Heavy precipitation events occur often over the western Sichuan Basin in summer, near the transition zone between the Sichuan Basin and the steep terrain of the Tibetan Plateau. One such event — a heavy precipitation process that occurred on 18–20 August 2010, with clear nocturnal peaks — is chosen as a case to tentatively explore how the convection associated with convective-scale precipitation is initiated and propagated. By utilizing the vertical momentum equation from the viewpoint of separating perturbation pressure into dynamic and thermal parts, it is demonstrated that the vertical momentum is induced by the imbalance of several forces, including the dynamic/buoyant part of the perturbation pressure gradient force and the buoyancy force, with the latter dominating during the nocturnal-peak period. Although a negative value of the dynamic perturbation pressure gradient force partly offsets the positive buoyant forcing inside the strong updraft, the pattern of vertical motion tendency is largely attributable to its buoyancy because of its larger magnitude. Relative to the buoyancy component, the dynamic part of the vertical perturbation pressure gradient is also examined, revealing a smaller order of magnitude. Thus, it is the thermal effect that should be responsible for the initiation and propagation of convection. As for the convective-scale precipitation, it always presents a trailing morphology relative to the strong leading-side updraft. Furthermore, overlapping strong signals of vertical motion and its tendency point towards strong precipitation in the future.

For Super Typhoon Maria (2018), the multi-intensity change stages are identified and reproduced by numerical simulation. It is rather difficult to perform a perfect simulation for such a repeatedly reinforced typhoon during its long life-cycle and remote path. In this study, the rapid intensification (RI) episode is focused on to investigate the convective burst (CB) characteristics and the relationship between the CBs and the RI of Maria. For Typhoon Maria, 1) the spatial pattern of the inner-core CBs in distinct shear-relative quadrants, instead of the overall inner-core CBs frequently used in previous studies, presents cyclonic rotation from downshear to upshear quadrants during RI, producing a higher efficiency for tropical cyclone (TC) spinup, which accelerates the RI process. 2) Dual meanings/relationships exist between CBs and RI for Maria, in contrast to the previous argument that CBs might be an indicator or a precursor to RI. The sudden growth of CBs prior to RI provides a precursor for the upcoming RI. Additionally, the appearance of the CB peak soon after RI indicates RI could lead to more intensive deep convections. The overlap of CBs with high inertial stability inside the radius of maximum wind plays a significant role in the RI of TCs. 3) The synoptic attributions to CBs are also explored for the entire troposphere, fitting in the bottom-up thinking of convection growth. The CBs might be associated with high convective available potential energy in the boundary layer, a strengthening of the deep-layer secondary circulation, and an enhanced upper-level eddy momentum flux convergence.

Previous studies have mostly focused on the effect of anthropogenic heating (AH) on air pollution events. However, few studies have investigated the impact of AH on the warm-sector precipitation over South China. By using the Weather Research and Forecasting model (WRF) coupled with an urban canopy model with appropriate AH release values, the warm-sector heavy rainfall event that occurred over the Pearl River Delta (PRD) during 8 May 2014 was investigated. The results show that the warm-sector precipitation of the PRD is sensitive to the impact of AH. By affecting the convection in the initiation of precipitation, AH can reduce the total precipitation of urban areas by approximately 10%. The possible mechanism by which AH influences the warm-sector heavy precipitation is described as follows: AH induced local convergence shifts towards the border of the PRD and intensified the convection and precipitation therein, by rearranging the thermal distributions of the flow field. In addition, AH changed the local convergence within the urban PRD areas, which was weakened by the homogenous urban thermal environment, and thereby decreased the total urban precipitation.

Based on a 72‐hr simulation of the rapidly intensifying Typhoon Mujigae (2015), the spatiotemporal evolutions of various inner‐core convections and the associated latent heating (LH) features were investigated. Results showed two interesting turning points from the pre‐rapid intensification (RI) stage to RI onset. One was a change from convective–stratiform mixed precipitation to a convective precipitation (CP)‐dominant trend, while the other happened inside the CP. As the major contributor to LH, during the CP, the dramatic increase and radially inward movement of deep convection and associated LH release from −4 to −2 hr relative to RI, provided some useful clues for predicting the RI of a tropical cyclone (TC). But how do distinct convections act on the RI of a TC? From the potential temperature budget and flow vector intuitive display, there were upper‐ and lower‐level warm cores, fed by the centripetal transport from deep‐convection‐related LH sources and lower‐level radial inflow of weak‐to‐moderate convection‐associated LH sources. The former brought about higher heating efficiency, embodied by a higher rate (2.5 times greater) of pressure decline during RI. Thus, by comparing the LH effects of diverse convections on warm‐core formation, and the role of the warm core in the RI of a TC, the link between various convections and TC intensification can be established.

Spectral analysis of terrain height variance is conducive to quantitatively study the terrain characteristics and grid-size selection for mesoscale models. Improved topographic resolutions can lead to the variations of terrain characteristics and the appropriate grid size for a fixed analyzed area. Spectral methods of one-dimensional weighted average and arithmetic mean were used to investigate the specific impact on the distribution of terrain spectra and grid-size selection for mesoscale models of the landslide-prone areas in western Sichuan. The results indicate that the maximum spectral energy (the variance of the terrain height series) of 30″ resolution (R1) is larger than that of 90 m resolution (R2), indicating a gentler undulation of terrain for R2. The spectral curve of R2 almost overlaps with that of R1 because the difference in topographic resolution does not change the dominant distribution of the topography. Their differing spectral energies at longer wavelengths are related to the majority of grid points of R2 distributed at shorter wavelength bands. A least squares fit in the form of $S=a{\lambda }^b$ was used to estimate the decreasing trend of the spectral distribution. The difference in spectral slope between R1 and R2 is mainly caused by the spectral energy of R2 at shorter wavelengths. The exponent b is connected with grid-size selection for mesoscale models. A universal horizontal grid size of 2.5 km for R1 and 1.9 km for R2 are required to resolve 95% of the terrain height variance for a mesoscale model application without a subgrid-scale parameterization. The simulation tests show that the improved topographic resolution appears to perform better in reproducing precipitation, which is probably related to the finer details of the terrain recognized by the model.