Retrieval Of Main Greenhouse Gases Column Concentration Based On Mid-infrared Inter-band Cascade Laser Heterodyne Radiometer

The contents of greenhouse gases such as water vapor and methane and their absorption effects have a significant effect on the balance of radiation budget of the terrestrial atmosphere system and the evaluation of the laser propagation through the atmosphere.For some laser engineering applications,the traditional detection methods are difficult to meet the needs of high resolution and portable maneuvering.Therefore,based on a high sensitivity and high-resolution laser heterodyne solar spectrum detection technique,the direct measurement of atmospheric transmittance of the whole layer is carried out,and the column concentrations of water vapor and methane are inversed synchronously.The main results are shown as follows:1)Based on the laser heterodyne technique,a set of 3.53?m high-resolution laser heterodyne solar spectrum measuring instrument consists of a narrow linewidth tunable inter-band cascade laser as the local oscillator and a sun tracker is established,with spectral resolution of 0.002cm-1.2)The Langley-plot method is used to calibrate the high-resolution heterodyne solar spectrum measuring instrument.The field measurement was carried out in Yunnan Yaoan and Anhui Hefei,and the direct measurements solar spectrum in the range of 2831-2833cm-1 were obtained.The high-resolution total atmospheric spectral transmittance was also obtained.3)The atmospheric transmittance spectrum of the whole layer is calculated synchronously by using the line-by-line integral radiation transfer model,and the nonlinear iterative fitting with the measured spectrum is carried out to realize the integrated inversion of the water vapor and methane column concentration.The inversion results of water vapor are in good agreement with those measured by microwave radiometer and solar radiometer.The minimum relative deviation is 16.59%and 9.83%,respectively.4)The high-resolution laser heterodyne spectrometer,combined with its inversion algorithm,is an effective integrated device for detecting the atmospheric transmittance of the whole layer and the contents of water vapor,methane and other gases,which will be widely used in the detection of multicomponent gases.