This study evaluates the Integrated Multi‐satellitE Retrievals for Global Precipitation Measurement (IMERG) Version 07B (V07B) against its predecessor V06B to enable a seamless transition of the widely used global Mesoscale convective system tracking data set from V06B to V07B. We use ground‐based radar observations from five climatically diverse regions, the contiguous United States, the central Amazon, the mountains of central Argentina, the equatorial Indian Ocean, and northern Australia, across multiple temporal (1–3 hr) and spatial (0.1°–0.25°) scales. An updated global MCS tracking data set is generated by combining IMERG V07B with satellite infrared brightness temperature. Relative to the radar benchmark, IMERG exhibits a pronounced land‐ocean contrast in its biases: over most land regions, both versions underestimate heavy (10–25 mm hr −1 ) and intense (>25 mm hr −1 ) precipitation, with the bias larger in V07B than in V06B. Over the ocean, V07B improves the intense precipitation retrieval. The global spatial distribution of MCS precipitation contribution is consistent between versions, but MCSs tracked in V07B have lower mean rain rates and heavy rain volume ratios than those in V06B. Our results further suggest that, over the regions and at the spatiotemporal scales evaluated, the apparent overestimation of heavy‐to‐intense precipitation in kilometer‐scale models relative to IMERG may partly reflect low biases in IMERG. This does not imply that km‐scale models are free of bias; rather, the magnitude of model overestimation inferred from IMERG‐based evaluations should be interpreted with caution. These findings provide a critical context for applying IMERG V07B in extreme precipitation, MCS climatology and for evaluating next‐generation convection‐permitting models.
Peatlands influence the global carbon cycle by storing carbon and releasing greenhouse gases such as methane (CH4) and carbon dioxide (CO2). Imaging hot spots for gas accumulation in peat remains challenging due to spatial and temporal heterogeneity and the invasive nature of traditional techniques. Minimally invasive geophysical methods such as ground-penetrating radar (GPR) have been used to image gas distribution in peat, but the need for direct ground contact limits its applicability in isolated environments. To address these issues, this study evaluated the feasibility of laboratory-based air-coupled GPR, in which the antenna is suspended above the surface, to image hot spots for biogenic gas accumulation in peat. Air-coupled and ground-based GPR measurements were applied to a peat monolith (0.75 & times; 0.31 & times; 0.25 m) from the Everglades (FL, USA) and constrained by flux measurements from gas traps fitted with time-lapse cameras and analyzed via gas chromatography. Air-coupled GPR imaged hot spots for gas accumulation with lateral dimensions of 0.05 & times; 0.03 m to 0.15 & times; 0.20 m, with gas content up to 25%, fluxes up to 171.9 mg CH4 m-2 day-1, and CH4 contents exceeding 70%. Hot spots were associated with slightly higher porosity and distinct peat structure, suggesting that physical properties of peat may influence gas storage and release behavior. These results highlight the role of peat physical properties in CH4 emissions, demonstrate the potential of air-coupled GPR for non-invasive monitoring of biogenic gas dynamics under controlled conditions, and support future evaluation of drone-based GPR surveys in peatlands.
The rheology of geologic materials is crucial for understanding the dynamics of planetary interiors. However, there have been few experimental studies of geologic materials subjected to large cyclical strain, as might be imposed by periodic ice-sheet loading or tidal forcing. To investigate the effect of cyclical strain on microstructural evolution we conducted deformation experiments with the same absolute shear strain magnitude (gamma abs = 4, 8 or 16), same net strain (gamma net = 0), and different strain paths. We deformed Carrara Marble at high temperature (845 +/- 25 degrees C) and high pressure (1.5 +/- 0.1 GPa), at a constant shear strain rate of 5 & times; 10-5 s-1, in the Large Volume Torsion Apparatus at Washington University in St. Louis. Thin sections and EBSD maps were used to characterize deformation microstructures, including grain-size, the fraction of material that is dynamically recrystallized, and crystallographic preferred orientation. There is poor correlation between the areal fraction of recrystallized grains and either the net or the absolute shear strain imposed by cyclical loading. However, there is excellent correlation between the percentage of recrystallized grains and the maximum strain for any deformation stage (gamma max). We conclude that microstructural evolution during complex cyclical loading is controlled by the largest strain increment, regardless of when it occurs during the deformation history. Comparison of microstructures to single-stage deformation experiments indicates that, despite nearly identical total deformation work, the resulting recrystallized fraction vary substantially. It demonstrates that strain-path history, rather than total amount of deformation, exerts stronger control on evolution of recrystallized fraction.
