Water vapor has a significant impact on atmospheric circulations by moist processes. Subgrid-scale orographic drag (SOD) using effective moist stability can improve wind biases and change the location of precipitation. The southeastern coastal region of China, particularly northern Fujian and southern Zhejiang, is characterized by complex terrain and persistent biases in the simulation of summer precipitation. Using the Yin-He Global Spectral Model (YHGSM), this study evaluates the impact of a moist orographic gravity wave drag (moist-OGWD) parameterization on summer precipitation simulations in this region. One control experiment using the original dry OGWD scheme and one sensitivity experiment using the moist-OGWD scheme are conducted for the summers of 2022 and 2023. Results demonstrate that moist-OGWD significantly mitigates the model underestimation of precipitation over northern Fujian and southern Zhejiang. The underlying mechanism involves latent heat release associated with moisture, which reduces static stability in the lower troposphere and facilitates the breaking of orographic gravity waves in the lower atmosphere. Consequently, low-level gravity wave drag is substantially enhanced, while upper-level drag and blocking drag are reduced. Collectively, these changes induce an anomalous cyclonic circulation in the lower troposphere. This circulation anomaly strengthens water vapor transport from the ocean and enhances low-level convergence, and augments the regional net moisture budget, ultimately leading to increased precipitation. Plain language summary This study evaluates the impact of moist orographic gravity wave drag parameterization (moist-OGWD) on summer monsoon precipitation over southeastern coastal of China (part of the East Asian Summer Monsoon region). Simulations using the YHGSM model demonstrate that the moist-OGWD scheme can bring more precipitation than dry-OGWD scheme. The enhancement stems from moisture-induced latent heat release, which reduces lower-tropospheric static stability, facilitating earlier breaking of orographic gravity waves in the lower atmosphere and substantially strengthening low-level zonal gravity wave drag. This intensified drag triggers an anomalous cyclonic circulation over southeastern coastal of China, thereby promoting more realistic moisture convergence and precipitation.

A new formulation of the spectral horizontal kinetic energy (HKE) budget in cylindrical coordinates is developed to study multiscale kinetic energetics of tropical cyclones (TCs). Compared to previous studies, it precisely constructs the energy nonlinear transfer term and comprehensively represents budget contributions from various physical processes. With this formulation, the eyewall axisymmetry and asymmetries during the rapid intensification (RI) of an idealized TC simulation are investigated. The area-averaged eyewall HKE is mainly determined by the following physical processes at the axisymmetric mode: the vertical pressure gradient work term generates positive contributions nearly at the whole troposphere, with increased HKE redistributed downward by the pressure transverse (radial-vertical) circulation flux divergence and upward by the HKE transverse circulation flux divergence; at the low layer, the nonlinear transfer makes a significant negative contribution, even exceeding that from the vertical pressure gradient work term, and an additional negative contribution involving axisymmetric-asymmetric coupling is embedded in the HKE transverse circulation flux divergence. Decomposition of the nonlinear transfer reveals that the azimuthal and vertical components produce a weak upscale transfer, thereby feeding the eyewall axisymmetric HKE, whereas the radial component produces a much stronger downscale transfer, thereby consuming the eyewall axisymmetric HKE. Further analysis shows that the final-formed radius of maximum wind acts as a dynamical boundary separating inner and outer energy transfer regimes. This study provides direct evidence for the net negative role of asymmetries on the axisymmetric kinetic energy during TC intensification.

It is an urgent need to understand the ability of current artificial intelligence (AI) models in simulating atmospheric mesoscale aspects. This paper compares mesoscale kinetic energy spectra from an 11-day experiment simulated by a novel AI-based model (Pangu) and a physics-based model (MPAS), using ERA5 reanalysis as a reference. Based on the commonly used evaluation metrics of latitude weighted root mean square error (RMSE) and anomaly correlation coefficient (ACC), the AI-based model has better short to medium-range weather forecasting skill compared to the physics-based model. However, the AI-based model cannot replicate the mesoscale − 5/3 spectral slope and underestimates the mesoscale energy at wavelength smaller than 1000 km. As altitude increases and scale decreases, the deviation of the AI-based model from the reanalysis significantly increases. These features prove that the AI-based model has the lower effective resolution compared to the physics-based model with the close nominal resolution. Compared to the physics-based simulations, AI-based model has stronger downscale energy flux at larger mesoscales, which is dominated by divergent kinetic energy flux. But it rapidly becomes the weakest at smaller mesoscales. The diagnosed vertical velocity of AI-based model and its related budget terms are closest to those of the reanalysis at large scales. Overall, the AI-based model Pangu shows closer agreement with ERA5 at large scales, likely due to its use of the latter as training data, but significantly underestimates mesoscale kinetic energy compared to the physics-based model MPAS. Note that these findings are specific to the models and configurations used and should be interpreted with caution.

