摘要
本文利用营口、沈阳新一代多普勒雷达产品,分析了2004年-2007年3次东北南部强降雪天气过程。研究发现东北南部强降雪天气在基本反射率产品上18dBZ以上回波面积一般大于5000km2,1h降雪量与降雪回波呈正相关。雨雪交界处回波强度有较大梯度。强降雪回波强度一般在30dBZ以下,回波强度在40dBZ以上时,以液态降水粒子或处于融化状态的固态降水粒子为主。根据雷达回波强度及梯度,结合探空和地面温度可以判断降水性质和雨雪分界,具有一定预报意义。强降雪过程开始阶段零速度线较清晰,呈"S"型,为暖平流风场结构;发展成熟阶段暖平流与大尺度辐合风场叠加形成复合风场结构,预示降水回波将达到最强。风廓线产品中低空水汽输送对降水强度的变化有很直观的指示意义。强降雪过程中回波顶高度低,起伏不大,比较平整,面积略小于回波强度产品面积;垂直液态水含量产品对于降雪明显低估,其面积比回波面积小得多。
Hazards of heavy snow have become increasingly serious in recent years in the context global warming, which would result in great loss and damages of natural and social systems. Demands for analysis and warning methods for heavy snow are therefore increasing. There have been a series of studies on the features of Doppler radar products in heavy snow processes in some other countries but little work has been done in China so far. Therefore, there is an urgent need to investigate the features of Doppler radar products in heavy snow processes in China. In the present study, the authors analyzed the features of three major heavy snow events in the south of northeastern China during the period 2004-2007 based on Doppler radar and observation data. Results showed that when the heavy snowfall happens, the area of echo exceeding 18 dBZ is larger than 5, 000 km2, and the echo intensity is less than 20 dBZ in 1 mm of hourly snowfall. The hourly snowfall correlates positively with snow reflectivity. There is a large gradient of reflectivity at the boundary between rainfall and snowfall. When it snows, the reflectivity is usually below 30 dBZ. The reflectivity exceeding 40 dBZ can indicate mainly liquid precipitation particles or melting solid precipitation particles. The state of precipitation and the boundary between rainfall and snowfall can be distinguished in terms of the reflectivity and its gradient, and the air sounding observation and surface temperature, which is of great importance to forecasting. At the beginning of heavy snowfall processes, the zero velocity line is clear, showing an ＂S＂ shape, which can be taken as warm advection characteristics. At the development and mature stages, the combined wind field is formed by compounding the warm advection with large scale convergence, which could be indicative of the strongest echo. Weakened compounding wind corresponds to weakened precipitation echoes. Low-level water vapour transport of wind profile products can directly show changes in precipitation. In heavy snowfall processes, the height of the echo top is low, with slight changes and a relatively even shape. Its area is slightly smaller than the area of base reflectivity. In addition, the vertical liquid water content was found to be significantly underestimated than the snowfall, with an even smaller area compared with base reflectivity. Based on the derived features of the Doppler radar products on heavy snow, the area and intensity of echoes and the structure of wind field can be reasonably established for early warning of heavy snow over the south of northeastern China.
出处
《资源科学》
CSSCI
CSCD
北大核心
2010年第8期1471-1477,共7页
Resources Science
基金
中国气象局气象新技术推广项目:"东北南部强降雪天气的多普勒雷达产品特征"(编号:CMATG2007Y03)
关键词
回波强度
径向速度
东北地区
梯度
Echo intensity
Radial velocity
East-north
Gradient
