Evaporation Duct Research Articles

EDH-STNet: An Evaporation Duct Height Spatiotemporal Prediction Model Based on Swin-Unet Integrating Multiple Environmental Information Sources

Given the significant spatial non-uniformity of marine evaporation ducts, accurately predicting the regional distribution of evaporation duct height (EDH) is crucial for ensuring the stable operation of radio systems. While machine-learning-based EDH prediction models have been extensively developed, they fail to provide the EDH distribution over large-scale regions in practical applications. To address this limitation, we have developed a novel spatiotemporal prediction model for EDH that integrates multiple environmental information sources, termed the EDH Spatiotemporal Network (EDH-STNet). This model is based on the Swin-Unet architecture, employing an Encoder–Decoder framework that utilizes consecutive Swin-Transformers. This design effectively captures complex spatial correlations and temporal characteristics. The EDH-STNet model also incorporates nonlinear relationships between various hydrometeorological parameters (HMPs) and EDH. In contrast to existing models, it introduces multiple HMPs to enhance these relationships. By adopting a data-driven approach that integrates these HMPs as prior information, the accuracy and reliability of spatiotemporal predictions are significantly improved. Comprehensive testing and evaluation demonstrate that the EDH-STNet model, which merges an advanced deep learning algorithm with multiple HMPs, yields accurate predictions of EDH for both immediate and future timeframes. This development offers a novel solution to ensure the stable operation of radio systems.

A case study of offshore evaporation ducts in northeastern Taiwan during summer time

Over the ocean northeast of Taiwan, the summer is hot and the air-sea interaction is strong, so it is easy to produce various kinds of atmospheric duct phenomena due to the rapid change of temperature and water vapor in the vertical direction. Among the various atmospheric duct phenomena, Evaporation Duct (ED) occurs frequently and for a long time, which often affects electromagnetic wave transmission, causing errors in communication and search radar signals, and is the most valuable for research. In this study, we used an unmanned aerial vehicle (UAV) with a Storm Tracker (ST) which is a mini meteorological observation device to measure air temperature, pressure, and relative humidity near the ocean to get the Evaporation Duct Height (EDH) of Yilan in northeastern Taiwan in the summer of 2022. Through the 5-m vertical resolution observation, we understand the atmospheric factors affecting the EDH. Throughout the summer observation period, various types of atmospheric ducts also manifest in the northeastern region of Taiwan. In the numerical simulation, we use the WRF model with two sets of different boundary layer parameterizations, Mellor-Yamada-Janjic (MYJ) and Yon-Sei University (YSU), and import the simulation results into the Paulus-Jeske (P-J) ED model to compute the EDH. It was found that the EDH calculated by WRF using the MYJ boundary layer parameterization imported into the P-J ED model was closer to the observed results. This method can forecast the EDH in the northeastern Taiwan sea area, which is valuable for application.

Investigation of microwave power transfer near sea surface with 2D parabolic equation method

AbstractDue to the existence of the evaporation duct near‐sea‐surface described as an inhomogeneous refractive index of atmosphere, microwaves can be trapped in the duct and propagate along it. To investigate wireless power transfer (WPT) over the sea surface, we utilize the two‐dimensional parabolic equation to calculate the electric field distribution and to obtain the transferred power. By analysing the propagation results with specific evaluation functions, we obtained the proper conditions for long‐distance WPT over the sea surface. When the initial field distributes uniformly on the one‐meter aperture, the frequency is 12 GHz, and the centre position is 4 m, a unique focusing spot can be obtained in the duct and nearly 5%, 8%, and 12% of the initial power remains at a distance of 10 km with a receiving aperture of 1, 2, and 3 m, respectively. The presented WPT scheme near the sea surface has potential applications in the power supply or charging for ships or small islands.

Marine High-Speed Over-the-Horizon Communications and Channel Sensing in Evaporation Ducts Over the South China Sea

Marine High-Speed Over-the-Horizon Communications and Channel Sensing in Evaporation Ducts Over the South China Sea

The Horizontal Inhomogeneity of the Evaporation Duct Based on Surface Bulk Measurements Over the South China Sea

The Horizontal Inhomogeneity of the Evaporation Duct Based on Surface Bulk Measurements Over the South China Sea

Characterizing Range-Dependent Variations of the Evaporation Duct: A Meteorological Perspective

Characterizing Range-Dependent Variations of the Evaporation Duct: A Meteorological Perspective

