Features of the new climate normal 1991–2020 and possible influences on climate monitoring and prediction in China

Abstract

An update on the climate norms each decade is recommended by the World Meteorological Organization (WMO) partly to keep pace with conditions as climate changes over time. In accordance with such update, this study documents the features of the new climate normal defined for 1991–2020 and its impacts on climate monitoring and prediction in China. With on-site observation and model prediction datasets, our analysis reveals that the new normal of national average precipitation of China during winter and summer is respectively 3.0 and 10.8 mm higher than that of the period 1981–2010. As a result, precipitation observations during 1961–2020 consistently fall below the new normal. The adjustment of thresholds for precipitation extremes with new climate normals results in a decrease of extreme precipitation occurrence by 0.2–0.8 d on average over the winter and summer seasons during 1961–2020. Meanwhile, the application of new climate normals induces more pronounced negative temperature anomalies across most areas of China. The adjustments of extreme temperature thresholds have led to an increased occurrence of extremely cold days by 1–2 d on average over 1961–2020, while the frequency of extremely hot days decreases by more than 1.4 d. Furthermore, it is implied that with the development of global warming, the baselines for temperature and precipitation are rising. The application of the new climate normal may result in the omission of relative threshold based extreme events, promoting increased focus on climate risk reduction studies. Additionally, the average anomaly sign consistency rates (Pcs) of precipitation and temperature anomaly predictions, relative to the new normal and produced by the Beijing Climate Center, are consistently lower than those relative to the old normal. This decrease in Pcs implies new challenges for climate prediction, especially for temperature prediction.