Explore the vast range of titles available.

Vertical profiles of methane (CH4) are essential for validating satellite observations and quantifying regional sources and sinks. This study presents the first two high‐resolution CH4 profiles (0–25 km) over southeastern China, an economically developed region, using AirCore measurements. The profiles exhibited distinct variations: CH4 increased from 25 to 15 km, remained stable (15–6 km), decreased sharply (6–3 km), then rose toward the surface (∼600 ppb range). While trends align with observations in northwest China, concentrations were higher. Wind patterns and balloon trajectories influenced the profiles, with long‐range air mass transport from coastal megacities elevating upper‐atmosphere CH4. Comparisons with TCCON, TROPOMI, and GOSAT‐2 revealed 26–39 ppb discrepancies in column‐averaged CH4, exposing resolution limitations and retrieval uncertainties. Pronounced day‐to‐day variability highlight influence from meteorological conditions and regional transport. These findings emphasize the need for higher spatiotemporal resolution monitoring to improve CH4 assessments and climate modeling.

This study evaluates the prediction of MJO teleconnections in two versions of the NOAA Unified Forecast System (UFS): prototype 5 (UFS5) and prototype 6 (UFS6). The differences between the two prototypes in the number of vertical layers (64 in UFS5 vs. 127 in UFS6) and the model top (54 km in UFS5 vs. 80 km in UFS6) can potentially impact the prediction of MJO teleconnections. With respect to ERA-Interim, the global teleconnections of the MJO to the Northern Hemisphere show similar biases in 500 hPa geopotential height over the North Atlantic and European sectors in both prototypes, whereas UFS6 has slightly smaller biases over the North Pacific region. Both prototypes capture the extratropical cyclone activity occurring in weeks 3–4 over the North Atlantic after the MJO phases 6–7 and over the North Pacific and North America after MJO phases 4–5. Both prototypes successfully forecast the sign and approximate locations of 2-m temperature anomalies over the mid-to-high latitude continents occurring in weeks 3–4 after MJO phase 3 but fail to capture the sign reversal of anomalies over North America between weeks 3 and 4 after MJO phase 7. Overall, the two prototypes show similar performance in simulating the tropospheric basic state as well as prediction skill of the MJO and MJO teleconnections, suggesting that the increase in model vertical resolution and model top does not strongly improve the prediction of MJO teleconnections in the troposphere in UFS.

Internal tide generation and breaking play a primary role in the vertical transport and mixing of heat and other properties in the ocean interior, thereby influencing climate regulation. Additionally, internal tides increase sound speed variability in the ocean, consequently impacting underwater acoustic propagation. With advancements in large‐scale ocean modeling capabilities, it is essential to assess the impact of higher model resolutions (horizontal and vertical) in representing internal tides. This study investigates the influence of vertical resolution on internal tide energetics and its subsequent effects on underwater acoustic propagation in the HYbrid Coordinate Ocean Model (HYCOM). An idealized configuration with a ridge, forced only by semidiurnal tides and having 1‐km horizontal grid‐spacing, is used to test two different vertical‐grid discretizations, defined based on the zero‐crossings of horizontal velocity eigenfunctions and the merging of consecutive layers, with seven distinct numbers of isopycnal layers, ranging from 8 to 128. Analyses reveal that increasing the number of layers up to 48 increases barotropic‐to‐baroclinic tidal conversion, available potential energy, and vertical kinetic energy, converging with higher layer counts. Vertical shear exhibits a similar pattern but converges at 96 layers. Increasing the number of isopycnal layers, up to 48, increases the available potential energy contained in high (third‐to‐eighth) tidal baroclinic modes. Finally, sound speed variability and acoustic parameters differ for simulations with less than 48 layers. Therefore, the study concludes that a minimum vertical resolution (48 layers in this case) is required in isopycnal models to accurately represent internal tide properties and associated underwater acoustic propagation. Plain Language Summary Internal tides are waves that undulate along interfaces between waters of different densities inside the ocean and form when tides interact with sloping topography. Like waves at the beach, internal tides can break and mix cold, deep water with warmer surface water, helping to spread heat throughout the water column. This mixing can reduce the amount of heat at the ocean surface, affecting ocean‐atmosphere interactions and influencing the climate. Additionally, internal tides can impact acoustic propagation in the ocean interior. In the past decade, realistic numerical simulations have been able to model internal tides. However, model resolution (horizontal and vertical) may impact internal tide properties. This study uses “simplified” simulations with different vertical layers and forced only by tides to investigate the impact of the number of layers on the properties of modeled internal tides and subsequent effects on acoustic propagation. We find that increasing the number of layers up to 48 layers increases the vertical velocity and vertical shear, which have the potential to increase mixing of water and impact the way sound propagates in the ocean interior. Therefore, we conclude that at least 48 layers are required to accurately represent internal tides and associated underwater acoustic propagation. Key Points Model vertical resolution impacts internal tide‐induced kinetic energy, available potential energy, dissipation, and vertical shear Increasing the number of isopycnal layers, up to 48, increases the available potential energy contained in high (third to eighth) vertical modes At least 48 isopycnal layers are necessary to minimize variability in sound speed and acoustic propagation caused by the number of layers

