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Decrease in light precipitation (LP) frequency has been reported in many regions. However, reason for the decrease remains poorly understood. Here, we quantify urbanization effect on LP (< 3.0 mm day -1 ) trend in China over the period 1960-2018. We show that urbanization has significantly affected the decreasing LP trend. The urbanization effect becomes more significant as the definition of LP becomes stricter, with the largest effect appearing in trace precipitation change (< 0.3 mm day -1 ) (LP 0.3 ) during summer and autumn. We estimate that at least 25% of the decreases in LP 0.3  days and amount are due to urbanization near the observational stations. Our analysis thus confirms that urbanization has largely contributed to the observed downward trend in LP, and the large-scale change in LP is less than previously believed., (© 2022. The Author(s).)

Increasing of evidence suggests that rapid urbanization modifies precipitation and increases atmospheric instability in urban areas mainly due to urban heat island (UHI)-induced thermal effects and urban building-induced dynamic effects. However, few studies focus on the impact of urbanization on the diurnal variations in urban rainfall in terms of initiating time, frequency, amount, and intensity. Here, six years of hourly data from a relatively dense meteorological observation network in the Wuhan area in central China are used to quantify the issue of urbanization-induced diurnal variations in hourly rainfall and short-duration rainfall (SDR) events by comparing urban and surrounding rural stations during the summer dry period (13 July to 4 August), corresponding to hot weather with little rainfall and high evaporation. The results indicate that: (i) A higher frequency of hourly rainfall appears during night-time and afternoon over urban areas as compared to rural areas. The urban rainfall is more concentrated during the night-time; (ii) More and stronger urban SDR events are triggered during the night-time over urban areas, especially in terms of amount and intensity of rainfall events. A greater diurnal urban–rural difference in SDR events is detected than that in hourly mean rainfall; (iii) There is an enhancement in the night-time and afternoon urban SDR events when UHI intensity increases before they are initiated, and this is detectable in the frequency, amount, and intensity of SDR events. It is also found that the UHI-induced thermal effects are the main reason for the stronger nocturnal SDR events in Wuhan during the summer dry period, which is caused by increases in the convection current and water vapor flux convergence in the urban areas. [ABSTRACT FROM AUTHOR]

Under global warming, projected changes in precipitation have shown an asymmetrical shift from light to heavy precipitation over China. However, the role of urbanization in this shift remains unknown. Here, we show that increases in total rainy‐season (May‐September) precipitation over the Yangtze River Delta (YRD) urban agglomeration of East China are characterized by decreasing light precipitation and increasing heavy precipitation during 1961–2019. This asymmetrical shift toward heavier precipitation is even more prominent in urban than rural areas. Areas with faster urban expansion rates exhibit stronger negative (positive) trends in light (heavy) precipitation. Urbanization contributes to 44.4% (26.4%) of the decreasing (increasing) light (heavy) precipitation in the urban areas of the YRD. We suggest that urban managers should consider potential adverse impacts of this asymmetrical shift, which may favor increases in both the frequency of heatwaves and waterlogging. Plain Language Summary: China has experienced rapid urbanization in recent decades, alongside decreases in light precipitation and increases in heavy precipitation. This shift in precipitation patterns is also observed in the Yangtze River Delta (YRD), a typical densely populated region of China. Over the period 1961–2019, urban areas of the YRD have witnessed intensifying precipitation characterized by sharper decreases in light precipitation as well as sharper increases in heavy precipitation than rural areas. We estimate that 44.4% of the decrease in light precipitation and 26.4% of the increase in heavy precipitation in urbanized areas can be attributed to urbanization. Key Points: Changes in rainy‐season precipitation over the YRD show an asymmetrical shift toward less light and more heavy precipitationThis asymmetrical shift has been amplified by rapid urban expansion in recent decadesUrbanization contributes to 44.4% of the decrease in light precipitation and 26.4% of the increase in heavy precipitation [ABSTRACT FROM AUTHOR]

