基于探空云识别方法的云垂直结构分布特征

Characteristics of Cloud Vertical Distribution Based on Cloud Identification by Radiosonde

云的垂直结构特征作为云重要的宏观特征之一,直接决定了云的类型,进而通过发射和吸收辐射的方式影响着地气系统的能量收支平衡,因此对云垂直结构特征的研究一直都是云物理研究的一个重要方向。作为观测云垂直结构特征的一种方式,探空气球通过获取沿路径方向高分辨率的廓线信息,采用一定反演方法从而能够较为准确的识别云的垂直结构。本文即利用我国业务布网探空站的观测资料,采用相对湿度阈值法识别云垂直结构,并同激光云高仪、"风云四号"静止卫星和毫米波云雷达对识别的云结构特征量进行了一致性检验。在此基础上,统计分析了2015~2017年单层、两层和三层云的垂直结构分布特征、日变化和季节变化特征以及全国区域分布特征,结果表明:(1)整体分布上,单层云在垂直方向上出现的高度范围介于多层云的高度范围内,并且随着云层数的增加,云在垂直方向上更为伸展,即高层云越高,低层云越低;(2)在日变化中,中午单层和多层云中最低层云的云底高度均高于早晨,而夜间单层和多层云中最高层云的云顶高度则高于早晨和中午,同时中间层云厚的变化要小于最上层和最下层云厚的变化;(3)在季节变化中,夏季云量较其他季节更多,云体发展也更为深厚,表明温暖的大气条件更有利于云的形成和发展;(4)我国云垂直结构分布特征具有明显的纬向变化趋势,从以青藏高原为中心的西南地区的云底较高云体较薄的云,逐步过渡到以东南沿海地区为中心的云底较低云体较为深厚的云,表明不同地形和气候带的差异与不同云类型的分布直接相关。

As an important feature in the macroscopic characteristics of clouds, the vertical structure characteristics of clouds determine different types of clouds and affect the energy budget balance of the earth’s atmosphere system through absorbing and emitting radiation. Therefore, research about the vertical structure characteristics of clouds is always an important subject of cloud physics. As an instrument for observing the vertical structure characteristics of clouds, a sounding balloon can penetrate clouds to achieve temperature and humidity profiles in high resolution. Based on this information, the vertical structure of the clouds can be precisely identified using some methods. This paper uses the observation data of national operational radiosonde sites to identify the vertical structure of the clouds by the relative humidity threshold method, and tests the cloud boundary by comparing it with the data from the ceilometer and "FengYun-4" satellite. Based on this, the mean vertical distribution of one-, two-, and three-layer clouds is obtained from 2015 to 2017 and analyzed in daily, seasonal, and regional variations. The results indicate that(1) one-layer clouds are generally located at altitudes between the altitudes of the two-and three-layer cloud configurations. With the increase of the number of cloud layers, the uppermost layer becomes higher and the lowest layer becomes lower.(2) In the diurnal variation, the lowest cloud base height of single and multilayer clouds at noon is higher than those in the morning, and the uppermost cloud top height of single and multilayer clouds in the evening is higher than those in the morning and at noon. The variation of the mid layer in multilayer clouds is less than that in the uppermost and lowest layers.(3) In the seasonal variation, there are more clouds that are more vertically developed during summer than other seasons, suggesting that the development of clouds is favorable under warm atmospheric conditions.(4) The regional variation of the vertical cloud distribution in China shows an obvious latitudinal variation trend. Thin clouds with a higher cloud base centered on the Tibetan Plateau in the southwest gradually transform to thick clouds but with a lower cloud base in the coastal area of the southeast. This indicates that different cloud types are directly affected by different geographical conditions and climate zones.