The increasing presence of unmanned aerial vehicles (UAVs) in urban environments presents challenges for reliable detection due to clutter caused by buildings, infrastructure, and other static structures. Conventional Doppler-based radar methods often struggle in such conditions, particularly when UAVs exhibit low radial velocities. This paper presents a non-Doppler scattering-point framework for UAV detection, based on a frequency-modulated continuous wave (FMCW) radar system operating in the X-band (9.950–10.026 GHz). The system utilizes a rotating platform for azimuth scanning and applies azimuth-range mapping combined with adaptive DBSCAN clustering and β-expanded convex hull boundary estimation to reduce false detections from static clutter. Experimental validation was conducted in a controlled urban setting with multiple buildings and varied UAV trajectories. The method was evaluated across several elevation angles, demonstrating consistent detection performance and improved distinction between UAV detections and points caused by environmental clutter. These results support the use of FMCW radar and spatial clustering techniques as an effective alternative to Doppler-independent methods for UAV monitoring in complex environments.
{"title":"Environmental boundary estimation of urban areas using FMCW radar with data clustering for UAV detection","authors":"Seksan Eiadkaew;Akkarat Boonpoonga;Lakkhana Bannawat;Krit Athikulwongse;Danai Torrungrueng","doi":"10.1029/2025RS008392","DOIUrl":"https://doi.org/10.1029/2025RS008392","url":null,"abstract":"The increasing presence of unmanned aerial vehicles (UAVs) in urban environments presents challenges for reliable detection due to clutter caused by buildings, infrastructure, and other static structures. Conventional Doppler-based radar methods often struggle in such conditions, particularly when UAVs exhibit low radial velocities. This paper presents a non-Doppler scattering-point framework for UAV detection, based on a frequency-modulated continuous wave (FMCW) radar system operating in the X-band (9.950–10.026 GHz). The system utilizes a rotating platform for azimuth scanning and applies azimuth-range mapping combined with adaptive DBSCAN clustering and β-expanded convex hull boundary estimation to reduce false detections from static clutter. Experimental validation was conducted in a controlled urban setting with multiple buildings and varied UAV trajectories. The method was evaluated across several elevation angles, demonstrating consistent detection performance and improved distinction between UAV detections and points caused by environmental clutter. These results support the use of FMCW radar and spatial clustering techniques as an effective alternative to Doppler-independent methods for UAV monitoring in complex environments.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 2","pages":"1-19"},"PeriodicalIF":1.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147362530","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Martin Füllekrug;Michael Kosch;Gavin Dingley;Xue Bai;Liliana Macotela
Low frequency electromagnetic waves emitted by sprite-producing lightning are normally measured using vertical electric fields or horizontal magnetic fields. Here we report for the first time the simultaneous measurement of electromagnetic waves from sprite-producing lightning in all six electromagnetic field components Ex, Ey, Ez, Hx, Hy, and Hz. A rigorous assessment of the horizontal electric field measurements with dipole antennas in two independent calibration experiments shows that a timing uncertainty of ∼ 1–2 ns can be achieved, well above the current fundamental limit of the timing accuracy ∼1–5 ps. The coupling between the electric and magnetic fields is quantified using a transfer matrix, allowing the magnetic field to be reconstructed accurately from electric field measurements. The cross product of electric and magnetic fields is used to calculate peak energy fluxes and arrival azimuths from sprite-producing lightning. It is found that peak energy fluxes vary between ∼ 10—1,000 μW/m2 and that the differences between the measured and expected arrival azimuths are practically normally distributed with a mean and standard deviation of −8.0° ± 2.2°. It is concluded that horizontal electric field measurements are well suited to characterize electromagnetic waves with added benefits, including the ease of deployment in harsh environments, cost-effectiveness and scalability, for example for polarisation measurements in large low frequency arrays. The significance of this study is that it can be used as a pathfinder mission to identify critical technical requirements for the array deployment during the Africa2Moon lander mission.
