Seasonal and interannual variations of MODIS Aqua chlorophyll-a (2003–2017) in the Upper Gulf of Thailand influenced by Asian monsoons

Abstract Seasonal and interannual variations of chlorophyll- a (chl- ) in the upper Gulf Thailand (uGoT) were obtained using new regionally tuned algorithms applied to Moderate Resolution Imaging Spectroradiometer-Aqua. This long time-series (2003–2017) data analyzed context environmental conditions associated with Southeast Asian Monsoon. Chl- distribution patterns distinct for non-monsoon (NOM), southwest-monsoon (SWM), northeast-monsoon (NEM) seasons. During SWM/NEM, high/low chl- concentrations precipitation river discharge. NOM generally low, because low precipitation. In general, variability was tightly coupled discharge from Chao Phraya Tha Chin rivers. higher north, but chl -a accumulation east/west uGoT could be linked piling freshwater during SWM/NEM caused by changes wind direction reversal currents. Interannual attributed El Niño-Southern Oscillation (ENSO) rather than Indian Ocean Dipole (IOD) driven precipitation, discharge, patterns. SWM, positive/negative anomalies coincided La Niña/El Niño. NEM, anomaly strong/weak Meanwhile, NOM, positive anomalous high speed