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51.
气候变化的研究依赖于可靠的气候数据。英国东英吉利大学气候研究中心推出的一套依据观测资料插值所得的月平均气候数据集(CRU),是目前使用较为广泛、质量较高的气候数据集。气候观测数据大多始于1950年,已有的研究也表明CRU数据在1950年后更具参考价值,但该数据集在1950年之前的可靠性不清楚。由于1950年之前缺乏器测数据,本研究使用树轮资料,对比每十年树轮重建温度(降水)与树轮附近CRU格点上的温度(降水)的距平和趋势的同号率,来评价CRU温度(降水)数据在不同地区的数据质量(可靠性),由此发现从1930年代开始,CRU温度数据在欧洲和中西伯利亚可信度较高;从1940年代开始,CRU温度数据在美国东部可信度较高;从1940年代开始,CRU降水数据在美国东部与西西伯利亚可信度较高。研究发现,气象站密度对CRU数据质量有很大影响;在气象站密度小的地区,CRU温度或降水数据与树轮序列的差异更为显著,气候数据质量偏低;而数据可信度较高的年代和地区,气象站密度往往较大。
相似文献52.
该文基于2001—2007年地表温度遥感反演产品 (MOD11A2),以基准气候站对其周围不同大小窗口内地表温度距平序列的解释方差作为度量,评估了我国142个基准气候站的环境代表性,并将代表性与土地覆盖和高程状况进行相关研究。结果显示:以解释方差大于0.75作为区分是否具有代表性的阈值,约41%的站点代表性较好,代表区域范围可超过51×51 km2,多分布于北方地区;约21%的站点代表性较差,代表区域范围不足7×7 km2,多分布于南方地区;其他代表区域范围居中的站点在南、北方均有分布;站点周围的土地覆盖多样性和地形起伏度与站点代表性存在负相关,且相关性随窗口的增大而加强。文中还评估了基准气候站对所属气候区的代表性,发现在气候特征复杂的西南地区和新疆部分地区,站点对气候区的代表性较差。 相似文献
53.
提出了一种新的光谱匹配算法——光谱角敏感森林方法。在位置敏感哈希函数算法的基础上引入光谱角度量,并利用新的数据桶检索结构改进了原位置敏感哈希函数算法中部分目标光谱点无法得到匹配光谱的缺陷。理论和实验证明,光谱角敏感森林算法的计算效率较传统高维数据匹配方法有较明显优势。 相似文献
54.
Jinchi Chu 《Mathematical Geology》1996,28(7):923-936
Sequential Indicator Simulation (SIS), although widely used, is relatively slow, and requires tedious inference of a large number of indicator variogram models. SIS is designed only to estimate class proportions and to reproduce indicator variogram models; the statistics of the continuous attribute being simulated,z-histogram and variogram, may be poorly reproduced. Several implementations of the SIS algorithm are proposed resulting in better reproduction of statistics yet with better CPU performance. 相似文献
55.
By adopting characteristic index data for the Western Pacific
Subtropical High (WPSH) from the National Climate Center of China, U.S.
National Centers for Environmental Prediction-National Center for
Atmospheric Research (NCEP/NCAR) reanalysis data, and the National
Oceanic and Atmospheric Administration (NOAA) sea surface temperature
(SST) data, we studied the WPSH variability considering the background
of climate warming by using a Gaussian filter, moving averages,
correlation analysis, and synthetic analysis. Our results show that
with climate warming over the past 60 years, significant changes in the
WPSH include its enlarged area, strengthened intensity, westward
extended ridge point and southward expanded southern boundary, as well
as enhanced interannual fluctuations in all these indices. The western
ridge point of the WPSH consistently varies with temperature changes in
the Northern Hemisphere, but the location of the ridgeline varies
independently. The intensity and area of the WPSH were both
significantly increased in the late 1980s. Specifically, the western
ridge point started to significantly extend westward in the early
1990s, and the associated interannual variability had a significant
increase in the late 1990s; in addition, the ridgeline was swaying
along the north-south-north direction, and the corresponding
variability was also greatly enhanced in the late 1990s. With climate
warming, the SST increase becomes more weakly correlated with the WPSH
intensity enhancement but more strongly correlated with the westward
extension of the ridge point in the equatorial central and eastern
Pacific Ocean in winter, corresponding to an expanding WPSH in space.
