摘要
S波段天气雷达在夜间往往能探测到大量晴空回波。根据生物随风迁飞迁徙的定向运动特征,结合L波段无线电探空数据与2018年3—10月北京S波段天气雷达数据,分析晴空回波在不同时段、不同风向下的变化,讨论晴空回波产生原因。通过天气雷达数据发现,晴空回波的反射率因子在6—8月初明显小于5月与9月,呈回波强度低谷,同时在5月与9月晴空回波高度可达2 km以上。通过与100 m,750 m和1.5 km高度的探空风向数据对比,反射率因子平均值未展现生物定向迁飞活动所导致的强度变化特征,反射率因子分布不随风向发生明显的季节性变化。与探空数据对比发现,温度垂直递减率与水平风切变大小的变化趋势与组合反射率因子变化趋势一致,认为北京地区晴空回波主要由大气边界层湍流造成。
S-band weather radar can often detect a large number of clear air echoes at night.However,there are different views on the mechanism of clear air echoes.According to characteristics of biological migration,combined with L-band radiosonde data and Beijing S-band weather radar data from 1 March to 18 October in 2018,changes of clear air echo reflectivity factor in different seasons and wind directions are analyzed to discuss causes of clear air echo.Firstly,characteristics of time variation of clear air echo are analyzed.The intensity of clear air echo in Beijing increases after sunset,weakens before sunrise,and changes little at night.The intensity of echo gradually increases from March to the middle of May,then weakens from July to the first ten days in August,and maintains at a high level since September.In vertical profiles,the fluctuation of high-level echoes,up to the altitude of 2 kilometers,is larger than that of low-level echoes,with an obviously seasonal variation.Secondly,by comparing the relationship between the wind direction and radar data in different periods of time,it is found that the echo is not consistent with the biological activity regularity.The entropy of radar data gray level co-occurrence matrix is also calculated,and there is no rule to follow the biology.Therefore,it is considered that the turbulence is the dominant cause of night clear air echo in Beijing.And then,radiosonde data show that the temperature lapse rate and wind shear are consistent with the seasonal variation of combined reflectivity factor at the altitude from 1 to 2 km.Finally,possible influence factors of clear air echo are inferred based on some phenomena observed.
作者
滕玉鹏
陈洪滨
马舒庆
李思腾
吴东丽
周燕
Teng Yupeng;Chen Hongbin;Ma Shuqing;Li Siteng;Wu Dongli;Zhou Yan(Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029;University of Chinese Academy of Sciences,Beijing 100049;CMA Meteorological Observation Center,Beijing 100081;Institute of Urban Meteorology,CMA,Beijing 100089;Institute of Plant Protection,Chinese Academy of Agricultural Sciences,Beijing 100193)
出处
《应用气象学报》
CSCD
北大核心
2020年第5期595-607,共13页
Journal of Applied Meteorological Science
基金
国家自然科学基金国家重大科研仪器研制(部委推荐)项目(31727901)。
关键词
S波段天气雷达
晴空回波
湍流散射
生物迁飞
S-band weather radar
clear air echo
turbulence scattering
biological migration
