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| Titel |
Meridionally tilted ice cloud structures in the tropical upper troposphere as seen by CloudSat |
| VerfasserIn |
J. Gong, D. L. Wu, V. Limpasuvan |
| 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. 11 ; Nr. 15, no. 11 (2015-06-09), S.6271-6281 |
| Datensatznummer |
250119797
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| Publikation (Nr.) |
 copernicus.org/acp-15-6271-2015.pdf |
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| Zusammenfassung |
It remains challenging to quantify global cloud properties and uncertainties
associated with their impacts on climate change because of our poor
understanding of cloud three-dimensional (3-D) structures from observations and unrealistic characterization of
3-D cloud effects in global climate models (GCMs). In this study we find
cloud 3-D effects can cause significant error in cloud ice and radiation
measurements if it is not taken into account appropriately.
One of the cloud 3-D complexities, the slantwise tilt structure, has not
received much attention in research and even less has been reported
considering a global perspective. A novel approach is presented here to
analyze the ice cloud water content (IWC) profiles retrieved from CloudSat
and a joint radar–lidar product (DARDAR). By integrating IWC
profiles along different tilt
angles, we find that upper-troposphere (UT) ice cloud mass between 11 and
17 km is tilted poleward from active convection centers in the tropics
[30° S, 30° N]. This systematic tilt in cloud mass
structure is expected from the mass conservation principle of the Hadley
circulation with the divergent flow of each individual convection/convective
system from down below, and its existence is further confirmed from
cloud-resolving-scale Weather Research and Forecasting (WRF) model
simulations. Thus, additive effects of tilted cloud structures can introduce
5–20% variability by its nature or produce errors to satellite
cloud/hydrometeor ice retrievals if simply converting it from slant to nadir
column. A surprising finding is the equatorward tilt in middle tropospheric
(5–11 km) ice clouds, which is also evident in high-resolution model
simulations but not in coarse-resolution simulations with cumulus
parameterization. The observed cloud tilt structures are intrinsic properties
of tropical clouds, producing synoptic distributions around the Intertropical
Convergence Zone (ITCZ). These findings imply that current interpretations
based on over-simplified cloud vertical structures could lead to considerable
cloud measurement errors and have a subsequent impact on understanding cloud
radiative, dynamical and hydrological properties. |
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