The Atmospheric Boundary Layer (ABL) is the lowest layer of the atmosphere and as such responsible for the Earth-atmosphere interaction in the climate system. It determines – from local to global scales – the exchange of energy, mass and momentum between ‘the surface’ and ‘the atmosphere’, and hence the water cycle, the energy balance, the carbon budget (to name only a few). Due to friction and radiative processes  at the surface, the flow in the ABL is turbulent – and turbulence is often considered the defining characteristic of ABL flows. In numerical models for weather and climate, turbulence is quite generally sub-grid scale (and will remain so at least for global scale models for the coming decades), so that the ‘lower boundary condition’, i.e., ABL turbulence, needs to be parameterized.

With almost 70 percent of the Earth’s land surface being covered by hills or mountains, the question arises whether current understanding of ABL turbulence is sufficient to adequately describe the surface-atmosphere exchange over non-flat or even mountainous terrain. In this contribution, a case is therefore made for the introduction of a Mountain Boundary Layer (MoBL). The MoBL is not just another variety of the boundary layer – such as the CBL or SBL  describing convective vs. stable boundary layer states, respectively: the lowest layer of the troposphere over complex mountainous terrain cannot be assumed to be horizontally homogeneous (what poses challenges for numerical modeling)  and is forced by gravitational processes as well as interactions with meso-scale flows. With this, ABL parameterizations in numerical models – which are based on the assumption of horizontal homogeneity, i.e., the ‘Boundary-Layer Approximation’, and the dominance of turbulence, e.g., in the diagnosis of the ABL height – are not likely to perform well. Some of the salient characteristics of the probably youngest in the ‘BL family’ will be presented, which emerge from recent research on boundary layer dynamics over complex terrain. Also, the largest challenges we still face in the description, physical characterization and modeling of the MoBL will be addressed.

How to cite: Rotach, M. W.:  The Mountain Boundary Layer (MoBL) – do we need yet another variety?, EMS Annual Meeting 2025, Ljubljana, Slovenia, 7–12 Sep 2025, EMS2025-701, https://doi.org/10.5194/ems2025-701, 2025.

Atmospheric boundary layer (ABL) processes influence the atmosphere’s general circulation. Thus, representing the ABL processes correctly in global climate and numerical weather prediction models (NWP) is important. For example, surface and turbulent friction affect the transport of mass across the globe. Cross-isobaric mass flow then plays a significant role in the lifecycle and intensity of extratropical cyclones at the midlatitudes. The direction and magnitude of it depends on both synoptic scale and ABL conditions such as friction and thermal stratification. This transport can be studied using the turning of the wind with height, from the surface up to the ABL top, to understand where, when and how much mass is transported across isobars.

In a new era of increasing resolution of climate and NWP models, storing data remains a challenge even with greater capacity. The full vertical structure, and high temporal resolution needed to study the ABL well, is rarely all stored nor easily accessible due to the great amount of storage required. We have therefore implemented on-line diagnostics into the open version of the European Centre for Medium Range Weather Forecast’s (ECMWF) Integrated Forecast System (IFS), the OpenIFS. During the computation of simulations, the process diagnoses the turning of the wind with height, as well as the vertically integrated cross-isobaric mass flow, both from the surface to the ABL top. These diagnostics makes it possible, in more detail, to study the role of the boundary layer turbulence on the evolution of the flow in various regimes such as mid-latitude cyclones and the trade regions as well as sensitivity to modelling of turbulence and friction. All without having to store great amounts of data. We’ve run experiments focused on the global scale, and on a more local scale, tracking an extratropical cyclone in one of the storm tracks. Here the first results of this study are presented as well as a walkthrough of the basics of the online diagnostics.

How to cite: Þórarinsson, P. Á., Svensson, G., and Lewinschal, A.: On-line diagnostics of boundary layer processes in numerical weather predication and climate models, EMS Annual Meeting 2025, Ljubljana, Slovenia, 7–12 Sep 2025, EMS2025-186, https://doi.org/10.5194/ems2025-186, 2025.

