12 Aug 2020
12 Aug 2020
High-resolution optical constants of crystalline ammonium nitrate for infrared remote sensing of the Asian Tropopause Aerosol Layer
- 1Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, Germany
- 2Department of Physics and Chemistry, University of Lyon, Lyon, France
- 3Institute of Energy and Climate Research, Stratosphere, Forschungszentrum Jülich, Jülich, Germany
- 1Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, Germany
- 2Department of Physics and Chemistry, University of Lyon, Lyon, France
- 3Institute of Energy and Climate Research, Stratosphere, Forschungszentrum Jülich, Jülich, Germany
Abstract. Infrared spectroscopic observations have shown that crystalline ammonium nitrate (AN) particles are an abundant constituent of the upper tropospheric aerosol layer which is formed during the Asian summer monsoon period, the so-called Asian Tropopause Aerosol Layer (ATAL). At upper tropospheric temperatures, the thermodynamically stable phase of AN is different from that at 298 K, meaning that presently available room-temperature optical constants of AN, that is, the real and imaginary parts of the complex refractive index, cannot be applied for the quantitative analysis of these infrared measurements. In this work, we have retrieved the first low-temperature data set of optical constants for crystalline AN in the 800–6000 cm−1 wavenumber range with a spectral resolution of 0.5 cm−1. The optical constants were iteratively derived from an infrared extinction spectrum of 1 micrometer-sized AN particles suspended in a cloud chamber at 223 K. The uncertainties of the new data set were carefully assessed in a comprehensive sensitivity analysis. We show that our data accurately fit aircraft-borne infrared measurements of ammonium nitrate particles in the ATAL.
Robert Wagner et al.


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RC1: 'Referee Report', Anonymous Referee #1, 05 Dec 2020
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AC1: 'Reply on RC1', Robert Wagner, 15 Jan 2021
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AC1: 'Reply on RC1', Robert Wagner, 15 Jan 2021
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RC2: 'Comments on the hi-res optical constants for ammonium nitrate at 223 K', Anonymous Referee #2, 22 Dec 2020
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AC2: 'Reply on RC2', Robert Wagner, 15 Jan 2021
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AC2: 'Reply on RC2', Robert Wagner, 15 Jan 2021


-
RC1: 'Referee Report', Anonymous Referee #1, 05 Dec 2020
-
AC1: 'Reply on RC1', Robert Wagner, 15 Jan 2021
-
AC1: 'Reply on RC1', Robert Wagner, 15 Jan 2021
-
RC2: 'Comments on the hi-res optical constants for ammonium nitrate at 223 K', Anonymous Referee #2, 22 Dec 2020
-
AC2: 'Reply on RC2', Robert Wagner, 15 Jan 2021
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AC2: 'Reply on RC2', Robert Wagner, 15 Jan 2021
Robert Wagner et al.
Robert Wagner et al.
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