Simulation of state-dependent high-frequency atmospheric variability associated with ENSO |
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Authors: | Jong-Seong Kug K P Sooraj Daehyun Kim In-Sik Kang Fei-Fei Jin Yukari N Takayabu Masahide Kimoto |
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Institution: | (1) Climate Environment System Research Center, Seoul National University, Seoul, 151-742, South Korea;(2) Department of Meteorology, SOEST, University of Hawaii, Honolulu, HI, USA;(3) Center for Climate System Research (CCSR), University of Tokyo, Tokyo, Japan |
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Abstract: | High-frequency atmospheric variability depends on the phase of El Nino/Southern Oscillation (ENSO). Recently, there is increasing
evidence that state-dependent high-frequency atmospheric variability significantly modulates ENSO characteristics. Hence,
in this study, we examine the model simulations of high-frequency atmospheric variability and, further, its dependency on
the El Nino phase, using atmospheric and coupled GCMs (AGCM and CGCM). We use two versions of physical packages here—with
and without convective momentum transport (CMT)—in both models. We found that the CMT simulation gives rise to a large climatological
zonal wind difference over the Pacific. Also, both the climate models show a significantly improved performance in simulating
the state-dependent noise when the CMT parameterization is implemented. We demonstrate that the better simulation of the state-dependent
noise results from a better representation of anomalous, as well as climatological, zonal wind. Our further comparisons between
the simulations, demonstrates that low-frequency wind is a crucial factor in determining the state-dependency of high-frequency
wind variability. Therefore, it is suggested that the so-called state-dependent noise is directly induced by the low-frequency
wind anomaly, which is caused by SST associated with ENSO. |
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Keywords: | ENSO High-frequency variability ENSO/MJO interaction Scale interaction |
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