Planetary boundary layer (PBL) dynamics are critical for understanding atmospheric processes and for accurate forecasts of surface weather. The diurnal cycle and local surface properties strongly affect boundary layer characteristics. However, especially over the ocean, where the surface is less responsive to radiation changes, synoptic-scale weather systems can play a dominant role in shaping the PBL.

Dry intrusion (DI) is a free tropospheric flow that moves downward and equatorward along isentropic surfaces, which often mixes into the PBL. This airstream is fundamental to the structure of mid-latitude cyclones, spreading behind their cold front. DIs can enhance surface heat fluxes and the surface wind speed, impacting the height of PBL and the inversion strength. The DI airstream thus provides a means to delineate the understudied connection between the PBL evolution and the synoptic forcings.

This study examines the influence of DI entrainment on PBL structure, focusing on the Azores islands — a domain within a climatologically high DI occurrence with rare operational profile observations of the marine boundary layer. Using high-resolution ICON simulations, we analyze a winter case study in which a cold front is followed by a DI, tracking its impact on PBL properties over time. A Lagrangian approach allows us to diagnose and follow the trajectories of DI airmasses, providing insight into their evolution and spatial influence on atmospheric conditions.

Our findings reveal coherent temporal changes in PBL properties, such as the PBL height, inversion properties, moisture content, and spatial extent of these changes during the course of the studied event. There are distinct stages of PBL modification due to DI entrainment. Initially, DI influx leads to enhanced surface heat fluxes and significant PBL deepening. However, as the entrainment progresses, the PBL undergoes a transition, ultimately becoming shallower and more stable, with extremely low relative humidity values above it. This case study shows the interplay between DIs and surface fluxes that can both enhance and suppress PBL deepening, while the nature and timing of these transitions are topics for further research.

This study improves our understanding of DI-driven PBL evolution, highlighting the connection between large-scale weather systems and boundary-layer dynamics. A better representation of these processes in weather and climate models may improve forecasts in regions affected by DIs.

How to cite: Shendrik, L., Magaritz-Ronen, L., Hochman, L., and Raveh-Rubin, S.: Case Study of Dry Air Intrusions Behind an Extratropical Cyclone and Their Impacts on Boundary Layer Evolution, EMS Annual Meeting 2025, Ljubljana, Slovenia, 7–12 Sep 2025, EMS2025-66, https://doi.org/10.5194/ems2025-66, 2025.

In the bulk of the convective boundary layer driven by surface heating, the vertical-velocity variance is known to scale with the convective velocity scale. This scaling relies on the quasi-equilibrium assumption that the surface heat flux (H , the water-vapor contribution to buoyancy is neglected) varies slowly compared to the adjustment time scale of the large scale convective eddies (or the eddy turnover time), a condition which over land is typically satisfied from the late morning to the early afternoon transition. Later on, when the surface heat flux starts decaying moderately compared to the eddy turnover time, a departure from the quasi-equilibrium regime is expected. A recent idealized large-eddy simulations (LES) study proposed a parameter for describing such departure during the late afternoon transition: r ≡ H^-1dH/dt^-1/t_*, where t_* is the eddy turnover time. The quasi-equilibrium assumption applies when r >> 1, and breaks down when r ∼ 1. Building on these results, we further investigate the scaling for the vertical-velocity variance during the very late afternoon transition, i.e. in the regime r << 1 where the surface heat flux decays rapidly compared to the eddy turnover time. In a first step, we use LES to reveal that the regime r << 1 is characterized by a new velocity scale w_*r ≡ ((g/θ )dH/dtzi²)^1/4 . Within the specific framework of this study using the parameter r for identifying the out-of-equilibrium regime r << 1, the proposed scaling is implicitly dependent on the surface heat flux magnitude at the initial state when r ≈ 0.1, through the definition of the parameter r . In a second step, we demonstrate that the new velocity scale can be deduced from scaling arguments applied to the budget-equation of the vertical turbulent heat flux.

