Seasonal Cycles of Phytoplankton Expressed by Sine Equations Using the Daily Climatology from Satellite-Retrieved Chlorophyll-a Concentration (1997–2019) Over Global Ocean

摘要: The global coverage of Chlorophyll-a concentration (Chl-a) has been continuously available from ocean color satellite sensors since September 1997 and the Chl-a data (1997–2019) were used to produce a climatological dataset by averaging values at same locations day year. constructed climatology can remarkably reduce variability clearly exhibit seasonal cycles, demonstrating that growth decay phytoplankton recurs with similarly cycles year after As shapes time series strong periodical change, we wonder whether seasonality be expressed mathematic equation. Our results show sinusoid functions are suitable describe cyclical variations in patterns daily matched sine equations parameters mean, amplitude, phase, frequency. Three types match Mean Relative Differences (MRD) 7.1%, 4.5%, 3.3%, respectively. equation four sinusoids modulate fitted various small MRD (less than 5%) about 90% oceans. reflect an overall pattern which taken as biomass baseline for describing state phytoplankton. amplitude images, spatial phytoplankton, identify transition zone chlorophyll fronts. timing blooms is identified biggest peak classify oceans different bloom seasons, indicating occur all seasons regional features. In within latitude domains (48°N–48°S), occupy approximately half (50.6%) during boreal winter (December–February) northern hemisphere more (58.0%) austral (June–August) southern hemisphere. Therefore, investigate underlying phenological characteristics.