This paper investigates the relationship between a Stochastic Grid Perturbation (SGP) and Location Uncertainty (LU). The LU formulation, which introduces random velocity fluctuations, has shown efficacy in organizing large-scale flow and replicating long-term statistical characteristics. SGP was created as a simpler approach which perturbs the computational grid for ensemble members, aiming to simulate small uncertainties in high-resolution predictability studies. We aim to clarify the link between SGP and LU. After introducing the LU formalism, we derive the SGP method and discuss its connection to LU. Correlated noise in time is introduced in the SGP method to preserve the structure of the original grid. A compensating advection term is shown to preserve LU properties despite the latter correlated noise. Numerical experiments on a 3-layer Quasi-Geostrophic model compare various SGP implementations with an explicit LU implementation, highlighting the importance of the compensating advection term to achieve strict equivalence.

This study explores the relationship between dinoflagellate cyst (dinocyst) assemblages and the mixed layer depth (MLD) using canonical correspondence analyses. Our results demonstrate that wintertime deepening of MLD, in response to deep convection events, can influence dinocyst assemblages and especially the relative abundance of Nematosphaeropsis labyrinthus, which can thus be used as a proxy of MLD and the associated deep convection intensity. The analysis of Holocene N. labyrinthus percentage records in the subpolar North Atlantic, along with quantitative reconstructions of MLD from dinocyst assemblages, further reveals a westward migration of potential deep convection region around 6 ka BP, from the Nordic Seas and eastern subpolar gyre (SPG) during the Early Holocene, to the western to central SPG during the Middle and Late Holocene. The intensification of deep convection in the Labrador Sea towards a modern-like situation started during the Late Holocene, one or two thousand years later than the major transition around 6 ka BP in other parts of the subpolar North Atlantic. These results strengthen the hypothesis of reduced deep-water formation in the eastern North Atlantic from the early to late Holocene.

• Earth system models (ESMs) have many tunable parameters that are difficult to estimate and weakly constrained by theory. • Kalman filter-based approaches are attractive options, but existing implementations require expensive offline hyperparameter selection. • We propose a new Kalman filter algorithm that estimates model parameters and its hyperparameter simultaneously.

Resilience is the ability of a system to withstand stressors while preserving its structure and functions. Various performance- and attribute-based resilience assessment frameworks have been developed to understand the behaviour and properties of individual water systems. However, in integrated water systems, the increased complexity presents new challenges in the application of these frameworks. This study first reviews the key elements in both frameworks, including system indicators, thresholds, and resilience metrics, across urban water supply, drainage, groundwater, and river systems. Challenges are identified in deriving consistent indicators from siloed subsystem models, robust threshold selection, and resilience metrics synthesis as well as their usefulness for management. Based on the insights, a bottom-up resilience assessment framework for integrated water systems is developed. A water system integration model (WSIMOD) is employed to derive indicators for subsystems. Four performance-based resilience metrics are designed and applied to the indicators to facilitate intercomparison between subsystems. The application of the metrics crosses from event-level assessments for understanding system behaviour to annual-level evaluations of long-term performance, which are ultimately synthesised at the system level for multi-stakeholder decision-making. The efficacy of this framework is demonstrated through a case study in Luton, UK. The findings highlight river water quality as the least resilient subsystem that needs prioritised management. Sensitivity analysis is conducted to examine the impacts of thresholds on resilience results, with subsequent interpretation linking these metrics to specific decision variables for enhanced management. This framework can be extended through stakeholder engagement to improve system performance under deep uncertainties.

