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| Titel |
Study of wind retrieval from space-borne infrared coherent lidar in cloudy atmosphere. |
| VerfasserIn |
Philippe Baron, Shoken Ishii, Kohei Mizutani, Kozo Okamoto, Satoshi Ochiai |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250108474
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| Publikation (Nr.) |
 EGU/EGU2015-8229.pdf |
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| Zusammenfassung |
| Future spaceborne tropospheric wind missions using infrared coherent lidar are currently
being studied in Japan and in the United States [1,2]. The line-of-sight wind velocity is
retrieved from the Doppler shift frequency of the signal returned by aerosol particles.
However a large percentage (70-80%) of the measured single-shot intensity profiles are
expected to be contaminated by clouds [3]. A large number of cloud contaminated profiles
(>40%) will be characterized by a cloud-top signal intensity stronger than the aerosol signal
by a factor of one order of magnitude, and by a strong attenuation of the signal
backscattered from below the clouds. Profiles including more than one cloud layer are also
expected.
This work is a simulation study dealing with the impacts of clouds on wind retrieval. We
focus on the three following points: 1) definition of an algorithm for optimizing the wind
retrieval from the cloud-top signal, 2) assessment of the clouds impact on the measurement
performance and, 3) definition of a method for averaging the measurements before the
retrieval. The retrieval simulations are conducted considering the instrumental characteristics
selected for the Japanese study: wavelength at 2 µm, PRF of 30 Hz, pulse power of
0.125 mJ and platform altitude between 200-400 km. Liquid and ice clouds are
considered. The analysis uses data from atmospheric models and statistics of cloud effects
derived from CALIPSO measurements such as in [3]. A special focus is put on
the average method of the measurements before retrieval. Good retrievals in the
mid-upper troposphere implie the average of measured single-range power spectra over
large horizontal (100 km) and vertical (1 km) ranges. Large differences of signal
intensities due to the presence of clouds and the clouds non-uniform distribution have
to be taken into account when averaging the data to optimize the measurement
performances.
References:
[1] S. Ishii, T. Iwasaki, M. Sato, R. Oki, K. Okamoto, T. Ishibashi, P. Baron, and T.
Nishizawa: Future Doppler lidar wind measurement from space in Japan, Proc. of SPIE Vol.
8529, 2012
[2] D. Wu, J. Tang, Z. Liu, and Y. Hu: Simulation of coherent doppler wind lidar
measurement from space based on CALIPSO lidar global aerosol observations. Journal of
Quantitative Spectroscopy and Radiative Transfer, 122(0), 79–86, 2013
[3] G.D Emmitt: CFLOS and cloud statistics from satellite and their impact on future
space-based Doppler Wind Lidar development. Symposium on Recent Developments in
Atmospheric Applications of Radar and Lidar, 2008 |
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