Performance of offline passive tracer advection in the Regional Ocean Modeling System (ROMS; v3.6, revision 904)

Abstract. Offline advection schemes allow for low-computational-cost simulations using existing model output. This study presents the approach and assessment passive offline tracer within Regional Ocean Modeling System (ROMS). An advantage of running code ROMS itself is consistency in numerics on- offline. We find that robust: after about 14 d simulation (almost 60 units time normalized by timescale), skill score comparing output to online TS_U3HADVECTION TS_C4VADVECTION (third-order upstream horizontal fourth-order centered vertical advection) 99.6 % accurate an step 20 times larger than as well saved with a period below timescale. For MPDATA scheme, accuracy more variable forcing input frequency choices, but it still over 99 many reasonable choices. Both are conservative. Important factors maintaining high outputting from often enough resolve timescale, realistic salinity diffusivity values simulation, double precision save results.