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| Titel |
Measurement and simulation of topographic effects on passive microwave remote sensing over mountain areas: a case study from Tibetan Plateau |
| VerfasserIn |
X. X. Li, L. X. Zhang, L. M. Jiang |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250058481
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| Zusammenfassung |
| Mountain areas, occupying one quarter proportion of terrene area on the earth,
characterize topography as the diversity of the mountain ecosystem and the hill-scale
climate change, and also provide resource and services for equivalent to the one
fourth global populations, among which Tibetan Plateau is known as the world
famous mountain plateau. Because of topography land-surface hydraulic energy and
thermal energy over mountain areas are redistributed, characterizing the diversity
of mountain ecosystem and spatial heterogeneity under coarse-scale microwave
pixels.
A ground-based experiment performed to measure relief effects on microwave radiation
for C band. Relief effects we observed were dived into two parts, one is the primary terms
varied with topographic geometry features (i.e. slope, orientation, elevation) with ±12K bias
against flat terrain, and the other is secondary terms caused by surface scattering from
circumambient elevated terrain arisen 4K brightness temperature bias. It is much more
important to prove relief effects, especially the primary effects, still have radiative influence
in microwave pixels underlying the method of spatial convolution statistic analysis.
The statistic analysis of the primary effects for normality indicates the presence of
relief effects in the Tibetan Plateau in the tens of kilometers microwave pixel scale.
Based on the microwave radiative transfer over the Tibetan Plateau mountain area
the brightness temperature (TB) simulation described the impact of topography
including terrain geometrical properties and the complexity of terrain related to
topographic roughness, on the microwave radiation of uncovered land surface at passive
C-band.
According to the statistic analysis results, relief effects cannot be counteracted by the
interaction from different topographic geometrical features in one microwave pixel. The
simulated results correlated relevantly with TB from the Advanced Microwave Scanning
Radiometer (AMSR-E), for both the vertical polarization and the horizontal polarization,
and their error within ±1K, which validates the reliability of the relief simulation
model. In this way, the maximal biases of TB (ΔTB = TB_relief - TB_flat)
for V-polarization is -16K, and 18K for H-polarization. The soil moisture error
(ΔSM=SMrelief-SMflat) due to relief effects is more than 4%, and the maximal error soars
to 16% volume percentage in the most rugged terrain of mountain areas. Exploring relief
effects on microwave radiation and soil moisture retrieval will contribute to a more
feasible possibility of the topographic correction for passive microwave remote
sensing, whereupon derived more accurate ecosystem information for mountains. |
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