Impact of El Nino Phenomenon on Drought Characteristic in Thailand Over the Period of 20 Years From 2002 to 2022

Drought, in recent decades, has emerged as one of the most complex hydroclimatic disasters affecting strongly on the economy, environment and resulting in difficult challenges for mankind. In Thailand, it is one of the persistent recurring issues which last from several months to years. Among different pressing factors, the El Nino Southern Oscillation (ENSO) is one which can directly affect drought distribution due to its impact in climatic characteristics such as temperature and precipitation. This study aims at analyzing spatial and temporal variations of drought from 2002 to 2022 and correlating the drought characteristics with ENSO for the whole Thailand by using remote sensing MODIS MOD09GQ and MOD11A1 daily data products and available ENSO index. The severity of drought characteristic is observed and analyzed through the Temperature Vegetation Difference Index (TDVI), calculated from linear regression of Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST), derived from thermal reflectance data. For validation, the study also analyses the correlation between TVDI and Land Surface Water Index (LSWI), measuring the water contained in soil and vegetation, derived by MODIS sensor. From the result, the driest zones are Eastern and Northeastern regions with the percentage of soil under drought condition for the whole country of approximately 43.36%. After 20 years, the percentage of drought level slightly decreases to 30.73% but the country has to suffer the dryer condition in the dry season. Related to water-related surface, the result shows the decrease in LSWI and Precipitation index during the increase in TVDI index, with the negative correlation of R2 value from 0.3732 to 0.6780, and 0.0278 to 0.8207, respectively. The result shows that although suffering decline in drought spatial distribution due to the effect of climatic phenomenon, drought can still strongly affect the water-related surface. As drought continues to challenge the nation, understanding the role of ENSO and its broader implications becomes increasingly critical for effective water resource management, agriculture, disaster preparedness, and well-being of Thai communities.