Abstract:Due to the influence of surface and other factors, the raindrop size distribution characteristics of rainfall in mountainous and plain areas have significant differences in some cases. Understanding their differences in mountain and plain is useful to deeply learn the microphysical characteristics of rainfall and improve the accuracy of radar quantitative precipitation estimation (QPE) with different underlying surfaces.Based on the raindrop spectrum data from laser optical disdrometer and the rainfall data from automatic weather stations over Beijing during summers of 2017 and 2018, the representative mountain-area Yanqing Station and plain-area Daxing Station were selected. The raindrop size distribution characteristics of convective and stratiform rain types at the two stations were studied by the rain type classification method.〖JP〗 The results show that the contribution of rainfall intensity (R) greater than 5 mm·h-1 with lower frequency to the total rainfall is dramatically larger than that (mountain/plain station is 33%/29%) less than or eaqual to 5 mm·h-1 with higher frequency （both stations are 86%） in the Beijing summer. Further research indicates that convective rain spectra has larger mass-weighted mean diameter Dm, logarithmic generalized intercept parameter lgNw and distribution spectrum width than the stratiform rain spectra. Comparing the two stations, we find the Dm (lgNw) of different rain types at Yanqing Station (mountain station) is larger than (less than) that at Daxing Station (plain station), indicating that the mountain area raindrop size is larger while number concentration is lower. Compared to foreign classical convective spectra, the convective rain spectrum at mountain (plain) area is more inclined to the continental (maritime) convection. Relationships among Dm-R, lgNw-R, μ (shape)-Λ (slope) and Z-R are in accordance with the classical findings, but the fitted parameters are different from those of other areas, which means the variations by different researches. The Z-R fitted relationships between Yanqing and Daxing are Z=764R1.20 and Z=386R1.32, of which the Z-R relationship at Daxing Station is consistent with Z=300R1.40, which represents the summer convective precipitation while the Z-R relationship at Yanqing is distinct from Z=300R1.40, revealing the rainfall difference between mountain and plain.