Comparative Study On The Meridional Transports Of North Pacific Oceanic Current In Climate Models

In this paper, climatology oceanographic data (WOA13 assimilated data and Argo Profiling float data) are used to calculate the absolute geostrophic velocity field in the north Pacific by P-vector method. The absolute geostrophic velocity fields are used to describe and analyze the basic structure of current in the studied ocean. For better understanding structure of the meridional transport, excepting the assimilated data,results come from 8 climate models in CMIP5 are also used to study the meridional transport by different aspects. The main research results are summarized as follows.Sea surface temperature (SST) depicts the dynamic mechanism of oceanic current to a certain degree. In order to get a relatively high accurate SST for the analysis of SST bias from climate models in the north Pacific, a shipboard observations from the 24th China Ocean Mineral Resources Research and Development Association (COMRA)cruise are used to evaluate both the Tropical Rainfall Measuring Mission Microwave Imager (TMI) SST and Operational Sea Surface Temperature and Sea Ice Analysis(OSTIA) SST. The results show that compared to observations, OSTIA SST errors are much lower than TMI SST errors. So in this paper, OSTIA SST are used to validate SST in CMIP5 models. Then we compared SST both from coupled climate models and OSTIA data sets qualitatively.Two sets of absolute geostrophic velocities calculated from WOA13 and Argo(2004-2015) respectively are used to compare with observations of previous scientists.The results show that Argo data describe the mean current structure of north Pacific more accurately than WOA13 data in the depth of above 2000m. So the absolute geostrophic velocities constructed from Argo data are chosen to evaluate Sverdrup transport,which is calculated by ECMWF ORA-S3 sea surface wind,and the results indicate that the Sverdrup balance theory only can be used for a small part of mid-east region of north Pacific. To verify the results further, we also used absolute geostrophic velocities and Sverdrup meridional transport come from 8 climate models in CMIP5,the analytical results show that Sverdrup transport in climate models even have a higher bias than assimilate data.Otherwise, Sverdrup meridional transports are compared with the real meridional transport in the models, we found that most of the models exist a large bias, while a small part of 8 models with low resolution show a small bias. We conclude that the real currents in most of the models with high resolution are influenced not only by linear dynamic process like Sverdrup balance but also nonlinear dynamic process like local eddy, but models with low resolution cannot simulate nonlinear dynamic process, which make the simulated current have lager bias.