic blocking events in winter are investigated by dividing the sector into three sub- regions: 60°-30°W (Greenland region); 20°W-30°E [eastern Atlantic-Europe (EAE) region]; and 50°-90°E (Ural region). It is shown that blocking events in winter are extremely frequent in the three sub-regions. Composite 500-mb geopotential height fields for intense and long-lived blocking events demonstrate that the blocking fields over Greenland and Ural regions exhibit southwest-northeast (SW-NE) and southeast-northwest (SE-NW) oriented dipole-type patterns, respectively, while the composite field over the EAE region exhibits an Ω-type pattern. The type of composite blocking pattern seems to be related to the position of the blocking region relative to the positive center of the climatological stationary wave (CSW) anomaly existing near 10°W.
The physical cause of why there are different composite blocking types in the three sub-regions is identified using a nonlinear multiscale interaction model. It is found that when the blocking event is in almost the same position as the positive CSW anomaly, the planetary-scale field can exhibit an Ω-type pattern due to the enhanced positive CSW anomaly. Neverthe- less, a SW-NE (SE-NW) oriented dipole-type block can occur due to the reduced positive CSW anomaly as it is farther in the west (east) of the positive CSW anomaly. The total fields of blocking in the three regions may exhibit a meandering flow comprised of several isolated anticyclonic and cyclonic vortices, which resembles the Berggren-Bolin-Rossby meandering jet type. 相似文献
The physical cause of why there are different composite blocking types in the three sub-regions is identified using a nonlinear multiscale interaction model. It is found that when the blocking event is in almost the same position as the positive CSW anomaly, the planetary-scale field can exhibit an Ω-type pattern due to the enhanced positive CSW anomaly. Neverthe- less, a SW-NE (SE-NW) oriented dipole-type block can occur due to the reduced positive CSW anomaly as it is farther in the west (east) of the positive CSW anomaly. The total fields of blocking in the three regions may exhibit a meandering flow comprised of several isolated anticyclonic and cyclonic vortices, which resembles the Berggren-Bolin-Rossby meandering jet type. 相似文献
5.
本文重点分析了2013年夏季格陵兰冰盖表面的融化特征, 并将2013年与2012年融化极值年的异常进行对比, 探讨二者之间存在的动力和热力差异及其对冰盖表面融化的影响和机制。结果表明:2013年夏季格陵兰冰盖表面最大融化范围仅为44%, 远小于2012年的97%, 持续的时间也比2012年短20天左右, 平均的融化面积和持续时间都接近气候平均态。2013年夏季大气环流异常与2012年近乎完全相反, 格陵兰及附近海域为低压异常, 500 hPa位势高度场为负异常, 大气环流和2012年相比更具有纬向型。格陵兰岛的北部和南部出现气旋异常, 有利于输送北极的冷空气到格陵兰岛, 不仅降低了夏季格陵兰冰盖表面的平均温度, 而且也减少了格陵兰高温事件发生的频率。同时, 2013年夏季格陵兰表面向下的辐射通量异常分布大体上呈西南—东北走向, 不同于 2012年的南北分布。尽管从分布上看, 总的向下辐射通量以正的短波分量为主, 但是长短波分量相互抵消使得 2013年夏季总的向下辐射通量接近气候平均态, 这使得辐射对冰盖表面温度的影响不明显。大气环流的动力和表面辐射收支的热力共同作用导致2013年夏季格陵兰冰盖表面融化经历了相对缓和的一年。 相似文献
7.
基于GRACE卫星重力数据估计格陵兰岛冰盖质量变化 总被引:1,自引:0,他引:1
重力场恢复与气候试验(GRACE)卫星为高分辨率地监测全球冰川质量变化提供了一种新的手段。本文利用2003年1月至2014年12月Level-2 RL05的GRACE产品,进行去相关误差滤波、高斯滤波和海洋-陆地信号泄漏改正后,得到了格陵兰岛冰盖质量变化的时间序列,分析了格陵兰岛冰盖质量变化的长期趋势项,并与ICESat的结果进行了比较验证。研究表明,在2003年1月至2014年12月之间,格陵兰岛冰盖质量减小速率约为(-260±43)Gt/a,对全球海平面的贡献约为(0.72±0.12)mm/a,对同时期海平面上升的贡献占25.8%,并且格陵兰岛冰盖消融有着很强的区域差异性,冰盖消融的区域主要集中在边缘区域,中部内陆地区的冰盖质量则有增加的趋势。并进一步和ICESat的结果进行了比较分析,ICESat的结果显示格陵兰岛冰盖质量减小速率约为(-174±43)~(-184.8±28.2)Gt/a,而GRACE的结果则为(-209.4±26.3)Gt/a,有着较好的一致性,并且区域分布特征也符合较好。 相似文献
8.
格陵兰岛的冰盖对全球气候有着极为重要的意义,冰盖的冻融情况可直观展示北极地区的气候变化状况。利用我国FY-3气象卫星的微波成像仪(Microwave Radiation Imager,MWRI)数据,基于增加干湿雪差异性的交叉极化比率(Cross-Polarized Gradient Ratio,XPGR)算法,通过支持向量机(Support Vector Machine,SVM)的超平面进行格陵兰岛冰盖表面冻融探测,与已有的阈值方法相比,理论上精度较高。与微波辐射计(Special Sensor Microwave Image,SSM/I)(阈值为–0.025)的数据结果进行对比验证,结果表明:XPGR结合SVM的格陵兰岛冰盖表面冻融探测方法是可行的。 相似文献
9.
Irina M. Artemieva Hans Thybo 《《幕》》2008,31(1):98-106
We present a review of geophysical models of the continental lithosphere of Norden, which includes the Nordic countries (Denmark, Iceland, Finland, Norway, Sweden), Greenland, and the adjacent regions of the neighbouring countries. The structure of the crust and the lithospheric mantle reflects the geologic evolution of Norden from Precambrian terrane accretion and subduction within the Baltic Shield and Greenland to Phanerozoic rifting, volcanism, magmatic crust formation, subduction and continent-continent collision at the edges of the cratons and at the plate boundaries. The proposed existence of a mantle plume below Iceland has not been uniquely demonstrated by the available seismic evidence. Its connection to the break-up of the North Atlantic Ocean c. 65 My ago is uncertain, but the 〉30 km thick crust in the strait between Iceland and Greenland may indicate the track of the plume. Using the results from seismic (reflection and refraction profiles, P- and S-wave, body-wave and surface-wave tomography), thermal, gravity, and petrologic studies,we review the structure of the crust and the lithospheric mantle of Norden and propose an integrated model of physical properties of the lithosphere of the region, including maps of lateral variation in crustal and lithospheric thicknesses and compositional variation in the lithospheric mantle. 相似文献