短波红外波段上辐射定标方法与整层大气透过率的测量研究

Research on radiometric calibration method and measurement of whole layer atmospheric transmittance in short wave infrared band

利用傅里叶红外光谱仪开展了短波红外波段上辐射定标方法和连续整层大气透过率的测量研究。由于在短波红外波段(0.9~2.2μm)上存在多个强吸收波段,导致常用的Langley法存在较大误差,且改进的Langley法对于强吸收波段的定标处理也无法得到较好的结果。为满足短波红外全波段上整层大气透过率的高精度测量要求,提出了一种改进的大气透过率计算方法,先利用Langley定标法得到非吸收波段的仪器定标值和响应函数K再结合仪器定标值与大气顶层太阳辐照度的关系确定仪器定标值,得到短波红外全波段上整层大气透过率。利用该方法得到的0.9~2.2μm波段上整层连续大气透过率的结果,与中等分辨率大气辐射传输计算模型软件CART计算结果对比,相对误差最大为6.3%,平均误差小于2.5%。

This article employs Fourier transform infrared spectroscopy to investigate radiometric calibration methods and the measurement of continuous atmospheric transmittance across the shortwave infrared band.The presence of multiple strong absorption bands within the shortwave infrared spectrum(0.9−2.2μm)leads to significant errors in the commonly used Langley method,and even the improved Langley method struggles to yield accurate results for the calibration of these strong absorption bands.To fulfill the high-precision measurement demands for atmospheric transmittance across the entire shortwave infrared band,this paper introduces an enhanced method for calculating atmospheric transmittance.Initially,the Langley calibration technique is utilized to determine the instrument calibration value and response function K in the non-absorption band.Subsequently,the instrument response function in the absorption band is derived by interpolating the wavelength based on the instrument response function calibrated in the non-absorption band.Ultimately,the instrument calibration value is established by correlating it with the solar irradiance at the atmosphere’s top,thereby obtaining the atmospheric transmittance across the entire shortwave infrared band.Compared to results calculated by the medium-resolution atmospheric radiative transfer model software CART,the atmospheric transmittance values obtained using this method within the 0.9−2.2μm band exhibit an average error of less than 2.5%.