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

Spatial, Temporal, and Geographical Factors Associated with Stranded Marine Endangered Species in Thailand during 2006–2015

“…Our results showed more clustering in some winters in the Gulf of Thailand than in other seasons, especially in 2013 ( Figure 2 ). In Thailand, monsoons start to have a very high influence in November in the Gulf of Thailand, with possible annual differences in severity [ 27 , 28 ]. This may be an important factor contributing to the higher stranding rates in some years during the study period.…”

A Simple Procedure to Preprocess and Ingest High-Resolution Ocean Color Data into Google Earth Engine

“…This sensor measures spectral radiance at 36 bands with bands 8-16 dedicated to ocean color, phytoplankton, and biogeochemistry (https://modis.gsfc.nasa.gov/about/ specifications.php). It has contributed immensely to studies of marine ecosystems variability and change, to monitoring coastal eutrophication, and in assisting policy making for the protection of our environment [2,[17][18][19]. Although MODIS/Aqua continues to collect valuable data, with its aging, it may reach the end of life at any time.…”