Trend, driving factors, and temperature-humidity relationship of the extreme compound hot and humid events in South China

With global warming and frequent occurrence of extreme hot events, the accompanying heat stress, which is believed to be the combined effects of temperature and humidity on human health, is also expected to increase. The temperature and precipitation both increased recently, which indicates a high incidence of extreme compound hot and humid events (CHHEs) in South China, while its trend and mechanism still need further research. Through the comparison of three types of extreme events (extreme hot events (HOEs), extreme humid events (HUEs), and extreme compound hot and humid events (CHHEs)), this study revealed the spatiotemporal characteristics, driving factors, and temperature-humidity relationships of CHHEs in South China. What's more, the temperature-humidity relationships of CHHEs with different dominant types and intensities were further explored. The research results are as follows: (1) HOEs and CHHEs significantly increased, while HUEs decreased, which is consistent with the trend of temperature and relative humidity. (2) The driving factors of HOEs were opposite to those of HUEs, and strong net thermal radiation, evaporation, and water vapor transport were favorable meteorological conditions for CHHEs in South China. (3) Most of CHHEs in South China were temperature dominant type, which covered longer duration and higher intensity than humidity dominant and non-dominant types. (4) There was a strong linear relationship between temperature and humidity during CHHEs. And for the same temperature range, the higher the intensity of CHHEs was, the lower the humidity difference would be.