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夏季长江中下游流域性极端日降水事件的环流异常特征及其与非极端事件的比较 总被引：7，自引：1，他引：6
利用1979—2008年夏季(6—8月)的NCEP/NCAR再分析逐日资料与中国743测站的逐日降水资料,对长江中下游地区流域性极端降水(99百分位,也称为极端强降水)、85～90百分位、75～80百分位降水事件进行合成分析,比较了不同百分位降水事件的环流异常特征。结果表明:长江中下游地区流域性极端日降水量的99百分位阈值为25 mm/d。各类降水事件在梅雨汛期出现频率较高。1990年代以后的极端日降水事件明显偏多。在各百分位降水事件中,在对流层中、低层,长江中下游地区均受气旋性异常环流控制,但对流层高层异常环流特征明显不同。无论在低层还是高层,极端事件的异常环流比非极端事件的异常环流强。不同百分位降水事件的水汽主要来源亦有所不同。极端降水事件中,由孟加拉湾直接辐散至长江流域的水汽较强,而在非极端降水事件中,则是来自南海地区的水汽明显偏强。非绝热加热率、与-的异常分布在各百分位降水事件中的分布较为一致,但强度随降水强度的减小而明显减小。另外,极端日降水事件与85～90百分位的降水事件在太平洋上都存在着北负南正的海温分布,但极端降水事件相应的海温异常明显偏强。而在75～80百分位降水事件中,海温并未出现明显异常。说明极端日降水事件的形成与较强的局地环流异常、与中纬度和热带西太平洋-南海区域的环流异常直接相关,与太平洋海温异常存在可能的密切联系,而非极端事件则主要与局地性异常环流有关。这些结果有利于人们认识和预测极端日降水事件的发生。 相似文献
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Aliphatic alkanes and polycyclic aromatic hydrocarbons in atmospheric PM10 aerosols from Baoji, China: Implications for coal burning 总被引：1，自引：0，他引：1
Mingjie Xie Gehui Wang Shuyuan Hu Qingyou Han Yajuan Xu Zhongchao Gao 《Atmospheric Research》2009,93(4):840-848
Normal alkanes and PAHs in atmospheric PM10 aerosols collected during 2008 winter and spring in Baoji, a mid-scale inland city of China, were determined on a molecular level. Concentrations of n-alkanes ranged from 232 to 3583 ng/m3 with an average of 1733 ng/m3 in winter and from 124 to 1160 ng/m3 with an average of 449 ng/m3 in spring, while PAHs in the PM10 samples were 594 ± 405 and 128 ± 82 ng/m3 in the two seasons. Molecular compositions showed that CPI (odd/even) values of n-alkanes were close to unity for all the samples especially in winter, and diagnostic ratios of PAHs (e.g., Phe/(Phe + Ant), CPAH/ΣPAHs and IcdP/(IcdP + BghiP)) were found similar to those in coal burning smoke with a strong linear relationship (R2 ≥ 0.85) between PAHs and fossil fuel derived n-alkanes, demonstrating that coal burning is the main source of n-alkanes and PAHs in the city, especially in winter due to house heating. Concentrations of the determined compounds in Baoji are much higher than those in Chinese mega-cities, suggesting that air pollution in small cities in the country is more serious and need more attention. 相似文献
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主要阐述了利用天狼星Sirius Pro无人机为项目施工提供高分辨率、高精度的DOM和DEM影像图、数字地表模型（DSM）,对银西铁路YXZQ-4标段施工中遇到的一些问题提供了更好、更高效的解决途径。 相似文献
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中尺度区域内暴雨落区预报的探讨 总被引：1，自引：0，他引：1
以天气学原理和预报员经验为基础，通过对影响宝鸡地区４５场暴雨天气的分析，探讨了不同尺度系统对暴雨落区的经向分布与纬向分布的影响。由此建立了暴雨落区的预报模型，对中尺度区域内暴雨落区的预报进行了有益的尝试。 相似文献
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复杂地形对西南低涡生成和移动影响的数值试验分析 总被引：1，自引：0，他引：1
为探讨四川盆地周边复杂地形对西南低涡发生发展以及移动的影响,利用NCEP 1°×1°再分析资料和中尺度非静力平衡模式WRF V3.4.1,对2010年7月16日至18日发生在四川盆地的一次西南低涡暴雨过程进行了再现模拟(控制试验)以及降低盆地周边不同地形高度的3组敏感性试验。结果表明,控制试验模拟出的西南低涡位置和强度与实况基本吻合。秦岭、大巴山山脉对西南低涡的形成不具有决定性影响,但对西南低涡的维持和发展具有非常重要的作用;横断山脉、云贵高原对西南低涡的生成位置、强度以及移动路径均很重要;青藏高原大地形对偏东气流的阻挡而产生的绕流有利于西南低涡的生成,对西南低涡的移动也有重要影响。除西南低涡以外,四川盆地周边地形所产生的一些局地小低涡的现象也值得关注。 相似文献
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利用2000-2004年711雷达观测的稳定性层状云降雨回波资料，结合雨滴谱和地面雨量自记资料，使用统计方法，分析了引起稳定性层状云降雨量大小改变的因子，得出稳定性层状云降雨量大小除与雷达回波强度关系最为密切外，还和云顶高度、暖云厚度等因素有关，分析了产生误差的原因，建立了多元回归方程，为使用雷达回波对降雨量的估算提供了一种方法。 相似文献
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《Atmospheric Research》2007,83(3-4):663-679
The objective of this study was to investigate the correlation of visibility with chemical composition of Kaohsiung aerosols. Daytime visibility was observed around noon at two observation sites in metropolitan Kaohsiung, Taiwan in the years of 1999 and 2000. Both seasonal and diurnal variation patterns of visibility were observed in the region. Ambient aerosols were sampled and analyzed for 11 constituents, including water-soluble ionic species (Cl−, NO3−, SO4−2, NH4+, K+, Na+, Ca+2, and Mg+2) and carbonaceous contents (OC, EC, and TC), to characterize the chemical composition of Kaohsiung aerosols. Furthermore, a stepwise multiple linear regression model was developed to elucidate the influence of aerosol species on visibility impairments. The results showed that sulfate was the dominant species that affected both light scattering coefficient and visibility. On average, the percentage contributions of visibility degrading species to light scattering coefficient were 29% for sulfate, 28% for nitrate, 22% for total carbon, and 21% for PM2.5-remainder. An empirical regression model of visibility based on sulfate, nitrate, and relative humidity was also developed. The model showed that sulfate in PM2.5 was the most sensitive species to visibility variation, suggesting that the reduction of sulfate in PM2.5 could effectively improve the visibility of metropolitan Kaohsiung. During the investigation period, an event of Asian dusts intruded metropolitan Kaohsiung and dramatically increased the aerosol loadings, especially in the coarse particles. However, local visual air quality did not degrade accordingly during the Asian dust event because both visibility and light scattering coefficient are affected mainly by the fine particles. The results are discussed in detail in the paper. 相似文献
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