Real-Time Simulation of Clear Sky Background Radiation in Gas Infrared Remote Sensing Monitoring

During the process of infrared remote sensing monitoring, obtaining real-time measurements of sky background radiation is extremely inconvenient. The current methods incur a certain amount of lag. In this study, within the existing theoretical framework, a fast transmittance calculation method using interpolation was adopted, and a simplified transmission model was established. This led to the development of a new and simplified method for rapid temperature and humidity retrieval. Compared to the line-by-line integration method, the interpolation method significantly improves the speed of transmittance calculation by several tens of times, while maintaining a high level of accuracy. The relative deviation between the results obtained using the interpolation method and those obtained through line-by-line integration is less than 1 ‱. With the proposed method, temperature and humidity profile information can be retrieved from measured spectra within 5 min and corresponding background spectra can be obtained. The differences between the calculated background radiation and the measured spectra using the new method are smaller, making it more suitable for calculating sky background radiation. Additionally, the rapid retrieval results of the temperature profiles in the lower atmosphere have a certain level of accuracy (the mean deviation is less than 2 K).