Chunyan Zhou

Observation Study on the Size Distribution of Sand Dust Aerosol Particles over Yinchuan, China

The Yinchuan area, which lies in the eastern part of Northwest China, is one of the main transportation paths and origins of sand dust in China. In order to investigate the aerosol number size distribution and its temporal-spatial evolution over this area, direct solar radiation data taken from September 2012 to October 2013 by a sun photometer CE-318 located at Beifang University of Nationalities (106°29′E, 38°13′N) were analyzed. The particle number size distributions were retrieved from the aerosol optical depth (AOD) by use of the extinction inversion method. The experiment results show that although the averaged size distribution satisfies basically the Junge function, there are two obvious peaks at the particle radius of 0.6 m and 1.4 m, respectively. Because sand-dust weather occurs frequently, the particle size distribution in Spring is obviously larger than that in other seasons, which coincides with AOD variation tendency. Moreover, in sand-dust weather the particles number concentration is larger than that of background weather with one order of magnitude, especially for the number of concentration of large particles and giant particles. The research results have very important reference value for quantitative study of the influence of aerosol on atmosphere physics and chemistry process and monitoring of sand-dust weather and air pollution of this area.

Inversion of particle size distributions based on wavelet analysis

ABSTRACT In the Earth’s radiative budget, the role aerosols play in climate change depends on their particle size distribution. To address disadvantages linked to obtaining particle size distributions using traditional inversion algorithms, we propose a novel method combining wavelet analysis and Tikhonov regularization to solve the Fredholm integral equation of the first kind. This method can retrieve aerosol particle distributions, using aerosol optical thickness (AOT) from a CE-318 sun photometer. Experiments were carried out to verify the information retrieved using this new algorithm. AOT and particle size distributions were analysed and retrieved during various weather conditions, including dust storms, haze, fog, thunderstorms, and sunny skies. In addition, the seasonal average optical thickness and aerosol particle size distributions for the Yinchuan area in China were studied over a recent four-year period. Our results showed that particle size distributions were bimodal during dusty conditions, but unimodal during all other weather conditions studied. Moreover, our results indicate that air quality improved over two recent years.

Analysis of influence factors for coupling efficiency of single mode fiber

In many research fields the coupling efficiency of single mode fiber is an important issue and is influenced by some parameters. In this paper, the influence factors on coupling efficiency of single mode fiber were investigated, especially the influence of position of waist of laser beam is analyzed. For verifying these influence factors some numerical simulations were carried out. The results show that when the waist position being farther away from the laser emission system, the coupling efficiency is larger; when the waist position is located at infinite distance and the number of Airy speckles is 0, the relationship curve between the coupling efficiency and parameter a is unimodal; and also with parameter a tending towards zero the coupling efficiency is close to a bigger stable value, which differs from computation result in previous reference. These conclusions have important directive significance to the engineering design of coupling of single mode fiber.