East Asian summer monsoon precipitation (EASMP) features complicated interdecadal variability with multiple time periods and spatial patterns. Using century-long datasets of HadISST, CRU precipitation, and the ECMWF twentieth-century reanalysis (ERA-20C), this study examines the joint influence of three oceanic interdecadal signals [i.e., Pacific decadal oscillation (PDO), Atlantic multidecadal oscillation (AMO), and Indian Ocean Basin mode (IOBM)] on the EASMP, which, however, is found not to be simply a linear combination of their individual effects. When PDO and AMO are out of phase, the same-sign SST anomalies occur in the North Pacific and North Atlantic, and a zonally orientated teleconnection wave train appears across the Eurasian mid-to-high latitudes, propagating from the North Atlantic to northern East Asia along the Asian westerly jet waveguide. Correspondingly, the interdecadal precipitation anomalies are characterized by a meridional tripole mode over eastern China. When PDO and AMO are in phase, with opposite sign SST anomalies in the North Pacific and North Atlantic, the sandwich pattern of anomalous stationary Rossby wavenumber tends to reduce the effect of the waveguide in the eastern Mediterranean region, and the teleconnection wave train from the North Atlantic travels only to western central Asia along a great circle route, causing Indian summer monsoon precipitation (ISMP) anomalies. The ISMP anomalies, in turn, interact with the teleconnection wave train induced by the PDO and AMO, leading to a meridional dipole mode of interdecadal precipitation anomalies over eastern China. Through the impact on the ISMP, the IOBM exerts significantly linear modulation on the combined impacts of PDO and AMO, especially over northern East Asia.

A significant challenge with dynamical downscaling of climate simulations is the ability to accurately represent convection and precipitation. The use of convection‐permitting resolutions avoids cumulus parameterization, which is known to be a large source of uncertainty. A regional climate model (RCM) based on the Weather Research and Forecasting model is configured with a 4 km grid spacing and applied to the U.S. Great Plains, a region characterized by many forms of weather and climate extremes. The 4 km RCM is evaluated by running it in a hindcast mode over the central U.S. region for a 10 year period, forced at the boundary by the 32 km North America Regional Reanalysis. The model is also run at a 25 km grid spacing, but with cumulus parameterization turned on for comparison. The 4 km run more successfully reproduces certain observed features of the Great Plains May‐through‐August precipitation. In particular, the magnitude of extreme precipitation and the diurnal cycle of precipitation over the Great Plains are better simulated. The 4 km run more realistically simulates the low‐level jet and related atmospheric circulations that transport and redistribute moisture from Gulf of Mexico. The convection‐permitting RCM may therefore produce better dynamical downscaling of future climate when nested within global model climate projections, especially for extreme precipitation magnitudes. The 4 km and 25 km simulations do share similar precipitation biases, including low biases over the central Great Plains and high biases over the Rockies. These biases appear linked to circulation biases in the simulations, but determining of the exact causes will require extensive, separate studies.

This study investigates anthropogenic aerosol effects on East Asian winter monsoon (EAWM) with Community Atmospheric Model version 5. In winter, the anthropogenic aerosol optical depth is the largest over southern East Asia and adjacent oceans. The associated EAWM change, however, is the most significant in northern East Asia, which is characterized by a significant surface cooling in northern East Asia and an acceleration of the jet stream around 40°N, indicating an intensification of the EAWM northern mode. Such an intensification is attributed to anthropogenic black carbon (BC)‐induced Tibetan Plateau (TP) warming. The BC is mostly transported from northern South Asia by wintertime westerly and southwesterly and then deposited on snow, giving rise to a reduction of surface albedo and an increase of surface air temperature via the snow‐albedo feedback. The TP warming increases meridional temperature gradient and lower tropospheric baroclinicity over northern East Asia, leading to the jet stream acceleration around 40°N and the westward shift of East Asian major trough via the transient eddy‐mean flow feedback. Such upper tropospheric pattern favors more cold air outbreak, leading to a large surface cooling in northern East Asia. In southern East Asia, the effect of nonabsorbing aerosols is dominant. The solar flux at surface is significantly reduced directly by scattering of nonabsorbing aerosols and indirectly by intensification of short wave cloud forcing. Accordingly, the surface air temperature in southern East Asia is reduced. The precipitation is also significantly reduced in South China and Indo‐China Peninsula, where the aerosol indirect effect is the largest.

Accompanying with the rapid urbanization in Yangtze River Delta (YRD), large amounts of anthropogenic heat are released into the atmosphere, which is becoming a more and more severe issue for the local climate. To understand what role anthropogenic heat release (AHR) plays in the urbanization‐induced regional warming, high‐resolution (3 km) Weather Research and Forecast WRF model experiments are carried out for 7 years (2001–2007) with different configurations of urban land use (ULU) and AHR. The results show that AHR can cause notable warming in almost the whole YRD rather than confining to the local cities where it releases, which is more significant in winter than in summer if the same amounts of AHR apply, especially at winter night. And furthermore, it can decrease (somewhat increase) the diurnal temperature range (DTR) in winter (summer). On the contrary, urban canopy effect due to the change from rural to ULU can produce a stronger warming in summer than in winter, and always reduce DTR in both winter and summer. Contribution of AHR to the sensible heat flux in urban regions is responsible for those AHR‐caused warming and DTR features, because it is larger in winter and at winter night but much smaller in summer and at summer night. Without ambient wind effect, AHR‐caused warming centres in cities and spreads around homogeneously. However, under the prevailing wind, it has less magnitude, shifts to the downwind city edges and forms a warming belt along the wind direction, which may favour linking the adjacent AHR‐caused warming together. On the other hand, AHR‐caused warming depends on the city sizes that are proportional to the total amount of AHR emitted.