How to cite: El guernaoui, O., Li, D., and Reuder, J.: Scaling the Vertical-Velocity Variance During the Very Late Afternoon Transition of the Convective Boundary Layer , EMS Annual Meeting 2025, Ljubljana, Slovenia, 7–12 Sep 2025, EMS2025-354, https://doi.org/10.5194/ems2025-354, 2025.

Sea breezes are mesoscale winds formed in coastal regions under weak synoptical surface-pressure gradients. The theoretical scheme of daytime sea breezes includes surface winds from the sea and a return flow at a certain height above. However, this canonical picture is rarely detected from observations due to the complexity, high variability and heterogeneity of the different factors affecting the final atmospheric boundary layer structure. This is the case in the Gulf of Cádiz (SW Spain), where sea breezes have important effects during summer, especially due to their capacity to mitigate warm temperatures and transport humidity. In this region, two main types of sea breezes typically form depending on the dominant background synoptic flow: the so-called “pure” and “non-pure” sea breezes. The former take their name due to their greater similarity to canonical ones, while the latter present different characteristics and are more influenced by the synoptic conditions.

This study outlines the research strategy followed to investigate these phenomena in the area using the Weather Research and Forecasting (WRF) mesoscale model, along with new observational data from recently deployed instrumentation, as well as from radiosoundings launched at strategic sites during sea breeze conditions. Among the instrumentation used, we highlight a sonic anemometer and an IRGASON system, installed at 10 m and 65 m above sea level, respectively. Positioned directly on the shoreline, these instruments allow the evaluation of turbulent fluxes “above the sea” with different objectives. First, we aim to analyse variations in turbulence under sea breeze conditions with a well-formed internal boundary layer. Secondly, we seek to monitor sea surface fluxes at the coast to investigate their influence on breeze formation and evaluate the flux values simulated by WRF.

The work has been developed within the framework of the following research projects:

* The LATMOS-i project (PID2020-115321RB-I00) (Land-ATMOSphere interactions in a changing environment: How do they impact on atmospheric-boundary-layer processes at the meso, sub-meso and local scales in mountainous and coastal areas?), funded by MCIN/AEI/ 10.13039/501100011033.

** The WINDABL project (PR2022-055) (How are the Surface Thermally Driven Winds influenced by the vertical structure and horizontal inhomogeneities of the Atmospheric Boundary Layer?), funded by Plan Propio de la Universidad de Cádiz, Convocatoria 2022 de Proyectos para investigadores nóveles.

*** The WIND4US project (CNS2023-144885) (Disentangling the complexity of the WIND systems in coastal areas FOR a better Understanding of their impacts on Society), funded by Convocatoria 2023 de Proyectos de Consolidación Investigadora.

How to cite: Román-Cascón, C., Carbone, J., Ortíz-Corral, P., Luján-Amoraga, E., Jiménez-Rincon, J. A., Bolado-Penagos, M., Bruno-Mejías, M., Izquierdo, A., and Yagüe, C.: Improving the understanding of the horizontal and vertical characteristics of sea breezes from mesoscale numerical simulations and observations, EMS Annual Meeting 2025, Ljubljana, Slovenia, 7–12 Sep 2025, EMS2025-184, https://doi.org/10.5194/ems2025-184, 2025.

The frequency and impacts of heatwaves have significantly increased in the last years (1975-2020), with Spain experiencing a substantial rise in the occurrence these extreme events (Núñez-Mora, 2021). In coastal regions, breezes —driven by temperature gradients between land and sea surfaces— can play a crucial role in mitigating extreme temperatures. This study examines the impact of coastal breezes on thermal comfort during a heatwave period in the southwest of the Iberian Peninsula.

Coastal areas have undergone considerable urban development, with approximately 60% of the Spanish population residing in these regions (de Andrés et al., 2017). Consequently, urban heat exposure in these regions is shaped by meteorological variables operating across multiple spatial (meters to hundreds of meters) and temporal scales. Within cities, temperature and humidity exhibit local variations over hundreds of meters, while wind speed and shortwave/longwave radiation show highly microscale heterogeneity influenced by individual buildings and fluctuating over just a few meters.

