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Ann. Geophys., 21, 639-647, 2003
www.ann-geophys.net/21/639/2003/
© European Geosciences Union 2003
Space-borne clear air lidar measurements in the presence of broken cloud
I. Astin1 and C. Kiemle2
1Environmental Systems Science Centre, University of Reading, Reading, UK
2Institut für Physik der Atmosphäre, DLR, D82234, Oberpfaffenhofen, Germany
Abstract. A number of proposed
lidar systems, such as ESA’s AEOLUS (formerly ADM) and DIAL missions (e.g.
WALES) are to make use of lidar returns in clear air. However, on average,
two-thirds of the globe is covered in cloud. Hence, there is a strong
likelihood that data from these instruments may be contaminated by cloud.
Similarly, optically thick cloud may not be penetrated by a lidar pulse,
resulting in unobservable regions that are overshadowed by the cloud. To
address this, it is suggested, for example, in AEOLUS, that a number of
consecutive short sections of lidar data (between 1 and 3.5 km in length) be
tested for cloud contamination or for overshadowing and only those that are
unaffected by cloud be used to derive atmospheric profiles. The prob-ability of
obtaining profiles to near ground level using this technique is investigated
both analytically and using UV air-borne lidar data recorded during the CLARE’98
campaign. These data were measured in the presence of broken cloud on a number
of flights over southern England over a four-day period and were chosen because
the lidar used has the same wavelength, footprint and could match the
along-track spacing of the proposed AEOLUS lidar.
Key words. Atmospheric composition
and structure (aerosols and particles) Meteorology and atmospheric dynamics
(instruments and techniques; general circulation)
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