Underestimated Change of Wet-Bulb Temperatures Over East and South China

Abstract

Wet-bulb temperature (TW), which combines dry-bulb temperature and relative humidity (RH), is a key variable for human health and heat stress because in hot environments evaporation is the main process by which bodies cool down. For this study, we use two independent RH data sets: a new homogenized network of daily ground observations in China and the recent ERA5 reanalysis, for which we highlight the need to apply humidity correction. Based on these data sets, we show that Chinese wet-bulb temperatures since 1980 have increased largely due to a rise in dry-bulb temperatures while RH has remained approximately constant. We also find that TW change has been previously underestimated due to humidity bias in reanalysis and nonhomogenized observation where RH was decreasing sharply after 2000s, greatly limiting changes in TW.