Evaporation Duct Anomalies Caused by Mesoscale Eddies in the Kuroshio Extension

AbstractEvaporation duct anomalies are always present above various oceanic processes, and their response to ubiquitous mesoscale eddies in the Kuroshio Extension region is quantitatively analyzed for the first time in this study using a synthetic analysis method based on reanalysis data sets and eddy trajectory data sets. The results indicated that the spatial distribution of evaporation duct anomalies is characterized by a monopole pattern, mainly modulated by the amplitude of anticyclonic eddies (AEs) and by the radius of cyclonic eddies (CEs). For AEs, the coupling strength is 0.7 m (2.9 M) per meter increase in amplitude, while for CEs, the coupling strength is 0.2 m (0.6 M) per 100 km increase in radius for the average evaporation duct height anomalies (evaporation duct strength anomalies) within the radius range. The modulation of evaporation duct anomalies by eddies is further examined.

Near-Surface Thermodynamic Influences on Evaporation Duct Shape

This study utilizes in situ measurements and numerical weather prediction forecasts curated during the Coupled Air–Sea Processes Electromagnetic Ducting Research (CASPER) east field campaign to assess how thermodynamic properties in the marine atmospheric surface layer influence evaporation duct shape independent of duct height. More specifically, we investigate evaporation duct shape through a duct shape parameter, a parameter known to affect the propagation of X-band radar signals and is directly related to the curvature of the duct. Relationships between this duct shape parameter and air sea temperature difference (ASTD) reveal that during unstable periods (ASTD < 0), the duct shape parameter is generally larger than in near-neutral or stable atmospheric conditions, indicating tighter curvature of the M-profile. Furthermore, for any specific duct height, a strong linear relationship between the near-surface-specific humidity gradient and the duct shape parameter is found, suggesting that it is primarily driven by near-surface humidity gradients. The results demonstrate that an a priori estimate of duct shape, for a given duct height, is possible if the near-surface humidity gradient is known.

Investigating the Role of Wave Process in the Evaporation Duct Simulation by Using an Ocean–Atmosphere–Wave Coupled Model

Investigating the Role of Wave Process in the Evaporation Duct Simulation by Using an Ocean–Atmosphere–Wave Coupled Model

A study of evaporation duct characteristics in the South China Sea during the Winter of 2017

The evaporation duct (ED) near the sea surface is the most frequent type of duct that traps and redirects electromagnetic waves over longer or shorter distances. This study uses radiosonde data from the South China Sea Two-Island Monsoon Experiment (SCSTIMX) in 2017 and the Weather Research and Forecasting (WRF) model to study the ED and ED height (EDH). We enhanced the vertical resolution to 26 layers in the lowest 134 m. The simulations indicate that EDs were prevalent throughout the South China Sea (SCS) area in winter 2017, where the prevailing surface winds are strong northeasterly. The EDH exhibits diurnal variations and significant variability across the SCS. The WRF simulations of ED and EDH generally agree with observations of the trajectory of Taiwan-O.R.1. Our results indicate that the WRF model can simulate the pattern of ED and EDH over SCS. Results reveal that Yonsei University (YSU) boundary layer (BL) parameterization more accurately simulates the vertical temperature and humidity variations in the lower atmosphere, with stronger winds and higher EDH in most areas. The YSU and the Medium Range Forecast Model (MRF) BL schemes show similar ED patterns to the Taiwan-O.R.1 SCS radiosonde observations but consistently underestimate the EDH. While strong surface winds in the winter SCS may contribute to a higher EDH, the strong surface wind-induced vertical mixing also modifies sea surface air temperature, relative humidity, and vapor pressure, affecting the vertical refractivity. Our results indicate that sea surface air temperature is a more reliable factor affecting EDH in the simulations.

Spatiotemporal Characteristics of the Evaporation Duct in the Kuroshio Extension

The evaporation duct over the sea affects the propagation of electromagnetic waves, impacts the performance of electromagnetic systems accordingly, such as the shipborne radars. In order to reveal the spatiotemporal variations of the evaporation duct in the Kuroshio Extension (KE) region, where is one of the most intense air-sea interaction regions, the study utilized a 30-year ERA5 reanalysis dataset (from 1993 to 2022) and conducted statistical analysis on the monthly, seasonal variations and spatial distribution characteristics of the evaporation duct based on the NPS evaporation duct diagnostic model. The results enrich the database of maritime evaporation duct characteristics and improve the resolution and accuracy compared to previous studies.

