Method of Adaptive Control of Calibration of Multispectral Photometric Systems of Atmospheric Measurements
Keywords:
Adaptiveness, Photometer, Calibration, Atmosphere, MeasurementAbstract
Purpose: Sun photometers are versatile measuring instruments, allowing to study aerosol, certain atmospheric trace gases and
water vapors, as well as some parameters of solar radiation. Correct calibration of sun photometers is an important condition of
reaching high authenticity of measurement results. The well-known method of calibrating a sun photometer upon two different optical
air masses has a specific aerosol error. This error is caused by temporal variability of the atmospheric aerosol within the time interval
formed by the two above-mentioned optical air masses. A modification of this method could allow us to increase the accuracy of sun
photometer calibration. Results: As an implementation of the new method, a special algorithm was developed. According to it, the
calibration coefficient should be calculated taking into account the photometer output signals taken in such diurnal time moments when a special condition is met about the equality of functional values of temporal ratios for the optical air mass and the aerosol optical depth calculated separately. A model research performed with due regards for the dependence of the optical air mass on the sun elevation angle showed that the formulated calibration condition can be met during the time interval from 9:00 to 11:00 when the air aerosol pollution level increases. Practical relevance: The algorithm for the proposed method is developed and a block scheme of the instrument is composed. The results of the performed model research are given, confirming the feasibility of the calibration accuracy increase. Social implications: The increase in sun photometer calibration accuracy enables more precise estimation of atmospheric aerosol pollution level. This is important for climate prediction and for solving certain ecological problems linked to people's health.