云是地气系统的重要组成部分， 为深入分析黄土高原地区云特征， 利用2007 -2016年搭载首部云探测雷达云卫星（CloudSat）与云-气溶胶激光雷达和红外探测者观测卫星（The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation， CALIPSO）资料， 选取黄土高原半湿润、 半干旱、 干旱和寒旱四个区域， 对云的宏、 微观物理特征进行了分析。结果表明： （1）黄土高原各区域云出现频率年均值达到了55%以上， 其中， 春、 夏季云出现频率最高， 秋冬两季相对较低； 半湿润区云出现频率高于其他区域， 但其他三个区域云出现频率最高的月份均早于半湿润区。（2）各区域中单层云出现频率最高， 占到总云量的60%以上， 多层云中主要是双层云， 约占总云量的25%。云层高度在不同区域表现为春、 夏季节大于秋、 冬季节， 半湿润区的云层高度在四季均大于其他区域。各区域云几何厚度季节变化不显著， 均在1~4 km之间， 主要以薄云为主， 且78.13%的云几何厚度不超过2 km。（3）各区域的云液态水含量年均值均达到了220.5 mg·m^-3， 约为冰水含量年均值的6.5倍， 主要分布在8.5 km以下的高度层。随着高度的减小， 液态水含量逐渐增多， 其中半湿润区云液态水含量大于其他区域。各区域全年冰水含量占比较小， 主要分布在16.5 km以下的高度层。（4）液滴有效半径在各区域的值主要集中在12~16 μm， 在半干旱区的春季出现了最大值， 约为24 μm； 冰粒子有效半径最大值出现在半湿润区的夏季。液滴数浓度在各区域的值集中在60~80 cm^-3， 均小于冰粒子数浓度平均值， 其峰值出现在各区域的夏季， 冰粒子数浓度的峰值出现在半湿润和半干旱区的春季。该研究结果有助于深入认识黄土高原云的特征， 为区域气候模式对黄土高原地区云特征的模拟提供一定的参考依据。

Clouds play an important role in the Earth-atmosphere system.To deeply analyze the cloud characteristics in the Loess Plateau region （LP）， the macro and micro physical characteristics of clouds were analyzed by using the CloudSat-CALIPSO data from 2007 to 2016 in four regions of the Loess Plateau， namely， semi-humid， semi-arid， arid， and cold arid.The findings indicate that： （1） In the LP， the annual average frequency of clouds exceeds 55%， with the highest frequency in spring and summer， and relatively lower in autumn and winter.The frequency of clouds in semi-humid region is higher than that in other regions.However， the months with the highest frequency of cloud occurrence in the other three regions are earlier than those in the semi-humid region.（2） The frequency of single-layer clouds is the highest in all regions， accounting for over 60% of the total cloud amount， with double-layer clouds being the main type among multi-layer clouds， accounting for about 25% of the total cloud amount.The seasonal variation of cloud height in each region shows that it is greater in spring and summer than in autumn and winter， and that it is greater in semi-humid region than in other regions in all seasons.The seasonal variation of cloud geometric thickness is not significant in all regions， which is between 1 km and 4 km， with mainly thin clouds， and 78.13% of the cloud geometric thickness is less than 2 km.（3） The annual average value of cloud liquid water content in all regions reaches more than 220.5 mg·m^-3， about 6.5 times of the annual average ice water content.It is mainly distributed in the altitude below 8.5 km， and the liquid water content gradually increases as the altitude decreases， in which the cloud liquid water content in the semi-humid region is larger than that in other regions.The ice water content in each region is small throughout the year， mainly distributed in the altitude layer below 16.5 km.（4） The values of the effective radius of liquid droplets in each region are mainly concentrated in the range of 12~16 μm， with a maximum of about 24 μm in the spring in the semi-arid region； the maximum value of the effective radius of ice particles occurs in the summer in the semi-humid region.The values of droplet number concentration in all regions were concentrated at 60~80 cm³， which were smaller than the mean value of ice particle number concentration， with peaks occurring in the summer in all regions， and the peak of ice particle number concentration occurring in the spring in the semi-humid and semi-arid regions.The results of this study can help to understand the cloud characteristics of the Loess Plateau and provide a reference basis for the simulation of cloud characteristics in the Loess Plateau by regional climate models.