Diurnal Variation Characteristics of Heavy Precipitation and Its Causes of Northeast Cold Vortex during the Warm Season

• Published in: Gaoyuan qixiang
• Main Authors: Li REN, Ying LIU
• Format: Article
• Language: Chinese
• Published: Science Press, PR China 2025-08-01
• Subjects: northeast cold vortex （necv）; daily variation; spatial distribution; terrain; heavy precipitation
• Online Access: http://www.gyqx.ac.cn/EN/10.7522/j.issn.1000-0534.2025.00004
• ISSN: 1000-0534

Using the hourly precipitation data of 80 national stations in Heilongjiang Province， the NCEP/ NCAR and the EC-ERA5 reanalysis data， the diurnal variation characteristics of heavy precipitation （hourly precipitation≥5 mm） by Northeast Cold Vortex （NECV） during the warm season （from May to September） from 1981 to 2022 were analyzed.Multiple typical cases at four times a day were selected for synthesis， which was used to eliminate the influence of intensity change caused by the generation and extinction process of a single case system， and analyze the reasons for the diurnal variation characteristics of heavy precipitation.The results showed that： （1） the heavy rainfall in the warm season was concentrated in June to August， and the heavy rainfall occurred mostly in July， and the maximum precipitation was the heaviest in June and August.The high frequency region of heavy precipitation was located in the southeast quadrant of NECV， the lower frequency could be found in the northeast quadrant.（2） The central position and intensity of NECV corresponding to the large-scale heavy precipitation had obvious diurnal variation characteristics： NECV was stronger at night， and its location was north and west.During the day， NECV was weak， and its position was south to east.The large range of heavy rainfall coupled with the high and low air jet stream appeared： the strong rainfall area was located in the upper jet stream core right back or left front side， the lower jet stream front and left front side.The distribution of the high and low air jet showed significant diurnal variation： the strongest in the afternoon and the best dynamic conditions； the upper level jet stream is weakest at night， and the corresponding upper level divergence conditions are weakest.The southerly air vapor transport was the main at night； During the day， the water vapor transport of the southwest air stream was significantly enhanced， and in the afternoon， the water vapor transport of the southwest air stream was mainly.（3） The wide range of heavy precipitation was corresponded to strong cyclonic activities， and there was little difference in the central positions of cyclones among different times.Both the cyclone intensity and the surface dew point temperature had significant diurnal variation characteristics.The high frequency area of heavy precipitation generally appeared in the large pressure gradient area of the cyclone center and its north or east side， corresponding to the larger dew point temperature.（4） The high frequency of heavy precipitation was related to the distribution of local topography.The mesoscale vertical circulation at night played a more prominent role in the magnitude and high frequency distribution of heavy precipitation on the east side of NECV.The cold air at night was more active， the spatial gradient of nighttime precipitation was larger， and the heavy precipitation was more localized and affected by terrain more significantly.The effect of topography on increased precipitation in daytime was not obvious.The amount of water on the leeward slope was generally greater than that on the windward slope.