Analysis of cloud base height from ceilometer measurements in Seoul of Korea

Although the cloud is one of the important factors in the climate, the Earth's radiation budget and the cloud height's role on energy budget, it is very difficult to determine its contribution to climate change and energy budget. Ceilometer measurements can provide the sky-condition such as cloud base height (CBH), cloud vertical structure (CVS) and so on. The CBH derived from the ceilometer CL51 has been analyzed at two urban stations in Seoul during a period of 2 years from January 2014 to December 2015. The datasets including an analysis of the frequency distributions of CBH and CVS are compared with measurements at Seoul station provided by Korea Meteorological Administration (KMA). The averaged frequency of cloud occurrence throughout the ceilometer CL51 reveals the 54% for the whole analyzed period in Seoul, Korean peninsula. The maximum of cloud occurrence reveals in summer of around 70% and the minimum of around 32% shows in spring and autumn both 2014 and 2015. For the CVS, the frequency of vertical distribution has been calculated the total number of CBH with 500 m vertical intervals from surface to 13000 m. There is estimated the 66%, 28% and 6.8% of the total CBHs at first, second, and third layer for the whole period, respectively. Low clouds below 2000 m by the ceilometer CL51 represent the 57% and the 63% at all CBH aggregated and single-layered CBH, respectively. All histograms have the maximum for the bin between 1000 and 1500 m and they show gradually decreasing frequencies up to the maximum level. The results suggest that statistical analysis of CBH and CVS characteristics by the ceilometer can be provided a better information about cloud in urban area.