Source brightness fluctuation correction of solar absorption fourier transform mid infrared spectra

Atmospheric Measurement Techniques

T.Warneke¹  T.Ridder¹  J.Notholt¹ 

DOI  :  10.5194/amt-4-1045-2011

学科分类：几何与拓扑

来源: Copernicus Publications

【 摘 要 】

The precision and accuracy of trace gas observations using solar absorptionFourier Transform infrared spectrometry depend on the stability of the lightsource. Fluctuations in the source brightness, however, cannot always beavoided. Current correction schemes, which calculate a corrected interferogramas the ratio of the raw DC interferogram and a smoothed DC interferogram, areapplicable only to near infrared measurements. Spectra in the mid infraredspectral region below 2000 cm⁻¹ are generally considered uncorrectable,if they are measured with a MCT detector. Such measurements introduce anunknown offset to MCT interferograms, which prevents the established sourcebrightness fluctuation correction. This problem can be overcome by adetermination of the offset using the modulation efficiency of theinstrument. With known modulation efficiency the offset can be calculated, andthe source brightness correction can be performed on the basis ofoffset-corrected interferograms.We present a source brightness fluctuation correction method which performsthe smoothing of the raw DC interferogram in the interferogram domain by anapplication of a running mean instead of high-pass filtering thecorresponding spectrum after Fourier transformation of the raw DCinterferogram. This smoothing can be performed with the onboard software ofcommercial instruments.The improvement of MCT spectra and subsequent ozone profile and total columnretrievals is demonstrated. Application to InSb interferograms in the nearinfrared spectral region proves the equivalence with the establishedcorrection scheme.

【 授权许可】

Unknown