【作者】 曹爱琴；

【导师】 傅云飞；

【作者基本信息】 中国科学技术大学 ， 大气物理学与大气环境， 2010， 硕士

【摘要】 本文利用CloudSat卫星上的云廓线雷达(Cloud Profile Radar,CPR)探测的雷达反射率因子和地表降水率资料,分析研究了2006年6月至2009年5月亚洲地区云顶高度分布特征,并统计研究了亚洲洋面地区云顶高度与地表雨强的关系。研究结果表明,由于受西太平洋副高和大气低层季风气流的影响,亚洲季风区云顶高度和平均地表降水率的季平均分布变化规律有很好的一致性;通过云顶高度概率密度分布可以发现,亚洲洋面云顶高度具有双峰结构:对流层下层3.5km和对流层上层12-16km处,且各季节云顶具有相似的垂直分布规律,其中夏季主要以高云为主,冬季中低云所占比例较多,春秋两季位于两者之间,且降水云顶高度要比非降水云顶高1-2km左右。此外,陆地上云顶高度概率密度分布较为分散。在对亚洲云顶高度水平和垂直分布研究的基础上,我们对云顶高度与地表降水之间的关系进行了研究,并给出了定量关系表达式,发现云顶高度随降水强度的增加而呈指数增长趋势,关系表达式为R=AHb,且当云顶高度大于10km时,降水强度增加较快,即高云对地面降水贡献较大。由于CPR为毫米波雷达,可以同时探测云粒子和小雨粒子,从而可以弥补热带测雨卫星(Tropical Rainfall Measuring Mission,TRMM)上测雨雷达(Precipitation Radar,PR)对弱降水探测的局限性。根据PR降水廓线资料,我们可以定义雨顶高度,而CPR的第一个回波高度为云顶高度,从而利用CloudSat官网提供的2D-CLOUDSAT-TRMM资料,比较2006年8月至2009年2月亚洲地区两部雷达回波信号特点和降水率差异,并统计了亚洲洋面地区雨顶高度、云顶高度及其与地表降水率的关系。研究结果表明,PR对对流型降水(强降水)的反演具有绝对的优势,而由于层云降水为弱降水,两部雷达探测的样本数相当,对于同一降水样本,甚至出现了CPR比PR探测的降水强度大的现象,但当降水强度变大(8mm/h以上),CPR不具有优势。此外,无论是对流降水还是层云降水,云顶高度和雨顶高度都随地表降水增加而单调递增,且满足指数增长规律,其中对于对流降水,云顶和雨顶高度差较小;随着雨强的增加,无论是哪类降水,云顶和雨顶高度愈来愈接近。更多还原

【Abstract】 The horizontal and vertical distribution of Cloud Top Height(CTH) on seasonal scale and the quantitative relationship between CTH and rain rate in ocean of Asia are investigated based on rain rate and radar reflectivity measured by CloudSat Cloud Profiling Radar(CPR) in the Asia from June 2006 to May 2009. Results indicate that a significantly consistent distribution at 1.5 degree horizontal resolution between CTH and rain rate on seasonal scale due to the Western Pacific Subtropical High and Asia monsoon. As found in previous studies, the probability density distribution of the CTH in ocean displays two main peaks: 3.5 lower troposphere and upper troposphere between 12 and 16 km. In each season, Cloud Top Height in ocean has a similar vertical distribution of high clouds mainly in summer and higher proportion of low clouds in winter, and spring and autumn are in between them, however, more dispersed distribution of vertical structure in land Furthermore, In addition, precipitation Cloud Top altitude is higher than non-precipitation about 1-2km. According to the horizontal and vertical distribution of Cloud Top Height, clouds are classified into two categories, namely, the low clouds(CTH<10km)and high clouds (CTH>10km), and no matter what type of Cloud Top Height increases exponentially with surface rainfall rate, which are fit the form R=AHb, the results show that the height of clouds increases rapid as rain intensity increases especially for clouds deeper than 10 km.The high-frequency of CPR is also highly sensitive to the presence of both solid and liquid precipitation, that is to say CloudSat bridges a critical gap between the precipitation measurement of TRMM at low latitudes and the more global precipitation measuring goals of GPM. Therefore, radar echo characteristics, precipitation, Rain Top Height (RTH) and Cloud Top Height observed by PR and CPR are compared in Asia from August 2006 to February 2009 using 2D-CLOUDSAT-TRMM combined data provided by CloudSat official website. It is showed that PR has absolute advantage on the convective heavy of precipitation, otherwise almost the same stratiform-type precipitation samples detected by two radars because of CPR is most applicable to weak precipitation, even the rain intensity of CPR is higher than PR value besides rain rate greater than 8 mm/h. For two kinds of precipitation, the height of cloud from CPR is greater than Rain Top Height retrieved from PR, and both of them are exponentially increased with surface rain rate, and with the increase of rainfall rate, the difference between the two heights become smaller and smaller, but in terms of convective type clouds, the echo top height obtained from PR and CPR are more closer.更多还原