Saturn's magnetosheath hosts a mixed population of water-group neutrals and solar wind plasma. We present a 3-D model of soft X-ray emission by ion-neutral charge exchange in the near-equatorial magnetosheath. The model employs MHD simulation data of plasma properties at Saturn, Enceladus-genic neutral populations extrapolated from existing physical chemistry models, and circumscribes the magnetosheath region using existing magnetopause and bow shock models. Emission is concentrated in the equatorial plane and toward the magnetosheath nose, with volumetric emission rates of 10-10-10-11 photons cm-3 s-1. We explore viable imaging distances for a SMILE-like instrument. We conclude that imaging of Saturn's magnetopause is viable within 40 R S, with integration times on the order of similar to 1 min. However, the SMILE SXI field of view would only image 0.5% of the emission region at this distance. Enhancements in effective area comparable to MIXS on BepiColombo or closer viewing with a wider field of view would enable the whole magnetosheath to be imaged on few-minute timescales. Soft X-ray emission observations can be used to study the location, structure, and global dynamics of the magnetosheath region, and to inform neutral density models, especially of the outer system. Finally, far viewing of the emission region as a point source may be sufficient to capture variability in emission rate driven both by Saturn's internal plasma environment and varying solar wind conditions.
The deep carbon cycle of the Earth remains poorly understood in spite of its importance to the evolution of our planet. Here we consider estimated carbon fluxes for plume-related volcanism from the lower mantle as an independent constraint on the deep carbon cycle, avoiding uncertainties regarding high pressure mineralogy. We perform parameterized carbon cycle models using plume and other volcanic fluxes as constraints, including both an upper and lower mantle reservoir, and employ Monte Carlo sampling to discover the distribution of unconstrained parameters that satisfy our target constraints. For a nominal global carbon budget of kg, models satisfying these constraints require that less than 5% of carbon involved in mantle magmatic processes is degassed to the surface, unless undegassed carbon is recycled to the lower mantle which then permits up to 50% degassing efficiency. 100% degassing is only achieved when global carbon budgets are below kg, although higher budgets may be permitted if there exist additional carbon sinks not included in our model. Achieving a higher degassing efficiency requires upper mantle carbon concentrations below similar to 1 kg /. The balance of carbon in the upper and lower mantle is mainly determined by the fate of undegassed carbon, and our results suggest that the lower mantle contains a significant fraction of the Earth's carbon. We also find that variations in insolation, temperature-dependent weathering, initial conditions, and early tectonics have negligible influence on the long-term deep carbon cycle.
The Gulf of Corinth is one of the fastest-extending continental rifts in Europe, yet the link between present-day strain, inherited crustal structure, and lithospheric dynamics remains debated. We investigate crustal thickness and Vp/Vs variations using receiver functions from 31 seismic stations. Robustness is ensured through H-k stacking combined with bootstrap resampling, over a wide range of crustal P-wave velocities, and careful evaluation of alternative phase interpretations where slab-related conversions interfere with Moho signals. Moho depths range from 25 to 42 km (average 31.9 +/- 2.9 km). The thickest crust lies beneath the external Hellenides in the west, whereas the thinnest crust occurs along the northeastern rift margin within the internal Hellenides. Bootstrap uncertainties (typically 2-3 km) are smaller than the observed lateral variations, supporting the robustness of relative Moho gradients. Notably, maximum crustal thinning is offset by more than 50 km from the highest present-day extension rates in the western Gulf and from the major active southern faults. Vp/Vs ratios (1.67-1.93) and intracrustal negative conversions reveal lateral heterogeneities and low-velocity zones at depths of similar to 14 and similar to 20 km, interpreted as mechanically weak levels within the middle to lower crust. In the western forearc, strong conversions from the subducting African slab obscure the Aegean Moho and constrain the mantle wedge boundary. We propose that Corinth Rift evolution reflects interaction between inherited nappe-scale crustal thickness variations and a weak lower crust enabling rheological decoupling, explaining the spatial offset between crustal thinning and present-day strain localization.
