Abstract
Citization significantly changes original surface properties. City areas can cause surface winds to decrease; furthermore, ground friction can be transferred layer by layer through the momentum exchange of air movement, which affects the air layers above. Precipitation modification by city environments has been an active research area. Under the conditions of high wind speed, the dynamic effects of cities on precipitation are relatively obvious. Generally, the dynamic effects fall into two main categories: (1) for weather systems under weak forcing synoptic backgrounds, such as local convective systems, shorter-lived extreme precipitation events and fronts and city barrier effects can delay the movement of weather systems, directly change the horizontal distribution characteristics and occurrence time for precipitation, change the flow field and structure, cause the bifurcation of weather systems, and change the horizontal distribution characteristics of precipitation; (2) for weather systems under strong forcing synoptic backgrounds, such as extratropical systems (with large-scale moisture transport), monsoon systems, landfalling tropical cyclones, and supercell storms, the impact of the dynamic effects of cities cannot lead to the bifurcation of the weather system, nor can it change the horizontal distribution characteristics of the whole precipitation field, but it can have an impact on the local precipitation intensity and distribution. However, currently, people do not agree on the impact of cities on precipitation, especially regarding tropical cyclones. Hence, we provide a review and provide insights into the dynamic effects of cities on precipitation.
Highlights
The industrial revolution led to the rapid development of city areas
Citization, which refers to the process of population concentration to city areas and which causes the continuous expansion of city areas, is accompanied by the replacement of natural land surfaces by artificial surfaces that significantly change the original surface properties of the land where the city is located
Investigating the influence of citization on a typical frontal precipitation event that occurred in June 2008 over the greater Beijing metropolitan area (GBMA), Zhong and Yang found that the underlying city surface retards the movement of cold fronts
Summary
The industrial revolution led to the rapid development of city areas. This has continued unremittingly over the last 200 years or so. Studies have revealed that city land cover can have an impact far beyond its physical boundaries, such as storm splitting, the modification of large-scale precipitation patterns, the modification of storm morphology, or the alteration of the spatial location of storm cells due to increased frictional convergence [7,11,16,17,18,19]. The impacts of cities on precipitation involve thermodynamic, dynamic, and chemical effects. Dynamic effects involve increases in surface roughness and enhancements to the drag and lift effects on the airflow This is due to increased city roughness. With the continuous expansion of a city area and with the increase in high-rise buildings, the “precipitation enhancement effect” will be more significant.
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