Predicting the relative susceptibility of reef areas to storm damage is important to stakeholders. Damage susceptibility depends primarily on exposure to waves and the fragility of the resident corals. Coral fragility is primarily related to shape and size which are related to species. Calculations based on colony measurements implies a large difference, O(10-100:1) between the fragility of massive and branching species. Here we estimate the relative fragility of various species using detailed damage survey data from 150 sites in Puerto Rico (PR) and 67 sites in Florida following the passage of hurricanes Irma and Maria in September of 2017. In PR both a transect and a roving survey were conducted near most sites. The damage measured in the two surveys near the same sites were not well correlated, making them relatively independent. We estimate species fragility as the average fraction damaged across all surveys of each type where that species was reported. Contrary to the same site damage results, the relative fragility between species was highly correlated across the different survey types. The difference between the measured fragility of branching and massive species was much smaller O(4:1) than the geometric calculations imply and there were variations within the massive species which were consistent and were significant when used in a simple reef damage model.

This work presents the characterization of the effective conductivity of additive manufacturing materials used for the fabrication of high-frequency communication devices. Factors such as material type, porosity, roughness, and oxidation reduce this conductivity, leading to increased insertion loss in the manufactured devices. For characterization, an X-band cavity resonator on a rectangular waveguide was designed, and the quality factor was measured for different implementations using various techniques and materials. Conductivity values of up to 17.70 MS/m were obtained for metallized polymeric materials and up to 6.44 MS/m for metallic alloys.

The use of spherical modes offers an efficient solution for storing embedded element patterns with significant angular structure for large scale arrays, such as the Square Kilometre Array (SKA)-Low radio telescope. These patterns are required for calibration of the numerous stations comprising the telescope, each containing several hundred elements, and operating over a 7:1 bandwidth. However, implementation is significantly complicated by the many differences in the notation used in the literature for the Legendre special functions. The differing phasor conventions used in electrical engineering and physics further complicate this. This paper synthesises much of the existing literature on this topic, paying special attention to these issues. Mathematical implementation issues are also addressed. A number of suitable tests using canonical dipole radiators to verify correct implementation are outlined. The paper concludes with tests on an individual SKALA4 antenna and a full-scale SKA-Low prototype station comprising 256 of these antennas. The storage saving afforded is some three orders of magnitude; this is very significant for a full SKA-Low station. Supporting material addresses some mathematical issues, outlines industry-standard storage schemes and summarises differing conventions encountered in the literature.

The ice phase is a major contributor to precipitation formation over continents due to its efficiency in growing hydrometeors to large enough sizes for sedimentation. One prominent growth mechanism is the vapor deposition onto ice crystals. However, its actual growth rates remain ambiguous. In the CLOUDLAB project, we conducted field experiments in supercooled clouds with the goal to infer ice crystal growth rates through local perturbations from cloud seeding. In this study, we combine the high-resolution model setup of 65\,\unit{m} with Lagrangian trajectories to achieve a more straightforward comparison to the observations. We first show that the chosen field experiments can be reproduced in the model in terms of ice crystal number concentration. Second, we perform a series of sensitivity studies by perturbing two parameters in the vapor depositional growth equation. The goal is to understand what change is needed to achieve an agreement between simulated and observed ice crystal growth rates since the default model configuration fails to do so. Increasing the vapor deposition efficiency by a factor of up to 3 yields comparable growth rates to the observations. Last, we try to quantify the different contributions to the vertical motions within the seeding plume, such as the large-scale forcing, the underlying topography, and latent heat release upon ice nucleation and growth. We show the different factors are superposed with the large-scale forcing being a dominant factor. The Lagrangian trajectories proved to be crucial to bridge dynamics and cloud microphysical processes.

This Work has been submitted to the American Meteorological Society - Journal of Atmospheric Sciences. Copyright in this Work may be transferred without further notice.

A document by Mike Coughlan. Click on the document to view its contents.

A document by Aymeric Fleury. Click on the document to view its contents.

