Investigating the climatology of North China's urban inland lake based on six years of observations

There are unclear characteristics of the effect of lake breeze in small urban inland lakes due to little research on lake breezes. In this work, six-year observations were performed to study the comprehensive climatologic characteristics of lake breezes on North China's urban inland lake, Lake Hengshui (75 km2). By removing background winds calculated by ERA5 data and successfully recording the lake-land breeze cycle, we devised a succinct and effective approach for distinguishing lake-land breezes. Lake-land breeze had a high annual occurrence frequency of 13.4%-24.7% and a yearly mean lake-breeze speed of 1.6 m/s and yearly mean lake-breeze duration of 4.8 h; spring has the highest frequency and summer has the lowest frequency because of the greater thermal differences between lake and land in spring. The lake breeze mostly started at 06:00-07:00 and 10:00-13:00 (LST), showing a double-peak pattern, and ended at 17:00-19:00 (LST). On the other hand, the land breezes mainly started at 00:00-01:00 (LST) and ended at 05:00-06:00. The distance between each station and the lake has a negative correlation to the frequency and duration of the lake-land breeze, showing the higher frequency and duration at the near stations and the lower frequency and duration at the stations far from the lake. The land breeze has similar spatial characteristics. Winter has relatively lower seasonal average wind speeds of the lake breeze at most stations; spring and winter have high average wind speeds of the land breeze at each station, while summer and autumn have low. The study of the city lake's lake-land breeze will shed new insights into addressing the urban layout.