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| Titel |
Analysis of actinic flux profiles measured from an ozonesonde balloon |
| VerfasserIn |
P. Wang, M. Allaart, W. H. Knap, P. Stammes |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 8 ; Nr. 15, no. 8 (2015-04-21), S.4131-4144 |
| Datensatznummer |
250119656
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| Publikation (Nr.) |
 copernicus.org/acp-15-4131-2015.pdf |
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| Zusammenfassung |
| A green light sensor has been developed at KNMI to measure actinic flux
profiles using an ozonesonde balloon. In total, 63 launches with ascending
and descending profiles were performed between 2006 and 2010. The measured
uncalibrated actinic flux profiles are analysed using the Doubling–Adding
KNMI (DAK) radiative transfer model. Values of the cloud optical thickness
(COT) along the flight track were taken from the Spinning Enhanced Visible
and Infrared Imager (SEVIRI) Cloud Physical Properties (CPP) product. The
impact of clouds on the actinic flux profile is evaluated on the basis of the
cloud modification factor (CMF) at the cloud top and cloud base, which is the
ratio between the actinic fluxes for cloudy and clear-sky scenes. The impact
of clouds on the actinic flux is clearly detected: the largest enhancement
occurs at the cloud top due to multiple scattering. The actinic flux
decreases almost linearly from cloud top to cloud base. Above the cloud top
the actinic flux also increases compared to clear-sky scenes. We find that
clouds can increase the actinic flux to 2.3 times the clear-sky value at
cloud top and decrease it to about 0.05 at cloud base. The relationship
between CMF and COT agrees well with DAK simulations, except for a few
outliers. Good agreement is found between the DAK-simulated actinic flux
profiles and the observations for single-layer clouds in fully overcast
scenes. The instrument is suitable for operational balloon measurements
because of its simplicity and low cost. It is worth further developing the
instrument and launching it together with atmospheric chemistry composition
sensors. |
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