Flux Partitioning Research Articles

Ramifications of groundwater model in WRF/Noah‐MP coupled system: Effects on soil‐moisture and regional climate simulation

AbstractSoil moisture is a key variable that contributes for flux partitioning into sensible and latent heat components. There is a pressing need to study the impacts of shallow groundwater table dynamics on antecedent soil moisture and corresponding feedbacks to atmosphere. In this study, we evaluate WRF‐NoahMP simulated soil moisture using two experimental configurations: one with the default, free drainage approach (CTL) and with Miguez‐Macho groundwater scheme (GW). Results are presented for the study conducted over Ganga River basin, India between the years 2008 and 2014 for all the three seasons (pre‐monsoon, monsoon, post‐monsoon). It was observed that the GW model runs, improve soil moisture in topmost and bottom‐most layers. We discovered that the simulations improved temporal negative bias of seasonal accumulation during monsoon by around 91 mm. In addition, the average negative bias in latent heat flux improved by around 28 W/m2. Compared to CTL, GW was found to contribute additional atmospheric moisture content ranging between 3% and 5%. Comparison with in‐situ ground water showed that model overestimates the ground water table depth. This can be attributed to the ability of the model to only simulate natural occurring variabilities and lack of inclusion of anthropogenic factors such as ground water pumping in the model. The groundwater trend in Ganga is declining at alarming rate. In addition, if over exploitation of groundwater is not monitored properly, water and food scarcity is an imminent threat to the country's economy. To the best of authors knowledge, this is the first study of its kind to be implemented over Ganga basin, which evaluates the role of shallow ground water table on regional climate using coupled atmosphere‐land surface‐groundwater model. In summary, we highlight that the groundwater component along with WRF‐NoahMP coupled model improves soil moisture and precipitation representation over the Ganga basin.

Computational fluid dynamics prediction of subcooled boiling of water using a mechanistic bubble-departure model

This paper presents computational fluid dynamics (CFD) simulations of subcooled convective boiling flows. The simulation methodology is based on a Eulerian two-fluid approach. Heat transfer due to wall-boiling phenomena is captured with a well-established wall heat flux partitioning model. Bubble departure sizes are supplied to the wall-boiling model by calculating the lift-off diameter using a single formula derived from a mechanistic thermodynamic equilibrium model. In contrast to empirical correlations that typically are used in CFD modelling of boiling flows, the current bubble-departure model represents mechanistically the force balance on a bubble as it grows on a surface, up to its lift-off towards the bulk flow. A simplified approach is employed to estimate the relative velocity of a sliding bubble involved in the calculation of the lift off condition, based on a force balance in the flow direction. The model is extensively tested via comparison with an experimental database from the literature, in terms of vapour distribution along the flow, covering a wide range of conditions in terms of pressure from about 3 MPa to 15 MPa, mass flowrate (400–2100 kg/m2s) and heat flux (420–2200 kW/m2). It is demonstrated that predictions of the current method are in satisfactory agreement for low to moderate pressures up to around 7 MPa, without need for any model adjustment or use of fitting parameters. As the pressure increases, the model succeeds in tracking the basic trends, however, deviations of quantitative predictions of the vapour fraction distribution from the experimental values increase. The trend suggests that other closure terms, such as the nucleation site density, may also need to be modified, possibly using a mechanistic approach, to increase further the confidence in predictions of the current methodology in high-pressure conditions.