This work explores the density-driven overturning circulation of the ocean using a process-oriented three-dimensional hydrodynamic model with a free sea surface. As expected, dense-water formation in polar regions creates a deep western boundary current (DWBC) spreading southward ward along the continental slope. Near the equator, the DWBC releases its water eastward into the ambient ocean to form a large upwelling zone. This upwelling is coupled with a slow westward surface recirculation feeding into a swift surface return flow along the western boundary that closes the mass budget. This recirculation pattern, which is fundamentally different to the Stommel-Arons model, is a consequence of geostrophic adjustment to anomalies of the surface pressure field that form under the influence of both coastal and equatorial Kelvin waves and Rossby waves. Based on the findings, the author presents a revised model of the ocean’s meridional overturning circulation to supersede earlier, incorrect suggestions.

Incoherent scatter radar measurements rely on the application of a priori parameters from empirical models to initialize the analysis of incoherent scatter spectra. Currently, there is a need to transform ionosphere models to enable reliable space weather predictions through data assimilation of observations. Very often the data assimilation relies on electron densities measured with incoherent scatter radars. Erroneous a priori parameters would lead to the assimilation of flawed and physically inconsistent data depending on the ionospheric model. It might therefore be beneficial to assimilate the entire radar spectrum and infer the plasma parameters from the assimilated spectrum by applying the a priori parameters as given by the model. To assess the potential assimilation of incoherent scatter spectra into models, we investigate synthetic EISCAT incoherent scatter spectra calculated from TIE-GCM results. At F1 region altitudes, the atomic-to-molecular ion ratio strongly affects the shape of the incoherent scatter spectrum. Since the vertical profiles of the atomic-to-molecular ion ratio are distinctly different in the EISCAT a priori model and TIE-GCM, the assimilation of single plasma parameters induces additional, unbalanced forces into the model. A similar problem arises in the E region due to different ion-neutral collision frequency profiles. These problems could be solved by assimilation of the entire incoherent scatter spectrum followed by an in-model evaluation of the plasma parameters. We demonstrate the effect of different a priori profiles on the spectral analysis and how the derived plasma parameters are changing when leveraging a more comprehensive approach of using forward modeling with TIE-GCM.

We investigate properties of lower hybrid drift waves (LHDWs) near and inside the electron diffusion regions in 17 magnetopause and 9 magnetotail reconnection events using Magnetospheric MultiScale (MMS) mission observations. Our analysis show that LHDW type depend on the electron beta, as electron beta increases LHDWs become more electromagnetic in nature. The energy transfer from electromagnetic fields to particles is higher in electrostatic LHDWs and it is largely in parallel direction. Linear dispersion analysis shows that electrostatic LHDWs are perpendicular propagating while electromagnetic waves propagate in oblique directions and the normalized wavenumber of all LHDW types falls within 0.5 to 0.8 range. A simple estimate on the LHDW nonlinear saturation suggests possibly important roles played by these waves in supporting reconnection electric field.

 Wide convective cell depth responds most to available instability, while narrow cell depth responds most to mid-level relative humidity.  Entrainment-driven reduction of buoyancy decreases as updraft width increases, causing disparate narrow and wide cell depth responses.  A convection-permitting simulation with 3-km horizontal grid spacing generally reproduces observed relationships.

A document by Ray Nassar. Click on the document to view its contents.

The commercial synthetic aperture radar (SAR) market is experiencing year-over-year growth and is currently capable of imaging anywhere in the world within an hour at X-band. Surface Deformation and Change (SDC) is a mission study at NASA to investigate innovative architectures beyond the NASA-ISRO SAR (NISAR) mission in the next decade. In this article we present preliminary findings on the technical capabilities of the currently available commercial SAR data, and investigate their applicability to SDC goals, such as imaging quality and retrieval of surface motion.

• Time-frequency analysis of the the total solar irradiance (TSI) dataset recoreded by the FY3E/JTSIM/DARA • DARA observations (in WRR scale) on average higher than measurements recorded with other instruments: ∼ 2.2 Wm −2 (VIRGO/PMO6), ∼ 1.2 Wm −2 (TIM/TSIS-1) and ∼ 1 Wm −2 (SIAR). • Analysis of the integration of the new JTSIM-DARA dataset into the 43 year long TSI composite time series