Modulation of Madden-Julian Oscillation Activity by the Tropical Pacific-Indian Ocean Associated Mode

In this study, the impacts of the tropical Pacific–Indian Ocean associated mode(PIOAM) on Madden–Julian Oscillation(MJO) activity were investigated using reanalysis data. In the positive(negative) phase of the PIOAM, the amplitudes of MJO zonal wind and outgoing longwave radiation are significantly weakened(enhanced) over the Indian Ocean, while they are enhanced(weakened) over the central and eastern Pacific. The eastward propagation of the MJO can extend to the central Pacific in the positive ...     

综合137Cs，RS和GIS的土壤侵蚀评估和预测——以云南小江流域为例

综合应用137Cs技术、RS技术和GIS技术,进行云南小江流域土壤侵蚀的评估和预测研究,探索中国西部山区观测资料缺乏、USLE(Universal Soil Loss Equation)方程不适宜区域土壤侵蚀评估与预测方法。通过137Cs技术,采用非农耕地与农耕地土壤侵蚀模型确定区内林地、灌丛、草地、坡耕地和裸地的年均侵蚀模数分别为356—1531 t/(km2·a),330—1709 t/(km2·a),886—3885 t/(km2·a),5197—12454 t/(km2·a)和15000 t/(km2·a)以上。解译小江流域1987年(Landsat TM)、1995年(Landsat TM)和2005年(Landsat ETM)遥感影像,获得流域不同时期土地利用图,将其与1∶50000 DEM模型进行叠置分析,建立小江流域土地利用的空间分布图,结合利用137Cs确定的土壤侵蚀速率数据,进行土壤侵蚀分区与制图,分析土壤侵蚀的时空变化。结果表明:1987年—2005年流域轻度以上侵蚀面积占总面积的66.0%—67.3%,变化不大,但侵蚀强度明显加剧,1987年—1995年间尤为明显;中度侵蚀、强度侵蚀、极强度侵蚀区面积分别增加30%、23%和26%;小江流域1987年、1995年和2005年土壤侵蚀量分别为7.51×106t/a,8.19×106t/a和8.18×106t/a。进而选用1995年和2005年的土壤侵蚀数据构建Markov-CA(马尔可夫—元胞自动机)预测模型,获得2015年流域土壤侵蚀分区图,并预测2015年土壤侵蚀量为8.17×106t,与2005年侵蚀量接近。研究结果真实地反映了小江流域土壤侵蚀的变化过程与主要驱动因子,研究方法适合中国西部山区土壤侵蚀评估与预测。     

油气田钻井岩芯及岩芯裂缝方位确定的古地磁原理与方法

岩石在现代地磁场中获得的粘滞乘磁可以通过分离乘磁低温分量获得，并且它与现代地磁场方向一致，因此，通过提取岩芯乘磁的低温分量，可以恢复岩芯的现代磁坐标，进而确定岩芯在现代地理坐标中的位置，本文对吐哈油田，长庆油田岩芯及地表露头样品作了系统热磁分析，讨论了乘磁低温分量与现代地磁场关系，建立了岩芯方位古地磁学定向方法。并将这种方法用于长庆油田钻井岩芯定向及裂缝方位确定，通过对长庆油田４０口井的含裂缝岩芯     

U-Pb Zircon Geochronology and Geochemistry of Granitoids in the Douling Group in the Eastern Qinling

LA-ICPMS U-Pb zircon dating of the Sanpinggou, Gangou and Fengzishan granitoids in the Douling Group of the Eastern Qinling yields ages of 760-685 Ma, which represents a strong tectono-magmatic event in the southern Qinling during the late Neoproterozoic. Geochemical data show that these intrusions have wide compositions ranging from minor gabbros through diorites to granodiorites. They are relatively enriched in LILE, poor in HFSE and strongly depleted in Nb and Ta, displaying affinities of Ⅰ-type granites formed in an active continental margin with oceanic subduction. In contrast to granitoids, gabbros and enclaves in the granitoids have higher REE abundances, relatively flat REE patterns, lower LILE, slightly higher HFSE and more depletion in Nb and Ta. All these suggest that the gabbros were formed by partial melting of the upper mantle above the subduction zone and the granitoids by the partial melting of the lower crust. Combined with regional geological data, the subduction-related granitoids in     

Model Projections of Precipitation Minus Evaporation in China

Changes in precipitation minus evaporation (P -E) are analyzed to investigate the possible impacts of climate change on water resource conditions in China. Simulations of SRES A1B and 20C3M scenarios from the WCRP CMIP3 GCMs are employed in the study. Time slice analysis shows that there would be more annual mean P -E across China in 2040-2055 and 2080-2099, compared to 1980-1999, with the largest percentage change over Northwest China and the Bohai Rim area. Precipitation and evaporation would also increase over entire China during these two periods. Annual mean P -E, precipitation, and evaporation averaged over the whole China and its eight sub-areas all yield generally upward trends during the 21st century. This indicates that on annual mean scale, the global warming related precipitation dominates the hydroclimate conditions in China. On seasonal mean scale, although precipitation is projected to increase over China, P -E exhibits both decreasing and increasing trends over certain regions of China. This suggests that the variation of global warming related evaporation dominates hydroclimate conditions over some parts of China, especially in northern China. Therefore, in hydroclimate condition projections, considering both evaporation and precipitation changes should be more reasonable than considering only precipitation.     