A Methodology for Estimating the Energy and Moisture Budget of the Convective Boundary Layer Using Continuous Ground-Based Infrared Spectrometer Observations

Abstract Land–atmosphere interactions play a critical role in both the atmospheric water and energy cycles. Changes in soil moisture and vegetation alter the partitioning of surface water and energy fluxes, influencing diurnal evolution of the planetary boundary layer (PBL). The mixing-diagram framework has proven useful in understanding the evolution of the heat and moisture budget within the convective boundary layer (CBL). We demonstrate that observations from the Department of Energy Atmospheric Radiation Measurement (ARM) Southern Great Plains site provide all of the needed inputs needed for the mixing-diagram framework, allowing us to quantify the impact from the surface fluxes, advection, radiative heating, encroachment, and entrainment on the evolution of the CBL. Profiles of temperature and humidity retrieved from the ground-based infrared spectrometer [Atmospheric Emitted Radiance Interferometer (AERI)] are a critical component in this analysis. Large-eddy simulation results demonstrate that mean mixed-layer values derived are shown to be critical to close the energy and moisture budgets. A novel approach demonstrated here is the use of network of AERIs and Doppler lidars to quantify the advective fluxes of heat and moisture. The framework enables the estimation of the entrainment fluxes as a residual, providing a way to observe the entrainment fluxes without using multiple lidar systems. The high temporal resolution of the AERI observations enables the morning, midday, and afternoon evolution of the CBL to be quantified. This work provides a new way to use observations in this framework to evaluate weather and climate models. Significance Statement The energy and moisture budget of the planetary boundary layer (PBL) is influenced by multiple sources, and accurately representing this evolution in numerical models is critical for weather forecasts and climate predictions. The mixing-diagram approach, driven by profiling observations as illustrated here, provides a powerful way to quantify the contributions from each of these sources. In particular, the energy and moisture mixed into the PBL from above the PBL can be determined accurately from ground-based remote sensors using this approach.

Assessment of State-of-the-art multiphase CFD modeling for subcooled flow boiling in reactor applications

Multiphase Computational Fluid Dynamics (M-CFD) has the potential to provide high fidelity simulation of complex boiling phenomena in Light Water Reactors (LWRs), thereby accelerating the development cycle and reducing the need for expensive large-scale experiments. M-CFD relies on two-phase closure models to consistently represent the relevant physical phenomena in flow boiling. However, the still incomplete understanding of the ability of these closures to accurately capture the underlying physics, limits the adoption of M-CFD in reactor development and design optimization. Due to the interaction of complex physical phenomena present in subcooled flow boiling, local measurements are necessary to assess the performance of existing closures. Furthermore, because previous validation was performed mostly on low pressure data, measurements at high pressure are needed to understand the performance of multiphase closures at PWR conditions. In this work, benchmarking was conducted using measured radial profiles of void fraction from subcooled flow boiling experiments of R12 refrigerant that reproduced density ratios and scaled flow conditions corresponding to PWR operation, called the DEBORA experiments. This work leverages recent advancements in momentum closures to perform a systematic assessment of the wall boiling representation by evaluating heat flux partitioning formulations and the associated closure relations. The influence and sensitivity of bulk boiling and condensation models were also evaluated. Using separate effect assessments and recent advancements in experimental understanding, this work presents a closure representation that demonstrates consistent predictions and is applicable to prototypical PWR conditions, while identifying areas for future improvement.

Validation of the Eulerian–Eulerian Two-Fluid Method and the RPI Wall Partitioning Model Predictions in OpenFOAM with Respect to the Flow Boiling Characteristics within Conventional Tubes and Micro-Channels

Flow boiling within conventional, mini and micro-scale channels is encountered in a wide range of engineering applications such as nuclear reactors, steam engines and cooling of electronic devices. Due to the high complexity and importance of the boiling process, several numerical and experimental investigations have been conducted for the better understanding of the underpinned physics and heat transfer characteristics. One of the most widely used numerical approaches that can analyse such phenomena is the Eulerian–Eulerian two-fluid method in conjunction with the RPI model. However, according to the current state-of-the-art methods this modelling approach heavily relies on empirical closure relationships derived for conventional channels, limiting its applicability to mini- and micro-scale channels. The present paper aims to give further insights into the applicability of this modelling approach for non-conventional channels. For this purpose, a numerical investigation utilising the Eulerian–Eulerian two-fluid model and the RPI wall heat flux partitioning model in OpenFOAM 8.0 is conducted. Initially the parameters comprising the empirical closure relationships used in the RPI sub-models are tuned against the DEBORA experiments on conventional channels, through an extensive sensitivity analysis. In the second part of the investigation, numerical simulations against flow boiling experiments within micro-channels are performed, utilising the previously optimised and validated model setup. Furthermore the importance of including a bubble coalescence and break-up sub-model to capture parameters such as the radial velocity profiles, is also illustrated. However, when the optimal model setup, in conventional tubes, is used against micro-channel experiments, the need to develop new correlations from data obtained from mini and micro-scale channel studies, not from experimental data on conventional channels, is revealed.

