The University of Tokyo · Environmental Science
Professor Yu Kosaka's research lab specializes in atmospheric and climate dynamics, with a primary focus on tropical-extratropical interactions in the Asia-Pacific region. The lab investigates teleconnection patterns such as the Pacific–Japan (PJ) pattern, examining their dynamics, predictability, and role in linking tropical convection to midlatitude climate variability. Key research directions include air-sea coupled modes in the Indo–western North Pacific warm pool, atmospheric wave dynamics, and feedback mechanisms involving the Indian Ocean and tropical cyclones. The lab also emphasizes model evaluation and seasonal climate predictability using observational data and multimodel ensembles.
Figures are computed from collected data and may differ slightly.
Convective activity over the tropical western Pacific is known to influence the extratropical circulation over East Asia in the boreal summer in the form of teleconnection, called the ‘Pacific–Japan (PJ) pattern’, but its structure and dynamics have not yet been studied in depth. In this study, a composite analysis is performed for 32 monthly events of enhanced convection observed to the east of the Philippines. The composited monthly mean vorticity anomalies associated with the PJ pattern are e
Summer climate in the Northwestern Pacific (NWP) displays large year-to-year variability, affecting densely populated Southeast and East Asia by impacting precipitation, temperature, and tropical cyclones. The Pacific-Japan (PJ) teleconnection pattern provides a crucial link of high predictability from the tropics to East Asia. Using coupled climate model experiments, we show that the PJ pattern is the atmospheric manifestation of an air-sea coupled mode spanning the Indo-NWP warm pool. The PJ p
Abstract Summertime atmospheric circulation over the midlatitude western North Pacific (WNP) is influenced by anomalous convective activity near the Philippines. This meridional teleconnection, observed in monthly anomalies and known as the Pacific–Japan (PJ) pattern, is characterized by zonally elongated cyclonic and anticyclonic anomalies around the enhanced convection center and to its northeast, respectively, in the lower troposphere, with an apparent poleward phase tilt with height. The aut
Abstract The summertime mei-yu–baiu rainband over East Asia displays considerable interannual variability. A singular value decomposition (SVD) analysis for interannual variability reveals that precipitation anomalies over the mei-yu–baiu region are accompanied by in situ anomalies of midtropospheric horizontal temperature advection. Anomalous warm (cool) advection causes increased (decreased) mei-yu–baiu precipitation locally by inducing adiabatic ascent (descent). The anomalous precipitation a
Predictability of summer climate anomalies over East Asia and the northwestern Pacific is investigated using observations and a multimodel hindcast ensemble initialized on 1 May for the recent 20–30 yr. Summertime East Asia is under the influence of the northwestern Pacific subtropical high (PASH). The Pacific–Japan (PJ) teleconnection pattern, a meridional dipole of sea level pressure variability, affects the northwestern PASH. The forecast models generally capture the association of the PJ pat
Abstract A set of multimodel twentieth-century climate simulations for phase 3 of the Coupled Model Intercomparison Project (CMIP3) is analyzed to assess the model reproducibility of the Pacific–Japan (PJ) teleconnection pattern. It is the dominant low-frequency anomaly pattern over the summertime western North Pacific (WNP), characterized by a meridional dipole of zonally elongated vorticity anomalies in the lower troposphere and by anomalous precipitation over the tropical WNP. Most of the mod
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