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.
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.
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.
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.
The complex refractive index of aerosol particles has a vital influence on the radiation effect of aerosols. From July to October 2020, a long-term observation of marine aerosols in the Pacific Ocean was carried out by a surveying vessel.Based on the number concentration of marine aerosol particles measured by optical particle counter (OPC), the extinction coefficient and scattering coefficient of marine aerosol measured by single scattering albedo monitor (CAPS), combined with meteorological data, and through Mie scattering theory, the influence of the change of real and imaginary parts of marine aerosol particle refractive index on particle single scattering albedo is studied. The measurement results show that the range of single scattering albedo of marine aerosol is about 0.7-0.9. The inversion results show that the real part of aerosol refractive index varies from 1.335 to 1.45 and the imaginary part varies from 0.011 to 0.018.
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.
As an important part of the atmospheric environment, aerosols play a critical role in the study of the relationship between light and radiation. However, due to the complex spatiotemporal distribution of aerosols, it is much difficult to measure their microphysical properties and to determine their optical properties in coastal areas. In this paper, basic meteorological elements (e.g., wind speed, temperature, humidity) are simulated with the numerical weather forecasting (WRF) model. Then, the coastal aerosol model (CAM) together with the observation data is used to simulate the aerosol particle size distribution (APSD) and extinction coefficient for the coastal environment of Qingdao. Finally, data measured by the automatic weather station and particle counter in the coastal area are compared to their corresponding simulations. According to the comparisons results, temperature simulations were higher from an overall perspective (<2°C) with the correlation coefficient larger than 0.96; humidity simulations were comparatively lower on the 11th and 12th day (<10%) than those onthe 13th day (<20%), but the correlation coefficient was still larger than 0.8. With the meterological parameters simulations, the CAM model was used to predict the APSDs. It is founded that simulations for large particles are generally larger, while those for giant particles are generally smaller, but the simulated temperature, humidity, APSD and extinction coefficient are very consistent with their corresponding measurements. The method established in this paper is promising for the simulation and forecast of both the meteorological elements and aerosol microphysical properties.
Selecting the solar radiometer and ground-based laser-radar data of several typical regions, we could invert the laser-radar ratio of each region by using the entire aerosol optical thickness measured by the solar radiometer as a constraint, and we conducted vertical aerosol distribution observation research based on this. The average laser-radar ratio in the four regions of Delingha Qingha(i spring), Hefei Anhu(i summer), Zhangye Gansu (summer), and Maoming Guangdong(winter)are 38, 62, 47, and 17 respectively. Comparing with selecting fixed LR,the extinction tends to change with the height approximately similarly,but the values of the extinction at different heights are different evenly.The vertical distribution of aerosols in different spatial and temporal distribution characteristics.
In this study, we investigate the fractal properties of optical turbulence profiles. Through rescaled range analysis, optical turbulence profiles roughly exhibit three different regimes. The effects of stratifications are the underlying mechanism contributing to this phenomenon. The results of detrended fluctuation analysis and multifractal detrended fluctuation analysis indicate that optical turbulence profiles have multifractal structure.
When light-wave propagates in the turbulent atmosphere, it will be affected by atmospheric turbulence and brought various effect , such as flicker, phase fluctuation. So the investigation of atmosphere optics parameters always must be important. Because of the differences in geographical conditions and climate, atmospheric optical parameters in different regions have different spatial and time distribution. In this paper, various atmosphere optics parameters are measured by atmosphere optics parameters measure system in the Delingha area of Qinghai province and Xinjiang Korla area, through statistical analysis of atmospheric optical parameters corresponding area, we know clearly different geographical climate character of the northwest area of atmospheric optical parameters of structure characteristics, the results provide a valuable reference for further practical engineering application of optical remote sensing location and atmospheric optical transmission and atmospheric properties.
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