Spatiotemporal characteristics and forcing mechanism of precipitation changes in the Nanling Mountains and surrounding regions in South China over the past 60 years

Mountainous precipitation has different characteristics due to differences in climatic or topographical backgrounds. However, the variation characteristics of modern precipitation in the Nanling Mountains, which are located at the front edge of the Asian summer monsoon, remain poorly understood. Based on monthly precipitation data from twenty-two meteorological stations from 1959 to 2019, we analysed the spatiotemporal characteristics of seasonal and annual precipitation and discussed the possible driving mechanisms in the study region. Annual, spring, summer, and winter precipitation increased, while autumn precipitation decreased from 1959 to 2019; these variation trends will continue as inferred from the Hurst index of the R/S analysis. Annual and seasonal precipitation exhibit periods within a scale of 2-8 years, and their mutation times mostly occurred in the 1980s and 2010s. Spatially, the peak centre of precipitation shifted gradually from the south to the north from spring to winter, as it was influenced by variations in the water vapour source. The eastern and northern weather stations with bimodal patterns of monthly precipitation within the year have longer flood seasons than the southern and western stations with unimodal patterns. Due to the loss of water vapour during northwards and upwards migration, significant negative correlations existed between latitude and annual/spring/summer precipitation, as well as between altitude (below 500 m) and annual/spring precipitation. Regional comparisons revealed that mountainous precipitation exhibited significantly decreasing trends with increasing latitude in China. This study further demonstrated the vital roles of the Asian summer monsoon, sunspots, and ENSO forcings in regulating annual precipitation variations in the study region.