The upper ocean plays a critical role in determining the Madden–Julian Oscillation (MJO) characteristics through modulating the tropical atmosphere–ocean interaction. By increasing the oceanic vertical resolution, its impacts on the MJO eastward propagation are discussed in this study by using a climate system model. With a refined vertical resolution in the upper ocean, warmer surface ocean and shallower mixed layer depth are produced in the tropics, which induces associated atmospheric changes as the response to the ocean feedbacks. Enhanced November–April-mean vertically-integrated specific humidity is found around the equatorial region with the increased vertical resolution, which strengthens the zonal and meridional moisture gradients. The lead-lag correlation of MJO precipitation demonstrates that the simulated MJO eastward propagation is improved with increased oceanic vertical resolution by improving the simulations of convective instability at the east of the MJO convective center, the boundary layer moisture convergence, the low- and upper-level circulation, and the vertical structure of equivalent potential temperature and diabatic heating. Moreover, the zonal asymmetry of the tendency of specific humidity is also improved by increasing the oceanic vertical resolution. The vertically-integrated moisture budget analysis is applied to further investigate the dominance of the moistening and drying processes. Results reveal that the drying processes are successfully reproduced over the central Indian Ocean in the case of increased oceanic vertical resolution, whilst the moistening processes are not well captured over the Maritime Continent and the MJO “detour” region. It suggests that additional modifications are needed to further improve the MJO simulation.

Atmospheric Infrared Ultraspectral Sounder (AIUS) aboard the Chinese GaoFen-5 satellite was launched on 9 May 2018. It is the first hyperspectral occultation spectrometer in China. The spectral quality assessment of AIUS measurements at the full and representative spectral bands was presented by comparing the transmittance spectra of measurements with that of simulations. AIUS measurements agree well with simulations. Statistics show that more than 73% of the transmittance differences are within ±0.05 and more than 91% of the transmittance differences are within ±0.1. The spectral windows for O3, H2O, temperature, CO, CH4, and HCl were also analyzed. The comparison experiments indicate that AIUS data can provide reliable data for O3, H2O, temperature, CO, CH4, and HCl detection and dynamic monitoring. The H2O profiles were then retrieved from AIUS measurements, and the precision, resolution, and accuracy of the H2O profiles are discussed. The estimated precision is less than 1.3 ppmv (21%) below 57 km and about 0.9–2.4 ppmv (20–31%) at 60–90 km. The vertical resolution of H2O profiles is better than 5 km below 32 km and about 5–8 km at 35–85 km. Comparisons with MLS Level 2 products indicate that the mean H2O profiles of AIUS have a good agreement with those of MLS. The relative differences are mostly within ±10% at 16–75 km and about 10–15% at 16–20 km in 60∘–80∘ S. For 60∘–65 ∘ S in December, the relative differences are within ±5% between 22 km and 80 km. The H2O profiles retrieved from AIUS measurements are credible for scientific research.

