Abstract
Abstract. We performed a feasibility study of constraining the vertical profile of the tropospheric ozone by using a synergetic retrieval method on multiple spectra, i.e., ultraviolet (UV), thermal infrared (TIR), and microwave (MW) ranges, measured from space. This work provides, for the first time, a quantitative evaluation of the retrieval sensitivity of the tropospheric ozone by adding the MW measurement to the UV and TIR measurements. Two observation points in East Asia (one in an urban area and one in an ocean area) and two observation times (one during summer and one during winter) were assumed. Geometry of line of sight was nadir down-looking for the UV and TIR measurements, and limb sounding for the MW measurement. The retrieval sensitivities of the ozone profiles in the upper troposphere (UT), middle troposphere (MT), and lowermost troposphere (LMT) were estimated using the degree of freedom for signal (DFS), the pressure of maximum sensitivity, reduction rate of error from the a priori error, and the averaging kernel matrix, derived based on the optimal estimation method. The measurement noise levels were assumed to be the same as those for currently available instruments. The weighting functions for the UV, TIR, and MW ranges were calculated using the SCIATRAN radiative transfer model, the Line-By-Line Radiative Transfer Model (LBLRTM), and the Advanced Model for Atmospheric Terahertz Radiation Analysis and Simulation (AMATERASU), respectively. The DFS value was increased by approximately 96, 23, and 30 % by adding the MW measurements to the combination of UV and TIR measurements in the UT, MT, and LMT regions, respectively. The MW measurement increased the DFS value of the LMT ozone; nevertheless, the MW measurement alone has no sensitivity to the LMT ozone. The pressure of maximum sensitivity value for the LMT ozone was also increased by adding the MW measurement. These findings indicate that better information on LMT ozone can be obtained by adding constraints on the UT and MT ozone from the MW measurement. The results of this study are applicable to the upcoming air-quality monitoring missions, APOLLO, GMAP-Asia, and uvSCOPE.
Highlights
The World Health Organization (WHO) estimates that around 7 million people died as a result of the effects of air pollution in 2012 (WHO, 2014), and it cites air pollution as being one of the world’s greatest environmental health risks
We report a feasibility study of the tropospheric ozone profile retrieval based on the concept of Air POLLution Observation (APOLLO), i.e., utilizing synergetic observations afforded by UV, thermal infrared (TIR), and MW instruments to obtain vertically resolved information on tropospheric ozone at the boundary layer, and in the middle and upper troposphere
We evaluated the sensitivities of tropospheric ozone profile retrieval for the three vertical regions (UT, 215– 383 hPa; middle troposphere (MT), 383–749 hPa; and lowermost troposphere (LMT), > 749 hPa) in terms of the degree of freedom for signal (DFS) based on the optimal estimation method (OEM) calculation
Summary
The World Health Organization (WHO) estimates that around 7 million people died as a result of the effects of air pollution in 2012 (WHO, 2014), and it cites air pollution as being one of the world’s greatest environmental health risks. A feasibility study of the tropospheric ozone profile retrieval using the optimal estimation method (OEM; Rodgers, 2000) combining UV and TIR measurements was performed by Landgraf and Hasekamp (2007). We performed a feasibility study of obtaining a vertically resolved ozone amount in the troposphere by using synergetic retrieval from a combination of UV, TIR, and MW measurements covering wide wavelength ranges. We report a feasibility study of the tropospheric ozone profile retrieval based on the concept of APOLLO, i.e., utilizing synergetic observations afforded by UV, TIR, and MW instruments to obtain vertically resolved information on tropospheric ozone at the boundary layer, and in the middle and upper troposphere. The simulation was performed under ideal conditions for synergetic retrieval of the tropospheric ozone profile
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