Gravity waves (GWs) can manifest and exert influence across various scales, challenging their direct separation from large-scale background flows through spectral filtering. Horizontal divergence is commonly used as a proxy for GWs, but the rotational motion of GWs and the divergent motion of Kelvin and mixed Rossby gravity (MRG) waves may introduce uncertainties. To evaluate the reliability of the methods above, this study examines the variation in vertical and lateral momentum fluxes among three GW separation methods: spherical harmonic filtering (SHF), divergent wind from Helmholtz decomposition with SHF (DIVF), and inertia-gravity (IG) mode from normal-mode decomposition with SHF (IGF). The analysis of selected boreal winter and summer cases shows that DIVF and IGF exhibit similar results, whereas direct SHF shows notable discrepancies, particularly in the upper troposphere. This finding suggests that the rotational motion of GWs and divergent motion of Kelvin and MRG waves only minimally affect the estimation of GW momentum flux (GWMF), whereas the rotational motion of non-IG (Rossby, Kelvin, and MRG) modes can introduce significant biases. The differences in the upper troposphere are larger than those in the stratosphere, where divergent motion dominates both the total and the GW circulation fields. In the stratosphere, although the vertical GWMF shows minimal variation between methods, the lateral GWMF obtained by direct SHF exhibits visible biases. Given the similarity between DIVF and IGF, using divergent wind components is recommended for diagnosing GW quantities related to horizontal wind perturbations. This comparison offers valuable insights into accurately extracting GWMF. SIGNIFICANCE STATEMENT: The purpose of this study is to evaluate the effectiveness of direct spectral truncation and divergent wind proxy for separating gravity waves in the upper troposphere and stratosphere from the perspective of wave momentum flux. The findings suggest that divergent wind proxy provides more reliable estimates of gravity wave momentum flux, especially in the upper troposphere where direct spectral truncation introduces significant biases due to the rotational motion of non-IG (Rossby, Kelvin, and MRG) modes. The effects of rotational motion in gravity waves and the divergent motion of Kelvin and mixed Rossby gravity waves are minimal in momentum flux estimation. This work offers valuable insights for guiding gravity wave separation and is expected to promote future research in gravity wave dynamics.

Exploring the links between moist processes, convection, and intensification in modeled tropical cyclones (TCs) remains an important object in the TC internal dynamics. In this study, the full life cycle of an idealized TC is diagnosed by a local moist available energy budget. In general, the diabatic term in available potential energy (APE) mainly from the microphysical processes dominates the rapid intensification (RI) of the TC, while the uplift term makes a negative and considerable contribution, implying the importance of water lifting in TC development. The budgets at different layers in the inner region are further explored. In the lower troposphere, the downward transport of the vertical pressure flux dominates the growth of the available elastic energy (AEE); the planetary boundary layer (PBL) and the microphysical processes contribute more to APE in the pre-RI and RI stage, respectively. In the mid-upper troposphere, the diabatic term mainly from the microphysical processes leads to the growth of APE; then the increased APE is converted into mechanical energy and ultimately the cyclone intensifies. The vertical pressure fluxes transport downward below 10 km and upward above 10 km, with the AEE being deposited in the lower troposphere and removed in the mid-upper troposphere. Compared to previous budget analyses, our approach emphasizes the conditional instability of the atmosphere and the corresponding result aligns more closely with the conditional instability of the second kind (CISK) mechanism. Also, the divergence of the APE flux at high levels indicates an instantaneous strengthening of the wind speed model.

