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| Titel |
Comparison of MODIS cloud microphysical properties with in-situ measurements over the Southeast Pacific |
| VerfasserIn |
Q. Min, E. Joseph, Y. Lin, L. Min, B. Yin, P. H. Daum, L. I. Kleinman, J. Wang, Y.-N. Lee |
| 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 ; 12, no. 23 ; Nr. 12, no. 23 (2012-12-03), S.11261-11273 |
| Datensatznummer |
250011628
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| Publikation (Nr.) |
 copernicus.org/acp-12-11261-2012.pdf |
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| Zusammenfassung |
| Utilizing the unique characteristics of the cloud over the Southeast Pacific
(SEP) off the coast of Chile during the VOCALS field campaign, we compared
satellite remote sensing of cloud microphysical properties against in-situ
data from multi-aircraft observations, and studied the extent to which these
retrieved properties are sufficiently constrained and consistent to reliably
quantify the influence of aerosol loading on cloud droplet sizes. After
constraining the spatial-temporal coincidence between satellite retrievals
and in-situ measurements, we selected 17 non-drizzle comparison pairs. For
these cases the mean aircraft profiling times were within one hour of Terra
overpasses at both projected and un-projected (actual) aircraft positions
for two different averaging domains of 5 km and 25 km. Retrieved quantities
that were averaged over a larger domain of 25 km compared better
statistically with in-situ observations than averages over a smaller domain
of 5 km. Comparison at projected aircraft positions was slightly better than
un-projected aircraft positions for some parameters. Overall, both
MODIS-retrieved effective radius and LWP were larger but highly correlated
with the in-situ measured effective radius and LWP, e.g., for averaging
domains of 5 km, the biases are up to 1.75 μm and 0.02 mm whilst the
correlation coefficients are about 0.87 and 0.85, respectively. The observed
effective radius difference between the two decreased with increasing cloud
drop number concentration (CDNC), and increased with increasing cloud
geometrical thickness. Compared to the absolute effective radius difference,
the correlations between the relative effective radius difference and CDNC
or cloud geometric thickness are weaker. For averaging domains of 5 km and
25 km, the correlation coefficients between MODIS-retrieved and in-situ
measured CDNC are 0.91 and 0.93 with fitting slopes of 1.23 and 1.27,
respectively. If the cloud adiabaticity is taken into account, better
agreements are achieved for both averaging domains (the fitting slopes are
1.04 and 1.07, respectively). Our comparison and sensitivity analysis of
simulated retrievals demonstrate that both cloud geometrical thickness and
cloud adiabaticity are important factors in satellite retrievals of
effective radius and cloud drop number concentration. The large
variabilities in cloud geometrical thickness and adiabaticity, the
dependencies of cloud microphysical properties on both quantities (as
demonstrated in our sensitivity study of simulated retrievals), and the
inability to accurately account for either of them in retrievals lead to
some uncertainties and biases in satellite retrieved cloud effective radius,
cloud liquid water path, and cloud drop number concentration. However,
strong correlations between satellite retrievals and in-situ measurements
suggest that satellite retrievals of cloud effective radius, cloud liquid
water path, and cloud drop number concentration can be used to investigate
aerosol indirect effects qualitatively. |
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