Substantiation of the possibility of direct measurements of radiative heat influx in the atmosphere

Numerical experiments simulating measurements with ideal (linear) and real receivers are performed to estimate the possibility of using an optical-acoustic detector for measuring a radiative heat influx (RHI) based on line-by-line calculations. The error of the real receiver is estimated with respect to an ideal one. To this end, a long-wave RHI is calculated in detectors of different sizes where the concentrations of water vapor and carbonic acid gas and the spectral composition of incident radiation is characteristic for the atmospheric surface layer. The consideration of some hypothetical situations allows us to simulate a wide range of conditions in the atmospheric surface layer and to evaluate how they affect measurement errors. Line-by-line calculations of absorption are performed using the HITRAN database. A connection between the relative error attributed to the nonlinearity of absorption, the size of the receiver, and the measurement conditions is analyzed. This is vitally important in the case when large vertical temperature gradients are observed at the point of measurements. For a receiver not larger than 2 cm and in case of normal conditions in the atmospheric surface layer, the error does not exceed 10–20%. The calculation confirms the admissibility of using optical-acoustic detectors for direct measurements of the radiative heat influx in the atmosphere.