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991.
INFLUENCE OF THE SURFACE AIR TEMPERATURE OVER ASIAN-PACIFIC REGION ON THE SUMMERTIME NORTHEASTERN ASIAN BLOCKING HIGH* 下载免费PDF全文
Synthesis analysis and singular value decomposition (SVD) methods were used to study the impact of surface air temperature (SAT) over Asian-Pacific region on the summertime northeastern Asian blocking high (NABH) with NCEP/NCAR Reanalysis Data.The results showed that 500 hPa geopotential height and SAT fields over Asian-Pacific region shared the similar pattern of East Asian Pacific (EAP) wave train;there was steady remote response relationship between the EAP wave train in summer and the "+-+" pattern of tropical SAT in zonal direction from former winter to summer;there were two relative negative(positive) Walker circulations over the tropical Indian Ocean and Pacific when being more(less) summertime NABH. The influence of sea surface temperature anomaly (SSTA) on the summertime NABH was possibly as follows.The special distribution of SSTA in tropical zonal direction continuously forced the tropical convection and zonal circulation from former winter to summer,and led them to act anomaly.Finally the abnormal conditions were transported to middle-high latitudes through EAP wave train and yielded the advantageous or disadvantageous atmospheric circulation background for the summertime NABH. 相似文献
992.
南海北部一百万年以来的表层古生产力变化:来自ODP1144站的蛋白石记录 总被引:7,自引:1,他引:6
通过南海北部ODP 1144站蛋白石含量测定及其堆积速率的计算,并结合氧同位素记录等相关资料,获得南海北部1050ka以来高分辨率的表层古生产力变化与冰期旋回和东亚季风的关系。约900ka以来,蛋白石含量及其堆积速率较900ka以前明显增加,反映了“中更新世革命”事件之后,全球气候变冷,并导致表层生产力的提高。由于第四纪冰期旋回中的冬、夏季风的加强,加上1144站特殊的地理位置,使该站在冰期时表层生产力增加,间冰期时表层生产力降低。浮游有孔虫氧同位素记录与蛋白石含量及其堆积速率的时间序列频谱分析结果显示,三者均出现了相对应的偏心率周期、斜率周期和岁差周期,说明该站表层生产力的变化主要受地球轨道周期的驱动。 相似文献
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Brian P. Reen David R. Stauffer Kenneth J. Davis Ankur R. Desai 《Boundary-Layer Meteorology》2006,120(2):275-314
The importance of soil moisture inputs and improved model physics in the prediction of the daytime boundary-layer structure during the Southern Great Plains Hydrology Experiment 1997 (SGP97) is investigated using the non-hydrostatic fifth-generation Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) Mesoscale Model MM5. This is Part II of a two-part study examining the relationship of surface heterogeneity to observed boundary-layer structure. Part I focuses on observations and utilizes a simple model while Part II uses observations and MM5 modelling. Soil moisture inputs tested include a lookup table based on soil type and season, output from an offline land-surface model (LSM) forced by atmospheric observations, and high-resolution ( 800 m) airborne microwave remotely sensed data. Model physics improvements are investigated by comparing an LSM directly coupled with the MM5 to a simpler force-restore method at the surface. The scale of land surface heterogeneities is compared to the scale of their effects on boundary-layer structure.The use of more detailed soil moisture fields allowed the MM5 to better represent the large-scale (hundreds of km) and small-scale (tens of km) horizontal gradients in surface-layer weather and, to a lesser degree, the atmospheric boundary-layer (ABL) height, which was evaluated against observations measured by differential absorption lidar (DIAL). The benefits of coupling an LSM to the MM5 were not readily evident in this summertime case, with the model having particular difficulty simulating the timing of maximum surface fluxes while underestimating the depth of the mixed layer. 相似文献
995.
We examine hypotheses for the formation of light-toned layered deposits in Juventae Chasma using a combination of data from Mars Global Surveyor's Mars Orbiter Camera (MOC), Mars Orbiter Laser Altimeter (MOLA), and Thermal Emission Spectrometer (TES), as well as Mars Odyssey's Thermal Emission Imaging System (THEMIS). We divide Juventae Chasma into geomorphic units of (i) chasm wall rock, (ii) heavily cratered hummocky terrain, (iii) a mobile and largely crater-free sand sheet on the chasm floor, (iv) light-toned layered outcrop (LLO) material, and (v) chaotic terrain. Using surface temperatures derived from THEMIS infrared data and slopes from MOLA, we derive maps of thermal inertia, which are consistent with the geomorphic units that we identify. LLO thermal inertias range from ∼400 to 850 J m−2 K−1 s−1/2. Light-toned layered outcrops are distributed over a remarkably wide elevation range () from the chasm floor to the adjacent plateau surface. Geomorphic features, the absence of small craters, and high thermal inertia show that the LLOs are composed of sedimentary rock that is eroding relatively rapidly in the present epoch. We also present evidence for exhumation of LLO material from the west wall of the chasm, within chaotic and hummocky terrains, and within a small depression in the adjacent plateau. The data imply that at least some of the LLO material was deposited long before the adjacent Hesperian plateau basalts, and that Juventae Chasma underwent, and may still be undergoing, enlargement along its west wall due to wall rock collapse, chaotic terrain evolution, and exposure and removal of LLO material. The new data allow us to reassess possible origins of the LLOs. Gypsum, one of the minerals reported elsewhere as found in Juventae Chasma LLO material, forms only at low temperatures () and thus excludes a volcanic origin. Instead, the data are consistent with either multiple occurrences of lacustrine or airfall deposition over an extended period of time prior to emplacement of Hesperian lava flows on the plateau above the chasm. 相似文献
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IPTA监测圣佩德罗湾港口地表时序沉降 总被引:1,自引:0,他引:1
常规D-InSAR技术已成功应用于由于火山、地震等引起的地表形变监测,然而受时间失相干和大气延迟等影响,该技术监测地表沉降形变的精度只能达厘米级。本文以美国圣佩德罗湾港口为研究对象,采用干涉点目标分析(IPTA)技术,选用二维线性相位模型对时序差分干涉相位图迭代回归分析,逐次去除大气延迟、DEM误差以及噪声等的影响,最终提取出准确可靠的形变序列相位信息。结果证明IPTA技术对长期微小的地壳累积形变探测具有广阔的应用前景,而且IPTA技术在实现效率和数据存储方面都优于常规的PS-InSAR。 相似文献