This study describes the simulation characteristics of a newly developed Global/Regional Integrated Model system-Chemistry Climate Model (GRIMs-CCM), which is listed in Chemistry Climate Model Initiative as a participating model. The GRIMs-CCM was run using a standard set of forcings, and historical sea surface temperatures and sea ice concentration from the Hadley Centre were prescribed. The simulation results of GRIMs-CCM were compared to the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data set 1. The GRIMs-CCM satisfactorily simulated the climatological (1960-2010) atmospheric features and atmospheric teleconnections resulting from tropical sea surface temperature forcing. However, the GRIMs-CCM also had some regional biases; for instance, particularly, the temperature bias over the Antarctic was noticeable. We further analyzed physical processes that caused such biases and the influence of coupled chemistryclimate processes in the GRIMs-CCM, which may provide further guidance to improve an earlier version of the GRIMs-CCM and other climate-chemistry models participating in the Chemistry Climate Model Initiative.

Arctic oscillation (AO), which is the most dominant atmospheric variability in the Northern Hemisphere (NH) during the boreal winter, significantly affects the weather and climate at mid-to-high latitudes in the NH. Although a climate community has focused on a negative trend of AO in recent decades, the significant positive trend of AO over the last 60 years has not yet been thoroughly discussed. By analyzing reanalysis and Atmospheric Model Inter-comparison Project (AMIP) datasets with pacemaker experiments, we found that sea surface temperature warming in the Indian Ocean is conducive to the positive trend of AO from the late 1950s. The momentum flux convergence by stationary waves due to the Indian Ocean warming plays an important role in the positive trend of AO, which is characterized by a poleward shift of zonal-mean zonal winds. In addition, the reduced upward propagating wave activity flux over the North Pacific due to Indian Ocean warming also plays a role to strengthen the polar vortex, subsequently, it contributes to the positive trend of AO. Our results imply that the respective warming trend of tropical ocean basins including Indian Ocean, which is either anthropogenic forcing or natural variability or their combined effect, should be considered to correctly project the future AO’s trend.

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The authors investigated the lagged effect of anthropogenic aerosols (AAs) during the premonsoon season (April–May–June) on the East Asian precipitation during the postmonsoon season (July–August) using the aerosol optical depth (AOD) from a satellite dataset and reanalysis datasets. When the AOD is high in Eastern China during the premonsoon season, the amount of precipitation increases in the western North Pacific, including the Korean Peninsula and Japan, during the postmonsoon season. The amount of cloud in the western-to-central North Pacific in the premonsoon season increases during the high-AOD period. Subsequently, it cools the sea surface temperature until the postmonsoon season, which strengthens the North Pacific High. The strengthened North Pacific High in the postmonsoon season expands to the western North Pacific, which leads to the enhancement of the moisture flows from the ocean. This results in the increase in precipitation in the western North Pacific, including the Korean Peninsula and Japan, during the postmonsoon season.

Ozone is one of the most important atmospheric components because it regulates a radiative balance in the atmosphere, which can lead to subsequent changes in temperature and precipitation. Changes in radiative forcing due to ozone have been studied extensively (de F.