On the Formation Mechanism for Wintertime Extreme Precipitation Events Over the Southeastern Tibetan Plateau. Issue 22 (26th November 2018)

• Record Type: Journal Article
• Authors: Huang, Wenyu; Qiu, Tianpei; Yang, Zifan; Lin, Daiyu; Wright, Jonathon S.; Wang, Bin; He, Xinsheng
• Is Part Of: Journal of geophysical research. Volume 123:Issue 22(2018)
• Page Start: 12, 692
• Page End: 12, 714
• Publication Date: 2018-11-26
• Subjects: extreme precipitation -- southeastern Tibetan Plateau -- formation mechanism -- moisture sources -- circumglobal teleconnection -- cold air intrusion; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2018JD028921
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: The formation mechanism for wintertime extreme precipitation events over the southeastern Tibetan Plateau (SETP) is explored. The crucial step in the development of these events was the emergence of a cyclonic anomaly above the Tibetan Plateau. Wave activity fluxes along a Rossby wave train embedded in the subtropical jet stream (i.e., the circumglobal teleconnection) played the dominant role in producing this cyclonic anomaly, supported by weaker wave activity fluxes along a second Rossby wave train originating over Scandinavia. The cyclonic anomaly then moved over the SETP, favored strong updrafts, large‐scale moisture convergence, and intense precipitation. Extreme precipitation was more likely to ensue when the arrival of the cyclonic anomaly was preceded by persistent warm anomalies over the SETP, which favored moisture accumulation there. Temperatures above the SETP dropped sharply around the onset of the extreme precipitation. A heat budget analysis indicates that adiabatic cooling associated with convective ascent along the downstream edge of the cyclone played a leading role in this temperature drop, while a cold air intrusion associated with an anticyclonic anomaly over western Siberia (one center of action along the second wave train) played a complementary role. An Eulerian moisture budget analysis shows that variations in precipitable water delayed the onset and enhanced the intensity of these events, with moisture for precipitation delivered to the SETP mainly through the western and southern boundaries. A companion Lagrangian moisture source analysis reveals that the land areas south of the Tibetan Plateau typically contributed 78.7% of the moisture supply for these events. Key Points: The circumglobal teleconnection pattern played a key role in the development of extreme precipitation over the southeastern Tibetan Plateau The evolution of precipitable water delayed the timing and increased the intensity of extreme precipitation events Land areas to the south of the Tibetan Plateau contributed 78.7% of the moisture for the extreme precipitation