This study utilizes radar, sounding observations, and convective-permitting simulations with a non-hydrostatic mesoscale model to investigate the effects of gravity waves originating from the southwest mountain on the intensification of the extreme precipitation event occurred in Henan Province, Central China, in July 2021 (referred to as the “21.7” event). The gravity waves have wave speeds of approximately 11.5 m s-1 and wavelengths ranging from 60 to 90 km. These gravity waves are generated by the interaction between a northwest-southeast direction mountain (Funiu Mountain, FNM) and a southwesterly flow originated from the mesoscale convective vortex (MCV) developing from an inverted trough southwest of the rainfall center. Then, these waves propagate northeastward through a wave duct featuring a stable layer between 5 and 9 km altitude, capped by a low-stability reflecting layer with a critical level. As they propagate, these waves trigger banded convective cells along their path. Upon the arrival of gravity wave peaks at the rainfall center, they induce the downward energy flux of gravity waves from high troposphere levels (~7 km). The downward wave energy dynamically interacts with the upward wave energy from gravity waves excited by latent heating at the lower tropospheric level (~1 km). This synergistic effect intensifies the ascending motion and results in a precipitation increase of over 20% at the rainfall center. This study highlights the significance of orographic gravity waves in shaping extreme precipitation events.

Water-heat transport in frozen soil impacts the hydrological processes in cold region through its influences on the surface energy budget and water storage. In this study, sensitivities of soil water-heat transport simulations to parameterizations of soil permeability, supercooled water and freezing temperature threshold that determines phase change criteria were assessed in the Noah with multi-parameterization (Noah‐MP) land surface model. The results showed that Noah-MP well reproduce the seasonal variations in soil temperature and moisture in the freeze-thaw (FT) process, while it still involves biases in soil temperature and moisture simulations with RMSE of 4.35 ℃ and 0.068 mm 3/mm 3 at shallow layer during soil thawing period. Performances of Noah-MP in soil water-heat transport simulations are not very sensitive to the optional combinations of soil permeability and supercooled water parametrizations. Nevertheless, instead of constant freezing temperature, a virtual temperature implemented to redefine the phase change criteria improves soil moisture simulations in the FT process evidently by about 20%–50% bias reduction, especially during soil thawing period, and the simulated soil water–heat coupling relation is consistent with the observations. Global simulations further validate the improvements of implemented frozen soil parameterizations in Noah-MP. Results in this study emphasize the importance of phase change criteria choice in land surface model for frozen soil hydrothermal regime simulations.