大气科学2011，Vol.35Issue(4)：607-619,13.
用氚的模拟比较被动示踪物平流输送方案
Comparisons of Advection Transport Schemes for Passive Tracers Using the Simulation of Tritium
摘要
Abstract
The centered difference scheme for advection transport may cause unphysically negative values when used in an ocean model to simulate oceanic passive tracers. Selecting positive definite schemes can suppress the generation of negative values. In order to examine the difference of advection schemes, second-order Centered Difference (CD), Flux-Corrected Transport algorithm (FCT), Multidimensional Positive Definite Advection Transport Algorithm (MPDATA), Piecewise Parabolic Method (PPM) and Second-Order Moments advection scheme (SOM) are chosen to simulate the distribution of oceanic tritium, respectively. Two cases are set to compare the differences between these schemes. The physical fields are exactly same for these runs with different advection schemes for tritium in a basinwide ocean general circulation model of the Pacific Ocean. In Case 1 that contains full physical processes, all runs give similar horizontal distributions along isopycnals from the subarctic to tropical regions. However, many negative values arise in the CD run, while for other runs much weaker negative values are generated in some grids. During model years 1968 - 1976, negative values in the CD run gradually become comparable in magnitude to main signals in the subsurface layer of the eastern Tropical Pacific. Those negative noises beneath the depth of maximum tritium concentration within the subsurface layer can disturb the lateral ventilation along isopycnals, leading to much larger subsurface values near 120°W. At 125°W below 200-m depth, negative values also exist, making the CD results meaningless, while the runs with other schemes all give acceptable values. Both FCT and SOM runs show a weaker numerical dissipation in the vertical direction than PPM and MPDATA runs. In Case 2, which does not have physical dissipation, the CD run fails to produce a valid solution, while other runs all succeed in getting nonnegative distributions. The SOM run gives the strongest meridional gradient near the western boundary in the North Pacific, while the PPM run produces the weakest one. In the Antarctic Circumpolar Current region, the results from both PPM and SOM are smooth everywhere, while the results from both FCT and MPDATA have severe fluctuations near the land boundary. By comparisons of these two cases, it can be concluded that the CD shows a poor performance in the simulation of oceanic passive tracers. The PPM and the SOM are much better than the FCT and the MPDATA in numerical stability. The results from the SOM can easily maintain a strong gradient because of its weak numerical dissipatioa However, it seems that the PPM is a better choice for the investigation of the long-term transport process of passive tracers in the ocean when the computational efficiency is taken into account.关键词
海洋环流模式/被动示踪物/氚/平流输送Key words
ocean general circulation model, passive tracer, tritium, advection schemes分类
海洋科学引用本文复制引用
巴琦,徐永福,李阳春..用氚的模拟比较被动示踪物平流输送方案[J].大气科学,2011,35(4):607-619,13.基金项目
中国科学院知识创新工程重要方向项目群KZCX2-YW-218,国家自然科学基金资助项目40730106,公益性行业(气象)科研专项2008416022 （气象）