Process-based soil carbon (C) models are increasingly used to project regional and global C cycle responses to climate change. However, the development and evaluation of these models has largely focused on temperate regions of North America and Europe. This geographic bias raises a critical question: Do these models capture generalizable mechanisms that can be applied to underrepresented pedological regions or encode processes specific to their developmental context? We evaluated three process-based models-Century, Millennial, and MIMICS-across 777 topsoil samples spanning the climate and pedological diversity of sub-Saharan Africa. Despite their differences in mechanistic detail, all three models performed similarly (adjusted R 2 = 0.09-0.18) in predicting soil organic carbon (SOC) stocks. Using random forest algorithms trained on observed and modeled SOC data, we identified divergences between the drivers of SOC. All three models overemphasized net primary productivity as a SOC driver and misrepresented the role of organo-mineral interactions. Bias analyses revealed that the three process-based models inadequately capture exchangeable calcium, which is increasingly recognized as an important control on SOC. Notably, increased mechanistic complexity did not improve transferability. These results have significant implications for regional C budgets and global climate projections. They underscore the importance of incorporating region-specific biogeochemistry into future soil C models in (sub-)tropical regions to enhance the precision of climate projections.
Turbulent flows over horizontally homogeneous rough surfaces are categorized as rough-wall boundary layer flows, while flows over homogeneous vegetated canopies are better described through a mixing-layer analogy. At present, numerous studies have investigated canopy density as a transition mechanism between rough-wall and mixing-layer-type flows. Yet, most considered canopies have been spatially homogeneous, with few exceptions investigating agricultural arrangements. However, most vegetated canopies are not homogeneously distributed, but instead contain gaps and spatial heterogeneities of different scales. In these cases, it remains unclear which are the dominant flow traits, and how spatial heterogeneity affects them. To help overcome these knowledge gaps, this paper aims to characterize flows over vegetated canopies with scales of spatial heterogeneity m randomly distributed, with a uniform under-canopy roughness and neutral stratification. Large Eddy Simulations of the atmospheric boundary layer with a geostrophic forcing are used. Canopy morphology and heterogeneity are quantified using the non-dimensional lacunarity metric. Lacunarity is further leveraged to investigate non-dimensional relations between canopy morphology and traditional turbulence statistics. Furthermore, canopy heterogeneity is investigated as a mechanism to transition from a mixing-layer-type flow to a rough-wall boundary layer flow. Results suggest revised formulations for the and scaling relations to account for the effects of canopy heterogeneity. Results also reveal a novel scaling between the equivalent surface roughness and the canopy heterogeneity parameter , providing a starting point to better understand the role of canopy heterogeneity in atmospheric boundary layer flows.
