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| Titel |
Sensitivities of Lagrangian modelling of mid-latitude cirrus clouds to trajectory data quality |
| VerfasserIn |
E. Kienast-Sjögren, A. K. Miltenberger, B. P. Luo, T. Peter |
| 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. 13 ; Nr. 15, no. 13 (2015-07-09), S.7429-7447 |
| Datensatznummer |
250119879
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| Publikation (Nr.) |
 copernicus.org/acp-15-7429-2015.pdf |
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| Zusammenfassung |
Simulations of cirrus are subject to uncertainties in model physics and
meteorological input data. Here we model cirrus clouds along air mass
trajectories, whose extinction has been measured with an elastic backscatter
lidar at Jungfraujoch research station in the Swiss Alps, with a
microphysical stacked box model. The sensitivities of these simulations to
input data uncertainties (trajectory resolution, unresolved vertical
velocities, ice nuclei number density and upstream specific humidity) are
investigated.
Variations in the temporal resolution of the wind field data
(COSMO-Model at 2.2 km resolution) between 20 s and 1 h have only a marginal impact on the
trajectory path, while the representation of the vertical velocity
variability and therefore the cooling rate distribution are significantly
affected. A temporal resolution better than 5 min must be chosen in order to
resolve cooling rates required to explain the measured extinction. A further
increase in the temporal resolution improves the simulation results slightly.
The close match between the modelled and observed extinction profile for
high-resolution trajectories suggests that the cooling rate spectra calculated by the
COSMO-2 model suffice on the selected day. The modelled cooling rate spectra are,
however, characterized by significantly lower vertical velocity amplitudes
than those found previously in some aircraft campaigns (SUCCESS, MACPEX). A
climatological analysis of the vertical velocity amplitude in the Alpine
region based on COSMO-2 analyses and balloon sounding data suggests large
day-to-day variability in small-scale temperature fluctuations. This
demonstrates the necessity to apply numerical weather prediction models with
high spatial and temporal resolutions in cirrus modelling, whereas using
climatological means for the amplitude of the unresolved air motions does
generally not suffice.
The box model simulations further suggest that uncertainties in the upstream
specific humidity (± 10 % of the model prediction) and in the ice
nuclei number density (0–100 L−1) are more important for the modelled
cirrus cloud than the unresolved temperature fluctuations if temporally
highly resolved trajectories are used. For the presented case the simulations
are incompatible with ice nuclei number densities larger than 20 L−1
and insensitive to variations below this value. |
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