Estimation of the Precipitable Water and Water Vapor Fluxes in the Coastal and Inland Cities of China Using MAX-DOAS

Abstract

Water vapor transport affects regional precipitation and climate change. The measurement of precipitable water (PW) and water vapor flux (WVF) is of great importance for the study of precipitation and water vapor transport. This study presented a new method of computing PW and estimating WVF using the water vapor vertical column density (VCD) and profile retrieved from multi-axis differential optical absorption spectroscopy (MAX-DOAS), combined with the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 wind profiles. We applied our method to MAX-DOAS observations in the coastal (Qingdao) and inland (Xi’an) cities of China from June 2019 to May 2020 and compared the results to the ERA5 reanalysis datasets. Good agreement with ERA5 datasets was found; the correlation coefficient (r) of the PW and the zonal and meridional WVFs were r ≥ 0.92, r = 0.77, and r ≥ 0.89, respectively. The comparison results showed the feasibility and reliability of estimating PW and WVF using MAX-DOAS. Then, we analyzed the seasonal and diurnal climatology of the PW and WVFs in Qingdao and Xi’an. The results indicated that the seasonal and diurnal variations of the PW in the two cities were similar. The zonal water vapor transport of the two cities mainly involved eastward transport, Qingdao’s meridional water vapor mainly involved southward transport, and that of Xi’an mainly involved northward transport. The WVFs of the two cities were higher in the afternoon than in the morning, which may be related to wind speed. The results also indicated that the WVF transmitting belts appeared at around 2 and 1.4 km above the surface in Qingdao and around 2.8, 2.6, 1.6, and 1.0 km above the surface in Xi’an. Before precipitation, the WVF transmitting belt moved from near the ground to a high level, reaching its maximum at about 2 km, and the PW and meridional vertically integrated WVF increased. Finally, the sources and transports of water vapor during continuous precipitation and torrential rain were analyzed according to a 24 h backward trajectory. The air mass from the southeast accounted for more than 84% during continuous precipitation in Xi’an, while the air mass from the ocean accounted for more than 75% during torrential rain in Qingdao and was accompanied by a high-level ocean jet stream. As an optical remote sensing instrument, MAX-DOAS has the advantages of high spatiotemporal resolution, low cost, and easy maintenance. The application of MAX-DOAS to meteorological remote sensing provides a better method for evaluating the PW and WVF.

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].…”

“…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.…”

Estimation of Precipitation During Kiremt and Belg Seasons And The Water Vapor Flux Convergence Layers in Ethiopia

“…Changes in tropospheric water vapor flux (WVF) directly affect the frequency of precipitation determine energy balance and provide resources for the study of global warming and climate change [15]. Vertically integrated moisture flux used to estimate the moisture sources, low-level moisture flux, or moisture flux convergence is considered a useful tool in the prediction of convection as well as precipitation [16].…”

Identification of Water Vapor Flux Convergence Layers and Estimation of Precipitation over Ethiopia

“…Changes in tropospheric water vapor flux (WVF) directly affect the frequency of precipitation and determine energy balance and provide resources for the study of global warming and climate change [15]. Vertically integrated moisture flux used to estimate the moisture sources, low level moisture flux or moisture flux convergence is considered as a useful tool in prediction of convection as well as precipitation [16].…”