Observing Changes in Cloud Base Height Using a Ceilometer in Guyuan City

Clouds exert first-order controls on Earth’s radiation budget and hydrological cycle, and cloud-base height (CBH) is a key parameter for climate modeling and aviation applications. Using a ceilometer (measurement range 15 m to 12 000 m) deployed in Guyuan, China (35°29′40″ N, 106°18′31″ E; 1984.2 m a.s.l.), we investigated CBH variability from 2020 to 2023. The cloud occurrence frequency was lowest in winter (62.5%), followed by spring (70.4%), summer (71.2%), and autumn (72.4%). Single-layer clouds dominated all year round (∼50%), whereas multilayer clouds were more frequent in summer. A pronounced diurnal cycle was observed in all seasons: daytime cloud occurrence exceeded nighttime values except in spring, where the difference was small. CBH showed distinct seasonal behavior: daytime CBH was lower than nighttime in all seasons; mean CBH was lowest in autumn with the smallest diurnal amplitude, and highest in spring with the largest amplitude, with daily minima at 14:00 in spring and at 11:00 and 12:00 in winter and summer, respectively. Layered statistical data indicated a persistent multilayer cloud structure over the study region. After classifying clouds by CBH, low-level clouds and mid-level clouds comprised the majority of occurrences. Histograms using 500-m bins revealed that low clouds below 500 m were most common in autumn; over the full year, clouds with CBH < 2000 m occurred far more frequently than those with CBH between 2000 and 6000 m, whereas CBH > 7000 m clouds were rare. In spring, high-level clouds (> 7000 m) exhibited a clear diurnal cycle with a midday minimum. Both spring and winter displayed a bimodal distribution of CBH. These results provided an observational baseline for the Guyuan region and offer actionable information for weather forecasting, climate model evaluation, and photovoltaic nowcasting and operations.