Statistical Characteristics of Cloud Heights over Lanzhou, China from Multiple Years of Micro-Pulse Lidar Observation

The macroscopic characteristics of clouds over Lanzhou, China were investigated using micro-pulse lidar data from September 2005 to November 2011. The results show that the mean of the cloud base height, cloud peak height, cloud top height and cloud thickness during the observation was 4.03 km, 4.81 km, 5.50 km and 1.47 km, respectively; the maximum frequency of the cloud base height, cloud peak height, cloud top height and cloud thickness was 25.7% in the range of 1-2 km, 16.2% in the range of 2-3 km, 14.6% in the range of 2-3 km and 42.2% in the range of 1-2 km, respectively; the maximum frequency of cloud base height was 24.2%, 24.6%, 29.7% and 21.4% in spring, summer, autumn and winter, respectively, all in the range of 1-2 km, and middle clouds occurred most frequently at 41.4%, followed by low clouds (33.7%) and high clouds (24.9%) during the observation period; the maximum frequency of cloud peak height was 15.8% in the range of 3-4 km, 18% in the range of 4-5 km, 20% in the range of 2-3 km in autumn and 18.6% in the range of 5-6 km in winter; the maximum frequency of cloud top height was 14% in the range of 3-4 km in spring, 16% in the range of 4-5 km in summer, 20.1% in the range of 2-3 km in autumn and 17.8% in the range of 7-8 km in winter; the maximum frequency of cloud thickness was 44.9%, 35.6% and 52% in the range of 1-2 km in spring, summer and winter, respectively, while it was 44.9% in the range of 0-1 km in autumn; the cloud thickness was mostly less than 3 km; generally, the thicker of cloud, the less the frequency.