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| Titel |
Intercomparison of snowfall estimates derived from the CloudSat Cloud Profiling Radar and the ground-based weather radar network over Sweden |
| VerfasserIn |
L. Norin, A. Devasthale, T. S. L'Ecuyer, N. B. Wood, M. Smalley |
| 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 ; 8, no. 12 ; Nr. 8, no. 12 (2015-12-01), S.5009-5021 |
| Datensatznummer |
250116711
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| Publikation (Nr.) |
 copernicus.org/amt-8-5009-2015.pdf |
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| Zusammenfassung |
| Accurate snowfall estimates are important for both
weather and climate applications. Ground-based weather radars and
space-based satellite sensors are often used as viable alternatives to
rain gauges to estimate precipitation in this context. In particular,
the Cloud Profiling Radar (CPR) on board CloudSat is proving to be
a useful tool to map snowfall globally, in part due to its high
sensitivity to light precipitation and its ability to provide near-global
vertical structure. CloudSat snowfall estimates play a particularly
important role in the high-latitude regions as other
ground-based observations become sparse and passive satellite sensors
suffer from inherent limitations.
In this paper, snowfall estimates from two observing systems – Swerad,
the Swedish national weather radar network, and CloudSat – are compared.
Swerad offers a well-calibrated data set of precipitation rates with
high spatial and temporal resolution, at very high latitudes. The
measurements are anchored to rain gauges and provide
valuable insights into the usefulness of CloudSat CPR's snowfall estimates
in the polar regions. In total, 7.2 × 105 matchups of CloudSat and
Swerad observations from 2008 through 2010 were intercompared, covering
all but the summer months (June to September). The intercomparison shows
encouraging agreement between the two observing systems despite their
different sensitivities and user applications. The best agreement is
observed when CloudSat passes close to a Swerad station (46–82 km),
where the observational conditions for both systems are comparable. Larger
disagreements outside this range suggest that both platforms have
difficulty with shallow snow but for different reasons. The correlation
between Swerad and CloudSat degrades with increasing distance from the
nearest Swerad station, as Swerad's sensitivity decreases as a function
of distance. Swerad also tends to overshoot low-level precipitating
systems further away from the station, leading to an underestimation of
snowfall rate and occasionally to missing precipitation altogether.
Several statistical metrics – including the probability
of detection, false alarm rate, hit rate, and Pierce's
skill score – are calculated. The sensitivity of these metrics to the
snowfall rate, as well as to the distance from the nearest radar station,
are summarised. This highlights the strengths and the limitations of
both observing systems at the lower and upper ends of the snowfall
distributions as well as the range of uncertainties that can be expected
from these systems in high-latitude regions. |
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