Numerical weather prediction (NWP) is the core technology for weather forecast and disaster prevention and mitigation. The research and operational applications of NWP have always been highly valued in China, and have achieved great progress with an appreciable international influence in the theories, algorithms, and operational system developments. This paper first summarizes the scientific and technological evolution of NWP in China, and then focuses on the current status and recent updates of the two homemade global NWP systems: GRAPES (Global/Regional Assimilation and PrEdiction System) and YHGSM (YinHe Global Spectral Model). (1) GRAPES possesses both deterministic and ensemble forecast systems, with global (regional) model versions running on 12–50-km (3–10-km) resolutions. Significant improvements have been made on its dynamic core, four-dimensional variational (4D-Var) assimilation, satellite and radar data assimilation, ensemble forecast, and cloud microphysics schemes, and so on. It is capable to perform subseasonal to seasonal forecast and has incorporated an atmospheric chemistry model, typhoon numerical forecast model, and ocean wave model. (2) YHGSM continues to follow the development route of spectral models, featured prominently with a dry-mass conserved spectral dynamical core, ensemble 4D-Var assimilation, coupled ocean–land–atmosphere ensemble forecast, and the medium-term and monthly-extended global high-resolution forecast as the baseline. These NWP systems autonomouly developed by the China Meteorological Administration and the national defense insitution benefit from long-term adherence to the national science and technology development strategies and close research to operation practices.

Numerical weather prediction (NWP) is the core technology for weather forecast and disaster prevention and mitigation. The research and operational applications of NWP have always been highly valued in China, and have achieved great progress with an appreciable international influence in the theories, algorithms, and operational system developments. This paper first summarizes the scientific and technological evolution of NWP in China, and then focuses on the current status and recent updates of the two homemade global NWP systems: GRAPES (Global/Regional Assimilation and PrEdiction System) and YHGSM (YinHe Global Spectral Model). (1) GRAPES possesses both deterministic and ensemble forecast systems, with global (regional) model versions running on 12u201350-km (3u201310-km) resolutions. Significant improvements have been made on its dynamic core, four-dimensional variational (4D-Var) assimilation, satellite and radar data assimilation, ensemble forecast, and cloud microphysics schemes, and so on. It is capable to perform subseasonal to seasonal forecast and has incorporated an atmospheric chemistry model, typhoon numerical forecast model, and ocean wave model. (2) YHGSM continues to follow the development route of spectral models, featured prominently with a dry-mass conserved spectral dynamical core, ensemble 4D-Var assimilation, coupled oceanu2013landu2013atmosphere ensemble forecast, and the medium-term and monthly-extended global high-resolution forecast as the baseline. These NWP systems autonomouly developed by the China Meteorological Administration and the national defense insitution benefit from long-term adherence to the national science and technology development strategies and close research to operation practices.

The rotational and divergent kinetic energy (RKE and DKE) spectra of geostrophic vortices (Rossby waves; RWs) and inertia-gravity waves (IGWs) in the global atmosphere are investigated with ERA5 reanalysis. The separation of RWs and IGWs in physical space is based on the normal-mode decomposition, and the Helmholtz decomposition produces their RKE and DKE spectra at different layers, with a focus on spherical wavenumbers 10 <= l <= 100. In the upper troposphere and the middle and lower stratosphere, the RKE spectra of the total mode closely resemble the horizontal kinetic energy (HKE) spectra of RWs over most wavenumbers; the DKE spectra of the total mode are more comparable to the DKE spectra rather than the HKE spectra of IGWs, although their slopes are similar. The HKE of RWs is dominated by its rotational component, accounting for more than 80% of the HKE in most ranges of concern. Although the HKE of IGWs is dominated by its divergent component, its rotation component is also significant, with an average percentage exceeding 25% in all three vertical layers analyzed. Care must be taken when employing divergence as a proxy of IGWs, as the DKE may underestimate the HKE of IGWs. With the increase of altitude and the decrease of scale, the contribution of the divergent component increases in the horizontal circulation of both RWs and IGWs. The atmospheric horizontal kinetic energy (HKE) spectrum exhibits a mysterious -5/3 slope at mesoscales, but underlying physical mechanisms are still not fully understood. Evaluating the contributions of geostrophic vortices and inertia-gravity waves to the HKE spectrum helps us understand this issue. Combining the normal-mode and Helmholtz decompositions, we investigate the rotational and divergent kinetic energy (RKE and DKE) spectra of geostrophic vortices and inertia-gravity waves in the global atmosphere with ERA5 reanalysis. Our results verify that the RKE approximates the HKE of the vortex well, but the DKE underestimates the HKE of the wave, especially at larger scales. The HKE of vortices and waves is dominated by their respective rotational and divergent components. However, unlike the negligible divergent component in vortices, the contribution of the rotational component in waves is significant. In the vertically integrated HKE over three selected layers in the upper troposphere and stratosphere, the average percentage of RKE at l = 10-100 exceeds 25%. When using the intersection of RKE and DKE spectra to diagnose the mesoscale transition, it should be noted that the crossing scale of the HKE spectra of waves and vortices may be larger. The total rotational kinetic energy (RKE) spectra can be well approximated to the horizontal kinetic energy (HKE) spectra of Rossby waves The total divergent kinetic energy (DKE) spectra closely resemble the DKE spectra of inertia-gravity waves rather than their HKE spectra On average, the RKE component accounts for more than 25% in the HKE of inertia-gravity waves at wavenumbers 10-100

