Severe flooding occurred in Thailand during the 2011 summer season, which resulted in more than 800 deaths and affected 13.6 million people. The unprecedented nature of this flood in the Chao Phraya River Basin (CPRB) was examined and compared with historical flood years. Climate diagnostics were conducted to understand the meteorological conditions and climate forcing that lead to the magnitude and duration of this flood. Neither the monsoon rainfall nor the tropical cyclone frequency anomalies alone was sufficient to cause the 2011 flooding event. Instead, a series of abnormal conditions collectively contributed to the intensity of the 2011 flood: anomalously high rainfall in the pre-monsoon season especially during March; record-high soil moisture content thorough the year; elevated sea level height in the Gulf of Thailand which constrained drainage, as well as other water management factors. In the context of climate change, the substantially increased pre-monsoon rainfall in CPRB after 1980 and the continual sea level rise in the river outlet have both played a role. The rainfall increase is associated with a strengthening of the pre-monsoon northeasterly winds that come from East Asia. Attribution analysis using the Coupled Model Intercomparison Project Phase 5 historical experiments pointed to the anthropogenic greenhouse gases as the main external climate forcing leading to the rainfall increase. Together, these findings suggest increasing odds for potential flooding similar to the 2011 flood intensity.
Wednesday, October 28, 2015
Floods and climate change, continued
Just noticed a recent paper: