 |
| Titel |
Quantitative evaluation of seven optical sensors for cloud microphysical measurements at the Puy-de-Dôme Observatory, France |
| VerfasserIn |
G. Guyot, C. Gourbeyre, G. Febvre, V. Shcherbakov, F. Burnet, J.-C. Dupont, K. Sellegri, O. Jourdan |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1867-1381
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 10 ; Nr. 8, no. 10 (2015-10-15), S.4347-4367 |
| Datensatznummer |
250116642
|
| Publikation (Nr.) |
 copernicus.org/amt-8-4347-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
Clouds have an important role in Earth's radiative budget. Since the late
1970s, considerable instrumental developments have been made in order to
quantify cloud microphysical and optical properties, for both airborne and
ground-based applications. Intercomparison studies have been carried out in
the past to assess the reliability of cloud microphysical properties
inferred from various measurement techniques. However, observational
uncertainties still exist, especially for droplet size distribution
measurements and need to be reduced.
In this work, we discuss results from an intercomparison campaign, performed
at the Puy de Dôme in May 2013. During this campaign, a unique set of
cloud instruments was operating simultaneously in ambient air conditions and
in a wind tunnel. A Particle Volume Monitor (PVM-100), a Forward Scattering
Spectrometer Probe (FSSP), a Fog Monitor (FM-100), and a Present Weather
Detector (PWD) were sampling on the roof of the station. Within a wind tunnel
located underneath the roof, two Cloud Droplet Probes (CDPs) and a modified
FSSP (SPP-100) were operating. The main objectives of this paper are (1) to
study the effects of wind direction and speed on ground-based cloud
observations, (2) to quantify the cloud parameters discrepancies observed by
the different instruments, and (3) to develop methods to improve the
quantification of the measurements.
The results revealed that all instruments showed a good agreement in their
sizing abilities, both in terms of amplitude and variability. However, some
of them, especially the FM-100, the FSSP and the SPP, displayed large
discrepancies in their capability to assess the magnitude of the total
number concentration of the cloud droplets. As a result, the total liquid
water content can differ by up to a factor of 5 between the probes. The use
of a standardization procedure, based on data of integrating probes (PVM-100
or visibilimeter) and extinction coefficient comparison substantially
enhanced the instrumental agreement. During this experiment, the total
concentration agreed in variations with the visibilimeter, except for the
FSSP, so a corrective factor can be applied and it ranges from 0.44 to 2.2.
This intercomparison study highlights the necessity to have an instrument
which provides a bulk measurement of cloud microphysical or optical
properties during cloud ground-based campaigns. Moreover, the FM and FSSP
orientation was modified with an angle ranging from 30 to
90° angle with wind speeds from 3 to 7 m s−1. The results
show that the induced number concentration loss is between 29 and 98 %
for the FSSP and between 15 and 68 % for the FM-100. In particular, FSSP
experiments showed strong discrepancies when the wind speed was lower than 3 m s−1 and/or when the angle between the wind direction and the
orientation of the instruments is greater than 30°. An inadequate
orientation of the FSSP towards the wind direction leads to an
underestimation of the measured effective diameter. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|