Exploring the links between moist processes, convection, and intensification in modeled tropical cyclones (TCs) remains an important object in the TC internal dynamics. In this study, the full life cycle of an idealized TC is diagnosed by a local moist available energy budget. In general, the diabatic term in available potential energy (APE) mainly from the microphysical processes dominates the rapid intensification (RI) of the TC, while the uplift term makes a negative and considerable contribution, implying the importance of water lifting in TC development. The budgets at different layers in the inner region are further explored. In the lower troposphere, the downward transport of the vertical pressure flux dominates the growth of the available elastic energy (AEE); the planetary boundary layer (PBL) and the microphysical processes contribute more to APE in the pre-RI and RI stage, respectively. In the mid-upper troposphere, the diabatic term mainly from the microphysical processes leads to the growth of APE; then the increased APE is converted into mechanical energy and ultimately the cyclone intensifies. The vertical pressure fluxes transport downward below 10 km and upward above 10 km, with the AEE being deposited in the lower troposphere and removed in the mid-upper troposphere. Compared to previous budget analyses, our approach emphasizes the conditional instability of the atmosphere and the corresponding result aligns more closely with the conditional instability of the second kind (CISK) mechanism. Also, the divergence of the APE flux at high levels indicates an instantaneous strengthening of the wind speed model.

Two global atmospheric circulation datasets (ERA5 and NCEP FNL) with horizontal resolutions of 0.25 degrees 3 0.25 degrees are investigated in terms of kinetic energy (KE) spectra at 200 hPa (roughly between 11 and 12 km). The horizontal KE (HKE) in NCEP FNL is larger and flatter than that in ERA5 at subsynoptic scales and mesoscales. Restoring the energy of this wavenumber range to the physical space shows that the HKE in NCEP FNL is larger than that in ERA5 over most areas but smaller mainly in the Indo-Pacific warm pool. The spectral budgets show that at these scales, the positive contribution from net vertical flux in ERA5 is stronger than that in NCEP FNL, while the negative contribution from available potential energy (APE) conversion is smaller; assuming that the atmosphere is in a quasi-stationary state, more dissipation is found in ERA5 than in NCEP FNL, which should be responsible for the HKE spectrum in ERA5 to be steeper and weaker than that in NCEP FNL. Our formulation shows that the APE conversion and net vertical flux are related to the pressure vertical velocity (PVV). The APE conversion and net vertical flux differences between the two datasets, like the PVV difference, are mainly from the tropical region. At large scales, the vertical motion in ERA5 is larger than that in NCEP FNL. The amplitude differences of the PVV spectra between two datasets are consistent with those of the large-scale precipitation spectra associated with microphysics parameterizations. These results support that vertical motion is a key dynamical factor explaining energy discrepancies at mesoscales.