{"title":"Six-component electromagnetic wave measurements of sprite-associated lightning","authors":"Martin Füllekrug;Michael Kosch;Gavin Dingley;Xue Bai;Liliana Macotela","doi":"10.1029/2025RS008543","DOIUrl":"https://doi.org/10.1029/2025RS008543","url":null,"abstract":"Low frequency electromagnetic waves emitted by sprite-producing lightning are normally measured using vertical electric fields or horizontal magnetic fields. Here we report for the first time the simultaneous measurement of electromagnetic waves from sprite-producing lightning in all six electromagnetic field components E<inf>x</inf>, E<inf>y</inf>, E<inf>z</inf>, H<inf>x</inf>, H<inf>y</inf>, and H<inf>z</inf>. A rigorous assessment of the horizontal electric field measurements with dipole antennas in two independent calibration experiments shows that a timing uncertainty of ∼ 1–2 ns can be achieved, well above the current fundamental limit of the timing accuracy ∼1–5 ps. The coupling between the electric and magnetic fields is quantified using a transfer matrix, allowing the magnetic field to be reconstructed accurately from electric field measurements. The cross product of electric and magnetic fields is used to calculate peak energy fluxes and arrival azimuths from sprite-producing lightning. It is found that peak energy fluxes vary between ∼ 10—1,000 μW/m<sup>2</sup> and that the differences between the measured and expected arrival azimuths are practically normally distributed with a mean and standard deviation of −8.0° ± 2.2°. It is concluded that horizontal electric field measurements are well suited to characterize electromagnetic waves with added benefits, including the ease of deployment in harsh environments, cost-effectiveness and scalability, for example for polarisation measurements in large low frequency arrays. The significance of this study is that it can be used as a pathfinder mission to identify critical technical requirements for the array deployment during the Africa2Moon lander mission.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 2","pages":"1-13"},"PeriodicalIF":1.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147362528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The atmospheric surface layer over the ocean has a strong impact on electromagnetic (EM) wave propagation in the lowest 100 m of the atmosphere. Due to surface evaporation, a strong vertical gradient in water vapor forms in this layer, resulting in an evaporation duct which may greatly increase detection ranges for sensors and targets within the duct. When a warm air mass moves over cooler water, the surface layer forms a stable thermal stratification whose ducting characteristics are much less understood compared to its counterpart, the unstable surface layer. In this study, we perform a sensitivity study to examine the characteristics of the stable surface layer profiles and how their impacts on EM propagation differ from those in the unstable cases. Using buoy-based measurements from both coasts of the United States as input to a surface layer model, refractivity profiles were generated as input to a propagation model to characterize path loss. The results suggest that the stable surface layers present more complex propagation scenarios with a broad range of propagation loss including the maximum propagation loss in the subrefractive conditions and maximum trapping in cases of deep evaporation duct heights. The results also suggest strong dependance of propagation loss on evaporation duct height when the transmitter height is above the duct. In contrast, propagation loss is no longer sensitive to evaporation duct height once the transmitter is within the duct. This research also reveals the role of 2-m curvature of the M-profile in defining the propagation regimes.
{"title":"Behavior of evaporation ducts in stable and unstable surface layers","authors":"Katherine Mulreany;Qing Wang","doi":"10.1029/2025RS008402","DOIUrl":"https://doi.org/10.1029/2025RS008402","url":null,"abstract":"The atmospheric surface layer over the ocean has a strong impact on electromagnetic (EM) wave propagation in the lowest 100 m of the atmosphere. Due to surface evaporation, a strong vertical gradient in water vapor forms in this layer, resulting in an evaporation duct which may greatly increase detection ranges for sensors and targets within the duct. When a warm air mass moves over cooler water, the surface layer forms a stable thermal stratification whose ducting characteristics are much less understood compared to its counterpart, the unstable surface layer. In this study, we perform a sensitivity study to examine the characteristics of the stable surface layer profiles and how their impacts on EM propagation differ from those in the unstable cases. Using buoy-based measurements from both coasts of the United States as input to a surface layer model, refractivity profiles were generated as input to a propagation model to characterize path loss. The results suggest that the stable surface layers present more complex propagation scenarios with a broad range of propagation loss including the maximum propagation loss in the subrefractive conditions and maximum trapping in cases of deep evaporation duct heights. The results also suggest strong dependance of propagation loss on evaporation duct height when the transmitter height is above the duct. In contrast, propagation loss is no longer sensitive to evaporation duct height once the transmitter is within the duct. This research also reveals the role of 2-m curvature of the M-profile in defining the propagation regimes.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 2","pages":"1-14"},"PeriodicalIF":1.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147362529","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alexander V. Koustov;Mehdi Ghalamkarian Nejad;Hayden Fast;Pavlo V. Ponomarenko
This study is one of the first attempts to estimate statistically the real height of SuperDARN F region echoes in the polar cap. To achieve this, measurements of the electron density in the scattering volume of the Rankin Inlet SuperDARN radar are compared with the electron density profiles measured by the incoherent scatter radar RISR-C (located at Resolute Bay) in beams oriented toward Rankin Inlet. The scatter height of echoes was found to be in the range of 210–270 km with the most frequently occurring values of ∼230–250 km. Overall, no strong trend in echo height versus local time was identified although the tendency for heights to be lower during noon/afternoon hours was noticed. Seasonally, the echo heights were ∼10 km higher at equinox compared to winter. The echo heights were below F2 layer peak height by ∼45 km with largest offsets during morning/prenoon hours. Typical difference in the height of 12 and 10 MHz echoes was found to be 10–15 km with no obvious diurnal and seasonal trends.
