The atmospheric boundary layer is the layer most closely associated with human life, and the occurrence and development of atmospheric optical turbulence in the atmospheric boundary layer are of great significance for atmospheric optical transport, etc. Meanwhile, the study of optical turbulence in the whole ocean environment is also of vital importance, and it is important to statistically analyze the variations of the atmospheric optical turbulence parameters by using the existing optical turbulence models due to the lack of ocean data. In this paper, the atmospheric turbulence parameters are estimated by different external scale models (HMNSP99, Dewan, HV and WSTG models), and the atmospheric refractive index structure constant(C2n) computed by different models are compared by using the coastal sounding measured data, through error analysis and correlation studies, it has been found that the HV model changes with height in the atmospheric boundary layer, but cannot reflect the characteristics of the change of C2n well. The HMNSP99 model is about one order of magnitude smaller than the measured data, while the WSTG model is about one order of magnitude larger than the measured data. However, the trends of the two models are in good agreement. In contrast, the Dewan model and the HMNSP99 model show good consistency with the measured data, and the correlation is above 0.6. The Dewan and HMNSP99 model are closer in magnitude to the measured data, therefore, when studying optical turbulence parameters in the atmospheric boundary layer, the Dewan and HMNSP99 models are more reliable. They can also provide key indicators for optical turbulence prediction and astronomical site selection.
We verify a simple alternative method to estimate the Fried parameter over a horizontal propagation path using the refractive index measured by a pair of micro-thermometers. The results show a relatively reliable estimate, especially when the optical turbulence in the path is relatively strong. Moreover, we also discuss the relationship between the Fried parameter value with the overall intensity of optical turbulence and the length of the propagation path theoretically. The influence of these two factors shows a prominent exponential characteristic, which also can be speculated from the formula.
Atmospheric optical turbulence significantly impacts the efficacy of adaptive optics and various laser systems. The parameter known as the atmospheric refractive index structure constant, or C2n, is crucial for characterizing this turbulence. In response to this challenge, we have developed a model utilizing the Whale Optimization Algorithm combined with a Support Vector Machine (WOA-SVM) designed to estimate atmospheric optical turbulence profiles along Eastern China’s coast. The WOA-SVM model uses standard atmospheric sounding data from the region to forecast turbulence profiles at different times, subsequently comparing these estimates with actual observations. Our error analysis indicates that the model’s estimates have root mean square errors (RMSE) of 0.4441, 0.3012, 0.4734, and 0.4904 for the respective times, while correlation coefficients range from 85.10% to 93.66%. The research shows that despite minor discrepancies in atmospheric optical turbulence profiles estimated by the WOA-SVM model using standard atmospheric sounding data and those measured directly, the general trend is consistent. This consistency confirms the WOA-SVM model’s practicality for estimating atmospheric optical turbulence in coastal areas. Therefore, the study made an attempt for direct estimation of turbulence profiles using routine meteorological data and paves the way for future model development in this domain.
Using the continuous observation data of wind profiler radar, the temporal and spatial variation characteristics of wind direction and wind speed in the summer Boundary layer atmosphere wind field in the southern foot of Tianshan Mountains in Xinjiang are analyzed. The preliminary exploration of the impact of low-level jet streams on near surface atmospheric turbulence activity is of great significance for studying laser atmospheric transport, triggering convective weather, and atmospheric pollution and diffusion. Experimental area is located in a valley, and the circulation characteristics dominated by Mountain breeze and valley breeze are the basic characteristics of the daily variation of the wind field in the region, and also the main reason for the occurrence of low-level jet. Through statistics and analysis, it was found that the summer turbulent activity near the surface in this area is strong, which is caused by thermal stress on the underlying surface. During the day, the surface temperature is high, and there is a strong exchange of air flow near the surface with the upper layer, resulting in strong turbulent activity. In the evening, it may be the low-level jet that brings the horizontal wind shear near the ground, which intensifies the turbulence vortex activity and leads to the occurrence of turbulence.
Scintillation is a highly discussed problem in laser atmospheric transmission, which plays an important role in improving the reliability and performance of laser communication systems. In this study, numerical simulations are conducted using a computational model to investigate the variation of the on-axis scintillation index of the focused platform beam during horizontal atmospheric propagation, considering different transmitter aperture sizes. The simulation results indicate that the aperture size significantly affects the scintillation index. Under the same Rytov variance conditions, larger aperture sizes lead to stronger scintillation effects. For smaller aperture sizes, the scintillation index maintains a relatively linear relationship with the Rytov variance. The findings of this study provide further insights into the factors influencing the scintillation characteristics in laser atmospheric transmission and offer valuable references for the design and engineering applications of laser communication systems.
A comprehensive site testing campaign was carried on in the northwestern area of China from July to November 2022. We conduct the study focusing on the daytime optical turbulence and precipitable water vapor long-term variation in this area, which are essential for time-domain astronomy and site scheduling. A relatively quiet and dry atmosphere situation that benefits observation can be more easily found in September and October. The so-called ’conversion time’, an excellent condition for observation at dawn and dusk, behaved differently in different months. Meanwhile, better observation conditions can be found at dawn in July, August and September but at dusk in October and November in the daytime.
The distribution of wind speed with height will affect the optical turbulence parameters. Based on the reanalysis data of the National Centers for environmental prediction (NCEP), this paper analyzes the monthly and seasonal variations of wind speed in the Tibetan Plateau region during the past 15 years from 2005 to 2020 at Delingha observatory, It is found that the seasonal variation trend of the seeing and 200 hpa wind speed is consistent, and the Fried parameter is negatively correlated with 200 hpa wind speed, which verifies the possibility that the upper air speed can approximately represent the turbulence intensity of the whole layer. The experimental results show that: in autumn and winter, the high altitude wind speed is strong, the seeing is poor, and the astronomical observation imaging effect is poor; In summer, the high altitude wind speed is low and the seeing is good, which is the best time for astronomical observation.
This paper present the diurnal and seasonal variation of Turbulence Kinetic Energy (TKE) dissipation rate ( Ε ) in the Atmospheric Boundary-Layer (ABL) in Hefei area. Doppler spectrum width of wind profiler radar are used to separate the non-turbulent spectral width from the observed spectrum width and estimate ε .It is found that in the lower tropospheric height ε is in the range from 10-6 to 10-3 m2 s-3 . ε showed significant diurnal variation in the boundary-layer, with a smaller value at night and a larger value during the day, and the maximum value 10-3 m2 s-3 appears at the top of the ABL during the daytime. The diurnal variation of ε can be used to demonstrate the change of the boundary-layer height in Hefei area. The boundary-layer height begins to rise after sunrise and reaches the maximum at noon, about 1200 m. The parameter ε also shows significant seasonal variation. The ε and height of boundary-layer increased gradually since spring, reaching a maximum of about 1.3km in autumn and decreasing to the same level as in spring in winter. Because it is not affected by water vapor and temperature, ε from the data inversion of wind profile radar can describe turbulence information more accurately, and the results provide help for the study of matter and energy exchange between earth and air in Hefei area and laser atmospheric transmission etc.
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