The North Pacific Oscillation (NPO), which is characterized by a north‐south dipole‐like pattern of sea level pressure (SLP) in the North Pacific, is an atmospheric circulation that is a key to understanding tropical‐extratropical interactions in the Pacific. We show that the center of the southern lobe SLP in the NPO during boreal winter (December‐January‐February) is shifted to the east after the mid‐1990s compared to before the mid‐1990s. This leads to the change in the relationship between the NPO and El Niño and the Southern Oscillation (ENSO). The NPO is closely associated with the convective forcing in the tropical Pacific during boreal winter before the mid‐1990s. After the mid‐1990s, in contrast, the simultaneous relationship of the NPO and ENSO during boreal winter becomes weak. However, an eastward shift of the NPO's southern lobe SLP during boreal winter causes a close relationship with the ENSO in the winter of the following year through atmosphere‐ocean coupled processes after the mid‐1990s. These results indicate that atmospheric circulation in the North Pacific characterized by the NPO becomes more influential in the tropical Pacific with a lagged time after the mid‐1990s, likely due to the eastward shift in the NPO's structure. We also briefly discuss which processes cause an eastward shift in the NPO's southern lobe SLP.

Using 14 Coupled Model Intercomparison Projections Phase 5 (CMIP5) climate models, we examined the intermodel diversity when simulating East Asian Marginal Seas (EAMSs) sea surface temperature (SST) in the near future period (2020–2049) under four different Representative Concentration Pathway runs. We classified two groups for the CMIP5 climate models: for models that simulate SSTs in the EAMS that are higher (H_EAMS) and lower (L_EAMS) than the ensemble mean, respectively. Results show that compared to L_EAMS, H_EAMS tends to simulate weaker westerlies in the western‐to‐central North Pacific, together with a weaker Aleutian Low intensity, which causes higher EAMS SSTs through a reduction in latent heat flux. Furthermore, H_EAMS is characterized by cooler SST, less precipitation, and stronger trade winds in the central‐to‐eastern tropical Pacific than in L_EAMS. We argued that the intermodel diversity of simulated tropical Pacific SST is associated with the diversity of EAMS SST, which is related to atmospheric teleconnections from the tropics to the western‐to‐central North Pacific. It is also found that the bifurcation latitude of the North Equatorial Current is lower in H_EAMS than in L_EAMS, which is associated with the difference of tropical Pacific mean state between H_EAMS and L_EAMS. A lower bifurcation latitude transports more warm water into the EAMS, resulting in warmer SSTs in the H_EAMS than in the L_EAMS. These results show the importance of correctly simulating the tropical Pacific mean state to reduce the uncertainty in EAMS SST during the near‐future period.

The wind observations for multiple levels (40–200 m) have been conducted for a long time (2016–2020) on Jeju Island of South Korea. This study aims at understanding the vertical and temporal characteristics of lower atmosphere. Jeju Island is a region located at mid-latitude and is affected by seasonal monsoon wind. The maximum wind speed appears in the lower layer during day time and is delayed in the upper layer during latter time in diurnal cycle. In summer season, the surface layer increases up to 160 m during day time via dominant solar radiation effect, which is higher than those for other seasons. However, the maximum wind speed in winter season appears irregularly among altitudes, and the surface layer is ~100 m, which is lower than that in summer season. It can be attributed to the increase in the mean wind speed in diurnal cycle caused by the strong northwestern wind for winter season. These results imply that the relationship between near-surface and higher altitudes is primarily affected by solar radiation and seasonal monsoon winds. These results are expected to contribute to site selection criteria for wind farms and to the assessment concerning planetary boundary layer modeling.

Wind observations at multiple levels (40–200 m) have been conducted over a five-year time period (2016–2020) on Jeju Island of South Korea. This study aims to understand the vertical and temporal characteristics of the lower atmosphere. Jeju Island is a region located at mid-latitude and is affected by seasonal wind. The maximum wind speed occurs in the relatively lower altitudes during daytime and is delayed in the relatively higher altitude after sunset in a diurnal cycle. In the summer season, the altitudes appear earlier than in other seasons via the dominant solar radiation effect during daytime, and the altitude after sunset increases up to 160 m. However, the maximum wind speed in the winter season occurs irregularly among altitudes, and it is lower than that in the summer season. This can be attributed to the increase in the mean wind speed in the diurnal cycle caused by the strong northwestern wind in the winter season. These results imply that the relationship between near-surface and higher altitudes is primarily affected by solar radiation and seasonal winds. These results are expected to contribute to site selection criteria for wind farms.