{"title":"Real heights of SuperDARN F region echoes inferred from electron density measurements by the Rankin Inlet and RISR-C radars","authors":"Alexander V. Koustov;Mehdi Ghalamkarian Nejad;Hayden Fast;Pavlo V. Ponomarenko","doi":"10.1029/2025RS008436","DOIUrl":"https://doi.org/10.1029/2025RS008436","url":null,"abstract":"This study is one of the first attempts to estimate statistically the real height of SuperDARN F region echoes in the polar cap. To achieve this, measurements of the electron density in the scattering volume of the Rankin Inlet SuperDARN radar are compared with the electron density profiles measured by the incoherent scatter radar RISR-C (located at Resolute Bay) in beams oriented toward Rankin Inlet. The scatter height of echoes was found to be in the range of 210–270 km with the most frequently occurring values of ∼230–250 km. Overall, no strong trend in echo height versus local time was identified although the tendency for heights to be lower during noon/afternoon hours was noticed. Seasonally, the echo heights were ∼10 km higher at equinox compared to winter. The echo heights were below F2 layer peak height by ∼45 km with largest offsets during morning/prenoon hours. Typical difference in the height of 12 and 10 MHz echoes was found to be 10–15 km with no obvious diurnal and seasonal trends.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 2","pages":"1-15"},"PeriodicalIF":1.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147362515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Mondal;Y. Hobara;H. Kikuchi;J. Lapierre;P. Le Floch;O. Kameya;N. Kawaguchi;K. Motojima;K. Shiokawa;T. Eguchi;D. Okano;T. Nakamura
Recently, detailed spatio-temporal analysis utilizing X-band multi-parameter radar-derived 3D volume scan and total lightning data in Japan, have revealed the peak in-cloud (IC) lightning occurs 5–10 min prior to maximum ground rainfall in individual thunderstorm cells during heavy rainfall events. This temporal relation holds the potential for improving real-time monitoring and nowcasting of torrential rain causing natural disaster such as flash floods. However, cell interactions such as merging and splitting of the cells are often observed in multicellular thunderstorms, which cause abrupt fluctuation in the total lightning rate and make it difficult to track the storm evolution. To address this, we propose an area-correction method based on the lightning activity (in terms of cell area ratio before and after merging/splitting) of individual cell. Preliminary observation results of two multicellular thunderstorm events with heavy rainfall (∼100 mm/hr) that exhibited cell merging and splitting during their life cycle are demonstrated. The area-correction resulted in a reasonable and corresponding trend in the temporal behavior of IC lightning rate and ground precipitation volume, with the peak IC rate preceding the peak ground PV by 5–10 min. We also demonstrate a promising approach for short-term prediction of ground rainfall with high accuracy (correlation coefficient between observed and predicted PV was 0.84–0.94), by means of a moving linear regression model, using recent IC observations. These results highlight the potential of total lightning for short-term rainfall prediction in both isolated and multicellular thunderstorms.
