What causes the extremely heavy rainfall in Taiwan during Typhoon Morakot (2009)?

Abstract

Despite its category-2 intensity only, Typhoon (tropical cyclone in the Western Pacific) Morakot produced a record-breaking rainfall in Taiwan. A cloud-resolving model is used to simulate this extreme rainfall event and understand the dynamic aspect under this event. Due to the interaction between Morakot and a monsoon system, a peripheral gale force monsoon surge appears to the south of Taiwan. The monsoon surge remains even in a sensitivity experiment in which Taiwan terrain is reduced. However, the rainfall amount in Taiwan is greatly reduced without high topography over Taiwan, suggesting the important role the local topography plays in producing heavy rainfall. The overall numerical results indicate that it is the interaction among the typhoon, monsoon system, and local terrain that led to this extreme event.

Mesoscale processes for super heavy rainfall of Typhoon Morakot (2009) over Southern Taiwan

“…Ge et al (2010) suggested the critical role of the CMR and the large-scale conditions for Morakot in their numerical experiments. Here, we apply a numerical model (ARW) to identify the mesoscale processes that might explain what we observed in the data analysis.…”

“…1a) with an average terrain height of about 2000 m (Chen and Li, 1995;Lin and Chen, 2002) and a few steep peaks of almost 4 km. It is well known that damages are strongly related to the location of the typhoon's landfall and interactions between its circulation and the CMR (Brand and Blelloch 1974;Wu and Kurihara, 1996;Wu and Kuo, 1999;Lin et al, 2001;Chien et al, 2008;Ge et al, 2010). Previous studies pointed out that enormous amounts of rainfall occur and are enhanced due to mountain lifting when a typhoon passes over the CMR (Wu and Kuo, 1999;Lin et al, 2001Wu et al, 2002;Yang et al, 2008).…”

Mobilization and transport of coarse woody debris to the oceans triggered by an extreme tropical storm

“…htm). Though rated only as a category 3 storm and with lower wind speeds than some other 2009 cyclones, Morakot formed in a monsoon trough and consequently delivered anomalous moisture (Ge et al 2010). The resulting flooding caused significant loss of life and property damage (Ling et al 2009), partly associated with riverbank collapse but largely because of widespread landsliding on steep mountain slopes.…”

Statistical Modelling of Recent Changes in Extreme Rainfall in Taiwan

“…On substitutingμ ,σ and ξ into equations (6)- (7), we 1 We follow the same statistical methods as Nadarajah (2005) have the maximum likelihood estimates of the respective return levels.…”

“…In the past few years, the Kalmaegi and Sonlaku Typhoons in 2008 and Morakot Typhoon in 2009 have brought to Taiwan many casualties and serious injuries. Morakot Typhoon struck Taiwan from 7-9 August 2009 with abundant rainfall, reaching 2,777mm, and surpassing the historical record of Typhoon Herb, which had brought rainfall of 1,736mm ( [1]; [2]). The extremely heavy rainfall triggered severe flooding (the worst in the past 50 years) and enormous mudslides throughout southern Taiwan, leading to around 700 deaths and roughly NT$110 billion in property damage ( [3]).…”