Kim Young Ho

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Young Ho
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  • Article
    Late-1980s regime shift in the formation of the North Pacific subtropical mode water
    (American Geophysical Union, 2020-02-07) Kim, Sang‐Yeob ; Pak, Gyundo ; Lee, Ho Jin ; Kwon, Young-Oh ; Kim, Young Ho
    The formation mechanism as well as its temporal change of the North Pacific subtropical mode water (NPSTMW) is investigated using a 50‐year (1960–2009) ocean general circulation model hindcast. The volume budget analysis suggests that the formation of the NPSTMW is mainly controlled by the air‐sea interaction and ocean dynamics, but there is a regime shift of the relative importance between the two around late‐1980s. While the local air‐sea interaction process is a main driver of the NPSTMW formation prior to late‐1980s, ocean dynamics including the vertical entrainment become dominant since then. The NPSTMW formation is affected by the North Pacific Oscillation simultaneously in the early period, but with a few years lag in the later period. The interdecadal change of the driving mechanism of the interannual variability of the NPSTMW is probably due to the stronger (weaker) influence of local atmospheric forcing in the western North Pacific and unfavorable (favorable) wind stress curl condition for the remote oceanic forcing from the central North Pacific during the former (later) period. This regime shift may be related to the change of centers of the actions of the wind stress curl since the late‐1980s.
  • Preprint
    Comparison between a reanalyzed product by 3-dimensional variational assimilation technique and observations in the Ulleung Basin of the East/Japan Sea
    ( 2009-04-30) Kim, Young Ho ; Chang, Kyung-Il ; Park, Jong Jin ; Park, Seon Ki ; Lee, Sang-Hyun ; Kim, Young-Gyu ; Jung, Kyung Tae ; Kim, Kuh
    Reanalyzed products from a MOM3-based East Sea Regional Ocean Model with a 3- dimentional variational data assimilation module (DA-ESROM), have been compared with the observed hydrographic and current datasets in the Ulleung Basin (UB) of the East/Japan Sea (EJS). Satellite-borne sea surface temperature and sea surface height data, and in-situ temperature profiles have been assimilated into the DA-ESROM. The performance of the DA-ESROM appears to be efficient enough to be used in an operational ocean forecast system. Comparing with the results from Mitchell et al. (2005a), the DA-ESROM fairly well simulates the high variability of the Ulleung Warm Eddy and Dok Cold Eddy as well as the branching of the Tsushima Warm Current in the UB. The overall root-mean-square error between 100m temperature field reproduced by the DA-ESROM and the observed 100-dbar temperature field is 2.1°C, and the spatially averaged grid-to-grid correlation between the two temperature fields is high with a mean value of 0.79 for the intercomparison period. The DA-ESROM reproduces the development of strong southward North Korean Cold Current (NKCC) in summer consistent with the observational results, which is thought to be an improvement of the previous numerical models in the EJS. The reanalyzed products show that the NKCC is about 35 km wide, and flows southward along the Korean coast from spring to summer with maximum monthly mean volume transport of about 0.8 Sv in August-September.
  • Article
    Impact of poleward moisture transport from the North Pacific on the acceleration of sea ice loss in the Arctic since 2002
    (American Meteorological Society, 2017-07-26) Lee, Ho Jin ; Kwon, M. O. ; Yeh, Sang-Wook ; Kwon, Young-Oh ; Park, Wonsun ; Park, Jae Hun ; Kim, Young Ho ; Alexander, Michael A.
    Arctic sea ice area (SIA) during late summer and early fall decreased substantially over the last four decades, and its decline accelerated beginning in the early 2000s. Statistical analyses of observations show that enhanced poleward moisture transport from the North Pacific to the Arctic Ocean contributed to the accelerated SIA decrease during the most recent period. As a consequence, specific humidity in the Arctic Pacific sector significantly increased along with an increase of downward longwave radiation beginning in 2002, which led to a significant acceleration in the decline of SIA in the Arctic Pacific sector. The resulting sea ice loss led to increased evaporation in the Arctic Ocean, resulting in a further increase of the specific humidity in mid-to-late fall, thus acting as a positive feedback to the sea ice loss. The overall set of processes is also found in a long control simulation of a coupled climate model.