{"title":"Temporal dependencies between total lightning and rainfall in multicellular systems: A predictive approach for torrential rain during summer thunderstorms in Japan","authors":"D. Mondal;Y. Hobara;H. Kikuchi;J. Lapierre;P. Le Floch;O. Kameya;N. Kawaguchi;K. Motojima;K. Shiokawa;T. Eguchi;D. Okano;T. Nakamura","doi":"10.1029/2025RS008380","DOIUrl":"https://doi.org/10.1029/2025RS008380","url":null,"abstract":"Recently, detailed spatio-temporal analysis utilizing X-band multi-parameter radar-derived 3D volume scan and total lightning data in Japan, have revealed the peak in-cloud (IC) lightning occurs 5–10 min prior to maximum ground rainfall in individual thunderstorm cells during heavy rainfall events. This temporal relation holds the potential for improving real-time monitoring and nowcasting of torrential rain causing natural disaster such as flash floods. However, cell interactions such as merging and splitting of the cells are often observed in multicellular thunderstorms, which cause abrupt fluctuation in the total lightning rate and make it difficult to track the storm evolution. To address this, we propose an area-correction method based on the lightning activity (in terms of cell area ratio before and after merging/splitting) of individual cell. Preliminary observation results of two multicellular thunderstorm events with heavy rainfall (∼100 mm/hr) that exhibited cell merging and splitting during their life cycle are demonstrated. The area-correction resulted in a reasonable and corresponding trend in the temporal behavior of IC lightning rate and ground precipitation volume, with the peak IC rate preceding the peak ground PV by 5–10 min. We also demonstrate a promising approach for short-term prediction of ground rainfall with high accuracy (correlation coefficient between observed and predicted PV was 0.84–0.94), by means of a moving linear regression model, using recent IC observations. These results highlight the potential of total lightning for short-term rainfall prediction in both isolated and multicellular thunderstorms.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 2","pages":"1-20"},"PeriodicalIF":1.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147362527","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mini Rajput;P R Shreedevi;Sanjay Kumar;Abhay Kumar Singh
This study investigates Total Electron Content (TEC) variations across the Indian longitude sector (75°–85°E) from 2004 to 2014, spanning descending phase solar cycle 23 and ascending/peak phases of solar cycle 24, using GPS data from four stations: Bangalore (IISC), Varanasi (BHUP), Bishkek (POL), and Novosibirsk (NOVM). We analyze latitudinal, seasonal, and solar activity-driven TEC variability and evaluate IRI-2016 and IRI-2020 model performance. Low-latitude stations (IISC, BHUP) exhibit strong equinoctial peaks (∼40–70 TECU), semi-annual anomalies, noontime bite-outs driven by the equatorial ionization anomaly and E × B drifts, and nighttime enhancements during high solar activity. Mid-latitude stations (POL, NOVM) show lower TEC (∼20–35 TECU) with seasonal variations influenced by thermospheric winds. Equinoctial asymmetry is evident, with October TEC surpassing March-April in 2011–2013 due to rising solar EUV flux. TEC strongly correlates with F10.7/SSN (R2 ∼0.65–0.78, higher at low latitudes), reflecting strong solar control at low-latitudes. At low latitudes, IRI-2020 outperforms IRI-2016 with lower RMSE, while at mid-latitudes IRI-2016 shows slightly better performance. Differential TEC (DTEC) reveals larger deviations at low latitudes ranging from — 26.8 to +30.81 TECU, compared to smaller deviations at mid-latitudes ranging from — 8.71 to + 18.50 TECU. Both models capture equinoctial enhancements but overestimate winter anomaly occurrence and show large errors during equinoxes, particularly at low latitudes. Unlike prior studies, this work examines TEC across an entire solar cycle, revealing regional model limitations. These findings enhance ionospheric model validation, critical for improving satellite navigation and space weather forecasting in the Indian sector.
