河西走廊干旱区春季沙尘气溶胶对辐射的影响初步研究

Influence of spring dust aerosol on radiation over the arid area in Hexi Corridor

利用2008年春季中美沙尘暴联合观测实验中张掖站晴朗少云天正午的地表辐射和太阳光度计资料,计算分析了沙尘气溶胶对太阳辐射和大气逆辐射的影响,结果表明:沙尘对太阳总辐射有一定程度的削弱作用,经估算,大气浑浊度每增加0. 1,太阳总辐射平均减少约10. 45 W·m-2;当大气浑浊度一定时,沙尘粒子越小,对太阳总辐射的削弱效率就越高;大气浑浊度小于0. 3时,大气逆辐射有随大气浑浊度的增加而增加的趋势,大气浑浊度大于0. 3时,大气逆辐射随大气浑浊度增加有减小的趋势。

Dust aerosol, naturally generated and affected by the underlying surface and weather, is one of the main components of tropospheric aerosols. It also leads to severe dust retention in a storm. In northwest China, spring （from March to May） is the dust storm season. Sandstorms and local sandstorms lift large quantities of dust into the air and bring them to downstream area. This would cause a continuous high concentration of dust aerosols in northwest China. The frequent occurrence of sandstorm severely affects the normal life of the residents and causes great losses to property of residence and society as a whole. Moreover, dust carried by sandstorms also has impact on the radiation balance of the earth＇s atmosphere system through direct or semi-direct radiation, and then affects the regional and global climate. In order to analyze the influence of sand and dust on total solar radiation and atmospheric inverse radiation, the data of the surface radiation and solar photometer were obtained by both Lanzhou University and Maryland University at Zhangye station from April 18 to June 15 in 2008. The surface radiation and solar photo- metric data at cloudless and sunny noon was chosen to eliminate the influence of cloud on atmospheric transmit- tance. The atmospheric turbidity is obtained by optical thickness interpolation of different wavebands. The atmos- pheric transmittance is calculated by the function of atmospheric turbidity and atmospheric transmittance. Then, the value of total solar radiation is calculated. After comparison, the calculated value is basically in line with the observed value, and the error is below 1%. The results showed that dust in the air can reduce the solar radiation reached to the surface ,the estimation of reduction is 10.45 W · m -2 while 0.1 atmospheric turbidity is added. If the atmospheric turbidity is constant, the smaller the dust particles are, the higher the efficiency of reduction of dust will be. By analyzing the trend of the inversion of the gas and the atmospheric turbidity, it indicated that when atmospheric turbidity value is less than 0.3,there is a trend that atmospheric inverse radiation increases with the atmospheric turbidity; when atmospheric turbidity value is greater than 0.3, the atmospheric inverse radiation decreases with the atmospheric turbidity. In the process of atmospheric turbidity, the decrease of temperature is a main factor. The decrease amount of atmospheric inverse radiation caused by temperature is greater than that by dust. Therefore, there is an inverse relationship between atmospheric inverse radiation and atmospheric turbidity.