Delayed sea ice freeze-up and decreased sea ice extent in the Pacific Arctic region have altered light availability in marine waters, extending the ice-free season and increasing opportunities for photosynthetic activity and energy exchanges. This study investigates phytoplankton bloom progression during the fall using chlorophyll pigments and examines the impact phytoplankton have on heat distribution within the water column. Measurements of chlorophyll-a concentrations and its associated degradation product pheophytin were made in conjunction with optical measurements of light transmittance within the upper water column during the Synoptic Arctic Survey cruise in the Central Arctic Ocean and northeast Chukchi Sea in September-October 2022. Pheophytin proportions relative to chlorophyll-a generally increased over the course of the 2-month cruise, indicating an overall seasonal decline in biological production. However, renewed phytoplankton growth indicated by reduced pheophytin proportions was observed within the surface similar to 20 m of the water column on the Chukchi Shelf in late October. These subsurface blooms absorbed incoming solar radiation and enhanced ocean heating in the surface waters associated with the bloom while shading deeper depths from heating. Log-linear regressions of heating rates associated each 1 mu g L-1 increase of chlorophyll-a (at the observed chlorophyll-a maximum) with an approximate 15% decrease in heat input within the 10 m below the chlorophyll-a maximum depth. The altered vertical heat distribution caused by fall blooms trapping heat at the bloom depth can influence upper ocean stratification.
We quantify the asymmetry between the Birkeland currents (also known as field-aligned currents) in the Northern and Southern Hemispheres. We use data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) in 2010-2024 inclusive for both hemispheres, compute the observed asymmetry, and then subtract the modeled asymmetry. We use Block 1 data (based on the original Iridium constellation) and NEXT data (based on Iridium-NEXT spacecraft), and compare the effect of changing the data processing pipeline on the latter (yielding NEXT v1 and NEXT v2 subdatasets). We find that the asymmetry is significantly smaller in NEXT v2 data than in Block 1 or NEXT v1 data . The previously reported asymmetry seen in Swarm is , indicating that the new data processing pipeline goes from approximately twice the Swarm asymmetry to approximately half. This may indicate that the new AMPERE processing pipeline overestimates the amount of current flowing in the Southern Hemisphere, whereas the old one underestimated this quantity. We use frequency analysis to find that the asymmetry varies with frequencies corresponding to seasonal effects, CME occurrence, Iridium constellation orbit precession, and geomagnetic storms. We find a correlation with IMF , indicating that more current flows in the Northern Hemisphere during positive and vice versa. We find that Block 1 data in 2010-2017 shows correlations with AL, AU, , PCN, and PCS index which indicate that the asymmetry is less pronounced when Dungey Cycle convection is stronger, but NEXT data in 2019-2024 do not show this.
The propagation of magma through the Earth's crust often generates seismic signals and surface deformation, both key indicators of volcanic unrest. While surface deformation is attributed to magma emplacement within fractures, identifying the exact source of the seismic signal remains challenging. Such signals could stem from fracturing at the crack tip, closing of the tail, or fluid resonance within the fracture. To investigate seismic signal generation, we used analog modeling, a compelling method for replicating natural processes on a laboratory scale under well-defined parameters and conditions. Our experiments involved inducing crack propagation in gelatin by injecting a finite volume of air, with a camera capturing the crack shape, trajectory, and velocity. Sixteen high-frequency accelerometers on the gelatin surface recorded the seismic signals. Crack propagation produced several events characterized by frequencies ranging from 50 to 300 Hz. We analyzed three events not related to resonance of the gelatin-tank system or external sources. These events were associated with distinct changes in crack geometry and attributed to air resonance within the crack and potential reactivation of previously fractured gelatin. In addition to discrete events, a sustained tremor signal was observed and interpreted as being associated with crack propagation. Crack growth also generated surface displacements, quantified using video analysis and compared with numerical modeling results. Our findings highlight the seismogenic potential of air-filled cracks and improve our understanding of the origins of seismic and deformation signals during the final stages of dike propagation, with implications for interpreting geophysical observations and volcanic early warning.
