The Scattering Mechanism And Analysis Of Clear-air Echo

With the development of Doppler weather radar technology and the improvement of detection sensitivity, people could see more atmospheric structure details in the clear sky. Study on the clear air echo is involved in many research and application field of atmospheric science, such as the Doppler radar in the short term forecast and nowcasting, the quantitative precipitation evaluation, radar data quality control, radar data assimilation, relation between the gust front and convective precipitation on the clear air echo identification and elimination and so on. Scattering mechanism and characteristics of atmospheric turbulence therefore, the correct understanding of clear air echo, in-depth analysis of atmospheric physics process reflected reflectivity and radial velocity characteristics of clear air echo, has been the important theoretical significance and application value.This paper is studied in the following aspects, and to draw meaningful conclusions:According to the scattering mechanism of turbulent atmosphere on the electromagnetic wave, the relationship between it and Bragg’s law is discussed in detail; reveals the physical essence of turbulent scattering is:uneven causes the gradient, and the uneven distribution of the gradient causes the rotation. The gradients of atmospheric temperature, pressure, humidity and other factors produce the turbulent scattering; the turbulence scattering is the main reason of clear air echo.Clear air echo classification and its mechanism analyse. According to the turbulent scattering formula, the influence of gradient of atmospheric temperature, pressure and vapor pressure on the clear air echo is analyzed in detail. Diurnal variation mechanism of clear air echo is discussed, the difference of clear air echo mechanism between on the sea and on the land and their daily variation are revealed. From the view of clear air echo, there are discussed the reason of the gust front and the shuttle disintegrate events.According to the radial velocity echo phenomenon of clear air echo, wind vector characteristics are divided into three classes firstly:the background wind vector characteristics, wind vector characteristics of local turbulence, mixing wind vector characteristics of background wind and local turbulence. They are related to both the wind vector and the inversion structure of atmosphere boundary layer, also need to be distinguish carefully between inversion of temperature and dew point temperature inversion.