In the northern Pacific in winter, the SST decrease has a weaker
correlation with the southerly location of the ridgeline but also a
stronger correlation with the westward extension of the ridge point. In
the tropical western Pacific in winter, the correlations of the SST
decrease with the WPSH intensity enhancement, and the westward
extension of the ridge point is strengthened. These observations can be
explained by strengthened Hadley circulations, the dominant effects of
the southward shift, and additional effects of the weakened ascending
branch of the Walker circulation during warm climatological periods,
which consequently lead to strengthened intensities, increased areas,
and southward expansions of the WPSH in summer. 相似文献
56.
Xianhong MENG Shihua LYU Zhaoguo LI Yinhuan AO Lijuan WEN Lunyu SHANG Shaoying WANG Mingshan DENG Shaobo ZHANG Lin ZHAO Hao CHEN Di MA Suosuo LI Lele SHU Yingying AN Hanlin NIU 《大气科学进展》2023,40(6):1142-1157
Thousands of lakes on the Tibetan Plateau(TP) play a critical role in the regional water cycle, weather, and climate. In recent years, the areas of TP lakes underwent drastic changes and have become a research hotspot. However, the characteristics of the lake-atmosphere interaction over the high-altitude lakes are still unclear, which inhibits model development and the accurate simulation of lake climate effects. The source region of the Yellow River(SRYR) has the largest outflow lake and freshw... 相似文献
57.
Mountain range specific analog weather forecast model is developed utilizing surface weather observations of reference stations
in each mountain range in northwest Himalaya (NW-Himalaya). The model searches past similar cases from historical dataset
of reference observatory in each mountain range based on current situation. The searched past similar cases of each mountain
range are used to draw weather forecast for that mountain range in operational weather forecasting mode, three days in advance.
The developed analog weather forecast model is tested with the independent dataset of more than 717 days (542 days for Pir
Panjal range in HP) of the past 4 winters (2003–2004 to 2006–2007). Independent test results are reasonably good and suggest
that there is some possibility of forecasting weather in operational weather forecasting mode employing analog method over
different mountain ranges in NW-Himalaya. Significant difference in overall accuracy of the model is found for prediction
of snow day and no-snow day over different mountain ranges, when weather is predicted under snow day and no-snow day weather
forecast categories respectively. In the same mountain range, significant difference is also found in overall accuracy of
the model for prediction of snow day and no-snow day for different areas. This can be attributed to their geographical position
and topographical differences. The analog weather forecast model performs better than persistence and climatological forecast
for day-1 predictions for all the mountain ranges except Karakoram range in NW-Himalaya. The developed analog weather forecast
model may help as a guidance tool for forecasting weather in operational weather forecasting mode in different mountain ranges
in NW-Himalaya. 相似文献
58.
面对规模日益庞大的影像数据集合,提供一个高效的数据管理模式或配置一个高效的数据库管理系统,能够向用户提供影像可视化和快速查询功能,是影像数据管理中需要着重解决的问题。本文通过简介ArcGIS海量影像管理的方法,分析镶嵌数据集影像数据管理模型特点,从而提出高效管理海量影像数据的方法。 相似文献
59.
By using the climatological calculating method for each component of slope surface net radiation proposed by the authors,calculations and analyses are done of the distribution features of slope net radiation in China with emphasis on the discussion of variations of slope net radiation in typical stations and sites with slope direction,slope,latitude and season.The distribution features of net radiation on the north and south slopes are,for the first time,mapped and discussed,revealing the great difference on the national basis,and thus acquiringa new interesting result that the negative-value area of winter net radiation on the north slope(20°)can reach Yunnan and Guizhou Provinces and middle and upper reaches of the Changjiang River. 相似文献
60.
Activity–composition relations for the calculation of partial melting equilibria in metabasic rocks 下载免费PDF全文
E. C. R. Green R. W. White J. F. A. Diener R. Powell T. J. B. Holland R. M. Palin 《Journal of Metamorphic Geology》2016,34(9):845-869
A set of thermodynamic models is presented that, for the first time, allows partial melting equilibria to be calculated for metabasic rocks. The models consist of new activity–composition relations combined with end‐member thermodynamic properties from the Holland & Powell dataset, version 6. They allow for forward modelling in the system NaO–CaO–KO–FeO–MgO–AlO–SiO–HO–TiO–FeO. In particular, new activity–composition relations are presented for silicate melt of broadly trondhjemitic–tonalitic composition, and for augitic clinopyroxene with Si–Al mixing on the tetrahedral sites, while existing activity–composition relations for hornblende are extended to include KO and TiO. Calibration of the activity–composition relations was carried out with the aim of reproducing major experimental phase‐in/phase‐out boundaries that define the amphibolite–granulite transition, across a range of bulk compositions, at ≤13 kbar. 相似文献