In a typical non-hydrostatic spectral dynamic numerical weather prediction (NWP) kernel, all forecast variables are transformed between grid point and spectral spaces to compute their gradients and solve the implicit problem. This kernel requires numerous spectral transformations, which depend heavily on extensive global communication and significantly hinder parallel computing efficiency. This paper introduces an innovative non-hydrostatic spectral kernel that incorporates a finite-volume method within the spectral framework. We have developed a horizontal divergence (D)-based structure equation, allowing direct computation of most prognostic variables and their horizontal gradients at grid point space. By doing so, the need for spectral transformations is substantially decreased. Our experiments demonstrate that this new approach reduces the cost of spectral transformations by up to 40%, enhancing the overall model efficiency by 15%-22%. Additionally, a series of tests confirmed the accuracy and stability of this new solver. This paper proposes a new non-hydrostatic spectral solver by applying a finite-volume method (FVM) into the spectral framework, where a horizontal divergence (D)- based structure equation is constructed and most of the prognostic variables as well as their horizontal gradients are calculated in grid point space directly. The number of spectral transforms is dramatically reduced. In practice, the cost of spectral transform with the proposed solver is reduced up to 40%. image

The Yin‐He Global Spectral Model (YHGSM) is a dry‐mass conserving hydrostatic global spectral model, relying on spectral transforms to compute horizontal derivatives. We present an extension of YHGSM core named YHGSM‐FVM which uses a second‐order finite‐volume method (FVM) to compute the horizontal derivatives in grid‐point space instead of the spectral approach. With this approach, the computational efficiency of the spectral model is improved since part of the spectral transforms is superseded by FVM which only needs local data and the computational demand is lower. More importantly, YHGSM‐FVM is still a spectral model solving the Helmholtz equation directly in spectral space with a highly efficient semi‐implicit semi‐Lagrangian advection scheme. The comparisons between YHGSM‐FVM and YHGSM are conducted, and the results show that both models have comparable prediction skill, but YHGSM‐FVM outperforms YHGSM in computational efficiency.

A new formulation of the spectral budget of vertical vorticity and horizontal divergence suitable for the me-soscale atmosphere on an f plane is derived. Compared to previous formulations in large-scale studies, there are three main improvements: (i) both the squared vorticity (SV; i.e., enstrophy as usual) and squared divergence (SD) spectra are taken into account, (ii) the spectral transfers of SV and SD between scales are exactly constructed under the nonlinear ad-vection of the full horizontal velocity, and (iii) the general relationship between spectral energy and SV/SD transfers is de-rived. With this new formulation, the atmospheric spectra of divergent and rotational motion components are investigated through numerical simulation of idealized dry baroclinic waves. Spectral budget analysis shows that, in the present dry sim-ulation, the upper troposphere is almost completely dominated by the downscale SV transfer at all scales, while the lower stratosphere is dominated by the downscale SV transfer at synoptic scales and by the downscale SD transfer at mesoscales. The pressure-related term is largely cancelled out by the conversion term between SV and SD at both levels, but at the small-scale end of lower-stratospheric mesoscales there exists a significant net positive forcing, accounting for the distinct spectral transition of the total spectrum there. An explicit association between spectral energy and SV/SD transfers is fur-ther made. In the upper troposphere, the downscale energy cascade is mainly governed by the downscale SV transfer, while in the lower stratosphere, it is mainly governed by the residual term related to nonuniformly distributed vertical velocity. SIGNIFICANCE STATEMENT: The purpose of this study is to explore the dynamics underlying the atmospheric spectra of divergent and rotational motion components. The traditional analysis of enstrophy is first extended to include both squared vertical vorticity (SV) as usual and squared horizontal divergence (SD), and then a new formulation of the spectral SV and SD budget suitable for the mesoscale atmosphere is derived, with application to the dry baroclinic waves simulation. Our results clearly reveal the different physical processes governing the vorticity and divergence spectra at different heights. We also derive the general relationship between spectral energy and SV/SD transfers, which allows explicitly associating spectral energy and SV/SD fluxes and thus provides additional physical views on the mesoscale energy cascade. Further work should consider the effects of other physical processes neglected here.

Abstract The responses of atmospheric kinetic energy (KE) spectra to three convective parameterizations (CPs) in global high‐resolution simulations are revealed. The results show that the KE spectra exhibit high sensitivity to the CPs, mainly at mesoscales in the middle and upper troposphere. The New Tiedtke scheme produces the steepest mesoscale slope, followed by the Kain‐Fritsch scheme and then the Grell‐Freitas scheme. In general, there is a compensating relationship between latent heat released by the CP and microphysics parameterization (MP). The less latent heat released by the CP is compensated by the more latent heat released by the MP. The shallowest mesoscale spectra for the Grell‐Freitas scheme are related to the strongest downscale cascade dominated by the rotational component of the flow, and this is attributed to more latent heat released from MP enhancing the intensity of vorticity in the troposphere and producing more gravity wave activities in the lower stratosphere.