The Community Earth System Model currently contains two primary atmospheric configurations: the Community Atmosphere Model 6 (CAM6, 32 levels, ∼${\\sim} $ 40‐km top); and the Whole Atmosphere Community Climate Model 6 (WACCM6, 70 levels, ∼${\\sim} $ 140‐km top). For CAM7, a number of factors motivate a raising of the model top and enhancement of the vertical resolution and this study documents the decision making process toward this next generation vertical grid. As vertical resolution in the troposphere/lower stratosphere is increased, the role of the resolved waves in driving the Quasi‐Biennial Oscillation (QBO) is enhanced, becoming more similar in magnitude to ERA5 reanalysis. This can be traced to improved equatorial Kelvin waves and their vertical momentum fluxes. It is further shown that a model lid at ∼${\\sim} $ 80‐km does not have detrimental impacts on the representation of the QBO compared to a 140‐km top. Based on this analysis, the vertical grid for CAM7 will have an ∼${\\sim} $ 80‐km top with 93 levels, 500‐m grid spacing in the troposphere and lower stratosphere, and 10 additional levels in the boundary layer compared to CAM6. A 58‐level/∼${\\sim} $ 40‐km low‐top option will also be available. We further introduce new coupled simulations using CAM6 but with CAM7's vertical grid above the boundary layer and use these to demonstrate that basic features of the stratospheric circulation are similar to WACCM6, despite the lower model top. These simulations further show that despite the higher fidelity of the QBO, the observed connection between the QBO and the Madden‐Julian Oscillation is absent. Plain Language Summary This study explores the impacts of changing the vertical grid spacing and model lid height on the representation of the atmosphere within the Community Atmosphere Model (CAM) to inform decisions regarding the vertical grid choices for the next generation of this model (CAM7). It is shown that decreasing the grid spacing (increasing the resolution) in the troposphere and lower stratosphere can lead to a better representation of tropical waves and their role in driving the Quasi‐Biennial Oscillation (QBO)—a quasi‐periodic variation in the winds of the lower stratosphere. It is also shown that a viable representation of the stratospheric polar vortices and the QBO can be obtained with a model lid placed at approximately 80 km. Overall, this analysis motivates the decisions made with regards to the grid for CAM7 and a suite of simulations that use this new grid are described. These simulations are then assessed for their representation of the observed connection between the QBO and the Madden‐Julian Oscillation (MJO)—a mode of variability in the tropical troposphere. Despite the high fidelity of the QBO in this model, the QBO‐MJO connection remains absent. Key Points Resolved wave‐driving of the Quasi‐Biennial Oscillation (QBO) increases with vertical resolution A 93‐level mid‐top (∼${\\sim} $ 80‐km top) and a 58‐level low‐top (∼${\\sim} $ 40‐km top) grid are proposed for the next generation Community Atmosphere Model Despite an improved QBO in the mid‐top, its observed connection with the Madden‐Julian Oscillation is not reproduced

The aggregation of tropical convection greatly influences the mean‐state of the atmosphere, altering humidity distributions, total atmospheric radiative cooling, and cloud amounts. Although studies have demonstrated the sensitivity of convective aggregation to horizontal resolution and domain size, few studies have explored the impact of vertical resolution on convective aggregation. Here, we investigate the impact of vertical resolution on simulations of deep convection and convective aggregation using the System for Atmospheric Modeling convection resolving model. We analyze simulations of tropical radiative‐convective equilibrium with varying vertical levels (32, 64, 128, and 256) across small (100 km), medium (700 km) and large (1,500 km) domains. We demonstrate that relative humidity and cloud fraction decrease with increasing vertical resolution as a result of reduced turbulent mixing. Vertical resolution also influences the occurrence of, onset time, and equilibrium intensity of aggregated convection, and also appears to affect the sensitivity of convective aggregation to domain size. Understanding how simulated convection aggregates, as well as its simulated sensitivity to model formulation, is critical for making and interpreting future predictions of global climate change. Plain Language Summary We study the simulation of clouds and storms in simple computer models of the tropical atmosphere. These models calculate air movement on a grid. Large grid boxes result in a very coarse, pixelated representation of the atmosphere, while smaller grid boxes offer a much clearer, high‐resolution video. Ideally, the average air movement, cloud formation, and rainfall simulated by these models shouldn't be affected by the size of the grid boxes, with smaller boxes just providing additional detail. However, here we show that the height of grid boxes influences average properties of the simulations, such as the total cloud amount, the amount of rain that falls, and the relative humidity. Key Points The relative humidity and high cloud fraction both decrease with increasing vertical resolution in System for Atmospheric Modeling Vertical resolution impacts convective aggregation occurrence, onset time, and equilibrium intensity The sensitivity of convective aggregation to domain size may depend on vertical resolution

In order to investigate the impact of increasing the vertical resolution of the initial field on the 12–24 h forecasts of the TRAMS (Tropical Regional Atmosphere Model System) model, this study conducted numerical experiments focusing on a typical coastal warm sector rainfall event that occurred in the South China. The findings indicate that increasing the vertical resolution of the initial field led to improved simulation of coastal convection during the 0–12 h period. However, spurious convection was observed over the sea surface and continued to intensify in the 12–24 h period. Subsequent analysis revealed that the spurious convection is primarily associated with the hydrostatic adjustment of initial potential temperature in the TRAMS model. The hydrostatic adjustment leads to a reduction in the stability of the initial temperature stratification in the lower layers of the model, particularly when the number of vertical layers in the initial field increased from 17 to 32. A noticeable spurious unstable layer emerged between 0–200 m over the sea surface, triggering false convection. Further investigation revealed that the area where this unstable stratification occurs over the sea is situated below the height of the lowest level of the input analysis field (1000 hPa), indicating that the spurious disturbances are caused by an unreasonable vertical extrapolation process. Therefore, the findings of this study indicate that the extrapolation calculations using cubic splines in the initialization module of the TRAMS model introduce significant errors. Moreover, these errors increase with the enhancement of the vertical resolution of the initial field, which limits the improvement in model forecasting that could be achieved by increasing the vertical resolution of the initial field. We found that increasing the vertical resolution of the initial field in the TRAMS model led to spurious convection. This spurious convection is triggered by a false unstable layer near the surface. The computational errors during the hydrostatic adjustment of the initial perturbed potential temperature resulted in this false unstable layer.

