Cloud Macro-Physical Characteristics in Beijing Based on Ka Radar Data during 2014-2017

In this paper, Ka band radar data from January 2014 to December 2017 are used to statistically analyze the macro-physical characteristics of cloud in Beijing. The average cloud occurrence frequency during the four years is 36.3%. The maximum monthly averaged cloud occurrence frequency occurs in September, and the minimum is in December. Cloud occurrence frequency has significant daily variation in spring and summer, increasing by up to 15% from 1100 LST to 1700 LST and then decreasing gradually. The mean cloud base height (CBH) is 4.9 km, and cloud top height (CTH) is 7.2 km. The CBH and CTH rise from January gradually, reach the peak in June, and fall to minimum in December. From March to October, high-level clouds (CBH > 5 km) account for 50% of all clouds. Clouds with cloud thickness (CT) < 1 km are the majority in each month; from April to September, clouds with CT > 4 km account for the second-top proportion. Statistics show that single-layer clouds account for 66.7%, double-layers clouds account for 25.2%, and 8.1% are multiple-layers clouds. About 80% of clouds are single-layer in winter. The climatological characteristics, especially the vertical distribution of clouds in Beijing, are characterized numerically based on radar data in high temporal and spatial resolution. Results from this work will further clarify regional cloud climatic characteristics as well as cloud parameterization in climate models.