Observation‐Driven Characterization of Soil Moisture‐Precipitation Interactions in the Central United States

AbstractSoil moisture feedbacks that initiate, enhance, or suppress convection initiation and precipitation are important components of regional hydroclimatology. However, soil moisture feedbacks and the processes through which they operate are notoriously challenging to observe and study outside of model environments. In this study, we combine a climatological assessment of event frequency‐based measurements of soil moisture‐precipitation coupling in the central United States with a process‐based analysis of the mechanisms by which wet‐ and dry‐soil feedbacks may operate in the region. We use the Thunderstorm Observation by Radar algorithm to identify the location of convection initiation, circumventing the issue of using precipitation accumulation as a proxy for convection initiation. Results show substantial spatial variability in the climatological sign and strength of soil moisture‐precipitation coupling in the central United States, including regions that exhibit signs of both wet‐ and dry‐soil feedbacks. Within the regions with the strongest feedback signals, we find consistently strong coupling between soil moisture and the partitioning of surface heat flux, and strong coupling between surface heat flux—particularly sensible heat flux—and diurnal change in planetary boundary layer height. In all three regions assessed, the process‐based metrics confirmed the potential of wet‐ and/or dry‐soil feedbacks leading to convection initiation.

Evapotranspiration regulates leaf temperature and respiration in dryland vegetation

Evapotranspiration regulates energy flux partitioning at the leaf surface, which in turn regulates leaf temperature. However, the mechanistic relationship between evapotranspiration and leaf temperature remains poorly constrained. In this study, we present a novel mechanistic model to predict leaf temperature as a linearized function of the evaporative fraction. The model is validated using measurements from infrared radiometers mounted on two flux towers in Arizona, USA, which measure canopies of Prosopis velutina with contrasting water availability. Both the observations and model predictions reveal that leaf temperature equilibrates with air temperature when latent heat flux consumes all of the energy incident on the leaf surface. Leaf temperature exceeds air temperature when there is a net input of energy into the leaf tissue. The flux tower observations revealed that evaporative cooling reduced canopy leaf temperature by ca. 1–5 °C, depending on water availability. Evaporative cooling also enhanced net carbon uptake by reducing leaf respiration by ca. 15% in the middle of the growing season. The regulation of leaf temperature by evapotranspiration and the resulting impact on net carbon uptake represents an important link between plant water and carbon cycles that has received little attention in literature. The model presented here provides a mechanistic framework to quantify leaf evaporative cooling and examine its impacts on plant physiological function.

The impact of temperature on flux, protein transmission and energy usage during microfiltration of skim milk using polymeric membranes

Membrane performance during microfiltration (MF) of skim milk carried at 7 °C (cold MF) and 50 °C (hot MF) using 800 kDa spiral wound polymeric membranes was assessed. Permeate flux, protein and mineral partitioning, fouling resistance (Rf) and energy consumption as a function of temperature are reported. MF performance at 50 °C resulted in significantly (p < 0.05) higher flux than at 7 °C, with the energy requirements (in kW h kg−1 protein removed) significantly (p < 0.05) lower than cold MF. Overall Rf was significantly (p < 0.05) higher for the cold MF process, with reversible fouling accounting for 97 and 71% of the Rf in the cold and hot MF processes, respectively. On a dry matter basis, cumulative serum protein permeation was similar at both temperatures at 60.4 and 62.1% for the cold and hot MF processes, respectively, with higher β-casein and calcium permeation observed for the cold MF process.

