14 Jan 2021

14 Jan 2021

Review status: this preprint is currently under review for the journal ACP.

Estimating Radiative Forcing Efficiency of Dust Aerosol Based on Direct Satellite Observations: Case Studies over the Sahara Desert and Taklimakan Desert

Lin Tian1,2,3, Lin Chen3, Peng Zhang3, and Lei Bi4 Lin Tian et al.
  • 1Nanjing University of Information Science & Technology, Nanjing, China
  • 2Chinese Academy of Meteorological Sciences, Beijing, China
  • 3National Satellite Meteorological Center, China Meteorological Administration, Beijing, China
  • 4Department of Atmospheric Sciences, School of Earth Sciences, Zhejiang University, Hangzhou, China

Abstract. The direct radiative forcing efficiency of the dust aerosol (DRFEdust) is an important indicator to measure the climate effect of the dust. The DRFEdust is determined by the microphysical properties of the dust, which vary with the dust source regions. However, there are only sparse in-situ measurements of them, such as the distribution of the dust aerosol particle size and the complex refractive index in the main dust source regions. Furthermore, recent studies have shown that the non-spherical effect of the dust particle is not negligible. The DRFEdust is often evaluated by estimating given microphysical properties of the dust aerosols in the radiative transfer model (RTM). However, considerable uncertainties exist due to the complex and variable dust properties, including the complex refractive index and the shape of the dust. The DRFEdust over the Taklimakan Desert and the Sahara Desert is derived from the satellite observations in this paper. The advantage of the proposed satellite-based method is that there is no need to consider the microphysical properties of the dust aerosols in estimating the DRFEdust. For comparison, the observed DRFEdust is compared with that simulated by the RTM. The differences in the dust microphysical properties in these two regions and their impacts on DRFEdust are analyzed.

The DRFEdust derived from the satellite observation is −39.6 ± 10.0 W m−2 τ−1 in March 2019 over Tamanrasset and −48.6 ± 13.7 W m−2 τ−1 in April 2019 over Kashi. According to the analyses of their microphysical properties and optical properties, the dust aerosols from the Taklimakan desert (Kashi) scatter strongly. The RTM simulated results (−41.5 to −47.4 W m−2 τ−1 in the Taklimakan Desert and −32.2 to −44.3 W m−2 τ−1 in the Sahara Desert) are in good agreement with the results estimated by satellite observations. According to previous studies, the results in this paper are proved to be reasonable and reliable. The results also show that the microphysical properties of the dust can significantly influence the DRFEdust. The satellite-derived results can represent the influence of the dust microphysical properties on the DRFEdust, which can also validate the direct radiative effect of the dust aerosol and the DRFEdust derived from the numerical model more directly.

Lin Tian et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2020-1113', Anonymous Referee #1, 10 Feb 2021
    • AC1: 'Reply on RC1', Peng Zhang, 10 Mar 2021
  • RC2: 'Comment on acp-2020-1113', Anonymous Referee #4, 27 Mar 2021

Lin Tian et al.

Lin Tian et al.


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Short summary
The result shows dust aerosols from the Taklimakan Desert have higher aerosol scattering during dust storm cases of this paper, and this caused higher negative direct radiative forcing efficiency (DRFEdust) than aerosols from Sahara Desert. The microphysical properties and particle shapes of dust aerosol significantly influence the DRFEdust. Satellite based equi-albedo method has unique advantage in DRFEdust estimating, it could validate the results derived from the numerical model directly.