This study investigates the effects of the assumption on the types of air-mass conservation prescribed in numerical models. First, predictions of the July 2021 (“21.7”) Henan extreme rainfall event from the Integrated Forecast System (IFS) at ECMWF were compared with those from the Yin-He Global Spectral Model (YHGSM), which is a global spectral model with total air-mass conservation (TMC) and dry air-mass conservation (DMC) options. Then, a sensitivity test between simulations from the YHGSM adopting TMC and DMC was conducted. The results show that both the IFS and YHGSM predicted relatively well the 24-h rainfall amount less than 100 mm day−1 on 20 and 21 July 2021 at lead times of 84, 60, and 36 h. For heavy precipitation exceeding 100 mm day−1, however, both models obviously underestimated the daily rainfall amount on 20 July 2021, but the YHGSM produced more precise and stable precipitation forecasts on these two days than the IFS, especially the maximum 24-h precipitation amount, with better consistency at lead times of 84, 60, and 36 h. These differences are further examined in the sensitivity test. Predictions from the YHGSM with DMC show rainfall distributions and daily rainfall amounts closer to the observations at longer lead times. It is inferred that considering sources or sinks of total water in dynamical cores with DMC may have positive feedback for the precise prediction of condensates. For extreme rainfall events, the high local loss of total water may have caused a loss of the atmospheric mass, leading to an additional decrease in surface pressure. Subsequently, the unbalanced pressure gradient force enhances the cyclonic rotation of surface wind and strengthens convergence in the lower troposphere, which in turn further strengthens the vertical velocity, circularly contributing to the enhanced precipitation if the water vapor condition is favorable.

The accurate forecasting of tropical cyclones (TCs) is a challenging task. The purpose of this study was to investigate the effects of a dry-mass conserving (DMC) hydrostatic global spectral dynamical core on TC simulation. Experiments were conducted with DMC and total (moist) mass conserving (TMC) dynamical cores. The TC forecast performance was first evaluated considering 20 TCs in the West Pacific region observed during the 2020 typhoon season. The impacts of the DMC dynamical core on forecasts of individual TCs were then estimated. The DMC dynamical core improved both the track and intensity forecasts, and the TC intensity forecast improvement was much greater than the TC track forecast improvement. Sensitivity simulations indicated that the DMC dynamical core-simulated TC intensity was stronger regardless of the forecast lead time. In the DMC dynamical core experiments, three-dimensional winds and warm and moist cores were consistently enhanced with the TC intensity. Drier air in the boundary inflow layer was found in the DMC dynamical core experiments at the early simulation times. Water vapor mixing ratio budget analysis indicated that this mainly depended on the simulated vertical velocity. Higher updraft above the boundary layer yielded a drier boundary layer, resulting in surface latent heat flux (SLHF) enhancement, the major energy source of TC intensification. The higher DMC dynamical core-simulated updraft in the inner core caused a higher net surface rain rate, producing higher net internal atmospheric diabatic heating and increasing the TC intensity. These results indicate that the stronger DMC dynamical core-simulated TCs are mainly related to the higher DMC vertical velocity.