Contrasting Responses of Surface Heat Fluxes to Tropical Deforestation

AbstractDeforestation alters the exchange of heat, moisture, and momentum between the Earth's surface and the atmosphere, which can significantly affect the surface energy balance and water budget. However, changes in surface heat fluxes in response to deforestation are diverse among multi‐model simulations. This study explores factors that might cause different changes in surface heat fluxes due to tropical deforestation with NCAR Community Land Model. The results show that the changes in surface heat fluxes are related to the mean‐state flux partitioning conditions over the deforested areas. Deforestation tends to decrease both surface heat fluxes under conditions with smaller evaporative fractions (EFs), and tends to decrease the latent heat fluxes and increase the sensible heat fluxes under conditions with greater EFs. A similar relation can be found in the Land Use Model Intercomparison Project, which indicates that the varying simulated flux partitioning conditions might contribute to the diverse changes in surface heat fluxes among models.

The Sensitivity of Moisture Flux Partitioning in the Cold‐Point Tropopause to External Forcing

AbstractThe dryness of the stratosphere is the result of air entering through the cold tropical tropopause layer (TTL). However, our understanding of the moisture flux partitioning into water vapor and frozen hydrometeors is incomplete. This raises concerns regarding the ability of General Circulation Models to accurately predict changes in stratospheric water vapor following perturbations in the radiative budget due to volcanic aerosol or stratospheric geoengineering. We present the first results using a global storm‐resolving model investigating the sensitivity of moisture fluxes within the TTL to an additional heating source. We address the question how the partitioning of moisture fluxes into water vapor and frozen hydrometeors changes under perturbations. The analysis reveals the resilience of the TTL, keeping the flux partitioning constant even at an average cold‐point warming exceeding 8 K. In the control and perturbed simulations, water vapor contributes around 80% of the moisture entering the stratosphere.

Temperature field model of limited slip clutch based on dynamic heat flux partition characteristics

The interaxle torque distribution of off-road vehicle is interfered with temperature field variation of limited slip clutch during long-time sliding, which is controlled by actual heat flux input. The equivalent heat dissipation model is created based on the suggested calculation method of convective heat transfer equivalent coefficient in various lubrication phases. Further, thermal equilibrium equations of friction pair nodes are solved to produce the temperature field calculation model of dynamic heat flux partition. A clutch sliding bench is set up to verify and analyze the effect of heat flux partition on temperature field by organizing different operating conditions. The results demonstrate that the temperature difference of contact surface calculated by the constant heat flux partition model increases significantly along with sliding time and heat flux. In addition, the deviations of temperature rising rate at stage A and average temperature at stage B of separator plate higher than the experimental result also increases. On the contrary, the decrease value of actual input heat flux of separator plate from initial to steady state gradually increases with the increase of relative speed difference in dynamic heat flux partition model. The calculation deviations of temperature rising rate and average temperature are less than 0.1°C/s and 3°C, respectively. This model offers a novel approach for calculating clutch temperature field.

Comparing ecosystem gaseous elemental mercury fluxes over a deciduous and coniferous forest

Sources of neurotoxic mercury in forests are dominated by atmospheric gaseous elemental mercury (GEM) deposition, but a dearth of direct GEM exchange measurements causes major uncertainties about processes that determine GEM sinks. Here we present three years of forest-level GEM deposition measurements in a coniferous forest and a deciduous forest in northeastern USA, along with flux partitioning into canopy and forest floor contributions. Annual GEM deposition is 13.4 ± 0.80 μg m−2 (coniferous forest) and 25.1 ± 2.4 μg m−2 (deciduous forest) dominating mercury inputs (62 and 76% of total deposition). GEM uptake dominates in daytime during active vegetation periods and correlates with CO2 assimilation, attributable to plant stomatal uptake of mercury. Non-stomatal GEM deposition occurs in the coniferous canopy during nights and to the forest floor in the deciduous forest and accounts for 24 and 39% of GEM deposition, respectively. Our study shows that GEM deposition includes various pathways and is highly ecosystem-specific, which complicates global constraints of terrestrial GEM sinks.