{"title":"Ionospheric variability across solar cycles 23 and 24 in the Indian longitude sector: GPS observations and IRI model validation","authors":"Mini Rajput;P R Shreedevi;Sanjay Kumar;Abhay Kumar Singh","doi":"10.1029/2025RS008458","DOIUrl":"https://doi.org/10.1029/2025RS008458","url":null,"abstract":"This study investigates Total Electron Content (TEC) variations across the Indian longitude sector (75°–85°E) from 2004 to 2014, spanning descending phase solar cycle 23 and ascending/peak phases of solar cycle 24, using GPS data from four stations: Bangalore (IISC), Varanasi (BHUP), Bishkek (POL), and Novosibirsk (NOVM). We analyze latitudinal, seasonal, and solar activity-driven TEC variability and evaluate IRI-2016 and IRI-2020 model performance. Low-latitude stations (IISC, BHUP) exhibit strong equinoctial peaks (∼40–70 TECU), semi-annual anomalies, noontime bite-outs driven by the equatorial ionization anomaly and E × B drifts, and nighttime enhancements during high solar activity. Mid-latitude stations (POL, NOVM) show lower TEC (∼20–35 TECU) with seasonal variations influenced by thermospheric winds. Equinoctial asymmetry is evident, with October TEC surpassing March-April in 2011–2013 due to rising solar EUV flux. TEC strongly correlates with F10.7/SSN (R<sup>2</sup> ∼0.65–0.78, higher at low latitudes), reflecting strong solar control at low-latitudes. At low latitudes, IRI-2020 outperforms IRI-2016 with lower RMSE, while at mid-latitudes IRI-2016 shows slightly better performance. Differential TEC (DTEC) reveals larger deviations at low latitudes ranging from — 26.8 to +30.81 TECU, compared to smaller deviations at mid-latitudes ranging from — 8.71 to + 18.50 TECU. Both models capture equinoctial enhancements but overestimate winter anomaly occurrence and show large errors during equinoxes, particularly at low latitudes. Unlike prior studies, this work examines TEC across an entire solar cycle, revealing regional model limitations. These findings enhance ionospheric model validation, critical for improving satellite navigation and space weather forecasting in the Indian sector.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 2","pages":"1-20"},"PeriodicalIF":1.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147362517","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper introduces SPARROW, an efficient forward propagator for Radio Occultation (RO) configurations, capable of simulating electromagnetic wave propagation through both atmospheric and vacuum regions. A shift-map approach is used to reduce the atmospheric computation domain, speeding up simulations compared to traditional Split Step Fourier (SSF) methods. A wavelet-based technique is used for the vacuum propagation step, reducing computational complexity by exploiting wavelet sparsity. Numerical validation shows that SPARROW achieves a high accuracy for extreme atmospheric profiles while optimizing both the computational efficiency and memory usage.
{"title":"A fast and accurate full-wave propagator for modeling the electromagnetic propagation in a radio occultation configuration","authors":"Clémence Allietta;Rémi Douvenot;Sonia Cafieri","doi":"10.1029/2025RS008247","DOIUrl":"https://doi.org/10.1029/2025RS008247","url":null,"abstract":"This paper introduces SPARROW, an efficient forward propagator for Radio Occultation (RO) configurations, capable of simulating electromagnetic wave propagation through both atmospheric and vacuum regions. A shift-map approach is used to reduce the atmospheric computation domain, speeding up simulations compared to traditional Split Step Fourier (SSF) methods. A wavelet-based technique is used for the vacuum propagation step, reducing computational complexity by exploiting wavelet sparsity. Numerical validation shows that SPARROW achieves a high accuracy for extreme atmospheric profiles while optimizing both the computational efficiency and memory usage.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 2","pages":"1-13"},"PeriodicalIF":1.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147362531","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Imaging and targeting missions parallel or at an angle to the surface are impacted by spatial variations in the refractive index structure function coefficient (Cn2) in the atmospheric boundary layer. However, measuring and modeling Cn2 in both the vertical and transverse directions in the atmospheric boundary layer remains difficult. Using a suite of atmospheric and surface measurements available through the DOE Atmospheric Radiation Measurement Facility Southern Great Plains near Lamont, Oklahoma, including radiosonde soundings, high-acquisition-rate meteorological towers, and an eddy covariance tower, we investigate the influence and importance of surface and atmospheric measurements on C2n within the atmospheric boundary layer. Over a three-year period from Apr 2020–Apr 2023, corresponding to 3,000 soundings, vertical profiles of C2n in the boundary layer and surface-based C2n obtained from the meteorological towers are correlated and classified by atmospheric stability and surface fluxes. Vertical profiles are decomposed into an average profile, based on the Hufnagel-Valley model, and a fluctuation profile, based on sounding statistics. Random forest regression is used to aggregate the Hufnagel-Valley model parameters with surface measurements trained with surface measurements corresponding to soundings. A fourth year, Apr 2023–Apr 2024, of data is used for testing and validation. The most important surface parameters include boundary layer height estimates and surface C2n measurements. Unstable conditions are more influenced by sensible energy surface fluxes than stable conditions. The random forest enables the modeling of Cn2 in the atmospheric boundary layer based on surface measurements providing profiles at faster intervals between soundings.
