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西安咸阳机场雷暴天气统计分析及其观测方法 被引量:1
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作者 周线娅 胥洁 杨海蓉 《陕西气象》 2014年第3期23-25,共3页
利用西安咸阳机场1997—2012年的地面气象观测资料,对本场近16a雷暴发生情况进行统计分析,结果表明:咸阳机场夏季雷暴最为频繁,高峰期在7—8月,而且持续时间也较长;雷暴发生时间有明显的日变化特点,晚上多于白天,前夜多于后夜;西方、北... 利用西安咸阳机场1997—2012年的地面气象观测资料,对本场近16a雷暴发生情况进行统计分析,结果表明:咸阳机场夏季雷暴最为频繁,高峰期在7—8月,而且持续时间也较长;雷暴发生时间有明显的日变化特点,晚上多于白天,前夜多于后夜;西方、北方、西北方向是机场产生雷暴最多的区域,其余方位的雷暴概率较小。雷暴过境时气温普遍下降,平均气温下降2.1℃,1h气压平均上升约1hPa,风速骤增,小时平均风速的平均值为5.1m/s,日降水量平均为8.1mm。 展开更多
关键词 雷暴天气 地面观测方法 咸阳机场
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Combining Spectral with Texture Features into Objectoriented Classification in Mountainous Terrain Using Advanced Land Observing Satellite Image
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作者 LIU En-qin ZHOU Wan-cun +2 位作者 ZHOU Jie-ming SHAO Huai-yong YANG Xin 《Journal of Mountain Science》 SCIE CSCD 2013年第5期768-776,共9页
Most existing classification studies use spectral information and those were adequate for cities or plains. This paper explores classification method suitable for the ALOS (Advanced Land Observing Satellite) in moun... Most existing classification studies use spectral information and those were adequate for cities or plains. This paper explores classification method suitable for the ALOS (Advanced Land Observing Satellite) in mountainous terrain. Mountainous terrain mapping using ALOS image faces numerous challenges. These include spectral confusion with other land cover features, topographic effects on spectral signatures (such as shadow). At first, topographic radiometric correction was carried out to remove the illumination effects of topography. In addition to spectral features, texture features were used to assist classification in this paper. And texture features extracted based on GLCM (Gray Level Co- occurrence Matrix) were not only used for segmentation, but also used for building rules. The performance of the method was evaluated and compared with Maximum Likelihood Classification (MLC). Results showed that the object-oriented method integrating spectral and texture features has achieved overall accuracy of 85.73% with a kappa coefficient of 0.824, which is 13.48% and o.145 respectively higher than that got by MLC method. It indicated that texture features can significantly improve overall accuracy, kappa coefficient, and the classification precision of existing spectrum confusion features. Object-oriented method Integrating spectral and texture features is suitable for land use extraction of ALOS image in mountainous terrain. 展开更多
关键词 Texture features Object-orientedclassification Land use MOUNTAIN ALOS
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