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| Titel |
FAME-C: cloud property retrieval using synergistic AATSR and MERIS observations |
| VerfasserIn |
C. K. Carbajal Henken, R. Lindstrot, R. Preusker, J. Fischer |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 7, no. 11 ; Nr. 7, no. 11 (2014-11-25), S.3873-3890 |
| Datensatznummer |
250115958
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| Publikation (Nr.) |
 copernicus.org/amt-7-3873-2014.pdf |
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| Zusammenfassung |
| A newly developed daytime cloud property retrieval algorithm, FAME-C (Freie
Universität Berlin AATSR MERIS Cloud), is presented. Synergistic
observations from the Advanced Along-Track Scanning Radiometer (AATSR) and
the Medium Resolution Imaging Spectrometer (MERIS), both mounted on the
polar-orbiting Environmental Satellite (Envisat), are used for cloud
screening. For cloudy pixels two main steps are carried out in a sequential
form. First, a cloud optical and microphysical property retrieval is
performed using an AATSR near-infrared and visible channel. Cloud phase,
cloud optical thickness, and effective radius are retrieved, and subsequently
cloud water path is computed. Second, two cloud top height products are
retrieved based on independent techniques. For cloud top temperature,
measurements in the AATSR infrared channels are used, while for cloud top
pressure, measurements in the MERIS oxygen-A absorption channel are used.
Results from the cloud optical and microphysical property retrieval serve as
input for the two cloud top height retrievals. Introduced here are the AATSR
and MERIS forward models and auxiliary data needed in FAME-C. Also, the
optimal estimation method, which provides uncertainty estimates of the
retrieved property on a pixel basis, is presented. Within the frame of the
European Space Agency (ESA) Climate Change Initiative (CCI) project, the
first global cloud property retrievals have been conducted for the years
2007–2009. For this time period, verification efforts are presented,
comparing, for four selected regions around the globe, FAME-C cloud optical
and microphysical properties to cloud optical and microphysical properties
derived from measurements of the Moderate Resolution Imaging
Spectroradiometer (MODIS) on the Terra satellite. The results show a
reasonable agreement between the cloud optical and microphysical property
retrievals. Biases are generally smallest for marine stratocumulus clouds:
−0.28, 0.41 μm and −0.18 g m−2 for cloud optical
thickness, effective radius and cloud water path, respectively. This is also
true for the root-mean-square deviation. Furthermore, both cloud top height
products are compared to cloud top heights derived from ground-based cloud
radars located at several Atmospheric Radiation Measurement (ARM) sites.
FAME-C mostly shows an underestimation of cloud top heights when compared to
radar observations. The lowest bias of −0.3 km is found for AATSR cloud
top heights for single-layer clouds, while the highest bias of −3.0 km is
found for AATSR cloud top heights for multilayer clouds. Variability is low
for MERIS cloud top heights for low-level clouds, and high for MERIS cloud
top heights for mid-level and high-level single-layer clouds, as well as for
both AATSR and MERIS cloud top heights for multilayer clouds. |
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