边界层气溶胶类型对中红外光波传输的影响

Influence of the boundary layer aerosol model on the mid-infrared light-wave transmission

主要利用MODTRAN5.0分析了2-5μm波段五种类型的边界层气溶胶对整层大气透过率的影响及背景对流层气溶胶对高空上行传输背景下透过率的影响。结果表明：对于2-5μm波段的整层大气,在2.0-2.5μm及3.5-4.0μm波段气溶胶对大气透过率的影响较大,且相同背景下大气能见度越低,气溶胶对大气透过率的影响越大,因此,计算整层大气透过率时不仅需要考虑气溶胶类型对透过率的贡献,同时需要考虑能见度对透过率的影响;对于高空上行传输背景下的大气,绝大多数波段内的透过率随着初始高度的增加而增加,且两种类型下的背景对流层气溶胶下的最大透过率相对不考虑气溶胶时分别降低了9.25%及8.97%,就其绝对偏差而言,计算高层大气透过率时可以不考虑背景对流层气溶胶类型的影响。因此对于地基测量系统需要考虑边界层气溶胶对其辐射的衰减,尤其是能见度较低的时候;对于机载光电系统气溶胶对其能量衰减小,尤其在10 km以上传输高度,且适当地提高初始传输高度可以减小大气对其衰减。

The influence of five types of the boundary layer aerosol on the atmospheric transmittance and the influence of background troposphere aerosol on the transmittance under uplink condition in 2 - 5μm waveband were analyzed by using MODTRAN 5. 0 software. The results show that the effects of atmospheric aerosol on atmospheric transmittance in 2 - 2. 5μm and 3. 5 - 4. 0μm spectral range are heavy. The aerosol has greater influence on the atmospheric transmittance with the reduction of atmospheric visibility,thus it needs to consider the influences of aerosol models and visibility on atmospheric transmittance when atmospheric transmittance is calculated. The maximum absolute deviations of the atmospheric transmittance of tropospheric aerosol for two kinds of background are 9. 25% and 8. 97% respectively. In terms of its absolute deviation,tropospheric aerosol can not be considered when the atmospheric transmittance of high-altitude transmission is calculated. The attenuation of the boundary layer aerosol on radiation is considered for ground based measurement system,especially when visibility is low. The attenuation of the aerosol on energy is small for airborne photoelectric system,especially when transmission altitude is above 10km. So to decrease the attenuation of atmosphere,the initial transmission altitude should be increased.