The anthropogenic‐induced global warming and local urbanization exert important influences on temperature extremes in Eastern China. Here we use China station observations and climate models to investigate their effects on the warm and cold days and nights simultaneously. We quantified the contribution from these two factors based on an optimal fingerprinting method. We find that both anthropogenic and urbanization signals can be clearly detected and separated from each other in the nighttime temperature extremes. The effect of urbanization may explain as much as one third of the observed changes in cold and warm nights while the urbanization signal is weak in the daytime extremes. The results are robust against sampling uncertainty in the estimate of urbanization signal, but uncertainty due to collinearity between the urbanization signal and global warming is difficult to assess. Plain Language Summary: Understanding the causes behind changes in temperature extremes is of significance for reliably projecting future climate change. Previous studies have separately shown that global warming and the urbanization effects are the two important drivers for the increase of warm extremes and decrease of cold extremes in Eastern China. In this study, we consider these two factors simultaneously using an optimal fingerprinting method. We find that climate models can well reproduce the observed changes in extreme temperature when the urbanization effects are included. Both global warming and urbanization have contributed to changes in nighttime temperature extremes, with global warming contributing slightly more. On the other hand, changes in daytime temperature extremes seem to be predominantly due to global warming. Key Points: Global warming and urbanization exert important influences on both warm and cold days and nights in Eastern ChinaBoth anthropogenic and urban signals are detected in nighttime extreme temperatures while only the former is detected in daytime extremesThe effect of urbanization is estimated to have contributed as much as one third of the observed warming in nighttime temperature extremes [ABSTRACT FROM AUTHOR]

Based on a homogenized data set of monthly mean temperature, minimum temperature, and maximum temperature at Shijiazhuang City Meteorological Station (Shijiazhuang station) and four rural meteorological stations selected applying a more sophisticated methodology, we reanalyzed the urbanization effects on annual, seasonal, and monthly mean surface air temperature (SAT) trends for updated time period 1960–2012 at the typical urban station in North China. The results showed that (1) urbanization effects on the long-term trends of annual mean SAT, minimum SAT, and diurnal temperature range (DTR) in the last 53 years reached 0.25, 0.47, and − 0.50 °C/decade, respectively, all statistically significant at the 0.001 confidence level, with the contributions from urbanization effects to the overall long-term trends reaching 67.8, 78.6, and 100%, respectively; (2) the urbanization effects on the trends of seasonal mean SAT, minimum SAT, and DTR were also large and statistically highly significant. Except for November and December, the urbanization effects on monthly mean SAT, minimum SAT, and DTR were also all statistically significant at the 0.05 confidence level; and (3) the annual, seasonal, and monthly mean maximum SAT series at the urban station registered a generally weaker and non-significant urbanization effect. The updated analysis evidenced that our previous work for this same urban station had underestimated the urbanization effect and its contribution to the overall changes in the SAT series. Many similar urban stations were being included in the current national and regional SAT data sets, and the results of this paper further indicated the importance and urgency for paying more attention to the urbanization bias in the monitoring and detection of global and regional SAT change based on the data sets. [ABSTRACT FROM AUTHOR]

The spatial and temporal pattern of sub-daily temperature change in mainland China was analysed for the period from 1973 to 2011 using a 3-hourly dataset based on 408 stations. The increase in surface air temperature was more significant by night between 1973 and 1992, with the fastest upward trend around local midnight being about 0.27 °C/decade, while it was more significant by day between 1992 and 2011, with the fastest upward trend being about 0.46 °C/decade in mid-late morning. The season with rapid temperature increase also shifted from winter in 1973-1992 (the largest increase happened near midnight in December, 0.75 °C/decade) to spring in 1992-2011 (the largest increase happened at in the early afternoon in March, 0.82 °C/decade). The change in the spatial distributions of the sub-daily temperature trends shows that Northeast China warmed more significantly in 1973-1992 than elsewhere, but it cooled in 1992-2011, when Southwest China was the new focus of temperature increase whereas it had previously been cooling. A preliminary analysis of the possible causes implies that changes in solar radiation, cloud cover, aerosols and the observational environments near the stations might have contributed to these observed temperature changes. [ABSTRACT FROM AUTHOR]