Deep learning segmentation to analyze bubble dynamics and heat transfer during boiling at various pressures

Today, neural networks have increasingly gained the attention of researchers and become an effective instrument for a wide range of scientific applications, including issues related to the boiling. However, there are no universal tools in the literature that would allow detecting the life cycle of individual vapor bubbles and automatically measure a wide range of main boiling characteristics based on the high-speed visualization data. In this study, the U-net and Mask R-CNN convolutional neural networks were used to detect and segment bubbles obtained by visualization from the bottom side of a transparent heater during water boiling at various subatmospheric pressures. The key feature of the trained CNN architectures is the ability to detect bubbles located on a heated wall, while ignoring the bubbles that lift-off, and to determine the moment of their departure. The verification of various neural networks demonstrated that the Mask R-CNN architecture is more preferable to measure dynamic boiling characteristics. Through trained convolutional neural networks, a wide array of data on local boiling characteristics, including the nucleation site density, bubbles growth rate, life-time and departure diameters, waiting time between moments of bubbles departure and nucleation frequencies were automatically obtained for water boiling at various heat fluxes and pressures in the range of 42–103 kPa. Based on the parameters obtained, heat transfer simulation was carried out using various heat flux partitioning approaches and the ranges of their applicability were demonstrated.

Transdermal drug delivery in horses: An in vitro comparison of skin structure and permeation of two model drugs at various anatomical sites.

Oral and parenteral drug delivery in horses can be difficult. Equine-specific transdermal drug formulations offer improved ease of treatment; development of such formulations requires a deeper understanding of the structural and chemical tissue barrier of horse skin. To compare the structural composition and barrier properties of equine skin. Six warmblood horses (two males, four females) with no skin diseases. Routine histological and microscopic analyses were carried out with image analysis for skin from six different anatomical locations. In vitro drug permeation was analysed using a standard Franz diffusion cell protocol coupled with reversed phase-high-performance liquid chromatography detailing flux, lag times and tissue partitioning ratios of two model drug compounds. Epidermal and dermal thicknesses varied between sites. The dermal and epidermal thicknesses of the croup were 1764 ± 115 μm and 36 ± 3.6 μm, respectively, and were significantly different (p < 0.05) from the inner thigh thicknesses which were 824 ± 35 μm and 49 ± 3.6 μm. Follicular density and size also varied. The highest flux for the model hydrophilic molecule (caffeine) was for the flank (3.22 ± 0.36 μg/cm2 /h), while that for the lipophilic molecule (ibuprofen) was for the inner thigh (0.12 ± 0.02 μg/cm2 /h). Anatomical location differences in equine skin structure and small molecule permeability were demonstrated. These results can aid in the development of transdermal therapies for horses.

Investigating the representation of heatwaves from an ensemble of km-scale regional climate simulations within CORDEX-FPS convection

