VAHCOLI, a new concept for lidars: technical setup, science applications, and first measurements
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Published:2021-05-26
Issue:5
Volume:14
Page:3815-3836
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ISSN:1867-8548
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Container-title:Atmospheric Measurement Techniques
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language:en
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Short-container-title:Atmos. Meas. Tech.
Author:
Lübken Franz-Josef,Höffner Josef
Abstract
Abstract. A new concept for a cluster of compact lidar systems named VAHCOLI (Vertical And Horizontal COverage by LIdars)
is presented, which allows for the measurement of temperatures, winds, and aerosols
in the middle atmosphere (∼ 10–110 km) with high temporal and vertical
resolution of minutes and some tens of meters, respectively,
simultaneously covering horizontal scales from a few hundred meters to
several hundred kilometers (“four-dimensional coverage”).
The individual lidars (“units”) being used in VAHCOLI are
based on a diode-pumped alexandrite laser, which is
currently designed to detect potassium (λ=770 nm), and on
sophisticated laser spectroscopy measuring all relevant frequencies (seeder laser,
power laser, backscattered light) with high temporal resolution (2 ms)
and high spectral resolution applying
Doppler-free spectroscopy. The frequency of the lasers and
the narrowband filter in the receiving system are stabilized
to typically 10–100 kHz, which is a factor of roughly 10−5 smaller
than the Doppler-broadened Rayleigh signal. Narrowband
filtering allows for the measurement of Rayleigh and/or resonance scattering
separately from the aerosol (Mie) signal during both night and day.
Lidars used for VAHCOLI are compact (volume: ∼ 1 m3)
and multi-purpose systems which employ contemporary electronic, optical, and mechanical
components. The units are designed to autonomously operate under harsh field conditions in
remote locations. An error analysis with parameters of the anticipated system
demonstrates that temperatures and line-of-sight winds
can be measured from the lower stratosphere to the upper mesosphere
with an accuracy of ±(0.1–5) K and ±(0.1–10) m s−1, respectively,
increasing with altitude.
We demonstrate that some crucial dynamical processes in the middle atmosphere, such as gravity
waves and stratified turbulence, can be covered by VAHCOLI
with sufficient temporal, vertical, and horizontal sampling and resolution.
The four-dimensional capabilities of VAHCOLI allow for the performance of
time-dependent analysis of the flow field,
for example by employing Helmholtz decomposition, and for carrying out
statistical tests regarding, for example, intermittency and helicity.
The first test measurements under field conditions with a prototype lidar
were performed in January 2020. The lidar operated successfully during a 6-week period (night and day) without
any adjustment. The observations covered a height range of ∼ 5–100 km and demonstrated the capability
and applicability of this unit for the VAHCOLI concept.
Funder
Bundesministerium für Wirtschaft und Energie Deutsche Forschungsgemeinschaft Leibniz-Gemeinschaft
Publisher
Copernicus GmbH
Subject
Atmospheric Science
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