Diurnal variation of warm-season precipitation at different altitudes of Changbai Mountain

Based on the hourly precipitation data of the warm season (June-September) at six different altitudes and slopes of the Changbai Mountain from 2015 to 2023,the diurnal variation characteristics of precipitation were analyzed.Results show that the precipitation amount was the highest at the mountaintop,followed by two hillsides,and were higher than those at the bottom station on the same slope.Among the three stations at the bottom of the mountain,the station on the west slope was the highest.The diurnal variations in precipitation amount and frequency at multiple stations exhibited a double peak-valley pattern,with the peaks and sub-peaks occurring in the afternoon to evening and morning,respectively.The precipitation intensities at the two hillsides reached their maximum from afternoon to evening and were higher than those at the mountaintop station.The precipitation amount peaks in the afternoon to evening were mainly caused by the high precipitation frequency in June,and the high precipitation intensity in July,while the morning peak was primarily associated with high precipitation frequency and intensity in August.The difference in precipitation amounts between the mountaintop and the base stations was mainly evident during the early morning hours.In addition,the precipitation amount with a duration of 4-7 hours from morning to afternoon corresponded to a large value area,while precipitation starting in the evening and early morning lasted longer.The precipitation amount at the mountaintop was the highest in both short and medium durations.Among the three bottom stations,the precipitation amounts at the North Slope,West Slope,and South Slope were the most prominent in short duration,medium duration,and long duration,respectively.Short-duration precipitation concentrated in the afternoon to evening and morning had a high frequency.By contrast,the long-duration precipitation amount occupied the largest proportion,which depended on the changes in the position and intensity of the Northeast Cold Vortex,the subtropical high,and tropical cyclones.