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| Titel |
The influence of non-spherical particles and land surface emissivity on combined radar / radiometer precipitation retrievals |
| VerfasserIn |
B. T. Johnson, G. Skofronick-Jackson |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250024478
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| Zusammenfassung |
| 1. Introduction
One of the newer atmospheric research areas is remote sensing of falling snow. Falling
snow retrieval algorithms typically rely on radar signatures or passive high frequency
channels (>= 90 GHz) that relate scattering by ice to the falling snow. In physically-based
retrievals of falling snow, algorithms necessarily employ a number of subjective
assumptions regarding the relationship between precipitation particles and the observed
microwave radiances and radar reflectivities. One common and persistent assumption
is that frozen precipitation-sized particles may be treated as spherical particles,
which may or may not be reasonable, depending on the precipitation type. Another
standard assumption is that the surface emissivity of land surface at passive microwave
frequencies is "constant", and is often based on a pre-existing categorization of surface
type.
This research seeks to explore the forward modeled brightness temperature and radar
reflectivity sensitivity to continuous variations in particle shape from a sphere to an
idealized aggregate and/or pristine dendrite. We also examine the sensitivity of
snowfall detection to land surface emissivity against forested and snow covered
backgrounds.
2. Particle Properties
Recent research has shown that the scattering and absorption properties of non-spherical
particles can vary significantly from spherical particles [Kim, M.-J., et al., 2008]. However,
the true particle shapes (and spatial distributions thereof) within a precipitating
cloud remain unknown without in-situ observations. The choice of using spherical
particles to simulate realistic frozen precipitation particles (e.g., needles, dendrites,
graupel, etc.) is often motivated by computational convenience, through the use of
well-tested Mie-theory based codes, and by the lack of practical alternatives. For
small size parameters (x |
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