Search

Extreme precipitation has been reported to occur more frequently, and intensified extreme precipitation can cause considerable socioeconomic losses. Extreme precipitation can be measured by the concentration index (CI) and the precipitation concentration index (PCI). The former indicates the degree to which daily precipitation is unevenly distributed in the time domain, and the latter represents the degree to which monthly precipitation is unevenly distributed throughout the year. In this paper, we analyzed spatiotemporal characteristics of extreme precipitation by using CI and PCI and examined whether links exist between extreme precipitation and urban extent. We found that the spatial patterns of PCI and CI are different over China. The two are consistent in being high in Northeast China and low in Southwest China. However, they differ significantly; Northwest China is where CI is low but PCI is high, which indicates that precipitation is highly concentrated in a few months of the year, but daily precipitation is more evenly distributed during the wet season in Northwest China. The trends of both PCI and annual CI are spatially heterogeneous and are significant at the 90 % confidence level for approximately 20 % of China, and seasonal CI exhibits very different trends. Possible links between precipitation concentration and urbanization are investigated by analyzing the correlation coefficient between CI (PCI) and population density. Precipitation concentration is found positively correlated with urbanization at the 99 % confidence level in the three selected regions. [ABSTRACT FROM AUTHOR]

Using data collected from 22 urban and 65 rural meteorological stations in northwestern China between 1961 and 2009, this paper presents a study concerning the effects of urbanization on air temperature trends. To distinguish among the potential influences that stem from the economic development levels, population scales, and geographic environments of the cities in this region, the 49-year study period was divided into two periods: a period of less economic development, from 1961 to 1978, and a period of greater economic development, from 1979 to 2009. Each of the cities was classified as a megalopolis, large, or medium-small, depending on the population, and each was classified as a plateau, plain, or oasis city, depending on the surrounding geography. The differences in the air temperature trends between cities and the average of their rural counterparts were used to examine the warming effects of urbanization. The results of this study indicate that the magnitude of warming effects due to urbanization depends not only on a city's economic level, but also on the population scale and geographic environment of the city. The urbanization of most cities in northwestern China resulted in considerable negative warming effects during 1961-1978 but evidently positive effects during 1979-2009. The population scale of a city represents a significant factor: a city with a larger population has a stronger warming influence, regardless of whether the effect is negative or positive. Among the three geographic environments of the cities considered, plateaus and plains more significantly enhance warming effects than oases. The urban population trend has a very significant logarithm relationship with the urban temperature effect, but no clear relationships between urban temperature effects and city elevation were detected. The majority of the temperature trends, accounting for more than 60 % of the trends during 1961-2009, can be explained by natural factors, although urbanization has had some obvious effects on temperatures in northwestern China. [ABSTRACT FROM AUTHOR]

Based on homogenized land surface air temperature (SAT) data (derived from China Homogenized Historical Temperature (CHHT) 1.0), the warming trends over Northeast China are detected in this paper, and the impacts of urban heat islands (UHIs) evaluated. Results show that this region is undergoing rapid warming: the trends of annual mean minimum temperature (MMIT), mean temperature (MT), and mean maximum temperature (MMAT) are 0.40 C decade−1, 0.32 C decade−1, and 0.23 C decade−1, respectively. Regional average temperature series built with these networks including and excluding “typical urban stations” are compared for the periods of 1954–2005. Although impacts of UHIs on the absolute annual and seasonal temperature are identified, UHI contributions to the long-term trends are less than 10% of the regional total warming during the period. The large warming trend during the period is due to a regime shift in around 1988, which accounted for about 51% of the regional warming. [ABSTRACT FROM AUTHOR]

Due to rapid economic development, China has experienced one of the greatest rates of change in land use/land cover during the last two decades. This change is mainly urban expansion and cultivated land reduction in urban growth regions, both of which play an important role in regional climate change. In this paper, the variation of the urban heat island (UHI) caused by urbanization has been evaluated with an analysis of land use change in China. First, meteorological observation stations were grouped by different land cover types (dry land, paddy field, forest, grassland, water field, urban, rural inhabitable area, industrial and mineral land, and waste land) throughout China. These stations were subdivided into urban and non-urban classes. Then, a new method was proposed to determine the UHI intensity from the difference between the observed and the interpolated air temperature of urban type weather stations. The results indicate that the trends of UHI intensity in different land use change regions are spatially correlated with regional land use and its change pattern. During 1991–2000, the estimated UHI intensity has increased by 0.11 °C per decade in the spring and has fluctuated in other seasons throughout China resulting from land use change. [ABSTRACT FROM AUTHOR]