 |
| Titel |
A new method for nocturnal aerosol measurements with a lunar photometer prototype |
| VerfasserIn |
A. Barreto, E. Cuevas, B. Damiri, C. Guirado, T. Berkoff, A. J. Berjón, Y. Hernández, F. Almansa, M. Gil |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1867-1381
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 6, no. 3 ; Nr. 6, no. 3 (2013-03-05), S.585-598 |
| Datensatznummer |
250017833
|
| Publikation (Nr.) |
 copernicus.org/amt-6-585-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
| This paper presents the preliminary results of nocturnal Aerosol Optical
Depth (τa) and Angström Exponent (α) obtained from a new
lunar photometer prototype, trade name Cimel CE-318U. Due to the variation of
the moon's illumination inherent to the lunar cycle, the typical Langley-plot
Method used in solar photometry to calibrate these instruments cannot be
applied. In this paper, we propose three different methods to carry out the
lunar-photometer calibration. In order to validate the results, we have
selected three events which encompass seven nights and ten days under
different atmospheric conditions, including several saharan dust intrusions
episodes. Method#1 is introduced in this work as a modification of the usual
Langley Method. This technique, called Lunar-Langley Method, requires the
extraterrestrial irradiances from a lunar irradiance model, providing similar
accuracies on τa to those of AERONET (±0.01–0.02). It makes
comparable daytime and nighttime measurements. Method#2 consists of
transferring the current calibration from a master used by sunphotometers.
Its results are again within the limit of accuracy expected for the
instrument. Method#3 uses an integrating sphere and the methodology proposed
by Li et al. (2008) to determine sky calibration coefficients (Cj) and the
instrument's solid angle field-of-view (Ω), respectively. We observe
significant τa differences between Method#1 and #3 (up to 0.07),
which might be attributed to the errors propagation in Method#3. The good
results obtained from the comparison against a second CE-318U prototype, and
against daytime data from a Precision Filter Radiometer (PFR), constitute a
valuable assessment of CE-318U performance. Results of α and its
spectral variation (δ α) show good agreement between daytime and
nighttime, being able to identify the aerosol properties associated with each
event. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|