Forecasting Ocean Chlorophyll in the Equatorial Pacific

Area of Science:

• Oceanography
• Biogeochemistry
• Climate Science

Background:

• Accurate forecasting of ocean chlorophyll is crucial for understanding marine ecosystems and predicting the impacts of climate events like El Niño.
• The Equatorial Pacific is a key region for global ocean productivity and climate regulation.

Purpose of the Study:

• To assess the skill of a global ocean biogeochemical model in forecasting chlorophyll concentrations in the Equatorial Pacific.
• To evaluate the model's ability to predict the onset of the 2015 El Niño event and its impact on chlorophyll levels.
• To identify uncertainties and areas for improvement in the biogeochemical forecasting system.

Main Methods:

• Utilized a global ocean biogeochemical model coupled with physical oceanic and atmospheric forecasts from NASA.
• Conducted retrospective 9-month hindcasts for chlorophyll concentration from 2012-2015.
• Compared monthly forecasted chlorophyll data with satellite observations from Suomi-National Polar-orbiting Partnership Visible Infrared Imaging Radiometer Suite (S-NPP VIIRS).

Main Results:

• The forecast successfully reproduced the phasing of chlorophyll variability, including the onset of the 2015-2016 El Niño.
• Significant anomaly correlation coefficients (ACC) were found for 1, 8, and 9-month lead times (R=0.33-0.42, p<0.05).
• Root mean square error (RMSE) increased with lead time, indicating reduced accuracy in predicting chlorophyll amplitude, with 3-month lead forecasts being closest to observations.

Conclusions:

• The study demonstrates the potential of the biogeochemical forecasting system for predicting chlorophyll concentrations in the Equatorial Pacific.
• Forecast accuracy, particularly for amplitude, diminishes with longer lead times, highlighting areas for system improvement.
• The system provides a foundation for future applications, such as assessing El Niño's effects on fisheries and ocean resources.