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101.
Comparison of surface variables from ERA and NCEP reanalysis with station data over eastern China 总被引:1,自引:1,他引:1
Zhaofei Liu Zongxue Xu Zhijun Yao Heqing Huang 《Theoretical and Applied Climatology》2012,107(3-4):611-621
This study compared precipitation, mean air temperature (MAT) and mean sea level pressure (MSLP) from two widely used reanalysis datasets (ERA-40 and NCEP) with those from observed stations across eastern China. The evaluation was based on a comparison of both temporal and spatial variability and included several assessment criteria such as the mean values, normalized root mean square error, Mann–Kendall test, empirical orthogonal functions (EOFs) and probability density functions. The results showed that both the ERA-40 and NCEP datasets could capture temporal and spatial variability of the observed precipitation, MAT and MSLP over eastern China. The results showed that the two reanalysis datasets performed better for MAT and MSLP than for precipitation. Overall, the two reanalysis datasets revealed reasonable agreement with observations according to the evaluation. ERA-40 was better at capturing the temporal and spatial distributions for these three variables than NCEP, especially for MAT and MSLP. NCEP tended to overestimate the annual precipitation for both mean and extreme values, while ERA-40 tended to underestimate it, particularly for extreme values. The two reanalysis datasets performed better in the east and northeast regions of the study area than in other regions for capturing the temporal variability of MAT and MSLP. ERA-40 was poor at capturing the temporal variability of precipitation in northeastern China. According to the trend analysis, the two reanalysis datasets showed lower trends for MAT and precipitation and higher trends for MSLP. Both ERA-40 and NCEP had larger explained variances for the first two EOFs than the observed precipitation. This implies that both reanalysis datasets tend to simulate a more uniform spatial distribution for precipitation in the study area. 相似文献
102.
In mountainous lake areas, lake–land and mountain–valley breezes interact with each other, leading to an "extended lake breeze". These extended lake breezes can regulate and control energy and carbon cycles at different scales. Based on meteorological and turbulent fluxes data from an eddy covariance observation site at Erhai Lake in the Dali Basin,southwest China, characteristics of daytime and nighttime extended lake breezes and their impacts on energy and carbon dioxide exchange in 2015 are investigated. Lake breezes dominate during the daytime while, due to different prevailing circulations at night, there are two types of nighttime breezes. The mountain breeze from the Cangshan Mountain range leads to N1 type nighttime breeze events. When a cyclonic circulation forms and maintains in the southern part of Erhai Lake at night, its northern branch contributes to the formation of N2 type nighttime breeze events. The prevailing wind directions for daytime, N1, and N2 breeze events are southeast, west, and southeast, respectively. Daytime breeze events are more intense than N1 events and weaker than N2 events. During daytime breeze events, the lake breeze decreases the sensible heat flux(Hs) and carbon dioxide flux(FCO_2) and increases the latent heat flux(LE). During N1 breeze events, the mountain breeze decreases Hs and LE and increases FCO_2. For N2 breeze events, the southeast wind from the lake surface increases Hs and LE and decreases suppress carbon dioxide exchange. 相似文献
103.
地温资料的计算机自动审核方法 总被引:1,自引:2,他引:1
地温观测资料的计算机自动审核技术,是地面气象观测资料计算机自动审核中的一个关键性技术难点。综合分析了地温观测资料的特点和地温观测资料的人工审核方法,提出了地温观测资料“相邻差”的标准差分析方法,详细说明了该方法在计算机自动审核中的具体实现步骤和该方法的特点。由于该方法从本质上讲是对人工审核方法的计算模拟,同时由于采用客观计算方法,避免了主观因素,所以审核质量能达到人工审核质量的要求,且比人工审核更全面。该方法在浙江省地面气象资料计算机自动审核软件中进行了试用,实践证明该方法对提高地温观测资料的审核质量具有明显效果。 相似文献
104.
现有的水下地形SAR(Synthetic Aperture Radar)探测模型尚未综合应用SAR的极化信息。本文基于Valenzuela的雷达散射截面表达式与袁业立提出的海波高频谱表达式,并结合全极化SAR相干斑抑制的极化白化滤波法,将极化信息有效地运用到水下地形SAR探测中去。最后,以中国台湾浅滩为例,分别利用Radarsat-2单一极化和全极化影像开展水下地形SAR探测研究,探测结果表明充分利用全极化信息的探测精度明显优于单一极化信息的探测精度,利用极化信息可以有效地提高水下地形SAR探测精度。 相似文献
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本文对表格文件转换工作机理进行了分析,阐述了表格线条和表格文字的转换过程,提高了在AutoCAD中文字标注的灵活性. 相似文献
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The 2nd Member of Kongdian Formation has been made up of a large number of oil shale and mudstone in the Kongnan aera of Huanghua depression around the Bohai Bay. In the Kongnan area, the lake basins were very large and deep during the deposition of the 2nd Member of Kongdian Formation. During that period,the lakes were sealed, uncommunieated with the sea water and the paleoclimate was very warm and wet in Kongnan area. Analyzing the content of the trace element and the rare earth element, carbon and oxygen isotope in the disquisition, The authors prove the two views correct. 相似文献