Abstract
Continuous and accurate ceilometer measurements can provide the sky-condition such as cloud base height (CBH), cloud vertical structure (CVS), and cloud cover at around the sites of meteorological stations. In this study, ceilometer measurement data over a period of 3 years (January 2017 to December 2019) were analyzed to compare the characteristics of CBH at inland and coastal stations sharing the same climate characteristics in Korea. The annual averaged frequency of cloud occurrence between 0 and 7750 m at the first CBH is similar in both inland (41.8 ± 10.2%) and coastal (40.3 ± 9.5%) areas. However, there are differences in monthly and seasonal trends. The maximum cloud occurrence appears in summer (winter) of 64.3% (60.1%) in inland (coastal) areas, while the minimum of 25.6% (21.9%) shows in transient seasons of spring and autumn. In winter, the cold surge of northwest wind tends to increase the cloud occurrence from the ocean at coastal rather than in the inland area. It is shown that monthly cloud occurrence in each station is closely related to its monthly precipitation variation. The CVS frequency calculated from the total number of CBH with 250 m vertical bins shows the maximum between 500 to 1500 m (0 to 1000 m) in inland (coastal) areas, indicating more frequent occurrence at a lower height in the coastal area. It is mainly caused by the seasonal variability of the low-level clouds in the coastal region, which occurs two to three times higher in spring and summer than in other seasons. The study implies that long-term measurements of ceilometer would provide a better understanding of the characteristics of cloud behaviors in inland and coastal areas.
Highlights
Clouds are one of the important players in both climate and weather [1,2], but their roles vary depending on regional characteristics [3,4,5]
The cloud occurrence and cloud vertical distribution are analyzed from the measured cloud base height (CBH)
Cloud occurrence is defined as the ratio between the number of at least one detected CBH and the total available observations, i.e., Cloud Occurrence = × 100 [%]
Summary
Clouds are one of the important players in both climate and weather [1,2], but their roles vary depending on regional characteristics [3,4,5]. Another study [28] using ceilometer observations showed the seasonal CBHs variation together with annual cloud occurrence frequency over western India (Ahmedabad, urban area). These existing studies do not address the comparison of cloud occurrence between inland and coastal areas within the same climate characteristics in spite of CBH evaluation in North American regional reanalysis using ceilometers [5]. We try to analyze the CBH and CVS from the ceilometer observations in Seoul (urban inland area, Vaisala’s CL51) and in Taean (rural coastal area, CL31) over the Korean peninsula for a period of three years from 2017 to 2019.
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