Heatwaves (HWs) are high-impact phenomena stressing both societies and ecosystems. Their intensity and frequency are expected to increase in a warmer climate over many regions of the world. While these impacts can be wide-ranging, they are potentially influenced by local to regional features such as topography, land cover, and urbanization. Here, we leverage recent advances in the very high-resolution modelling required to elucidate the impacts of heatwaves at these fine scales. Further, we aim to understand how the new generation of km-scale regional climate models (RCMs) modulates the representation of heatwaves over a well-known climate change hot spot. We analyze an ensemble of 15 convection-permitting regional climate model (CPRCM, ~ 2–4 km grid spacing) simulations and their driving, convection-parameterized regional climate model (RCM, ~ 12–15 km grid spacing) simulations from the CORDEX Flagship Pilot Study on Convection. The focus is on the evaluation experiments (2000–2009) and three subdomains with a range of climatic characteristics. During HWs, and generally in the summer season, CPRCMs exhibit warmer and drier conditions than their driving RCMs. Higher maximum temperatures arise due to an altered heat flux partitioning, with daily peaks up to ~ 150 W/m2 larger latent heat in RCMs compared to the CPRCMs. This is driven by a 5–25% lower soil moisture content in the CPRCMs, which is in turn related to longer dry spell length (up to double). It is challenging to ascertain whether these differences represent an improvement. However, a point-scale distribution-based maximum temperature evaluation, suggests that this CPRCMs warmer/drier tendency is likely more realistic compared to the RCMs, with ~ 70% of reference sites indicating an added value compared to the driving RCMs, increasing to 95% when only the distribution right tail is considered. Conversely, a CPRCMs slight detrimental effect is found according to the upscaled grid-to-grid approach over flat areas. Certainly, CPRCMs enhance dry conditions, with knock-on implications for summer season temperature overestimation. Whether this improved physical representation of HWs also has implications for future changes is under investigation.

Modeling 3D sliding electrical contact considering fully coupled thermal-mechanical-electrical effects

The 3D sliding electrical contact model considering thermal-mechanical-electrical coupling is presented in this paper. The semi-analytical method (SAM) is used to solve this complex multi-physical contact model. Firstly, the frequency response functions (FRFs) for thermal-mechanical-electrical fields are derived. Then, with discrete convolution and fast Fourier transform (DC-FFT) speeding calculation, a solving procedure, including the conjugate gradient method for force balance and algorithms for electrical potential equilibrium and heat flux partition, is proposed for the first time to solve the fully coupled electrical contact problem. Last, the effects of multiple loadings including the current, normal force, and sliding velocity on electrical contact behaviors are systematically investigated.

Characterization of the Morning Transition over the Gentle Slope of a Semi-Isolated Massif

Abstract This paper investigates the surface-layer processes associated with the morning transition from nighttime downslope winds to daytime upslope winds over a semi-isolated massif. It provides an insight into the characteristics of the transition and its connection with the processes controlling the erosion of the temperature inversion at the foot of the slope. First, a criterion for the identification of days prone to the development of purely thermally driven slope winds is proposed and adopted to select five representative case studies. Then, the mechanisms leading to different patterns of erosion of the nocturnal temperature inversion at the foot of the slope are analyzed. Three main patterns of erosion are identified: the first is connected to the growth of the convective boundary layer at the surface, the second is connected to the descent of the inversion top, and the third is a combination of the previous two. The first pattern is linked to the initiation of the morning transition through surface heating, and the second pattern is connected to the top-down dilution mechanism and so to mixing with the above air. The discriminating factor in the determination of the erosion pattern is identified in the partitioning of turbulent sensible heat flux at the surface. Significance Statement The purpose of this study is to improve our understanding of the thermally driven slope circulations with a focus on the unsteady processes associated with the morning transition and the erosion patterns of the nocturnal temperature inversion, so far in the literature less investigated and understood than the evening transition. Understanding this diurnal process will advance our abilities to model it and to improve the accuracy of weather forecasting in complex terrain.

