Changes in the mean and extreme temperature in the Yangtze River Basin over the past 120 years

Abstract

Much attention has been paid to extreme temperature changes since 1961 because of the absence of data in the early 20th century. Based on the sub-daily meteorological records prior to 1950 and modern daily meteorological records from 1951 to 2020, we established a daily maximum/minimum temperature series that was processed for data quality control, data interpolation, data merging, and homogeneity in 10 cities in the Yangtze River Basin from 1901 to 2020. The anomalies of the annual mean temperature showed a significant upward trend, especially in the last 40 years. Most stations observed a slight decrease before 1961, whereas they experienced a significant increase in the last 60 years. The upward trend of the entire time period in Chongqing and Shanghai was significant in the last 120 years, with the increase in Shanghai being higher than that in Chongqing. The extreme temperature indices also showed significant trends as well as clear periodic variability. The extreme high-temperature indices rapidly increased in the 1930s, decreased until the 1980s, and then increased again. The extreme low temperature indices fluctuated with positive and negative anomalous values, but generally increased prior to the 1970s and then decreased over the last 40 years. The changes in the extreme temperature indices in Chongqing and Shanghai were highly consistent, except for frost days. The upward/downward trend in Shanghai was more significant than that in Chongqing over the last 40 years. The analysis also showed that the observed changes in regional extreme events were due to rapid urbanization and multi decadal variability of East Asian monsoon, in addition to regional and global warming.

Keywords

• Temperature
• Extreme temperature index
• Yangtze River Basin
• Recent 120 years
• Urbanization effect