To assess the impact of coastal breezes on thermal comfort, we analyse observational data from meteorological stations and radiosoundings launched at strategic coastal sites during sea breeze conditions. We also employ the Weather Research and Forecasting (WRF) model with the urban parameterization WRF-Comfort (Martilli et al., 2024). This integrated approach enables us to evaluate the thermoregulatory effects of coastal breezes and compare the simulations against both surface and vertical atmospheric observations.

Understanding the vertical structure of the atmospheric boundary layer (ABL) is crucial, particularly for sea breezes, phenomena theoretically characterised by surface inflow and upper-level return flow. However, this simplified view is rarely captured fully by observations alone, due to the complexity, high variability, and heterogeneity of the various factors influencing the ABL's vertical structure. Therefore, this study leverages the WRF model to investigate the vertical characteristics of the coastal urban boundary layer during heatwave events, complementing the surface and upper-air observational analyses.

Our findings offer insights into mesoscale interactions between urban dynamics and regional climate processes during extreme heat events, highlighting the importance of integrating mesoscale modelling with urban-scale processes and evaluating against comprehensive observational datasets to better understand and potentially mitigate the impacts of weather extremes in coastal urban environments.

How to cite: Carbone, J., Luján-Amoraga, E., Ortiz-Corral, P., Sanchez, B., Martilli, A., Sastre, M., Yagüe, C., Bolado-Penagos, M., Alvarez, O., and Román-Cascón, C.: Coastal breezes and thermal comfort during a heatwave event in the southwestern Iberian Peninsula: an integrated modelling and observational study., EMS Annual Meeting 2025, Ljubljana, Slovenia, 7–12 Sep 2025, EMS2025-311, https://doi.org/10.5194/ems2025-311, 2025.

Droughts in the Netherlands have been exacerbated by climate change, urging better scientific understanding of the hydrological cycle and the role of evapotranspiration. Evapotranspiration is the combined process in which liquid water is transferred from the surface to the atmosphere as water vapor, occurring through evaporation as well as transpiration from vegetation leaves. In addition to better understanding how water leaves the Earth’s surface, accurate surface water observations are crucial for reliable predictions and effective management. Currently, the Royal Netherlands Meteorological Institute (KNMI) primarily estimates evaporation based on the meteorological conditions, such as precipitation and temperature. Also, their Cabauw Experimental Site for Atmospheric Research has maintained decades of in-situ evaporation observations, exploring various indirect methods, such as the eddy covariance and Bowen ratio method. Specifically, the moisture fluxes derived from turbulence and psychrometer measurements are used to determine latent energy. Although these established methods provide valuable climate insight, more direct approaches are required to improve our understanding of surface moisture loss. To address this, a new smart lysimeter has been deployed since 2020, measuring water inflow and outflow of a representative soil-vegetation column. While lysimeters offer precise measurements, they are spatially limited, sensitive to small-scale variations, and require rigorous validation. Therefore, in addition to providing an overview of the increasing evaporation observed at the Cabauw site, this study evaluates the lysimeter’s performance and potential as a reference through intercomparison. Additionally, by integrating supplementary in-situ measurements, our findings suggest that validated lysimeter data can contribute to improved closure of the surface energy balance. In this way, lysimeter observations can enhance hydrological research, improve modeling, and support environmental decision-making.

How to cite: Strickland, J. M. I. and de Bruijn, E. I. F.: Measuring Evapotranspiration at the Cabauw Experimental Site for Atmospheric Research, EMS Annual Meeting 2025, Ljubljana, Slovenia, 7–12 Sep 2025, EMS2025-38, https://doi.org/10.5194/ems2025-38, 2025.