To study the multiscale interactions between rotational and divergent components of atmospheric motion, a new formulation of spectral budget of rotational kinetic energy (RKE) and divergent kinetic energy (DKE) based on the primitive equations in the pressure coordinate is derived, with four main characteristics: 1) horizontal kinetic energy (HKE) spectral transfer is exactly divided into spectral transfer of RKE and DKE, 2) the exact spectral conversion term between DKE and RKE is constructed, 3) the Coriolis term is considered, and 4) both the baroclinic conversion from avail-able potential energy (APE) and the vertical flux of HKE act only on DKE. With this new formulation, outputs from ERA5 global reanalysis are investigated. At planetary scales, HKE spectral transfer, mainly attributed to f3 effect, is domi-nated by downscale DKE transfer. At synoptic scales, it is dominated by an upscale transfer of RKE energized by conver-sion of DKE mainly due to the Coriolis effect. The ultimate source of DKE in the upper troposphere is conversion of APE, while in the stratosphere it is the vertical flux. At mesoscales, the spectral transfers of RKE and DKE are both down-scale, and conversion from RKE to DKE exists at sub-800-km scales in the upper troposphere, which is mainly attributed to the contribution from relative vorticity. At different heights, the intersection scales of RKE and DKE spectra are af-fected by the scales of positive peaks of the local spectral conversion from DKE to RKE around total wavenumber 10. SIGNIFICANCE STATEMENT: The purpose of this study is to explore more physical insights on the dynamics un-derlying the atmospheric energy spectra from the perspective of rotational and divergent components of motion. We derive a new formulation of the spectral rotational and divergent kinetic energy budget in the pressure coordinate for the global atmosphere, with application to ERA5 global reanalysis. Our results reveal the differences of spectral energy budget between rotational and divergent motions at different heights and scales. This new formulation provides a good tool for revealing the multiscale cascade and interaction between atmospheric rotational and divergent motions. Future work should investigate these dynamical processes with higher-resolution simulations and datasets.

The newly developed nonhydrostatic（NH） global spectral dynamical core is evaluated by using three-dimensional（3D） benchmark tests with/without moisture. This new dynamical core differs from the original Aladin-NH like one in the combined use of a dry-mass vertical coordinate and a new temperature variable, and thus, it inherently conserves the dry air mass and includes the mass sink effect associated with precipitation flux. Some 3D dry benchmark tests are first conducted, including steady state, dry baroclinic waves, mountain waves in non-sheared and sheared background flows, and a dry Held–Suarez test. The results from these test cases demonstrate that the present dynamical core is accurate and robust in applications on the sphere, especially for addressing the nonhydrostatic effects.Then, three additional moist test cases are conducted to further explore the improvement of the new dynamical core.Importantly, in contrast to the original Aladin-NH like one, the new dynamical core prefers to obtain simulated tropical cyclone with lower pressure, stronger wind speeds, and faster northward movement, which is much closer to the results from the Model for Prediction Across Scales（MPAS）, and it also enhances the updrafts and provides enhanced precipitation rate in the tropics, which partially compensates the inefficient vertical transport due to the absence of the deep convection parameterization in the moist Held–Suarez test, thus demonstrating its potential value for full-physics global NH numerical weather prediction application.

Changes in the intensities of tropical cyclones (TCs) are a complex multiscale problem. Not only external atmospheric environmental factors, such as the ocean thermal environment and environmental vertical wind shear, but also internal dynamic processes, such as small-scale processes, balanced and unbalanced dynamics and multiscale interaction processes, result in changes in TC intensity. These factors interact in a nonlinear form, resulting in difficulty regarding TC intensity forecasts. At present, studies on the effects of external environmental factors are relatively complete and certain. As the key to breaking through the limitation of TC intensity prediction, most of the internal dynamic processes have not been unified. From the two aspects of environmental factors and internal dynamics, this paper reviews, summarizes and discusses the above main physical factors affecting changes in TC intensity by investigating the latest literature in the last decade to provide a theoretical basis and ideas for the further study of TC intensity changes.

Numerical weather prediction (NWP) has become an important method of predicting extreme weather events, but orography is one of the key factors affecting the performance of NWPs. In this paper, based on Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) elevation data, a method for constructing a global orographic dataset suitable for NWP spectral models is investigated. The Yin-He global spectrum model (YHGSM) is used to simulate the early and peak periods of the extreme rainfall event on 20 July 2021 in Henan Province, China, and the heavy rain in Beijing in order to verify the effectiveness and superiority of the proposed orographic construction method. It is demonstrated that in a few cases the direct two-dimensional filter can sometimes simulate more intense rainfall, but in general, the bidirectional one-dimensional filter is better than the direct two-dimensional filter in orographic processing, and the bidirectional one-dimensional filter can filter out more of the small-scale orographic information. The effect of the higher orographic resolution before conversion to spectral space is not very obvious, but it is demonstrated that the simulation results are better for the heavy-rainfall level. In conclusion, in most cases, the simulations conducted using the new global orographic dataset based on ASTER data are better than those obtained using the model’s original orography, especially for torrential and extreme rainfall. These conclusions provide a reference for future predictions of and research on extreme rainfall events.