Nighttime Atmospheric Scattering Phase Function Derived From the Scattered Light of a Laser Beam

Continuous monitoring of the atmospheric scattering phase function P(θ) $P(\theta )$ is difficult to perform since most observational techniques are limited to daylight hours. Among known aerosol optical properties, only atmospheric optical depth is measured routinely during clear nights at a few gr...

Full description

Saved in:
Bibliographic Details
Published in:Geophysical research letters 2022-05, Vol.49 (10), p.n/a
Main Authors: Kocifaj, M., Kundracik, F., Bará, S., Barentine, J., Wallner, S.
Format: Article
Language:English
Subjects:
Aerosol optical properties
Aerosols
Atmosphere
Atmospheric scattering
Daylight
Daytime
Earth surface
Electric power
Electric power sources
Ground stations
laser beam
Laser beams
Lasers
Light
Lower atmosphere
Methods
Monitoring
Night
Night-time
Nighttime
nighttime atmosphere
Optical analysis
Optical properties
Optical thickness
Physics
Polluted environments
Radiance
Radiometry
Scattering angle
scattering phase function
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Continuous monitoring of the atmospheric scattering phase function P(θ) $P(\theta )$ is difficult to perform since most observational techniques are limited to daylight hours. Among known aerosol optical properties, only atmospheric optical depth is measured routinely during clear nights at a few ground stations. In this paper we develop theoretical and experimental techniques to retrieve the scattering phase function from radiometry of a laser beam whose light is scattered in the lower nocturnal atmosphere. The field experiment we conducted in a night environment demonstrates the capability of the method to determine P(θ) $P(\theta )$ in real‐world settings. We show that extracting the scattering phase function from radiance data is realizable over a wide range of angles, which makes possible the use of an analytical extrapolation to approximate P(θ) $P(\theta )$ across the full range of scattering angles. Plain Language Summary In order to understand how light moves through the Earth's atmosphere, we must measure it in real‐world circumstances. Only a few metrics characterizing the optical properties of the atmosphere are routinely measured, and generally only during the daytime. We aimed to extend the ability to measure the atmosphere's optical properties to nighttime using simple light‐scattering physics and inexpensive, off‐the‐shelf equipment with low electric power requirements. We developed a method to probe conditions in the part of the atmosphere nearest the Earth's surface by observing how light from a green laser beam scatters from both air molecules and small particles suspended in the air called aerosols. By measuring how much laser light scatters in various directions, we can better understand the distribution of aerosols in the lower atmosphere over times ranging from hours to years. Combined with well‐established daytime measurements, our method enables continuous monitoring of aerosols during both day and night. The portability of the equipment we use makes this possible in naturally dark places and also in light‐polluted environments, and under both clear and cloudy conditions. Here we describe our method and show results from an experiment conducted under field conditions. Key Points The scattering phase function of the nighttime atmosphere is derived from ground‐based radiometry of a laser beam directed toward the sky The experiment is designed to be carried out in arbitrary settings with the use of a low‐power laser operated in the co
ISSN:0094-8276
1944-8007
DOI:10.1029/2022GL098608