A detailed assessment was carried out for extremely severe cyclonic storms (ESCSs) that developed over the Bay of Bengal during 1990–2020 using the India Meteorological Department (IMD) best-fit track data. During the past 30 years, the maximum intensity of land-falling ESCS has increased 26%, which is an average of about 8% increase per decade. Analysis signifies an increasing trend in the life cycle, duration of ESCS stage, and maximum wind speed of land-falling ESCSs. It is observed that the stage of land-falling ESCSs was very severe, and therefore, reliable forecast of land-falling ESCSs is very important having wide socioeconomic implications. Furthermore, a case study investigated the performance of Advanced Research of Weather Research and Forecasting (ARW) model for a 6-day forecast of ESCS Hudhud that developed over the Bay of Bengal during 2014. Performance evaluation was based on the impact of model domain size, vertical resolution, data assimilation, sea surface temperature (SST), gravity wave option (GWO), and air-sea flux parameterization schemes. Initial condition was improved through WRF 3D variational data assimilation (WRF-3DVAR) system. Thereafter, the simulated track, intensity, and intensification of the storm were validated against available IMD best-fit track datasets. Results from the ARW model indicate that the track and intensity of ESCS Hudhud were influenced by domain size, vertical resolution, data assimilation, SST, GWO, and air-sea flux schemes. Study deciphers that bigger domain, higher vertical resolution, data assimilation, and air-sea flux scheme with enthalpy coefficients provided a better forecast for ESCS Hudhud. The track errors on day 1 to day 4 was 61 km, 73 km, 85 km, and 96 km, respectively, and absolute error in terms of MSW was about 8 ms−1, 7 ms−1, 2 ms−1, and 8 ms−1 respectively at 9-km horizontal resolution.

The low cloud bias in global climate models (GCMs) remains an unsolved problem. Coarse vertical resolution in GCMs has been suggested to be a significant cause of low cloud bias because planetary boundary layer parameterizations cannot resolve sharp temperature and moisture gradients often found at the top of subtropical stratocumulus layers. This work aims to ameliorate the low cloud problem by implementing a new computational method, the Framework for Improvement by Vertical Enhancement (FIVE), into the Energy Exascale Earth System Model (E3SM). Three physics schemes representing microphysics, radiation, and turbulence as well as vertical advection are interfaced to vertically enhanced physics (VEP), which allows for these processes to be computed on a higher vertical resolution grid compared to the rest of the E3SM model. We demonstrate the better representation of subtropical boundary layer clouds with FIVE while limiting additional computational cost from the increased number of levels. When the vertical resolution approaches the large eddy simulation‐like vertical resolution in VEP, the climatological low cloud amount shows a significant increase of more than 30% in the southeastern Pacific Ocean. Using FIVE to improve the representation of low‐level clouds does not come with any negative side effects associated with the simulation of mid‐ and high‐level cloud and precipitation, that can occur when running the full model at higher vertical resolution. Plain Language Summary Most global climate models (GCMs) underestimate low‐level clouds. Increasing vertical resolution in GCMs is intended to address some of the issues contributing to the problem. In this study, we have implemented a new computational method, known as the Framework for Improvement by Vertical Enhancement (FIVE). FIVE can increase the vertical resolution for select aspects of a GCM, and in this study, we apply FIVE to the Energy Exascale Earth System Model. Our results show that when the vertical resolution approaches 5–10 m, the low cloud amount shows a significant increase of more than 30% in the southeastern Pacific Ocean, while the FIVE method also prevents the simulations from being too computationally expensive. Key Points A novel computational framework, Framework for Improvement by Vertical Enhancement (FIVE), has been implemented into Energy Exascale Earth System Model (E3SM) and allows select physics to be computed on a higher vertical grid When the vertical resolution approaches the large eddy simulation‐like in E3SM‐FIVE, the low cloud shows an increase of more than 30% in the Pacific Ocean E3SM‐FIVE is much less computationally expensive compared to E3SM with the same high vertical resolution