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David M. Winker, Mark A. Vaughan, Ali Omar, Yongxiang Hu, Kathleen A. Powell, Zhaoyan Liu, William H. Hunt, and Stuart A. Young

effect of cloud depends strongly on the multilayer structure, yet passive sensors have difficulty retrieving more than a single effective layer. Lidar is able to penetrate high optically thin cloud and profile a large fraction of the atmosphere. There are also limitations in current cloud ice–water phase retrievals from passive satellite sensors. CALIOP provides a vertically resolved measurement of ice–water phase through measurements of the depolarization of the lidar backscatter signal. CALIPSO was

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Stuart A. Young and Mark A. Vaughan

regions where the optical properties are uniform and the signal strengths are comparable ( Vaughan et al. 2009 ). The way in which the CALIPSO analysis can identify and process regions of different horizontal and vertical extents in the same atmospheric region is outlined in section 2 below. The CALIPSO lidar analysis is a multistage process that includes the correction of signals for instrumental effects; the detection, boundary location, and classification of atmospheric features; and, finally

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Mark A. Vaughan, Kathleen A. Powell, David M. Winker, Chris A. Hostetler, Ralph E. Kuehn, William H. Hunt, Brian J. Getzewich, Stuart A. Young, Zhaoyan Liu, and Matthew J. McGill

time, CALIOP can encounter a large number of dissimilar scenarios. In the span of ∼20 min, CALIOP observes instances of multiple cloud layers (e.g., at ∼43°N and ∼6°N); faint, possibly subvisible, cirrus (∼20°S, at ∼15 km MSL); lofted aerosol layers (∼32°N, ∼4 km vertically); aerosol layers beneath overlying cirrus (at the equator and at ∼16°S); cumulus embedded in boundary layer aerosols (∼26°N); and aerosol extending above broken cloud decks (∼10°S). The fundamental data products derived from the

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Zhaoyan Liu, Mark Vaughan, David Winker, Chieko Kittaka, Brian Getzewich, Ralph Kuehn, Ali Omar, Kathleen Powell, Charles Trepte, and Chris Hostetler

to complement current measurements and improve our understanding of weather and climate. The availability of a global, multiyear set of vertically resolved measurements of the earth’s atmosphere should ultimately lead to great improvements in both weather and climate models. CALIOP is the first satellite-borne lidar optimized specifically for aerosol and cloud measurements, and is also the first polarization lidar in space. CALIOP is a dual-wavelength, polarization-sensitive elastic backscatter

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William H. Hunt, David M. Winker, Mark A. Vaughan, Kathleen A. Powell, Patricia L. Lucker, and Carl Weimer

) was chosen because its much higher quantum efficiency at that wavelength more than compensates for its higher dark noise. The outputs of the three detectors go through transimpedance amplifiers (TIAs), which convert the detector output currents to voltages. To achieve the more than six orders of magnitude dynamic range required by CALIOP, each TIA output is split and sent in parallel to two amplifiers with different gains, each of which is followed by a 14-bit digitizer (designated the high

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Ali H. Omar, David M. Winker, Mark A. Vaughan, Yongxiang Hu, Charles R. Trepte, Richard A. Ferrare, Kam-Pui Lee, Chris A. Hostetler, Chieko Kittaka, Raymond R. Rogers, Ralph E. Kuehn, and Zhaoyan Liu

size distributions during SEAS yields S a values of 20 sr at 532 nm and 45 sr at 1064 nm. This 532-nm S a value for marine aerosols is consistent with marine aerosol S a estimates by others ( Ansmann et al. 2001 ; Flamant et al. 1998 ; Reagan et al. 2001 ). Measurements during INDOEX in the marine boundary layer of the tropical Indian Ocean report a value of 23.5 sr at 532 nm ( Müller et al. 2007 ). In their climatological study of oceanic AERONET sites, Cattrall et al. (2005) report an

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