Research on laser water vapor concentration detection technology in the air-sea flux observation

Abstract

In the observation of water vapor flux at air-sea interface, the collection frequency of water vapor concentration is more than 10 Hz. High-speed and high-precision measurement of water vapor concentration is an urgent problem to be solved in the observation of water vapor flux at air-sea interface. The ratio of the peak-peak value of second harmonic to the average value of first harmonic is used to measure water vapor concentration based on tunable diode laser absorption spectroscopy. The sensitivity of laser water vapor concentration detection equipment caused by marine salt fog and dust is reduced through precise optical design, and the water vapor concentration at the air-sea interface is calculated using a binary polynomial fitting algorithm. The response frequency of the laser water vapor concentration analyzer is 40 Hz. The water vapor concentration values from the laser water vapor concentration analyzer and LI-7500 CO2/H2O gas analyzer are collected synchronously in real time using LabVIEW software. The comparison results show that they have good consistency in the trend and response speed of water vapor concentration, and the measurement deviation of water vapor concentration is within ±1%. The experimental results show that it can meet the needs of high-speed, high-precision measurement of water vapor concentration in the air-sea interface water vapor flux observation.

Temperature Compensation Algorithm of Air Quality Monitoring Equipment Based on TDLAS

“…The Lambert-Beer law describes the attenuation relationship between transmitted light and incident light when monochromatic light with a specific wavelength passes through the gas to be measured, as shown in Figure 2. When an incident laser passes through the measured gas, if the wavelength and frequency of the laser are consistent with a certain absorption frequency of the measured gas, the energy of the laser will be absorbed by the measured gas [15], and the incident laser will be attenuated into the outgoing laser. The attenuation of laser energy can be obtained by Lambert-Beer's law.…”