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ISSN 1006-9895

CN 11-1768/O4

利用Ka波段云雷达对青藏高原三类重要天气系统云宏观参数日变化特征的观测研究
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中国科学院大气物理研究所

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Diurnal variation of cloud macro parameters in three important weather systems over the Tibetan Plateau using Ka-band Cloud Radar
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Institute of Atmospheric Physics, Chinese Academy of Sciences

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    摘要:

    青藏高原上空云宏观参数的日变化受大尺度环流、当地太阳辐射和地表过程的联合作用,对辐射收支、辐射传输及感热、潜热的分布等有重要影响。由于缺乏持续定量的观测手段,对各类天气系统云宏观参数日变化特征的了解还十分不足。多波段多大气成分主被动综合探测系统APSOS(Atmospheric Profiling Synthetic Observation System)的Ka波段云雷达是首部在青藏高原实现长期观测云的雷达。本文基于2019年全年APSOS的Ka波段云雷达资料,研究了西风槽、切变线和低涡三类重要天气系统影响下的有云频率、单层非降水云或者降水云非降水时段的云顶高度、云底高度和云厚日变化的时域和频域特征,给出了统计回归方程。主要结论有:(1)西风槽系统日均有云频率为56.9%,切变线系统为50.8%,低涡系统达73%;(2)尽管西风槽和切变线系统的成因不同,但两类系统云宏观参数的日变化趋势和主要谐波周期相似:日变化趋势基本为单峰单谷型,日出前最低,日落前最高。有云频率表现为日变化和半日变化,单层云云顶高度、云底高度和云厚主要表现为日变化;(3)低涡系统云宏观参数的日变化特征与前两类系统明显不同:日变化趋势表现为多峰多谷型,虽然有云频率和单层云云顶高度、云底高度主要谐波中均以日变化振幅最大,但频谱分布分散,云厚主要变化中振幅最大的是周期为4.8小时的波动;(4)给出了各系统有云频率、单层云云顶高度、云底高度和云厚日变化的统计回归方程。

    Abstract:

    The diurnal variation of cloud macro parameters over the Tibetan Plateau is affected by the combined effects of large-scale circulation, local solar radiation and surface processes, and has an important influence on the radiation budget, transmission of radiation and the distribution of sensible and latent heat. Due to the lack of continuous quantitative observation means, the understanding of the diurnal variation characteristics of cloud macro parameters in various weather systems is still very insufficient. Ka-band cloud radar of APSOS (Atmospheric Profiling Synthetic Observation System) is the first radar to realize long-term cloud observation in the Tibetan Plateau. In this paper, data of APSOS Ka-band cloud radar in 2019 are used to study the time-domain and frequency-domain diurnal variation characteristics of cloud frequency, single-layer cloud top height, cloud bottom height and cloud thickness under the influence of westerly trough, shear line and vortex system. Main conclusions are as follows: (1) The daily mean cloud frequency is 56.9% for the westerly trough system, 50.8% for the shear line system and 73% for the vortex system; (2) Although the genesis of westerly trough and shear line system is different, the diurnal variation trend and main harmonic period of cloud macro parameters of the two systems are similar: the diurnal variation trend is sinusoidal, the minimum value appears before sunrise and the maximum value appears before sunset. The main harmonics of cloud frequency are diurnal (24 hours) and semidiurnal (12 hours) harmonics, and the diurnal harmonics have the largest amplitude among the main harmonics of cloud top height, cloud bottom height and cloud thickness; (3) The diurnal variation characteristics of cloud macro parameters in vortex system is different from that in the first two systems. The diurnal variation of cloud parameters in the vortex system is multi-peak type. Although the harmonic amplitude of diurnal period is the largest among the main harmonics of cloud frequency, single layer cloud top height and cloud bottom height, the spectrum distribution is discrete, and the maximum harmonic period of cloud thickness amplitude is 4.8 hours; (4) The statistical regression equations of diurnal variation of cloud frequency, single layer cloud top height, cloud bottom height and cloud thickness are given.

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  • 收稿日期:2021-04-12
  • 最后修改日期:2021-06-07
  • 录用日期:2021-06-11
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