Deciphering the relationship between vegetation and Indian summer monsoon rainfall

Land surface utilization in the Indian subcontinent has undergone dramatic transformations over the years, altering the region’s surface energy flux partitioning. The resulting changes in moisture availability and atmospheric stability can be critical in determining the season’s monsoon rainfall. This study uses fully coupled global climate model simulations with idealized land cover to elucidate the consequences of land surface alterations. We find that an increase in forest cover, in general, increases precipitation in India. However, precipitation is not a linear function of forest-covered-area due to the spatially heterogeneous nature of the impact. A fully forest-covered India receives less precipitation than when the forest covers only the eastern side of India, occupying just about half the area. This signifies the importance of the east-west gradient in vegetation cover observed over India. Using an energy balance model, we diagnose that the diverse nature of this precipitation response results from three different pathways: evaporation from the surface, the net energy input into the atmosphere, and moist stability. Evaporation exhibits a linear relationship with forest-covered-area and reveals minimal spatial heterogeneity. On the contrary, the influence through the other two pathways is found to be region specific. Rainfall modulation via changes in net energy input is dominant in the head Bay of Bengal region, which is susceptible to convective systems. Whereas impact through stability changes is particularly significant south of 20∘ N. In addition, we find that moisture advection modulates the significance of these pathways over northwest India. Thus, the impact of land cover changes act via three effective mechanisms and are region dependent. The findings in this study have broader ramifications since the dominant region-specific mechanisms identified are expected to be valid for other forcings and are not just limited to the scenarios considered here.

Numerical simulation of subcooled flow boiling for nuclear engineering applications using OpenFOAM

Abstract This work is focused on the development and validation of models and methods for the simulation of wall boiling in nuclear engineering applications with the computational fluid dynamics (CFD) code OpenFOAM. The new chtMultiRegionReactingTwoPhaseEulerFoam solver was developed based on the reactingTwoPhaseEulerFoam solver of OpenFOAM Foundation version 7. The solver is used for the simulation of two-phase flow under consideration of wall boiling and conjugate heat transfer (CHT) between solid structure and two-phase fluid regions. The Euler–Euler approach for two-phase flows was used. The heat flux during wall boiling was calculated with the help of the extended Rensselaer Polytechnic Institute wall heat flux partitioning model, in which the convective heat flux between solid wall and two-phase flow with high void fractions was also considered. The solver was validated against experimental data from the OECD/NEA PWR Subchannel and Bundle Tests benchmark. This Nuclear Power Energy Corporation (NUPEC) database provides data for different fuel assembly subchannel geometries at different thermal-hydraulic conditions. 10 experimental runs with different boundary conditions of the benchmark exercise I-1 were simulated with the chtMultiRegionReactingTwoPhaseEulerFoam solver. The solver showed good numerical stability in all examined cases, which captured different boiling regimes with up to cross-section averaged void fractions of 0.6. The results were compared with measured data for the averaged over the cross-section of the investigated geometry void fractions. Good agreement with experimental data was observed.

Impact of land surface processes on convection over West Africa in convection‐permitting ensemble forecasts: A case study using the MOGREPS ensemble

AbstractSoil moisture (SM) affects weather through its impact on surface flux partitioning, influencing vertical atmospheric profiles and circulations driven by differential surface heating. In West Africa, observational studies point to a dominant negative SM‐precipitation feedback, where dry soils help to initiate and maintain convection. In this context, serious concerns exist about the ability of models with parameterised convection to simulate this observed sensitivity of daytime convection to SM. Here, we evaluate the effect of initial SM perturbations in a short‐range ensemble forecast over West Africa, comparing the UK Met Office Global and Regional Ensemble Prediction System (MOGREPS) with parameterised convection (GLOB‐ENS) to its regional convection‐permitting counterpart (CP‐ENS). Results from both models suggest SM perturbations introduce considerable spread into daytime evaporative fraction (EF) and near‐surface temperatures. This spread is still evident on Day 3 of the forecast. Both models also show a tendency to increased afternoon rainfall frequency over negative EF anomalies, reproducing the observed feedback. However, this effect is more pronounced in CP‐ENS than GLOB‐ENS, which illustrates the potential for process‐based forecast improvements at convection‐permitting scales. Finally, we identify persistent biases in rainfall caused by land cover mapping issues in the operational GLOB‐ENS setup, emphasising the need for careful evaluation of different mapping strategies for land cover.