Search

Besides the respective importance of the frequency, intensity and diurnal cycle of precipitation, the diurnal cycle of intensity–frequency structure could reveal more physical details about the evolution process of precipitation systems. Here, an objective method to quantitatively depict the diurnal cycle of intensity–frequency structure of precipitation is proposed, and applied to complex terrains of the southeastern Tibetan Plateau (TP) and its surroundings. Results show the diurnal cycle of precipitation over the high terrain has a unimodal night peak, while low terrain with a frequency‐dominated night peak and an intensity‐dominated afternoon peak. Both weak and intense precipitation are more frequent at night than those in the afternoon over unimodal regions compared to bimodal regions. Further analysis reveals different diurnal evolution process of intensity–frequency structure within unimodal and bimodal regions, respectively, which reflects different spatiotemporal traits and evolution process of precipitation. Among unimodal regions, the elevated southeastern TP is featured by the synchronous decrease in both weak and intense precipitation from the night peak to the afternoon minimum. While the decrease of total precipitation in regions with lower terrain is dominated by the decrease of intense precipitation, but with an increase in weak precipitation simultaneously. Regarding bimodal regions, the intense precipitation over southern Hengduan Mountains has a more prominent role in leading the diurnal cycle of precipitation amount, compared with that over the southeastern Yungui Plateau. The proposed method provides a new perspective with more physical details to investigate precipitation characteristics in complex terrains, which could be further used to reasonably evaluate and improve the performance of numerical models. [ABSTRACT FROM AUTHOR]

The atmospheric water cycle over the Hengduan Mountains (HM) is crucial to the local and downstream ecosystem and social economy, while its characteristics and variability have not been thoroughly revealed yet. Based on a bulk method, the atmospheric water cycle over the HM and its difference between wet and dry summers is analysed in this study. Results show that the summer precipitation recycling ratio over the HM is 11.5% in climatology and is significantly and negatively correlated with precipitation there on interannual timescale. In wet summers, the precipitation recycling ratio decreases by 13% compared to dry summers. The origin of water vapour for precipitation over the HM is mainly contributed by the external water vapour transport (local evaporation) in wet (dry) summers. August is found to have the strongest climatological mean precipitation recycling ratio (15.2%) and atmospheric water cycle among 3 months in summer. Also in August, the difference in precipitation recycling ratio between wet and dry summers is largest. In wet summers, although the increase in the external moisture inflow is the largest in June (3.0 × 107 kg·s−1), the increase of precipitation is the largest in August (2.6 × 107 kg·s−1) due to its stronger atmospheric water cycle. Our study promotes the knowledge of the atmospheric water cycle over the HM and provides a new perspective to understand the interannual variations of the precipitation over the HM. [ABSTRACT FROM AUTHOR]