Response of Climatological Normals to Climate Warming in Guangdong, South China

Climatological normals are 30-year averages of meteorological variables and their derived statistics, used as predictors of future climate conditions and climatic backgrounds for certain regions. Decadally updated normals have changed in response to climate warming. Therefore, it is essential to investigate the differences between the new (1991–2020) and old (1981–2010) climatological normals in Guangdong Province. In this study, basic climate warming facts were revealed through temperature analysis based on data from 86 national meteorological observatories. Subsequently, multiple climate indicators derived from daily temperature and precipitation were analyzed. Temperature-derived indicators show that in the new climatic stage, Guangdong Province experienced an increase of 3.9 d in the annual average of high-temperature days and a decrease of 1.1 d in low-temperature days, while cold-wave days decreased by 0.2 d, reflecting climate warming. Precipitation patterns shifted across various temporal scales: annually, seasonally, monthly, during the flood season, and the "Dragon Boat Water" period. Notably, the amount of rainstorms and the number of rainstorm days increased, whereas total rainfall and rainfall days decreased. Furthermore, the rainy season began an average of 5.0 d later in the new normal than in the old. Multi-scale analysis revealed that the temperature differences between the new and old climatological normals were primarily driven by a dominant linear warming trend, whereas precipitation differences were mainly dominated by interannual variability, which explains the insignificant change in annual total precipitation.