{"title":"Optical turbulence profile modeling in the atmospheric boundary layer: A random forest regression approach","authors":"Apratim Dasgupta;Christopher Cicalla;Bryan Mendoza;Daniel Foti","doi":"10.1029/2025RS008369","DOIUrl":"https://doi.org/10.1029/2025RS008369","url":null,"abstract":"Imaging and targeting missions parallel or at an angle to the surface are impacted by spatial variations in the refractive index structure function coefficient (C<inf>n</inf><sup>2</sup>) in the atmospheric boundary layer. However, measuring and modeling C<inf>n</inf><sup>2</sup> in both the vertical and transverse directions in the atmospheric boundary layer remains difficult. Using a suite of atmospheric and surface measurements available through the DOE Atmospheric Radiation Measurement Facility Southern Great Plains near Lamont, Oklahoma, including radiosonde soundings, high-acquisition-rate meteorological towers, and an eddy covariance tower, we investigate the influence and importance of surface and atmospheric measurements on C<sup>2</sup><inf>n</inf> within the atmospheric boundary layer. Over a three-year period from Apr 2020–Apr 2023, corresponding to 3,000 soundings, vertical profiles of C<sup>2</sup><inf>n</inf> in the boundary layer and surface-based C<sup>2</sup><inf>n</inf> obtained from the meteorological towers are correlated and classified by atmospheric stability and surface fluxes. Vertical profiles are decomposed into an average profile, based on the Hufnagel-Valley model, and a fluctuation profile, based on sounding statistics. Random forest regression is used to aggregate the Hufnagel-Valley model parameters with surface measurements trained with surface measurements corresponding to soundings. A fourth year, Apr 2023–Apr 2024, of data is used for testing and validation. The most important surface parameters include boundary layer height estimates and surface C<sup>2</sup><inf>n</inf> measurements. Unstable conditions are more influenced by sensible energy surface fluxes than stable conditions. The random forest enables the modeling of C<inf>n</inf><sup>2</sup> in the atmospheric boundary layer based on surface measurements providing profiles at faster intervals between soundings.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 2","pages":"1-21"},"PeriodicalIF":1.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147362499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present a field-theoretic framework for modeling electromagnetic energy propagation in heterogeneous media by introducing the concept of electromagnetic geodesics. Unlike traditional ray optics, which assumes either a straight-line propagation or a simple bending in refractive media, our approach formulates wave propagation as geodetic motion in a curved spatial geometry induced by variations in refractive index. Building on earlier work, we move beyond scalar refractive index analogies and instead construct a local Riemannian metric characterized by an orthogonal geometric tensor derived from the Helmholtz representation. This tensor encodes spatial anisotropy and curvature, enabling a rigorous description of energy flow through complex media. We derive the electromagnetic geodesics by formulating and solving a Lagrangian system, yielding equations of motion for wavefront trajectories, group velocity, and intensity distribution. The concept of refractive tension—the vector displacement between Euclidean and transformed positions—plays a central role in defining the transformation matrix and associated metric. Numerical simulations for a spherical inhomogeneity embedded in vacuum demonstrate the emergence of curved geodesics and localized energy redistribution, illustrating the model's potential for interpreting interstellar electromagnetic phenomena and refractive effects in astrophysical environments. In particular, it shows the spatial dispersion of a the energy flow in the vicinity of the spherical inhomogeneity.
{"title":"On the electromagnetic energy flow along geodesics","authors":"Jacob T. Fokkema;Peter M. van den Berg","doi":"10.1029/2025RS008508","DOIUrl":"https://doi.org/10.1029/2025RS008508","url":null,"abstract":"We present a field-theoretic framework for modeling electromagnetic energy propagation in heterogeneous media by introducing the concept of electromagnetic geodesics. Unlike traditional ray optics, which assumes either a straight-line propagation or a simple bending in refractive media, our approach formulates wave propagation as geodetic motion in a curved spatial geometry induced by variations in refractive index. Building on earlier work, we move beyond scalar refractive index analogies and instead construct a local Riemannian metric characterized by an orthogonal geometric tensor derived from the Helmholtz representation. This tensor encodes spatial anisotropy and curvature, enabling a rigorous description of energy flow through complex media. We derive the electromagnetic geodesics by formulating and solving a Lagrangian system, yielding equations of motion for wavefront trajectories, group velocity, and intensity distribution. The concept of refractive tension—the vector displacement between Euclidean and transformed positions—plays a central role in defining the transformation matrix and associated metric. Numerical simulations for a spherical inhomogeneity embedded in vacuum demonstrate the emergence of curved geodesics and localized energy redistribution, illustrating the model's potential for interpreting interstellar electromagnetic phenomena and refractive effects in astrophysical environments. In particular, it shows the spatial dispersion of a the energy flow in the vicinity of the spherical inhomogeneity.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 1","pages":"1-21"},"PeriodicalIF":1.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146116914","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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