Use of the long-wave range for remote sensing of atmospheric aerosols

2020 ◽  
Keyword(s):  
Remote Sensing ◽  
Atmospheric Aerosols ◽  
Long Wave ◽  
Wave Range

Remote Sensing of Arctic Atmospheric Aerosols

2020 ◽  
pp. 505-589
Author(s):  
Alexander Kokhanovsky ◽  
Claudio Tomasi ◽  
Alexander Smirnov ◽  
Andreas Herber ◽  
Roland Neuber ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Atmospheric Aerosols

scholarly journals Global scale variability of the mineral dust long-wave refractive index: a new dataset of in situ measurements for climate modeling and remote sensing

2017 ◽  
Vol 17 (3) ◽  
pp. 1901-1929 ◽  
Author(s):  
Claudia Di Biagio ◽  
Paola Formenti ◽  
Yves Balkanski ◽  
Lorenzo Caponi ◽  
Mathieu Cazaunau ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Refractive Index ◽  
Size Distribution ◽  
Climate Models ◽  
Mineral Dust ◽  
Complex Refractive Index ◽  
Mineralogical Composition ◽  
Global Scale ◽  
Long Wave

Abstract. Modeling the interaction of dust with long-wave (LW) radiation is still a challenge because of the scarcity of information on the complex refractive index of dust from different source regions. In particular, little is known about the variability of the refractive index as a function of the dust mineralogical composition, which depends on the specific emission source, and its size distribution, which is modified during transport. As a consequence, to date, climate models and remote sensing retrievals generally use a spatially invariant and time-constant value for the dust LW refractive index. In this paper, the variability of the mineral dust LW refractive index as a function of its mineralogical composition and size distribution is explored by in situ measurements in a large smog chamber. Mineral dust aerosols were generated from 19 natural soils from 8 regions: northern Africa, the Sahel, eastern Africa and the Middle East, eastern Asia, North and South America, southern Africa, and Australia. Soil samples were selected from a total of 137 available samples in order to represent the diversity of sources from arid and semi-arid areas worldwide and to account for the heterogeneity of the soil composition at the global scale. Aerosol samples generated from soils were re-suspended in the chamber, where their LW extinction spectra (3–15 µm), size distribution, and mineralogical composition were measured. The generated aerosol exhibits a realistic size distribution and mineralogy, including both the sub- and super-micron fractions, and represents in typical atmospheric proportions the main LW-active minerals, such as clays, quartz, and calcite. The complex refractive index of the aerosol is obtained by an optical inversion based upon the measured extinction spectrum and size distribution. Results from the present study show that the imaginary LW refractive index (k) of dust varies greatly both in magnitude and spectral shape from sample to sample, reflecting the differences in particle composition. In the 3–15 µm spectral range, k is between ∼ 0.001 and 0.92. The strength of the dust absorption at ∼ 7 and 11.4 µm depends on the amount of calcite within the samples, while the absorption between 8 and 14 µm is determined by the relative abundance of quartz and clays. The imaginary part (k) is observed to vary both from region to region and for varying sources within the same region. Conversely, for the real part (n), which is in the range 0.84–1.94, values are observed to agree for all dust samples across most of the spectrum within the error bars. This implies that while a constant n can be probably assumed for dust from different sources, a varying k should be used both at the global and the regional scale. A linear relationship between the magnitude of the imaginary refractive index at 7.0, 9.2, and 11.4 µm and the mass concentration of calcite and quartz absorbing at these wavelengths was found. We suggest that this may lead to predictive rules to estimate the LW refractive index of dust in specific bands based on an assumed or predicted mineralogical composition, or conversely, to estimate the dust composition from measurements of the LW extinction at specific wavebands. Based on the results of the present study, we recommend that climate models and remote sensing instruments operating at infrared wavelengths, such as IASI (infrared atmospheric sounder interferometer), use regionally dependent refractive indices rather than generic values. Our observations also suggest that the refractive index of dust in the LW does not change as a result of the loss of coarse particles by gravitational settling, so that constant values of n and k could be assumed close to sources and following transport. The whole dataset of the dust complex refractive indices presented in this paper is made available to the scientific community in the Supplement.

scholarly journals Exploring Atmospheric Aerosols by Twilight Photometry

2008 ◽  
Vol 25 (9) ◽  
pp. 1600-1607 ◽  
Author(s):  
B. Padma Kumari ◽  
S. H. Kulkarni ◽  
D. B. Jadhav ◽  
A. L. Londhe ◽  
H. K. Trimbake
Keyword(s):  
Remote Sensing ◽  
Atmospheric Aerosols ◽  
Integrated Circuit ◽  
Tropical Meteorology ◽  
Indian Institute ◽  
Experimental Setup ◽  
Vertical Profiles ◽  
Remote Sensing Technique ◽  
Passive Remote Sensing ◽  
The Vertical Distribution

Abstract The instrument twilight photometer was designed, developed, and installed at the Indian Institute of Tropical Meteorology (IITM), Pune, India (18°43′N, 73°51′E), to monitor the vertical distribution of atmospheric aerosols. The instrument, based on passive remote sensing technique, is simple and inexpensive. It is operated only during twilights, and the method of retrieval of aerosol profile is based on a simple twilight technique. It functions at a single wavelength (660 nm), and a photomultiplier tube is used as a detector. The amplifier, an important component of the system, was designed and developed by connecting 10 single integrated-circuit (IC) amplifiers in parallel so that the noise at the output is drastically reduced and the sensitivity of the system has been increased. As a result, the vertical profiles are retrieved to a maximum of 120 km. A brief description of the basic principle of twilight technique, the experimental setup, and the method of retrieval of aerosol profiles using the above photometer are detailed in this paper.

scholarly journals Remote sensing of atmospheric aerosols and noctilucent clouds from space

1990 ◽  
Vol 10 (10) ◽  
pp. 201-204
Author(s):  
O. Avaste ◽  
M. Gadsden ◽  
R. Rōōm
Keyword(s):  
Remote Sensing ◽  
Atmospheric Aerosols ◽  
Noctilucent Clouds
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