Optimized weighting function for IPDA lidar concerning the lower layer CO2 concentration fluctuation

Abstract

Weighting function can affect the retrieval of the column gas mixing ratio of integrated path differential absorption (IPDA) lidar because it contains the vertical distribution information of the target gas. In order to optimize the wavelengths within the 1.57 um spectral band for IPDA lidar for CO2 measurement. The temperature, pressure and water vapor (TPH) sensitivity and the proportion of the weight function integration in the lower layer part to the total atmosphere layer (R) of each wavelength are calculated. The measurement errors of each wavelength are simulated with CO2 fluctuation in the lower layer. The specific wavelength with the R value of 0.6 has been found to be a stable measurement bias which does not change with fluctuations, so the R value of 0.6 is used to optimize the wavelength for measurement CO2. The simulation results show that the measurement error via wavelength is smaller than 0.05 ppm, when the TPH sensitivity is smaller than 0.95 and when R is about 0.6. This proposed method can be applicable for the further airborne or space-borne lidar development.