Measurement of atmospheric water vapor vertical column concentration and vertical distribution in Qingdao using multi-axis differential optical absorption spectroscopy

Abstract

The method of retrieving the vertical column density (VCD) and the atmospheric vertical profile of water vapor in visible blue band (434.0–451.5 nm) were studied by using the multi-axis differential optical absorption spectroscopy (MAX-DOAS). First, the method of retrieving the VCD of water vapor was studied. Owing the the fact that the water vapor absorption cross section is of high resolution and it cannot be effectively measured by MAX-DOAS, a convolved cross section with the instrument slit function was used. In addition, the correction factor for water vapor saturation absorption was also used to obtain the true VCD. Second, the water vapor profile retrieved by applying the nonlinear optimal estimation of the trace gas retrieval method (PriAM) was studied, including the effects of aerosol state and the priori profile on the water vapor retrieval. Influence on the water vapor retrieval from the aerosol prior profile linear changes was unapparent. High aerosol state has a significant influence on the water vapor profile retrieval and it was still within the total error tolerance. This indicates that the PriAM is applicable in the water vapor profile retrieval. Using this method, a continuous observation experiment was carried out at the MAX-DOAS Aoshan regional station in Qingdao. The retrieved water vapor VCD results were compared with the daily average data of the European Centre for Medium-Range Weather Forecasts (ECMWF), and the <i>R</i><sup>2</sup> is 0.93. The comparison of the near-surface water vapor concentration of MAX-DOAS retrieval with the ECMWF and sounding data of the University of Wyoming shows that <i>R</i><sup>2</sup> is larger than 0.70 and 0.66, respectively. The two comparison results demonstrate that PriAM can retrieve the atmospheric water vapor VCD and profile accurately. The vertical distribution characteristics of water vapor in Qingdao was analyzed, and the profile results show that the concentration of water vapor in Qingdao was distributed mainly under 1.5 km in height.

Investigation of the Influence of Water Vapor on Heavy Pollution and Its Relationship With AOD Using MAX‐DOAS on the Coast of the Yellow Sea

“…Because H 2 O saturation absorption was neglected for this retrieval band (Lampel et al., 2015), it may have had some effect on the MAX‐DOAS data, when H 2 O concentration was higher. Studies have shown that when the H 2 O DSCD reaches 4 × 10 23 molec./cm 2 , the saturation absorption effect will reduce the OD by 1.76% (Ren et al., 2020), and when the H 2 O DSCD reaches 1 × 10 24 molec./cm 2 , the saturation absorption effect will reduce the OD by 4.23%. In this study, the maximum H 2 O DSCD was 9.85 × 10 23 molec./cm 2 , and the data between 4 × 10 23 and 9.85 × 10 23 molec./cm 2 in June, July, August, and September accounted for 23.38%, 44.02%, 64.66%, and 33.39% of the total data, respectively.…”

The Characterization of Haze and Dust Processes Using MAX-DOAS in Beijing, China

“…It can be set to 1 and then modified according to the iteration. The generality of the PriAM algorithm for aerosols, NO 2 , SO 2 , HCHO, and H 2 O has been proven in many comparative observation experiments [29,31,32,34,35,[50][51][52].…”

“…Multi-axis differential optical absorption spectroscopy (MAX-DOAS) is a passive DOAS remote sensing technology developed in recent years [26], featuring a low cost, simple instrument setup, mature algorithm, and high spatiotemporal resolution. MAX-DOAS can measure the vertical distribution of a variety of trace gases (NO 2 , SO 2 , HCHO, HONO, and CHOCHO), aerosols, and water vapor in the atmosphere [14,[27][28][29][30][31][32][33], thus providing a basis for the study of haze and dust pollution. In addition, the gas transport fluxes can be measured by coupling the gas profile retrieved from MAX-DOAS measurements with the wind profile [31,34], which is significant for the study of gas transport.…”

Measurements of Atmospheric Water Vapor by a 1.316 μm Optical Fiber Laser Heterodyne Radiometer

“…Although LIDAR detection accuracy is high, the detection range is limited. The sounding balloon can simultaneously detect a variety of atmospheric parameters and detection heights up to 30 km, but the cost is high, and the path is not controllable [7]. A ground-based Fourier transform spectrometer with high resolution is capable of trace gas measurement in atmospheric columns, but the device is usually large and expensive.…”