Serious floods, landslides, and debris flows often occur in the Sichuan Basin of China, which is located east of the Tibetan Plateau, south of the Qinling Heights, and north of the Yunnan–Guizhou Plateau, especially after two very violent earthquakes – Wenchuan earthquake with a Richter magnitude scale of 8.0 (2008) and Ya'an earthquake with a Richter magnitude scale of 7.0 (2013).
Fig.1 3D topography of Sichuan (Image by IAP)
Torrential rains could cause floods, landslides, debris flows and other geological hazards, being a great challenge to weather forecasters. And moisture sources, transport paths and uplifting motions are three indispensable conditions for torrential rainfall events.
Thus what are the main moisture sources of torrential rainfall events in the Sichuan Basin of China?
Recently, HUANG Yongjie and CUI Xiaopeng, researchers with the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences, investigated the main moisture sources and transport paths related to the torrential rainfall events in the Sichuan Basin of China, using a Lagrangian particle dispersion model, FLEXPART.
Four study areas were selected in the basin based on the analysis of the torrential rainfall distribution during 2009−2013. Particles that have a great contribution to the torrential rainfall events within the four study areas were traced back for 10 days, and quantitative analysis of the contributions from various moisture sources to the heavy rainfall events was also conducted.
The results showed that a large number of target particles start from the Arabian Sea and the Bay of Bengal, land the Indo-China Peninsula, and finally reach the study areas, being an important moisture transport path for the heavy rainfall events within the four study areas. Another important path is from the neighborhood of the Sichuan Basin. The total moisture supplies from all examined moisture sources within the whole atmospheric layer account for more than 90% of precipitation within the study areas. There are two major moisture sources, the Sichuan Basin and the Bay of Bengal, and the South China Sea could be another important moisture source region for the torrential rains in the northeastern Sichuan basin.
Fig. 2 Schematic diagram of the main moisture sources (pink areas) and transport paths (blue arrows) related to the torrential rainfall events in the Sichuan Basin of China (Image by IAP)
The results are published in Atmospheric Science Letters and Journal of Hydrometeorology.
Huang, Y. J., and X. P. Cui, 2015: Moisture sources of an extreme precipitation event in Sichuan, China, based on the Lagrangian method. Atmospheric Science Letters, 16, 177-183. http://onlinelibrary.wiley.com/doi/10.1002/asl2.562/full.
Huang, Y. J., and X. P. Cui, 2015: Moisture sources of torrential rainfall events in the Sichuan Basin of China during summers of 2009−2013. Journal of Hydrometeorology, doi:10.1175/JHM-D-14-0220.1 http://journals.ametsoc.org/doi/abs/10.1175/JHM-D-14-0220.1.
Huang, Y. J., and X. P. Cui, 2015: Dominant Cloud Microphysical Processes of a Torrential Rainfall Event in Sichuan, China.
Dr. CUI Xiaopeng
52 Sanlihe Rd., Xicheng District,
Beijing, China (100864)