云相态的卫星遥感研究进展

云相态不仅是气象学和气候学研究的重要参量,也是卫星云参数反演的关键要素,其识别的准确性直接关系到光学厚度、有效粒子半径等光学和微物理参数的反演精度.卫星遥感技术的发展为云相态的识别提供了前所未有的技术手段.对能够提取云相态信息的主要星载遥感源进行了介绍,重点总结了近30年来国内外利用星载被动光学遥感资料、偏振辐射资料以及主动雷达资料进行云相态反演的基本原理、方法以及技术特点,最后针对目前云相态反演工作中存在的一些问题和发展趋势进行了探讨.     

How the “Best” Models Project the Future Precipitation Change in China

Projected changes in summer precipitation characteristics in China during the 21st century are assessed using the monthly precipitation outputs of the ensemble of three “best” models under the Special Report on Emissions Scenarios (SRES) A1B, A2, and B1 scenarios. The excellent reproducibility of the models both in spatial and temporal patterns for the precipitation in China makes the projected summer precipitation change more believable for the future 100 years. All the three scenarios experiments indicate a consistent enhancement of summer precipitation in China in the 21st century. However, the projected summer precipitation in China demonstrates large variability between sub-regions. The projected increase in precipitation in South China is significant and persistent, as well as in North China. Meanwhile, in the early period of the 21st century, the region of Northeast China is projected to be much drier than the present. But, this situation changes and the precipitation intensifies later, with a precipitation anomaly increase of 12.4%–20.4% at the end of the 21st century. The region of the Xinjiang Province probably undergoes a drying trend in the future 100 years, and is projected to decrease by 1.7%–3.6% at the end of the 21st century. There is no significant long-term change of the projected summer precipitation in the lower reaches of the Yangtze River valley. A high level of agreement of the ensemble of the regional precipitation change in some parts of China is found across scenarios but smaller changes are projected for the B1 scenario and slightly larger changes for the A2 scenario.     

Strengthened influence of the East Asian trough on spring extreme precipitation variability over eastern Southwest China after the late 1980s

The relationship between variations in the East Asian trough (EAT) intensity and spring extreme precipitation over Southwest China (SWC) during 1961–2020 is investigated. The results indicate that there is an interdecadal increase in the relationship between the EAT and spring extreme precipitation over eastern SWC around the late 1980s. During the latter period, the weak (strong) EAT corresponds to a strong and large-scale anomalous anticyclone (cyclone) over the East Asia–Northwest Pacific region. The EAT-related anomalous southerlies (northerlies) dominate eastern SWC, leading to significant upward (downward) motion and moisture convergence (divergence) over the region, providing favorable (unfavorable) dynamic and moisture conditions for extreme precipitation over eastern SWC. In contrast, during the former period, the EAT-related circulation anomalies are weak and cover a relatively smaller region, which cannot significantly affect the moisture and dynamic conditions over eastern SWC; therefore, the response in extreme precipitation over eastern SWC to EAT is weak over the period. The interdecadal change in the relationship between eastern SWC spring extreme precipitation and the EAT could be related to the interdecadal change in the EAT variability. The large (small) variability of the EAT is associated with significant (insignificant) changes in spring extreme precipitation over eastern SWC during the latter (former) period.摘要本文研究表明东亚大槽强度与中国西南地区东部春季极端降水的关系在20世纪80年代末后显著增强, 这可能与东亚大槽自身变率的年代际变化有关. 在80年代末之后, 东亚大槽的变率显著增强, 其对应的大气环流异常也偏强, 范围偏大, 可以显著影响西南地区东部的水汽和动力条件, 从而引起该地区春季极端降水的显著变化. 而在80年代末之前, 东亚大槽的变率偏弱, 其对应的大气环流异常也偏弱, 范围偏小, 因此不能对西南地区东部春季极端降水的变化产生显著影响.     

全局收敛LM算法优化的机载激光测深信号提取方法

在机载激光测深系统中,水面与水底回波信号的提取精度是影响系统测深能力的关键因素,然而传统的信号提取方法易受噪声影响,精度低,对测量环境的适应性差。针对上述问题,提出一种全局收敛LM(Levenberg Marquardt)算法优化的机载激光测深信号提取方法。首先通过模糊筛选得到较为可靠的初值;然后利用基于全局收敛LM的波形分解算法对波形进行分析建模,从而获取每个初值点的高斯分解参数;最后通过多条件筛选确定精确的水面、水底回波信号位置。利用实测数据和模拟数据分别进行实验,结果表明提出方法对回波信号具有较高的检测正确率,且稳定性较强。