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气象:2024,50(3):291-302
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Ka波段毫米波云雷达对青藏高原东南缘降水回波的分析
王卫民,徐八林,雷勇,舒斌,马芳
(云南省大气探测技术保障中心,昆明 650034; 中国气象局气象探测中心,北京 100081)
Analysis of Precipitation Echoes from Ka-Band Millimeter Wave Cloud Radar on the Southeast Margin of the Tibetan Plateau
WANG Weimin,XU Balin,LEI Yong,SHU Bin,MA Fang
(Yunnan Atmospheric Detection Technology Support Center, Kunming 650034; CMA Meteorological Observation Centre, Beijing 100081)
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投稿时间:2023-04-19    修订日期:2023-02-18
中文摘要: 利用丽江站新建的Ka波段毫米波云雷达获得的高时间分辨率的垂直观测资料,结合同址的地面自动气象站和雨滴谱的分钟数据、常规探空数据和附近C波段天气雷达的强度回波,分析了两次降水过程前后云雷达反射率因子Z、径向速度Vr、速度谱宽Sw的垂直变化规律。分析表明:在发生弱降水时,云雷达Z在垂直方向的变化不明显;但Vr、Sw值在0℃层稍低位置有一个明显的分界层(融化层),粒子通过融化层后Vr、Sw都是快速变大,这个变化主要是粒子的相态由固态变成液态引发的,可以通过Vr、Sw突变值的位置来识别0℃层亮带的高度。从C波段天气雷达回波强度、剖面图及云雷达位置的时间-高度图看,对毛毛雨和小雨的回波,强度和高度差异比较明显,毛毛雨比小雨回波高度低、强度弱,与云雷达相比C波段雷达对高一些的云观测不到,对距离较远的弱降水回波无法观测到;由于相同粒子对不同波长电磁波的散射不一样,造成两种雷达垂直方向观测到的Z变化不同。对比弱降水回波,云雷达在强降水时:Z出现缺口;Vr在0℃层以上有较大的正值(弱降水的Vr都是负值);在0℃层以上Sw变得更大(弱降水时Sw在0℃层以上值较小,在0℃层以下较大)。在强降水时,从C波段雷达回波强度时间-高度图看,垂直方向回波强度变化明显,在同一时刻回波强度由地面向空中的变化是逐渐减小的;不同时间同一高度层强度也有变化,云雷达雨衰缺口时段回波明显强于其他时段。在个例分析中,发生分钟降水量在0.3mm以下强度的降水,云雷达可以观测到完整的云信息;发生分钟降水量在0.5mm以上强度的降水,云雷达会有严重的雨衰,无法观测到完整的云信息。
Abstract:This article analyzes the vertical variation patterns of the echo intensity (Z), radial velocity (Vr), and velocity spectral width (Sw) of the cloud radar before and after two precipitation processes, using high-resolution vertical observation data obtained from the newly built Ka-band millimeter wave cloud radar at Lijiang Station, combined with minutely data from ground automatic weather stations and raindrop spectra at the same site, conventional sounding data, and intensity echoes from nearby C-band weather radar. Analysis shows that during weak precipitation, the vertical variation of cloud radar Z is not significant, but there is a clear boundary layer (melting layer) at a slightly lower position of the 0℃ layer for Vr and Sw values. After particles pass through the melting layer, Vr and Sw rapidly increase. This change is mainly caused by the phase state of particles changing from solid to liquid. The height of the bright band in the 0℃ layer can be identified by the position of the sudden changes in Vr and Sw values.From the time-height maps of C-band weather radar echo intensity, profile, and cloud radar position, we can see a significant difference in intensity and height between the echoes of drizzle and light rain. The height of the echoes of drizzle is lower and weaker than that of light rain. Compared to cloud radar, C-band radar cannot observe higher clouds and weak precipitation echoes at longer distances. Due to the different scattering of electromagnetic waves of different wavelengths by the same particle, the Z changes observed in the vertical direction by the two radars are different. Compared with weak precipitation echoes, during strong precipitation cloud radar shows a gap in Z, Vr has a significant positive value above the 0℃ layer (Vr for weak precipitation is negative), and Sw becomes larger above the 0℃ layer (during weak precipitation, Sw values are smaller above the 0℃ layer and larger below the 0℃ layer). During heavy rainfall, from the C-band radar echo intensity time-height map, the vertical direction echo intensity changes significantly, and at the same time, the variation of echo intensity from ground to air gradually decreases. The intensity of the same altitude layer also varies at different times, and the echo during the rain attenuation gap period of cloud radar is significantly stronger than that in other periods. The case study shows that if precipitation occurs with an intensity of less than 0.3 mm per minute, cloud radar can observe complete cloud information; if precipitation with a minimum rainfall intensity of 0.5 mm or more occurs, cloud radar will experience severe rain attenuation and cannot observe complete cloud information
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基金项目:国家自然科学基金项目(42075013、41765003)、云南省重点研发计划-社会发展专项(202203AC10006)、中国气象局烤烟气象服务中心开放研究基金(KYZX2022-07)和中国气象局大气探测重点实验室课题共同资助
引用文本:
王卫民,徐八林,雷勇,舒斌,马芳,2024.Ka波段毫米波云雷达对青藏高原东南缘降水回波的分析[J].气象,50(3):291-302.
WANG Weimin,XU Balin,LEI Yong,SHU Bin,MA Fang,2024.Analysis of Precipitation Echoes from Ka-Band Millimeter Wave Cloud Radar on the Southeast Margin of the Tibetan Plateau[J].Meteor Mon,50(3):291-302.