A Lagrangian plankton model (LPM) is developed, in which the motion of a large number of Lagrangian particles, representing a parcel of plankton, is calculated under the turbulence field simulated by large-eddy simulation. A spring phytoplankton bloom is realized using the LPM, and the mechanism for its 1 generation is investigated. The criterion based on these results is proposed as (Formula presented.), where δ E (= u ∗/f) is the scale for the Ekman boundary layer, δ S (= (Formula presented.)) is the scale for the depth of a seasonal thermocline, u ∗ is the wind stress, Q 0 is the surface buoyancy flux, f is the Coriolis parameter, and C 1 and C 2 are constants. The critical depth hypothesis can be applied for the onset of a spring bloom, when (Formula presented.), using the mixing layer depth instead of the mixed layer depth, as z c> C 2 δ S, but the critical turbulence hypothesis can be applied, as z c> C 1 δ E, when (Formula presented.). A spring bloom is more likely to occur at higher latitudes, even if the atmospheric forcing is the same. The diurnal variation of Q 0 tends to increase the strength of the spring bloom at small u ∗. Furthermore, various statistics of Lagrangian particles, such as the mixing length of plankton, the residence time of plankton within the euphotic zone, and the growth of plankton clarify the movement and growth of plankton cells.
Bibliographical noteFunding Information:
This work was supported by the Korea Meteorological Administration Research and Development Program under Grant KMI2018‐07210, and by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (NRF‐2018R1A5A1024958). Most of the simulations have been carried out on the supercomputer system supported by the National Center for Meteorological Supercomputer of Korea Meteorological Administration (KMA). We also appreciate the support of Prof. Naoki Hirose, RIAM, Kyushu University, Japan, for providing the sabbatical visit and scientific discussion during this research.
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All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology
- Earth and Planetary Sciences (miscellaneous)
- Space and Planetary Science