Tropical cyclone (TC) vortex alignment and precipitation axisymmetrization are often precursors to rapid intensification (RI), yet precipitation is poorly observed in the open ocean due to the absence of ground-based radars and aircraft reconnaissance. This study identifies significant differences in precipitation patterns under similar environmental shear and TC intensity between RI and slowly intensifying (SI) cases using the Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (IMERG) dataset, a spatially and temporally consistent global dataset of microwave-based observations between 1998 and 2023. Results show precipitation magnitude is significantly greater in the inner core (within 100 km from the center) in RI cases than in SI cases. At intensities weaker than 75 kt (1 kt ' 0.51 m s21), heavier mean precipitation is related to a larger 24-h intensity change. For stronger TCs, mean precipitation and intensity change are less related. This study additionally examines how the radius of maximum precipitation (RMP) varies with vortex tilt magnitude and with the radius of maximum winds (RMW), using IMERG, ERA5, and tail-Doppler radar (TDR). All datasets capture a wavenumber-1 asymmetry in precipitation under varying vortex tilts, but the RMP is located further from the center in ERA5 and IMERG than in TDR, especially for small TCs, with the largest discrepancy in ERA5. The results demonstrate that TDR is superior to IMERG and ERA5 for diagnosing inner-core TC structure and its relationship to intensity change; however, satellite-based precipitation products, such as IMERG, remain a better alternative than reanalysis.
Northeast China frequently experiences tornadoes in moisture-limited environments that depart from the typical mesocyclonic tornado paradigm. Using a 2006-24 ERA5 dataset benchmarked against moist-environment tornadoes (METs) and the United States/East China cases, we characterize the distinct environmental footprints of these high lifting condensation level (LCL) events. Results reveal that dry-environment tornadoes (DETs) predominantly manifest as quasi-linear convective modes and operate in regimes with marginal convective available potential energy (CAPE), steep lapse rates, and negligible convective inhibition, contrasting with the high-energy, high-helicity environments of METs, a divergence closely tied to the diurnal evolution of environmental parameters. Crucially, DETs maintain significantly higher midlevel relative humidity than their nontornadic counterparts, suggesting a critical moisture threshold necessary to support tornadic potential in these marginal regimes. Notably, tornadic discrimination relies less on the absolute magnitude of shear or energy and more on structural efficiency, specifically the vertical concentration of buoyancy and the streamwise alignment of near-surface flow. Synoptically, composite analysis shows that DETs exhibit a nonclassic spatial distribution, clustering uniquely in the near-center southwest quadrant of extratropical cyclones a region characterized by a "freeconvection window" and a transition from environment-feeding tilting to local-stretching mechanisms. This "hybrid" configuration of marginal CAPE, strong deep-layer shear, and weak low-level helicity is consistent with the observed prevalence of linear storm modes in these regions. Given the diminished diagnostic utility of the significant tornado parameter in these moisture-limited environments, our findings suggest that an integrated approach combining efficiency-based metrics with synoptic pattern recognition may offer a more robust framework for forecasting tornadoes in these marginal regimes.
Abstract Through a suite of global simulations using the Global-to-Regional Integrated Forecast System (GRIST) model, this study investigates the impact of different scale-aware convective parameterization schemes (CPS) on typhoon simulation across resolutions from 60 to 3.75 km. Three implementations are examined: scaling convective adjustment time [control (CTRL)], scaling cloud-base mass flux (SA-MB), and scaling entrainment rate (SA-ER). All CPS show improved performance with increasing resolution. CTRL and SA-MB exhibit comparable scale adaptivity, whereas SA-ER demonstrates stronger CPS suppression and outperforms the other two, reducing mean track errors by 10–45 km and intensity underestimation by 8%–47%. Decomposition of the surface pressure tendency budget reveals that SA-ER enhances microphysical processes more vigorously, more than offsetting the reduction of convective component and yielding a net ∼10% increase in precipitation and diabatic heating, thereby deepening the storm. These benefits hold across most resolutions but diminish at the convection-permitting scale for typhoons that are not sufficiently compact and intense, where excessive outer-rainband warming disrupts the secondary circulation and weakens intensification. Explicit convection without CPS also performs poorly at this resolution, producing the largest track and intensity errors among all experiments—underscoring that even at convection-permitting scales, scale-aware CPS remain indispensable. The results of this study demonstrate the advantages of scale-aware CPS on typhoon modeling, with the entrainment scaling approach emerging as a particularly effective pathway for improving typhoon intensity forecasts. Significance Statement Typhoons are among the most devastating weather systems, posing severe threats to human life and economies. Accurate simulation of typhoon intensity remains a great challenge, as tropical cyclones involve complex multiscale interactions between cumulus convection and large-scale dynamics. By examining the impact of different scale-aware convective parameterization schemes on typhoon simulations and elucidating the mechanisms through which convection schemes affect typhoon intensity, this study offers an effective pathway toward improving typhoon intensity forecasts and optimizing convective parameterization in numerical models.
Abstract Understanding and accurately forecasting marine boundary layer dynamics in coastal areas is essential for resource management and strategic planning. These areas are characterized by intricate air–sea–land interactions, which pose challenges to predictability. Traditional high-resolution models treat wave–ocean effects through parameterization in stand-alone simulations, potentially overlooking fine-scale processes and simultaneous feedbacks. In this study, we employ the Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) system to investigate the impacts of ocean–wind–wave interactions on coastal processes and marine boundary-layer winds. Focusing on the Mid-Atlantic Bight, simulations from July 2021–June 2022 are validated against available buoy observations. Compared to stand-alone atmospheric simulations, the fully coupled system reduces wind-speed and direction errors within the lowest 50 m of the atmosphere above sea level. Targeted experiments are conducted to isolate the contributions of (i) sea-surface temperature (SST) and (ii) wave-dependent surface roughness, with specific emphasis on land–sea-breeze dynamics and high-wave conditions. SST feedbacks improve prediction of land–sea-breeze-driven low-level jets (LLJs), by enhancing skill in occurrence rates, jet-nose speed, and nose height at diurnal timescales. Over the continental shelf, diurnal SST variations statistically significantly alter LLJ occurrence by up to 5% and jet-nose speed by ∼ 1 ms −1 during the late afternoon. Incorporating wave-induced roughness statistically significantly reduces near-surface wind-speed biases and improves residuals during Nor’easter events by 𝒪 (1 ms −1 ). These findings underscore the importance of resolving SST and wave roughness dynamics to improve predictions of coastal wind profiles.
Abstract Tropical cyclones (TCs) induce strong oceanic responses that in turn modulate air-sea heat exchange and subsequent TC development, yet the cumulative impacts of multiple sequential TCs are insufficiently explored. This study investigates the ocean response to four sequential TCs in the northern South China Sea (SCS), emphasizing the interaction between TC forcing and pre-existing ocean thermal conditions. Using satellite observations and reanalysis data, we show that the successive TCs generated a distinct dual-core cooling structure in the surface and subsurface layers, accompanied by mixed layer deepening and barrier layer thickening. The oceanic response was jointly modulated by atmospheric environmental conditions, wind-driven vertical mixing, Ekman pumping, and surface heat flux exchange, with mesoscale eddies further adjusting its amplitude. The evolving upper-ocean state progressively reduced thermal favorability for intensification resulting in a stepwise weakening of the sequential TCs. These findings highlight the critical role of cumulative ocean preconditioning in modulating both ocean responses and TC intensity evolution, with implications for improving intensity prediction in regions prone to rapid cyclone succession.
