多普勒雷达的速度图像特征及其在一次降雪过程中的应用

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王丽荣, 汤达章, 胡志群, 赵瑞金. 多普勒雷达的速度图像特征及其在一次降雪过程中的应用[J]. 应用气象学报, 2006, 17(4): 452-458. 复制到剪切板

Wang Lirong, Tang Dazhang, Hu Zhiqun, Zhao Ruijin. The Doppler Radar Velocity Image Features and Its Application in a Snowfall Process[J]. Journal of Applied Meteorological Science, 2006, 17(4): 452-458 复制到剪切板

多普勒雷达的速度图像特征及其在一次降雪过程中的应用

王丽荣¹, 汤达章², 胡志群², 赵瑞金³

1. 河北省石家庄市气象局, 石家庄 050081;
2. 南京信息工程大学, 南京 210044;
3. 河北省气象局, 石家庄, 050021

2005-05-27 收到, 2006-01-24 收到修改稿.

资助项目: 国家自然科学基金项目 (40475017) 及江苏省科技厅项目 (BS2003054) 共同资助

摘要: 该文首先介绍了大面积降水的多普勒天气雷达径向速度PPI图像识别技术, 包括:①冷暖平流与大尺度辐合辐散运动叠加的图像特征; ②由零线的朝向和正负速度面积、径向速度值的大小判断风向风速辐合辐散的图像特征, 然后介绍了利用EVAD技术由雷达基数据定量计算大气平均散度和平均垂直速度的方法, 最后应用图像识别技术和EVAD方法对石家庄2004年冬季的一次大面积降雪过程进行了详细分析, 发现:此次大面积降雪过程有明显的辐合辐散图像特征, 径向速度值小, 辐合辐散弱, 始终存在暖平流。另外, 降雪强度和散度、垂直速度关系密切:辐合层厚度加大, 辐散抬高, 则降雪加强; 辐合、辐散层高度降低, 则降雪减弱。同时, 由EVAD技术定量计算的散度和相同时刻由径向速度图像产品定性分析的辐合、辐散基本一致。

关键词: 多普勒雷达大面积降水径向速度特征

The Doppler Radar Velocity Image Features and Its Application in a Snowfall Process

Wang Lirong¹, Tang Dazhang², Hu Zhiqun², Zhao Ruijin³

1. Shijiazhuang Meteorological Observatory, Shijiazhuang 050081;
2. Nanjing Institute of Meteorology, Nanjing 210044;
3. Hebei Provincal Meteorological Observatory, Shijiazhuang 050021

Abstract: A Doppler weather radar radial velocity PPI image identifying technique in large-scale rainfall is introduced:① The image characters of the cold (warm) advection combined with large-scale divergence (convergence) are that the bending degree increases on a side while decreases on the other, which forms the zero-speed line differing in bending on both sides of the display center. ② The wind direction-related convergence or divergence features display an bow-like zero-velocity line, thereby the convergence or divergence can be determined. If the bow's ends bending towards the positive (negative) speed area, the negative (positive) area is larger than the positive one (negative), which means pure convergence (divergence). ③ The wind speed-related convergence (divergence) character can be estimated by means of the positive and negative speed areas and measures in a same distance ring. It is convergence if negative velocities are bigger than positive ones, otherwise it is diver-gence. The bigger the different value between positive and negative, the stronger the convergence or divergence. Furthermore, a method is introduced to quantitively calculate the atmospheric average divergence and vertical speed using EVAD technique:① Extract average divergences in each height level from radar base data utilizing Thomas weighted coefficient method. ② In order to diminish the error added up while integrating along height when calculating air vertical speed by continuous equation, divergences are adjusted according to variation method. ③ Adjusted divergences are considered in continuous equation to calculate air vertical speeds. Applying the image identifying and EVAD techniques, a large-area snowfall process is analyzed in detail in Shijiazhuang, Hebei Province, in the winter of 2004, which suggests that there are obvious convergence (divergence) features during the process, radial velocities are small, convergences and divergences are weak and there is always the warm convection. In addition, the snowfall intensity is closely related to the divergence and vertical speeds, snowfall strengthens as soon as the thickness of convergence levels increases and divergence ascends up; otherwise snowfall weakens when the height of convergence and divergence levels descends down. The quantitive divergence calculated by EVAD is corresponded with those quality analyzed by radial speed picture produced in the same time.

Key words: Doppler radar large-area precipitation radial velocity characters

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图 1. 大尺度风向辐合辐散与冷暖平流叠加示意图 (a) 大尺度辐合与暖平流叠加, (b) 大尺度辐合与冷平流叠加, (c) 大尺度辐散与暖平流叠加, (d) 大尺度辐散与冷平流叠加


图 2. 大尺度风速性辐合、辐散示意图 (a) 辐合, (b) 辐散


图 3. 2004年12月21日02:00—23日14:00石家庄每6 h降雪量变化


图 4. 2004年12月21—22日石家庄多普勒雷达2.4°仰角径向速度图像 (单位:m/s, 扫描半径:115 km) (a) 21日03:30, (b) 21日06:03, (c) 21日09:02, (d) 21日22:58, (e) 22日09:30, (f) 22日11:56


图 5. 2004年12月21日13:00—22日13:00平均散度 (单位:10^-5/s) (a) 和平均垂直速度 (单位:10^-2m/s) (b) 时间-高度剖面图


应用气象学报 2006, 17 (4): 452-458	PDF