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Forecast of near surface refractive index structure parameter over the South China Sea is successful TEXT SIZE: A A A
Date:2016.11.08 Author:QING Chun Clicks:

It is well known that the electromagnetic wave will change when it propagates through the atmoshphere and encounters the inhomogeneities of refractive index caused by the atmospheric turbulence.This turbulence will degrade the image quality of the photoelectric system dramatically. The refractive index structure parameter,(m-2∕3), is essentialto evaluate the performance of photoelectric system. Butit is not available to systematically and directly measure for many climates and seasons, especially in severe environment.Moreover   varies considerably from location to location. In many cases, it is impractical and expensive to deploy instrumentation to characterize the atmospheric turbulence.How to deal with this problem?

Recently, the research fellow WU Xiaoqing’s group from Key Laboratory of Atmospheric Composition and Optical Radiation, CAS, has proposed an approach that Weather Research and Forecasting model (WRF) coupled with Monin-Obukhov Similarity (MOS) theory can be utilized to forecast atmospheric refractive index structure parameter and this approach has been successfully applied to the South China Sea. The research results have been published in journal “OPTICS EXPRESS” (Opt. Express. 24(12), 13303-13315 (2016)) 

QING Chun,a PhD student in this group,  uses the user-defined product of WRF model associated with MOS theory to forecast the near surface  over the ocean for the first time.The corresponding  values measured by the micro-thermometer are used to assess the performance of this approach. The results show that the forecasted  is consistent with the measured  in trend and magnitude as a wholeAnd the correlation coefficient is up to 77.57%. Besides, this approach can forecast some essential aspects of  andbe able to capture the correct magnitude of, which experiences fluctuations of two orders of magnitude. Obviously, this study guarantees a concrete practical advantage from the implementation of any potential optical engineering fields where the instruments are difficult to useAt the same time,itcan assist the laser atmospheric transmission measurements over the ocean near-surface. Furthermore, this work will be able to provide constructive feedback to the next-generation  model developers.

This work is supported by the National Natural Science Foundation of China (NSFC, Grant Nos. 41275020; 41576185).

 

 

Fig.1.Simulation area(The South Sea of China),the red solid star represents the center grid of simulation domain(17.5°N,109.5°E).

Fig.2.The correlation of near-surface  between forecasted by WRF model (abscissa) and measured by micro-thermometer (ordinate) over the ocean. Each point represents an average of 30 minutes(240 total points).

Figure 3. The diurnal feature comparison of  between forecasted by WRF (red solid star) and measured by micro-thermometer (black hollow circle) over the ocean near-surface. (a)Date from Jul 8 to 9, 2014; (b) Date from Jul 12 to 14, 2014, respectively.
 
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