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| Titel |
Detecting thin cirrus in MISR aerosol retrievals |
| VerfasserIn |
Jeffrey Pierce, Ralph Kahn, Matt Davis, Jennifer Comstock |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250043805
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| Zusammenfassung |
| Thin-cirrus clouds (optical depth < 0.3) are often undetected by standard cloud masking in
satellite aerosol retrieval algorithms. However, the Multi-angle Imaging SpectroRadiometer
(MISR) aerosol retrieval has the potential to discriminate between the scattering phase
functions of cirrus and aerosols, thus separating these components. Theoretical tests show
that MISR is sensitive to cirrus optical depth (OD) within Max{0.05, 20%}, similar to
MISR’s sensitivity to aerosol OD, and MISR can distinguish between small droxtal-like
cirrus crystals and larger hexagonal-like crystals, even at low latitudes, where the range of
scattering angles observed by MISR is smallest. Including just two cirrus components in the
aerosol retrieval algorithm would capture typical MISR sensitivity to the natural
range of cirrus properties; in situations where cirrus is present but the retrieval
comparison space lacks these components, the retrieval tends to underestimate
OD. Generally, MISR can also distinguish between cirrus and common aerosol
types when the proper cirrus and aerosol optical models are included in the retrieval
comparison space and total column OD >~ 0.2. However in some cases, especially
at low latitudes, cirrus can be mistaken for some combinations of dust and large
non-absorbing spherical aerosols, raising a caution about retrievals in dusty marine regions
when cirrus is present. Comparisons of MISR with lidar and AERONET show
good agreement in a majority of the cases, but situations where cirrus have optical
depths above 0.15 and are horizontally inhomogeneous on spatial scales shorter than
~50 km pose difficulties for cirrus retrieval using the MISR aerosol algorithm. |
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