The effects of stress perturbations on friction are crucial for understanding earthquake triggering. Previous experimental studies have primarily been conducted at room temperature, where fault gouge materials typically exhibit velocity-strengthening and frictionally stable behaviour. In this study, we investigate how variations in effective normal stress () influence fault (in-)stability by performing -perturbation experiments on simulated carbonate fault gouges under fluid-drained, hydrothermal conditions. Our results indicate that in the velocity-neutral or -weakening regime, perturbing can reinforce frictional instability, leading to accelerated slow slips or enhanced stick-slip events. This effect is particularly pronounced when the excitation period () approaches or exceeds the characteristic recurrence period () associated with pre-perturbation instabilities. Stress drops of the resulting events can have larger amplitudes than expected from quasi-steady-state. When cyclic perturbations are imposed, slip events tend to synchronize at specific phases when is close to - notably between 0.5 pi and 1 pi in radian, corresponding to maximum destressing rate and minimum , respectively. Additionally, short-period () perturbations can induce significant shear stress reduction (or fault weakening), with magnitudes comparable to the stress drops from stick slips, yet they are surprisingly associated with acoustically quiet slow slip, suggesting a stabilizing effect. These findings underscore the critical role of perturbation period in controlling fault response. In the context of induced seismicity, our results imply that cyclic or monotonic fluid injections should be carefully designed, considering both perturbation amplitude and period. Properly turned cyclic injections could potentially mitigate seismic risk by promoting quiet, slow slip over seismic fault slip.
In cold mountain regions, climate warming is driving the melting of ice-filled fractures, significantly influencing local hydrological cycles and geological activities. However, thermal-hydraulic (TH) coupling responses within these fractures during warming remain poorly understood. To address this, we conducted numerous visualized experiments of TH processes in ice-filled fractures with diverse geometries and flow conditions. A novel volume-based phase segmentation method was developed to track flow channel dynamics during ice melting. The results show that ice melting dynamically alters fracture permeability, which evolves through two distinct patterns: increase-stabilization and increase-decrease-stabilization. We established constitutive relations between apparent permeability and ice content, identifying two characteristic evolutionary modes during ice melting: an early-response type (deceleration followed by acceleration) and a late-response type (acceleration followed by deceleration). Furthermore, we uncovered how fracture transmissivity is controlled by flow channel geometry during ice melting. Channel width evolution moderates transmissivity in a sub-linear manner, while aperture changes enhance it following a super-cubic scaling law. Finally, the study summarizes the intertwined and temporally asynchronous nature of TH coupling in ice-filled fractures. These insights contribute to a deeper understanding of groundwater flow in frozen fractured aquifers and have important implications for water resource management in warming cold regions.
Knowledge of the Fe3+/Sigma Fe ratio of mantle minerals crystallized from a magma ocean under high pressures is important to constrain the initial distributions of Fe3+/Sigma Fe ratio and oxygen fugacity () of the mantle of terrestrial planets, such as Mars and Earth. Here we experimentally investigated the Fe3+/Sigma Fe ratio of majorite coexisting with reducing melts at 18 GPa, corresponding to the middle part of the Earth's mantle transition zone and the base of the Martian mantle. The results show that majorite coexisting with melts has Fe3+/Sigma Fe ratios ranging from 0.11 to 0.21, with typical analytical uncertainties of +/- 0.01-0.02, under metal- and diamond-saturated conditions. These values are higher than those of the upper mantle minerals and silicate melts, but lower than in bridgmanite under identical conditions. These results suggest the formation of a vertically heterogeneous distribution of Fe3+/Sigma Fe ratio in the mantle during magma ocean crystallization. For Earth, after the magma ocean crystallization, the phase transition of Fe3+-rich bridgmanite to majorite in an upwelling mantle flow could release an excess amount of Fe3+ and oxidize the mantle transition zone, generating redox heterogeneity in this region. For Mars, the Fe3+/Sigma Fe ratio of majorite coexisting with melt under metal-saturated conditions may explain the apparent discrepancy in between the molten silicate layer above the metallic core and the oxidized surface magmas recorded in Martian meteorites.
