| 基于北京多源资料的云宏观特征判识北大核心CSCD |
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| 引用本文： | 周青,李柏,张勇,陶法,胡树贞,李瑞义,杨荣康.基于北京多源资料的云宏观特征判识北大核心CSCD[J].应用气象学报,2023,34(2):206-219. |
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| 作者姓名： | 周青 李柏 张勇 陶法 胡树贞 李瑞义 杨荣康 |
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| 作者单位： | 中国气象局气象探测中心, 北京 100081 |
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| 基金项目： | 国家重点研发计划(2017YFC1501802,2017YFC1501701)； |
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| 摘 要： | 获取准确的云高及其变化特征,对于揭示天气系统的演变以及改进气候模式具有重要作用。由于不同设备观测云高的不确定性,将锋区要素不连续变化理论引入云高分析中,将云底部、云顶部大气的交界过渡带区域视为云锋区,研究探空、毫米波雷达、风廓线雷达等不同类型设备观测要素在云锋区及云外环境大气的变化特征。对流云和层状云个例研究表明:在云锋区,温湿度及雷达反射率因子随高度的一阶、二阶导数均呈不连续现象(即一阶、二阶导数值在云内外和云锋区表现为不相等),风廓线雷达信噪比垂直梯度也出现突变,因此不同设备观测云高具有较好空间一致性,并得到云底和云顶高度的合理范围和相应判据;相对于层状云,对流云内外温度梯度差异以及云体内反射率因子二阶导数的脉动变化幅度均偏大,因此可作为区分二者的参考指标。
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| 关 键 词： | 云锋区 二阶导数 不连续变化 判识方法 |
| 收稿时间： | 2022-08-04 |
Identification on Cloud Macroscopic Physical Characteristics Based upon Multi-source Observations in Beijing |
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| Affiliation: | Meteorological Observation Center, China Meteorological Administration, Beijing 100081 |
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| Abstract: | The knowledge of accurate cloud heights (including cloud base height and cloud top height) information and its variation is of great importance to elucidating synoptic variation and improving climate model and prediction precision. Utilizing the theory of variation continuity and first-order discontinuity of meteorological element in frontal zone, cloud front zone is defined as transitional zone between the cloud cluster and its adjacent area in vertical direction in order to solve the problem of cloud heights uncertainties observed by different equipments. According to the humidity, scattering and turbulence properties of cloud, using observation from L-band sounding, Ka-band millimeter wave cloud radar (MMCR) and the wind profiler, the variation characteristics of temperature, humidity, radar reflectivity and signal noise ratio (SNR) as well as their differences from the ambient atmosphere are studied. In addition, the differences between convective clouds and stratified clouds are studied in terms of the characteristics of element gradient variation inside and outside clouds. Finally, the identification for cloud front zone is verified by case study and the reasonable scope and identification criterion for cloud base height and cloud top height are concluded. The results show that the first-order and second-order derivative of temperature, humidity, and radar reflectivity are discontinuous in cloud front zone (they are not equal inside and outside the cloud front region), and the vertical gradient of SNR retrieved by wind profiler is also instable, which shows that the cloud boundary range with better spatial consistency can be obtained by different devices, based on the frontal theory. In addition, there are two indicators that can be utilized to distinguish the stratiform clouds from convective clouds. The first is the difference between the vertical gradient of temperature and humidity in clouds and that in ambient atmosphere, which is larger in convective clouds than that in stratiform clouds. The second is the fluctuation amplitude of the second-order derivative of reflectivity in clouds, which is also larger in convective clouds than that in stratiform clouds. The concept of cloud front zone can be used to comprehensively identify the common range of cloud height detected by different devices, indicating that there are consistent variation characteristics in a certain area near the cloud front zone for different devices. The similarity of cloud vertical structures retrieved by multi-source equipment observation are elucidated through the characteristics of cloud front zone, which is worth applying for collaborative observation of different devices. |
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