Observed spatial pattern of summer extreme precipitation in China and its potential links to rapid urbanization

Abstract

The variation and evolving tendency of extreme precipitation have received extensive concern worldwide in recent years under the background of global warming and rapid urbanization, which hold a great deal of significance for management of the risk of urban flood and waterlogging and water resources. The importance of anthropogenic factors represented by urbanization is recognized in the research of extreme precipitation variation, but its underlying mechanism and potential contribution remain unclear. Hense, the academic circles have not yet achieved consensus on this. Here we use daily precipitation dataset with 544 meteorological stations’ records to study spatial pattern of summer extreme precipitation and its potential response to urbanization from 1961 to 2010 in China. Frist, we gets each station’s threshold of extreme precipitation by using ordinary percentile method and the developed method named spatial sliding percentile. Then we define the proportion of extreme precipitation with total precipitation as the indicator to reflect extreme precipitation intensity. Based on the DMSP/OLS night light index dataset, the urbanization level of 544 meteorological stations are divided into six levels. Then we use ordinary percentile method, spatial sliding percentile and the developed method named spatial sliding anomaly to quantify the possible impact of urbanization on extreme precipitation threshold and intensity by doing a comparative analysis to 544 meteorological stations with different urbanization level. The results show that: The spatial pattern of extreme precipitation intensities derived from spatial sliding percentile is more distinguishable. Effects of urbanization make the threshold increased by 1.68% and there is a significant linear correlation between the average of extreme precipitation intensity and urbanization level, namely the intensity of extreme precipitation will increase by 0.62%, when the urbanization level increases by one grade. Therefore, effects of urbanization increase the risk of summer extreme precipitation of China.

Concentrations, Sources, and Correlation Analysis of Polycyclic Aromatic Hydrocarbons in Atmospheric Particulate Matter and Organic Film from Shanghai, China

“…Impervious surface cover within urban environments alters the hydrology, energy distribution, and non-point source pollution load [14,15]. Research has found that impervious surfaces can develop organic film 11-1000 nm thick and with an organic matter content of 5-40%.…”