Deep cyclones (DCs) are mesoscale, deep-reaching features that develop near meander troughs of large-scale currents, such as the Gulf Stream. Although, in some aspects, they could be viewed as oceanic analogs of synoptic-scale cyclones in the mid-latitude atmosphere, their dynamics and impacts are not fully understood. Notably, the roles of different vorticity sources in deep cyclogenesis and the relationship of DCs with "benthic storms" remain to be elucidated. Here we develop a regional configuration of a primitive-equation model with 1/20 degrees horizontal resolution and 10-m vertical resolution over the entire water column to study DCs in the western North Atlantic. In our simulation, DCs form both in the Hatteras Abyssal Plain, where DCs were observed during the 1980-90s SYNOP campaign, and in the Sohm Abyssal Plain, where observations are lacking. Their spatial scales, lifetimes, pressure drops, swirl velocities, and drift speeds compare favorably with observational estimates. During deep cyclogenesis, the pressure fall at abyssal depth reflects a small imbalance between the effects of the sea level drop and of the density increase in the overlying water column within tightening meander troughs. Below 1,500 m, the main source of cyclonic vorticity is vortex stretching, associated mainly with the curvature-induced ageostrophic flow, while vortex tilting is a sink of smaller magnitude. Near-bottom currents in DCs reach speeds comparable to those observed during benthic storms and, when present, dominate the basin-scale bottom energy dissipation. Overall, the study highlights the importance of DCs for sub-annual variability and material transport in the abyssal interior.
On 23 November 2022, during exceptionally quiet geomagnetic conditions, a distinct ultra-low frequency (ULF) wave in the Pc5 band (similar to 2.4 mHz) was observed in the duskside sub-auroral region by two Canadian SuperDARN (Super Dual Auroral Radar Network) radars. The wave exhibited a periodic Doppler velocity signature resembling a "caterpillar," characterized by anti-sunward propagation and an azimuthal wave number of similar to 12. Ground-based magnetometer data revealed latitudinal variations in wave amplitude and phase consistent with field line resonance, peaking at similar to 66 degrees magnetic latitude. The Arase satellite, whose ionospheric footprint traversed the region of the caterpillar ULF wave, detected toroidal oscillations in electric and magnetic fields at magnetically conjugate locations in the inner magnetosphere, with high coherence and phase consistency with ground-based observations. Arase observed the electric field variation preceding the magnetic field variation by similar to 45 degrees, which is unusual for a pure standing mode and suggests a departure from a simple standing-wave interpretation. Instead, the observations can be interpreted as mixed standing and propagating characteristics along the field line. Simultaneously, the clear anti-sunward azimuthal phase propagation and sustained wave activity suggest a driving mechanism by a large-scale surface perturbation at the magnetospheric flank. These properties are consistent with excitation by the Kelvin-Helmholtz instability. A minor enhancement in solar wind dynamic pressure was observed, potentially contributing to the wave onset. This study highlights SuperDARN's capability to detect ULF waves during quiet intervals and demonstrates the utility of multi-instrumental conjugate observations in revealing the spatiotemporal variations of ULF waves and their generation mechanisms.
Chorus waves are arguably the most important electromagnetic emissions in the Earth's magnetosphere, being responsible for both energization and loss of radiation belt electrons. Chorus generation, inherently related to nonlinear wave-particle interactions, as well as the frequency-time shapes of individual elements forming it, are not yet fully understood. We use multipoint high-resolution measurements performed by the Cluster spacecraft to address the north-south symmetry of the source with respect to the magnetic equator. The analyzed event offers a unique situation in which the Cluster spacecraft move along nearly the same field line, with one located north and the other south of the magnetic equator. A detailed wave analysis employing lower-resolution data is used to demonstrate that the emissions indeed propagate away from the equator, as expected. We then show that the structure of the upper band chorus is generally different at the two spacecraft, while the lower-band chorus emissions detected by both spacecraft are very similar. This indicates that the lower-band chorus source radiates nearly symmetrically toward both hemispheres, while the upper-band chorus does not.
