The 2011 Great Flood in Thailand: Climate Diagnostics and Implications from Climate Change

Abstract

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 led 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 premonsoon season, especially during March; record-high soil moisture content throughout the year; elevated sea level height in the Gulf of Thailand, which constrained drainage; and other water management factors. In the context of climate change, the substantially increased premonsoon 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 premonsoon northeasterly winds that come from East Asia. Attribution analysis using phase 5 of the Coupled Model Intercomparison Project historical experiments pointed to anthropogenic greenhouse gases as the main external climate forcing leading to the rainfall increase. Together, these findings suggest increasing odds for potential flooding of similar intensity to that of the 2011 flood.

Interannual variation of springtime biomass burning in Indochina: Regional differences, associated atmospheric dynamical changes, and downwind impacts

“…Based on these results, it is suggested that even though the changes of the India‐Burma Trough do not always follow the SCSA changes (or the ENSO signal changes), monitoring the SCSA changes (or the ENSO signal changes) does aid in the prediction of the interannual variation of biomass burning over northern Indochina and its impact on PM 10 in Taiwan. For instance, weakened SCSA and abnormally low biomass burning in 2011 (Figures a and a) are found consistently with the unusually high 2011 premonsoon rainfall, particularly in March, over northern Thailand [ Promchote et al ., ]. This likely suggests that high precipitation can reduce the burning activities over northern Indochina.…”

Pre-Monsoon Rain and Its Relationship with Monsoon Onset over the Indochina Peninsula

“…We can see that in case of Type A, an anomalous easterly covers the area from the northern South China Sea to the Indochina Peninsula. Promchote et al (2016) analyzed the 2011 great flood in Thailand, and pointed out that the great flood is caused by not only monsoon rain and tropical cyclone frequency but high rainfall during premonsoon. This high rainfall during pre-monsoon is provided by northeasterly from East Asia using anomaly of climatological wind field during the period from January to April.…”

Recent trends in the frequency and duration of global floods

“…An unusual increase in the bacillary dysentery risk in Baise (Guangxi Province, China) during the years 2004 to 2012 is a case in point (see more details in Liu et al, 2017). The recent Thailand floods that occurred in July 2011 and December 2014 also caused severe supply chain disruptions (Ziegler et al, 2012;Haraguchi and Lall, 2015;Promchote et al, 2016).…”