Kelvin–Helmholtz (K-H) or shear instability may occur in continuously stratified flows and along interfaces between fluids associated with strong vertical shear. This process is suspected to be a major source of clear air turbulence and a contributor to vertical mixing of momentum and scalars in the atmospheric boundary layer. It is believed that it plays a substantial role in intermittent turbulence generation and vertical mixing in a stable boundary layer. Occasionally, a K-H instability becomes visible as K-H billow clouds.  

Here we present an observation of a K-H instability on the early morning of July 25, 2022 at the Cabauw atmospheric research station in The Netherlands. The K-H instability is observed in Doppler lidar vertical stare measurements (with 1s temporal resolution) as a prominent wavelike pattern in the vertical velocity centered at altitude of 1000m, in which the upper and lower halves are shifted in phase. These K-H waves have a period a few minutes, with vertical velocity amplitudes up to 2m/s, and last for about 15 minutes. Maximum eddy dissipation rate is found to be 2x10^-3m²s^-3. The residual layer that night was up to 2000m, providing sufficient aerosol backscatter signal for Doppler lidar measurements to observe these K-H waves.

The Doppler lidar wind profile measured just before the appearance of the K-H instability showed a strong wind shear (0.04s^-1) with a shear layer depth of about 300m. The Richardson number (Ri) profiles, derived from combining the vector wind shear (Doppler lidar) and Brunt-Vaisala frequency profiles (microwave radiometer), shows Ri<0.25 just before to the appearance of the K-H waves, confirming the K-H instability scenario.

To our knowledge this is the first Doppler lidar vertical stare observation of a K-H instability in the nocturnal boundary layer with its signature in the vertical velocity. Within our four years of Doppler lidar operation at Cabauw this K-H wave observation is unique, while less prominent elevated intermittent turbulence patches in the nocturnal boundary layer are more often observed. The K-H waves are also distinct from the more often observed gravity waves [1].  Our observations demonstrate that Doppler lidar vertical stare measurements, preferably combined with wind and temperature profile measurements, can contribute to the understanding of waves and enhanced turbulence in the nocturnal boundary layer.

[1] Knoop, S., Assink, J., Tijm, S., and Leijnse, H.: High-resolution observations of a gravity wave event over the Netherlands, EMS 2024, https://doi.org/10.5194/ems2024-445

How to cite: Knoop, S., Assink, J., Unal, C., van der Linden, S., and van der Wiel, B.: Doppler lidar vertical stare observation of a Kelvin-Helmholtz instability in the nocturnal boundary-layer, EMS Annual Meeting 2025, Ljubljana, Slovenia, 7–12 Sep 2025, EMS2025-349, https://doi.org/10.5194/ems2025-349, 2025.

The diurnal cycle and vertical distribution of atmospheric CO2 in the lower troposphere is strongly influenced by multiple surface and atmospheric processes across different scales. For example, photosynthesis and CO2-assimilation at single leaves or the tree canopy, to the vertical and horizontal (turbulent) transport at scales of the boundary layer, clouds and large weather systems. Accurately capturing these multi-scale dynamics is essential for improving global estimates of the CO2 exchange in the lower troposphere. In this study, we evaluate the relative contribution of these multi-scale dynamics to the total CO2 exchange in the lower troposphere by examining how these processes are represented within the Integrated Forecasting System (IFS) of the ECMWF. More specifically, we assess their representation for three IFS horizontal resolutions: 25 km, 9 km (current operational resolution) and 4.4 km. We construct a framework with which we evaluate the CO2 budget in IFS through comprehensive sets of observations, simulations from a coupled surface-atmosphere mixed-layer model (CLASS) and large-eddy simulations (DALES). In this budget, we characterise tendencies of atmospheric CO2 into respective contributions from the different scales: (turbulent) diffusion, convective processes and large-scale dynamics. We focus on two comprehensive case studies across three ecosystems: the tropical clear-to-shallow moist convective Amazon rainforest and the temperate mid-latitudes with influences from large weather systems: the Cabauw (grass), and Loobos (pine forest) sites located in The Netherlands. Initial results reveal that the IFS accurately represents the vertical structure and diurnal evolution of the state variables (temperature, humidity and wind) within the lower troposphere for both case studies at the different model resolutions. However, larger uncertainties arise in the CO2 exchange, especially near the surface, as a result of discrepancies during the morning transition. Ongoing work focuses on investigating the underlying multi-scale dynamics to address these and other discrepancies in the CO2 exchange of the lower troposphere within IFS.

