This dissertation consists of three parts, each devoted to a particular
issue of significant importance for satellite-based remote sensing of cirrus clouds.
In the first part, we develop and present a fast infrared radiative transfer
model on the basis of the adding-doubling principle. The model aims to facilitate
the radiative transfer computations involved in hyperspectral remote sensing
applications. The model is applicable to a variety of cloud conditions, including
vertically inhomogeneous or multilayered clouds. It is shown that for
hyperspectral applications the model is two order-of-magnitude faster than the
well-known discrete ordinate transfer (DISORT) model, while maintains a similar
accuracy.
The second part is devoted to the investigation of uncertainties in the
FSSP (Forward Scattering Spectrometer Probe) measurement of cloud extinction
by small ice particles. First, the single-scattering properties of small ice particles
in cirrus clouds are derived and compared to those of equivalent spheres according to various definitions. It is found that, although small ice particles in
cirrus clouds are often “quasi-spherical”, their scattering phase functions and
asymmetry factors are significant different from those of ice spheres. Such
differences may lead to substantial underestimation of cloud extinction in FSSP
measurement, if small ice particles are assumed to be spheres.
In the third part, we present a comparison of cirrus cloud optical thickness
retrievals from two important instruments, MODIS (Moderate Resolution Imaging
Spectrometer) and POLDER (Polarization and Directionality of Earth’s
Reflection), on board NASA’s A-train satellite constellation. The comparison
reveals a large difference. Several possible reasons are discussed. It is found
that much of the difference is attributable to the difference between the MODIS
and POLDER retrieval algorithm in the assumption of cirrus cloud bulk scattering
properties. Potential implications of the difference for climate studies are
investigated. An important finding is that the use of an unrealistic cirrus bulk
scattering model might introduce artificial seasonal variation of cirrus optical
thickness and shortwave radiative forcing into the retrieval.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2876 |
| Date | 15 May 2009 |
| Creators | Zhang, Zhibo |
| Contributors | Yang, Ping |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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