Analysis of cloud macro-physical characteristics in Xiangyang of Hubei Province based on ceilometer data

In this study, the cloud macro-physical characteristics in Xiangyang of Hubei Province are statistically analyzed from the aspects of cloud occurrence frequency, number of cloud layers, and cloud base height by using the observation data of ceilometer from 2019 to 2021. The results are as follows. (1) The cloud coverage in Xiangyang is relatively high throughout the year, with an average cloud occurrence frequency of 61.3% in the three years. The frequency of cloud occurrence shows a seasonal variation of higher in summer but lower in winter, and a diurnal variation of higher level during nighttime but lower during daytime. (2) The cloud layer is dominated by single-layer clouds (78.3%), especially in winter (80.1%). In the multi-layer cloud system, two-layer clouds account for the largest proportion (18.5%). The occurrence frequency of multi-layer clouds decreases with the increase in the number of cloud layers, and it is usually high in summer but low in winter, which is mainly related to the relatively sufficient water vapor in summer and the strong convection caused by high temperatures. (3) For clouds with a cloud base height below 1.0 km, the occurrence frequency is 26% in January and 40% in July, indicating that the cloud distribution is relatively dispersed in January but relatively concentrated in July. However, for clouds with a cloud base height between 1.0 and 3.5 km, the occurrence frequency is 57% in January and 24% in July, that is, the cloud distribution is relatively concentrated in January, while relatively dispersed in July. (4) Convective precipitation clouds mainly occur from June to August, accounting for 83.3% of all convective precipitation clouds, and the probability of convective precipitation around the evening is the highest. In terms of cloud base height distribution, the average cloud base height of convective precipitation clouds is lower than that of all precipitation clouds, with a large occurrence frequency of low clouds.