决策树方法在环境物理量场与暴雨之间关系研究中的应用

An Application of Decision Tree in Studying the Relationship Between Rainstorm and Environmental Physical Field Values

根据香港天文台提供的2001年8月和2002年6-7月业务区域谱模式(ORSM)物理量场预报值,运用空间数据挖掘中的决策树方法研究了空间环境物理量场变化与暴雨中心降雨量之间的关系。结果表明,研究区暴雨中心降雨量的多少与周边相对湿度,海平面高度,温度和经向风速以及这些物理量场所处的纬度位置关系密切,而与这些物理量场所处的经度位置和纬向风速关系较小。

In this project, the operational regional spectral model （ORSM） environmental physical field forecast values, including geopotential height, temperature, relative humidity, meridional wind component and zonal wind component, provided by astronomical observatory of Hong Kong with rainfall data in August, 2001 and June- July, 2002, are used. The data cover an area of 20°-40°N and 90°-130°E at 0.5 degree resolution and six-hour time resolution at the vertical level of 400hPa. Based on the above-mentioned data, decision tree is used to analyze the relationship between the environmental physical field values and rainstorm. The achieved rules show that at the level of 400hPa, within the scope of latitude 28°,when meridional wind component is below 21.8 m/s, the center researched will form a rainstorm. Therefore, the rainfall changes with temperature and the higher the temperature is, the more the rainfall. In the region of latitude below 25.5°, the geopotential height is less than 767.3 gpm, the temperature ranges between 253.3K and 263.8K, and the meridional wind component is less than 21.8m/s, if the latitude of these physical field values becomes lower and the geopotential height larger, the rainfall will increase. When the geopotential height reaches 761.3 gpm, the rainfall will decrease. While in the region of latitude above or equal to 21.5°, when the temperature is below 261.2K, the meridional wind component is less than 21.8 m/s, the greater the relative humidity is, the more the rainfall of the center researched. In a word, the rainfall of the rainstorm center is related greatly to relative humidity, geopotential height, temperature, meridional wind component peripherally and latitude, but is less related to longitude and zonal wind component.