How to cite: de Feiter, V. S., Savazzi, A., Janssens, M., van Heerwaarden, C. C., Agusti-Panareda, A., and Vila-Guerau de Arellano, J.: Evaluating Multi-Scale CO2 Exchange of the Tropical and Temperate Troposphere in the ECMWF Integrated Forecasting System Using Observations and Large-Eddy Simulations , EMS Annual Meeting 2025, Ljubljana, Slovenia, 7–12 Sep 2025, EMS2025-340, https://doi.org/10.5194/ems2025-340, 2025.

Turbulent heat and momentum transfer in atmospheric surface layer plays a crucial role in determining the global and regional climate. They have a significant impact on various processes, such as the interaction between the atmosphere and the underlying surface, as well as on atmospheric circulation.

Methods based on the Monin-Obukhov similarity theory (MOST) and its generalizations are widely used in numerical weather and climate models. However, their limitations become especially evident in stable conditions, such as those found in the polar regions.  MOST assumes the existence of constant flux layer, where the dimensionless gradients of wind speed, temperature, and humidity depend on the height above the surface relative to the Obukhov length scale. This assumption is violated in conditions of a thin stably stratified boundary layer (about 10-100 meters). In addition, MOST does not take into account the non-gradient transport characteristics of the daytime convective boundary layer. It also does not consider the influence of topography and thermal heterogeneity, which can lead to systematic errors in the estimation of turbulent fluxes and increase uncertainty in climate predictions.

This study discusses the use of a neural network-based algorithm that can take into account complex, nonlinear relationships between meteorological parameters. This algorithm may compensate for some of the limitations of known semi-empirical approaches. The model was trained on extensive datasets obtained from field experiments, such as MOSAiC and SHEBA. This allows the model to capture not only the general physical relationships between input parameters and fluxes, but also to accurately reproduce the amplitude of turbulent fluxes, even under strongly stable conditions. The possibility of training a model using the output data from a single column atmospheric boundary layer model with fine resolution tuned to large-eddy simulation data is also being explored. This allows us to consider the influence of the height of the boundary layer, thereby expanding the applicability of the algorithm to climate models with coarse vertical resolution. The results obtained demonstrate a significant improvement in the accuracy of flux estimates compared to the surface layer parameterization used in the INMCM¹ Earth system model. This suggests the potential for integrating machine learning into surface layer models, which in turn may contribute to improving weather and climate forecast.

¹Link to INMCM: https://link.springer.com/article/10.1007/s00382-017-3539-7

Volodin, E.M., Mortikov, E.V., Kostrykin, S.V. et al. Simulation of the present-day climate with the climate model INMCM5. Clim Dyn 49, 3715–3734 (2017). https://doi.org/10.1007/s00382-017-3539-7

How to cite: Shishkov, E., Mortikov, E., Debolskiy, A., and Suiazova, V.: Application of neural networks for improving surface layer turbulent exchange parameterizations in general circulation models, EMS Annual Meeting 2025, Ljubljana, Slovenia, 7–12 Sep 2025, EMS2025-289, https://doi.org/10.5194/ems2025-289, 2025.

Understanding the atmospheric phenomena of the offshore wind sites helps inform the potential risks from wake propagation, an issue becoming more prominent as wind farms grow larger and more densely concentrated. The atmospheric boundary layer (ABL) represents a crucial component for evaluating wake recovery as it defines the limit of the atmosphere where all convective activity occurs, and where the wind speed is affected by phenomena at the surface (heating, friction, etc.), before reaching the free atmosphere. This parameter is directly linked to stability conditions and determines the “space” for momentum flux recovery in wakes.

