This study revealed the modulation of the impacts of Madden–Julian Oscillation (MJO) on winter rainfall in China by El Niño‐Southern Oscillation (ENSO) using reanalysis data and statistical analysis. When MJO is active over the Indian Ocean, its impacts are strengthened by El Niño, leading to enhanced positive rainfall anomalies in eastern China. However, the effects of MJO are counteracted by La Niña; thus, significant positive rainfall anomalies exist only in Zhejiang Province and adjacent areas. MJO activity over the western Pacific induces opposite rainfall anomalies in South China between El Niño and La Niña winters; rainfall in South China increases (decreases) in El Niño (La Niña) winters. Such differences in rainfall anomalies are closely related to anomalous circulation and moisture transport. Anomalous southwesterlies in eastern China are enhanced in El Niño winters when MJO is active over the Indian Ocean, which leads to increased moisture transport towards China and stronger ascending motion in eastern China. But the anomalous southwesterlies are weakened in La Niña winters, thereby resulting in less moisture transport and convergence. When MJO is active over the western Pacific, anomalous northeasterlies in mainland China are enhanced (weakened) in La Niña (El Niño) winters, which strengthens (weakens) the moisture divergence and descending motion in China. Moisture convergence anomalies that explain the rainfall anomalies in ENSO winters are mainly attributed to the effects of low‐frequency background state (LFBS) moisture and meridional winds. It was found that ENSO modulates the impacts of MJO by two main ways. First, ENSO can regulate the intensity and distribution of MJO activity. Therefore, MJO in the same phase will lead to different circulation and moisture transport anomalies in China. Second, ENSO‐induced LFBS circulation and moisture anomalies can also influence the moisture convergence in China, which will strengthen or weaken the effects of MJO.

The observed interannual impact of the North Pacific atmospheric blocking (PB) on the North Pacific storm track (PST) during boreal winter is investigated. There is a significant out‐of‐phase relationship between the intensities of PB and PST. The strong PB is accompanied by prominent geopotential height anomalies exhibiting a meridional dipole. PB‐related anomalous easterlies south of the anticyclonic anomaly reduce the low‐level atmospheric baroclinicity by weakening the upper‐level zonal wind, which may be responsible for the attenuated PST. The situations are opposite when PB is weak but with relatively weak magnitudes. However, the intensified PST associated with weak PB may not be determined by the strengthened baroclinicity. Additionally, by diagnosing the energy budget, the contribution of energy conversion from background available potential energy to the altered eddy available potential energy (EAPE) can be elucidated. PB‐related anomalous baroclinic energy conversion from EAPE to eddy kinetic energy (EKE) largely explains the altered EKE.

We examine the capability of thirteen Coupled Model Intercomparison Project (CMIP) phase 5 (CMIP5) models in simulating climatology and interannual variability of Winter North Pacific Storm Track (WNPST). It is found that nearly half of the selected models can reproduce the spatial pattern of WNPST climatology. However, the strength and spatial variation of WNPST climatology are weak in most of the models. Most differences among the models are in the northeast of the simulated multi-model ensemble (MME) climatology, while it is more consistent in the south. The MME can reflect not only the center position, but also the strength and spatial distribution of interannual variation of the WNPST amplitude. Except for CNRM-CM5, the interannual standard deviations of simulated WNPST strength and spatial variation in all other models are weak. ACCESS1-3 and CanESM2 have a better capability in simulating the spatial modes of WNPST, while the simulated second and third modes in some models are in opposite order with those in NCEP (National Centers for Environmental Prediction) reanalysis. Only five models and MME can capture “midwinter suppression” feature in their simulations. Compared with NCEP reanalysis, the winter longitude index is larger and latitude index is smaller in most of the models, indicating the simulated storm track is further east and south. CNRM-CM5, MME and CMCC-CM could be used to evaluate interannual variation of strength index, longitude index and latitude index respectively. Nevertheless, only INM-CM4 and CNRM-CM5 can simulate southward drift of WNPST.

The ability of RegCM4.5 using land surface scheme CLM4.5 to simulate the physical variables related to land surface state was investigated. The NCEP-NCAR reanalysis data for the period 1964–2003 were used to drive RegCM4.5 to simulate the land surface temperature, precipitation, soil moisture, latent heat flux, and surface evaporation. Based on observations and reanalysis data, a few land surface variables were analyzed over China. The results showed that some seasonal features of land surface temperature in summer and winter as well as its magnitude could be simulated well. The simulation of precipitation was sensitive to region and season. The model could, to a certain degree, simulate the seasonal migration of rainband in East China. The overall spatial distribution of the simulated soil moisture was better in winter than in summer. The simulation of latent heat flux was also better in winter. In summer, the latent heat flux bias mainly arose from surface evaporation bias in Northwest China, and it primarily arose from vegetation evapotranspiration bias in South China. In addition, the large latent heat flux bias in South China during summer was probably due to less precipitation generated in the model and poor representation of vegetation cover in this region.

Based on the daily ERA-Interim reanalysis, interactions between the winter North Pacific storm track (WNPST) and the East Asian trough (EAT) on the interannual scale are further explored from the perspective of energy conversion and the simplified quasi-geostrophic potential vorticity equation. There is a prominent out-of-phase relationship between the EAT and WNPST on the interannual scale. It is baroclinic energy conversion rather than barotropic energy conversion that is the main physical process that the EAT affects the WNPST. When the EAT is intensified, the energy conversion from mean available potential energy to eddy available potential energy decreases; further, the energy conversion from eddy available potential energy to eddy kinetic energy is attenuated, which leads directly to remarkable weakening in the strength of the WNPST in its peak area and the region west of the date line. In addition, when the WNPST is enhanced, the WNPST dynamic forcing contributes to lowering the geopotential height near the EAT and thus profits to recover the strength of the EAT, while the thermal forcing of WNPST is opposite. However, their joint effect is still to strengthen the EAT, indicating that the impact of WNPST dynamic forcing on the EAT is stronger than that of thermal forcing. The interaction between the WNPST and EAT may be a way for the WNPST to maintain itself.

Based on the regional climate model RegCM4.5 driven by National Centers for Environmental Prediction (NCEP) reanalysis, the influence of cumulus convection schemes (CCSs) on the winter North Pacific storm track (WNPST) is investigated. It is found that the climatology, interannual variation, spatial modes and characteristic indices of the WNPST are extremely sensitive to the choice of CCS. Among the selected CCSs, WNPST climatology and interannual variation in the Kuo scheme are better than in other CCSs, with a smaller root mean square error. The WNPST spatial modes and strength indices in the Kuo and Grell schemes are more consistent with NCEP reanalysis. The Kuo scheme has a stronger ability to simulate the WNPST latitude index and the interannual variation of winter characteristic indices. In addition, we attempt to reveal the possible reasons for the different performances of CCSs from the viewpoint of baroclinic energy conversion (BCEC). It is found that the energy conversion from the mean available potential energy to the eddy available potential energy (BCEC1) has no significant difference among the Kuo, Grell and Emanuel schemes, while energy conversion from the eddy available potential energy to eddy kinetic energy (BCEC2) in the Kuo scheme is obviously better than other CCSs, which means that the differences in BCEC2 among these CCSs may be one of the key reasons affecting the simulation results of the WNPST.