Research on optimization method of evaporation duct prediction model based on particle swarm algorithm

The sea surface roughness parameterization and universal stability functions, as key components of the evaporation duct prediction models rooted in the Monin-Obukhov similarity theory, dictate the model performance which further impacts the efficiency and accuracy of offshore electromagnetic applications. In this paper, layered meteorological and hydrological observations are collected during two cruises and processed to obtain the reference modified refractivity profiles close to the sea surface, and then particle swarm algorithm is utilized to optimize the parameters of the sea surface roughness parameterization and universal stability functions. The results show that compared with the pre-optimization model, the prediction accuracy of the optimized model is improved by 5.09% and 8.12% under stable conditions, and by 9.97% and 31.51% under unstable conditions for observation dataset from each cruise, which proves the feasibility of the proposed method for evaporation duct prediction model optimization.

Path Loss Prediction in Evaporation Ducts Based on Deep Neural Network

Path Loss Prediction in Evaporation Ducts Based on Deep Neural Network

The non-uniformity characteristics of the evaporation duct in the South China Sea based on CLDAS data

The non-uniformity of the evaporation duct has a significant impact on the propagation of electromagnetic waves. Based on the near real-time dataset from the China Meteorological Administration Land Data Assimilation System (CLDAS) and the National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) datasets, the non-uniformity characteristics of evaporation duct height (EDH) in the South China Sea (SCS) region at different distances of electromagnetic propagation and the main influencing factors of EDH non-uniformity are analyzed. The findings are given as follows. First, the SCS monsoon has a significant impact on the spatial and temporal distribution of EDH, particularly in the western coastal areas of Luzon Island and the eastern coastal areas of the Indochina Peninsula. Secondly, the non-uniformity of EDH is more pronounced in the western part of Luzon Island, the eastern coast of the Indochina Peninsula, and the sea-land boundary area of the Beibu Gulf. Besides, the non-uniformity of EDH in the western part of Luzon Island and the eastern part of the Indochinese Peninsula is greatly influenced by air-sea temperature difference and relative humidity. Finally, it is advisable to consider the influence of the non-uniformity of EDH when the distance of electromagnetic propagation in coastal areas exceeds 50 km. However, it can be disregarded within a range of 100 km on the broad ocean.

Research on Optimization Method of Evaporation Duct Prediction Model

The sea surface roughness parameterization and the universal stability function are key components of the evaporation duct prediction model based on the Monin–Obukhov similarity theory. They determine the model’s performance, which in turn affects the efficiency and accuracy of electromagnetic applications at sea. In this study, we collected layered meteorological and hydrological observation data and preprocessed them to obtain near-surface reference modified refractivity profiles. We then optimized the sea surface roughness parameterization and the universal stability function using particle swarm optimization and simulated annealing algorithms. The results show that the particle swarm optimization algorithm outperforms the simulated annealing algorithm. Compared to the original model, the particle swarm optimization algorithm improved the prediction accuracy of the model by 5.09% under stable conditions and by 9.97% under unstable conditions, demonstrating the feasibility of the proposed method for optimizing the evaporation duct prediction model. Subsequently, we compared the electromagnetic wave propagation path losses under two different evaporation duct heights and modified refractivity profile states, confirming that the modified refractivity profile is more suitable as the accuracy criterion for the evaporation duct prediction model.

The Observed Effects of a Cold Wave on Over-the-Horizon Propagation in Evaporation Ducts Across Multiple Sea Areas

The Observed Effects of a Cold Wave on Over-the-Horizon Propagation in Evaporation Ducts Across Multiple Sea Areas

A Practical Method to Detect Evaporation Ducts Based on BDS-3 Signals Received by a Single Antenna

A Practical Method to Detect Evaporation Ducts Based on BDS-3 Signals Received by a Single Antenna

Численный анализ влияния неопределенности высоты волновода испарения на тропосферное распространение радиоволн

This study is dedicated to the radio wave propagation modeling in the evaporation duct. Special attention is given to the fact that the parameters of tropospheric waveguides are practically always determined with some degree of error. An algorithm based on the parabolic equation method has been developed, which takes into account the measurement error of the tropospheric refractive index and assesses the statistical characteristics of the spatial distribution of radio wave amplitude. A series of numerical experiments have been conducted for various propagation conditions. It has been demonstrated that in many cases, ignoring the refractive index error can lead to significant discrepancies in simulation results.

The Evaporation Duct Characteristics of Typhoon Kompasu (202118) Based on Buoys Observation

The Evaporation Duct Characteristics of Typhoon Kompasu (202118) Based on Buoys Observation

The Influence of Sea Surface Temperature From ECMWF Reanalysis Data on the Nonuniformity of Evaporation Duct

The Influence of Sea Surface Temperature From ECMWF Reanalysis Data on the Nonuniformity of Evaporation Duct