Chinese Journal of Agrometeorology ›› 2025, Vol. 46 ›› Issue (10): 1414-1424.doi: 10.3969/j.issn.1000-6362.2025.10.004

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Impact of Underlying Surface Difference on Convective Precipitation over Beijing in Summer

WANG Yuan-yuan, ZHANG Yi-zhou, HAN Rui, YANG Yang, GUO Xiao-ran, QIU Yu-lu   

  1. 1. Meteorological Service Center for the Core Areas of the Capital, Beijing 100089, China; 2. Institute of Urban Meteorology, China Meteorological Administration, Beijing 100089; 3. Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081; 4. Heavy Rain and Drought-Flood Disasters in Plateau and Basin Key Laboratory of Sichuan Province, Chengdu 610072; 5.Beijing Weather Forecast Center, Beijing 100089
  • Received:2024-11-21 Online:2025-10-20 Published:2025-10-16

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Abstract:

In order to study the impact of the underlying surface on convective precipitation in Beijing and improve the convective precipitation prediction ability, simulations from RMAPS−Urban model and observations from the Beijing station were used to study a specific case that occurred on August 16, 2021. The simulation results showed that the RMAPS−Urban model was able to well model the temporal and spatial distribution of precipitation, with the heavy precipitation area located in the western part of the city and the main precipitation period occurring around 22:00 on 16th. In the early period of heavy precipitation, the urban heat island (UHI) was obvious in the urban area of Beijing, with UHI arriving 1.0−2.0℃. When the urban underlying surface was replaced by crop, the UHI was weakened below 1.0℃, the extreme precipitation decreased from 117.1mm to 56.6mm, and the rainstorm area in the western part of the urban area disappeared. Those indicated that the occurrence and development of convective precipitation was closely related to the urban underlying surface. Moreover, the sensible heat flux over the urban underlying surface was significantly higher than that over the surrounding regions, up to 100W·m−2, which enhanced the convergence over the urban areas and provided the uplift for the formation of the convection. In addition, the perturbations in the potential temperature of the lower atmosphere (below 600m) were also enhanced by the urban underlying surfaces, offering unstable stratification conditions. Finally, larger roughness over the urban underlying surface caused more precipitation in the windward side of the city of the low level surface for the lower water vapor and energy can be transported up with the intensity of the convergence reaching −30×10−4·s−1 and the rainwater mixing ratio exceeding 3g·kg−1, which was more favorable for the occurrence of convective precipitation. 

Key words: Urban underlying surface, Crop underlying surface, Convective precipitation, Urban heat island, Surface roughness