Groundwater is an important part of water storage and one of the important sources of agricultural irrigation, urban living, and industrial water use. The recent launch of Gravity Recovery and Climate Experiment (GRACE) Satellite has provided a new way for studying large-scale water storage. The application of GRACE in local water resources has been greatly limited because of the coarse spatial resolution, and low temporal resolution. Therefore, it is of great significance to improve the spatial resolution of groundwater storage for regional water management. Based on the method of random forest (RF), this study combined six hydrological variables, including precipitation, evapotranspiration, runoff, soil moisture, snow water equivalent, and canopy water to conduct downscaling study, aiming at downscaling the resolution of the total water storage and groundwater storage from 1° (110 km) and to 0.25° (approximately 25 km). The results showed that, from the perspective of long time series, the prediction results of the RF model are ideal in the whole research area and the observations wells area. From the perspective of space, the detailed changes of water storage could be captured in greater detail after downscaling. The verification results show that, on the monthly scale and annual scale, the correlation between the downscaling results and the observation wells is 0.78 and 0.94, respectively, and they both reach the confidence level of 0.01. Therefore, the RF downscaling model has great potential for predicting groundwater storage.

The seasonality of internal tides is particularly conspicuous in shelf seas due to the dramatical variations in the marine environment. In this paper, the seasonal and spatial variabilities of M2 internal tides in the Yellow Sea (YS) are investigated using a high‐resolution numerical ocean model. The freshwater runoff of the Yangtze River is also considered. Because most nonlinear internal waves are of tidal origin, the simulated internal tides show good spatial consistency with the satellite‐detected nonlinear internal waves. During summer, the M2 internal tides are ubiquitous and originate from multiple generation sites (e.g., the west coast of the Korean Peninsula and the Yangtze River estuary). During other seasons, the spatial coverage of the internal tides becomes very limited. Multiple sources combined with seasonal onset and decay lead to complex seasonal interference patterns. The wavelengths vary both spatially and temporally, depending on the water depth and ocean stratification. Between spring and autumn, a seasonally reversed pattern of radiation of baroclinic energy flux is found in the southern YS, which may be induced by the seasonal variability of the YS Warm Current. Seasonal stratification controls the seasonality of the generation, propagation, and dissipation of internal tides and is maintained by the monsoon, seasonal circulation, and Yangtze River runoff. Our simulations suggest that, although internal tide dissipation is dispensable for the tidal energy budgets in the YS, internal tides seem to be the leading order contributor to the midcolumn diapycnal mixing, as they are more efficient mixers than barotropic tides.

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