Currently the ABL is a parameterized variable in wake models, either defined by a theoretical model or adapted from reanalysis data such as ERA5. This becomes an issue for offshore applications as conditions are mostly stably stratified, thus highlighting the importance of correctly representing the ABL for accurate model wake propagation impacts on energy production.

Lidars present a viable solution to provide in-situ measurements that could help validate offshore ABL outputs from these models, which are highly relied upon in wind resource assessment and monitoring. This study presents a bias and sensitivity analysis of offshore lidar ABL measurements compared to ERA5 and WRF ABL model outputs. This analysis builds off Santos et al work from the GLOBE campaign of using scanning lidar measurements to validate ERA5 and WRF boundary layer heights by further investigating the sensitivity of this bias and adding a site with coastal conditions.  Two separate campaigns lasting 6+ months in the North Sea were assessed: one located completely offshore from the GLOBE campaign, and another coastal from the FLOW project. The method used for lidar ABL measurements consists of an image binarization method to retrieve mixing layer heights from vertical velocity profiles and residual layers heights from return signal profiles. Several averaging methods were assessed to combine both residual and mixing layer heights to be compatible with the singular ABL heights given by the models

How to cite: Mulet-Benzo, C., Black, A., Hung, L.-Y., Santos, P., and Gottschall, J.: Assessing boundary layer heights with ERA5, WRF, and scanning lidar measurements, EMS Annual Meeting 2025, Ljubljana, Slovenia, 7–12 Sep 2025, EMS2025-375, https://doi.org/10.5194/ems2025-375, 2025.

Over the past five decades (1970–2020), Madrid's population has doubled, while its urban area has expanded fivefold. By 2037, projections estimate further urban growth of 1.15 to 2.14 times compared to 2010, alongside a 15% population increase (INE, 2022). This rapid urbanization drives to poorer city air quality and an energy consumption increase, and can alter the mesoscale and local atmospheric circulations, affecting the Urban Heat Island (UHI) effect.

This study evaluates the impact of Madrid’s urban expansion on local meteorology using the mesoscale WRF model configured with the BEP-BEM urban parameterization (Martilli et al., 2002; Salamanca et al., 2010, Carbone et al., 2024). Urban parameters are integrated based on the city’s growth from 1970 to 2020. Results show that areas with increased urban fraction experience higher near-surface air temperatures, especially at night. Urbanization also modifies the Surface Energy Balance (SEB) and turbulent transport. These findings underscore the role of urban-induced changes in local meteorology and highlight the need for climate adaptation strategies to mitigate the effects of urban expansion on air quality and thermal comfort in Madrid.

This work is being developed in the framework of the MULTIURBAN-II ("Impacts of mesoscale thermally-driven flows on the urban heat island, local meteorology, and air quality in complex environments in the city”) research project, which will be also presented. This project analyses the dynamic and thermal impacts of these flows in different city zones, the role of turbulent mixing, their effects on UHI, and broader implications. To achieve these objectives, both field campaign data from meteorological stations (including radiative and turbulent fluxes in urban and rural environments) will be combined with simulations from the WRF model, enhanced with the WRF-Comfort urban canopy model (Martilli et al., 2024). This integrated approach allows us to assess the spatial and temporal dynamics of thermal comfort under the influence of breezes and validate the model's performance.

How to cite: Carbone, J., Sanchez, B., Román-Cascón, C., Martilli, A., Santiago, J. L., Ortiz-Corral, P., Cicuéndez, V., Inclán, R. M., Royé, D., Maqueda, G., Viana, S., Sastre, M., and Yagüe, C.: Impact of Urban Expansion and Thermally-Driven Flows on Madrid's Local Meteorology., EMS Annual Meeting 2025, Ljubljana, Slovenia, 7–12 Sep 2025, EMS2025-310, https://doi.org/10.5194/ems2025-310, 2025.