关键词: 降水结构, 演变特征, 时间尺度, 降水等级, 城市效应, 昆明市

Abstract: To investigate the precipitation structure evolution in plateau mountainous cities during urbanization, exemplified by Kunming City, we employed the Mann-Kendall test and R/S analysis to quantitatively examine the evolving characteristics of various precipitation structures and urbanization impacts. Results revealed the following: (1) Between 1960 and 2017, Kunming City exhibited a decreasing trend in annual precipitation and frequency, albeit an increasing trend in precipitation intensity. Notably, two distinct high-precipitation zones appeared in the main urban area and downwind region of Kunming. (2) Nighttime and daytime precipitation occurrences were comparable, with slightly stronger contributions and intensities observed during nighttime. Heavy nighttime precipitation events exhibited a trend of escalation. Summer and autumn dominated the yearly precipitation, with intensities in these seasons on the rise. As precipitation grades increased, the occurrences decreased exponentially, contribution rates changed quadratically, and intensity increased linearly. The transition from diminishing weak precipitation events to escalating heavy ones characterized the change of precipitation grade structure. (3) Urbanization exerted varying impacts on annual precipitation, frequency, and intensity, with respective R_CU of 10.62%, -0.91%, and 11.32%. Urbanization bolstered annual precipitation and intensity while tempering frequency, primarily through diminished winter precipitation days and light rain days. Urbanization disrupted diverse precipitation structures, concentrating heavy precipitation in summer, autumn, and nighttime, diminishing light events, and markedly intensifying extreme heavy precipitation occurrences.

Key words: precipitation structure, evolution characteristics, time scale, precipitation grades, urbanization effect, Kunming City