西风槽是诱发豫西北雷雨大风和暴雨等强对流天气的一种重要的天气系统。利用常规高空、地面观测和探空资料,对2001-2015年6-9月受西风槽影响在豫西北发生的区域性强对流天气过程的分析发现,由于近地面暖湿空气势力和侵入冷空气的强弱不...西风槽是诱发豫西北雷雨大风和暴雨等强对流天气的一种重要的天气系统。利用常规高空、地面观测和探空资料,对2001-2015年6-9月受西风槽影响在豫西北发生的区域性强对流天气过程的分析发现,由于近地面暖湿空气势力和侵入冷空气的强弱不同,致使天气系统配置差异显著。根据不同天气系统配置,将由西风槽入侵引起的强对流天气过程分为斜压锋生类和低层暖平流强迫抬升类两种。斜压锋生类的显著特征是配合高空槽的移近,影响系统在700 h Pa上有明显的冷槽,在近地面层有明显的锋生和锋面移近,锋面逼近使抬升运动增强是强对流天气启动的重要因素;低层暖平流强迫类的影响系统在700 h Pa上有位势高度槽而无冷槽,槽的南段紧贴或者落后于500 h Pa槽线,呈前倾结构,强的热力不稳定和深层垂直风切变所形成的动力不稳定是引发这类强对流天气的主要因素,地面辐合线、干线触发了强对流天气。二者在物理量场分布上也有着显著的异同:相同之处在于两类强对流天气均有较强的位势不稳定且积累了大量的不稳定能量,两类强对流过程的0℃层均接近或超过5km。不同之处主要有以下几点:1)斜压锋生类中低层湿度更大,湿层更厚。2)低层暖平流强迫类850-500 h Pa的温差均值为27. 7℃,大于斜压锋生类的温差。3)斜压锋生类K指数均值达39. 6℃,低层暖平流强迫类K指数均值为28. 7℃,二者差值高达10. 9℃,而其抬升凝结高度却明显偏低。4)斜压锋生类中低层的垂直风切变较大,而低层暖平流强迫类的对流层高层与近地面间的垂直风切变较大。展开更多
Band-to-band registration accuracy is an important parameter of multispectral data. A novel band-to-band registration approach with high precision is proposed for the multi-spectral images of HJ-1A/B. Firstly, the mai...Band-to-band registration accuracy is an important parameter of multispectral data. A novel band-to-band registration approach with high precision is proposed for the multi-spectral images of HJ-1A/B. Firstly, the main causes resulted in misregistration are analyzed, and a high-order polynomial model is proposed. Secondly, a phase fringe filtering technique is employed to Phase Correlation Method based on Singular Value Decomposition (SVD-PCM) for reducing the noise in phase difference matrix. Then, experiments are carried out to build nonlinear registration models, and images of green band and red band are aligned to blue band with an accuracy of 0.1 pixels, while near infrared band with an accuracy of 0.2 pixels.展开更多
文摘西风槽是诱发豫西北雷雨大风和暴雨等强对流天气的一种重要的天气系统。利用常规高空、地面观测和探空资料,对2001-2015年6-9月受西风槽影响在豫西北发生的区域性强对流天气过程的分析发现,由于近地面暖湿空气势力和侵入冷空气的强弱不同,致使天气系统配置差异显著。根据不同天气系统配置,将由西风槽入侵引起的强对流天气过程分为斜压锋生类和低层暖平流强迫抬升类两种。斜压锋生类的显著特征是配合高空槽的移近,影响系统在700 h Pa上有明显的冷槽,在近地面层有明显的锋生和锋面移近,锋面逼近使抬升运动增强是强对流天气启动的重要因素;低层暖平流强迫类的影响系统在700 h Pa上有位势高度槽而无冷槽,槽的南段紧贴或者落后于500 h Pa槽线,呈前倾结构,强的热力不稳定和深层垂直风切变所形成的动力不稳定是引发这类强对流天气的主要因素,地面辐合线、干线触发了强对流天气。二者在物理量场分布上也有着显著的异同:相同之处在于两类强对流天气均有较强的位势不稳定且积累了大量的不稳定能量,两类强对流过程的0℃层均接近或超过5km。不同之处主要有以下几点:1)斜压锋生类中低层湿度更大,湿层更厚。2)低层暖平流强迫类850-500 h Pa的温差均值为27. 7℃,大于斜压锋生类的温差。3)斜压锋生类K指数均值达39. 6℃,低层暖平流强迫类K指数均值为28. 7℃,二者差值高达10. 9℃,而其抬升凝结高度却明显偏低。4)斜压锋生类中低层的垂直风切变较大,而低层暖平流强迫类的对流层高层与近地面间的垂直风切变较大。
文摘Band-to-band registration accuracy is an important parameter of multispectral data. A novel band-to-band registration approach with high precision is proposed for the multi-spectral images of HJ-1A/B. Firstly, the main causes resulted in misregistration are analyzed, and a high-order polynomial model is proposed. Secondly, a phase fringe filtering technique is employed to Phase Correlation Method based on Singular Value Decomposition (SVD-PCM) for reducing the noise in phase difference matrix. Then, experiments are carried out to build nonlinear registration models, and images of green band and red band are aligned to blue band with an accuracy of 0.1 pixels, while near infrared band with an accuracy of 0.2 pixels.