The Southern Annular Mode (SAM) represents the dominant pattern of climate variability in the extratropical Southern Hemisphere. However, its signature in coastal East Antarctic ice core records is unclear. A daily synoptic typing data set for the southern Indian Ocean constructed using self-organizing maps on 500 hPa daily geopotential height anomalies was used to investigate the relationship between the SAM and ice core records from Law Dome and Mount Brown South. Results indicate that synoptic weather regimes can either enhance or suppress the signature of the SAM on surface weather and ice core records. Weather regimes that are more likely during negative SAM and are associated with positive temperature anomalies over East Antarctica support the observed relationship between the SAM and the Law Dome delta 18O record since 1979. In contrast, weather regimes that describe meridional moisture flux toward Antarctica explain more snowfall accumulation variability at the ice core sites compared to the SAM, which contributes to suppressing the SAM signal in snowfall accumulation records. Results highlight the importance of considering the synoptic-scale dynamics on the relationship and stationarity of the SAM influence on surface weather and interpretation of ice core records. Given the limited robust relationships between the SAM and the ice core records investigated, caution should be taken before using these records to reconstruct past SAM variability. Instead, the coastal East Antarctic ice core records provide insight into the occurrence of meridional weather regimes, which are often associated with extreme temperature and precipitation conditions.
A model of ocean tides is generally used to remove the dynamic tidal signal in satellite gravimetric observations, such as GRACE(-FO). Model imperfections can cause stripes and long period aliasing errors in monthly gravity solutions. Recent developments in ocean tide modeling have substantially improved accuracy at high latitudes and in shallow water regions. In this study, we compared the 8 major tidal constituents from three recent ocean tide models, namely EOT20, FES22 and GOT5.6, as well as GOT4.8, using 13-year long GRACE ranging observations. The improvements of the three recent models are significant, showing more than 2 postfit variance reduction. Among them, GOT5.6 generally performs the best in terms of postfit variance reduction (11% vs. GOT4.8) and residual ocean tide fitting, particularly near West Antarctica. The residual ocean mass RMS, computed from monthly gravity solutions using GOT5.6, is on average 1 mm (GOT4.8), 0.3 mm (EOT20) and 0.1 mm (FES22) smaller. These results make it our preferred model for the upcoming GRACE(-FO) Release 07 (RL07) re-processing. Regarding implementation, utilizing the minor tides in GOT5.6 and long period tides in FES22 as well as considering geographically varying seawater density can further enhance model performance (denoted GOT5.6p3), which on average reduces the residual ocean mass RMS by an additional 7%. Notably, using lateral varying seawater density largely reduces the anomalous M2 residuals in the North Atlantic Ocean. We anticipate that GOT5.6p3 will substantially reduce stripes and aliasing errors in forthcoming RL07 monthly solutions. The improvements will also benefit GOCE reprocessing and GRACE(-FO) sub-monthly solutions.
We use a newly developed tropical cyclone (TC) seed tracking data set in ERA5 to investigate how the tangential wind structure of a seed differs between those that develop into TCs ("developing seeds") and those that do not ("non-developing seeds"). Focusing on the concept of "structural compactness" , a vortex structural parameter that characterizes the planetary Rossby wave drag on vortex intensity, we find that most developing seeds maintain relatively compact low-level dynamical structure throughout their lifetimes, whereas non-developing seeds exhibit a broader range of structures, with many being significantly incompact. This structural difference is reflected in the genesis probability of seeds: a seed with a lower has a lower probability of developing into TC. Furthermore, for incompact seeds , the maximum time they persist in ERA5 tracks agrees well with a theoretical prediction that stronger planetary Rossby wave drag weakens such seeds more rapidly, limiting their persistence. This suggests that planetary Rossby wave drag will rapidly filter out incompact seeds within a few days after seed formation, and only seeds that are sufficiently compact would be expected to survive long enough to potentially undergo TC genesis. These findings highlight the importance of considering the seed's internal dynamical structure, rather than focusing solely on large-scale environmental conditions, when evaluating TC genesis potential. By incorporating seed compactness alongside traditional environmental parameters, we can gain a more comprehensive understanding of the seed-to-cyclone transition in different climates.
