Zhaoyan Liu
Resident at:
NASA Langley Research Center
MS 475, Hampton, VA 23681
Tel: (757) 864-7192; Fax: (757) 864-2571
Email: zhaoyan.liu@nasa.gov
Research Interests
- Optoelectronics and nonlinear optics
- System development of lasers and lidars
- Lidar atmospheric remote sensing
- Data analyses of spaceborne lidar measurements
- Dust aerosol generation and transport
Current Research
· The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission is a joint satellite project between NASA and the French space agency, CNES. The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), a two-wavelength polarization-sensitive lidar, is a key instrument aboard the CALIPSO satellite. Since the first collection of scientific data in June 2006, CALIOP has been providing nearly continuous observations of vertical-resolved global cloud and aerosol distributions. Currently, my research is related primarily to the CALIOP measurement of clouds and aerosols.
As a member of the CALIPSO Lidar Science Working Group, I lead the algorithm development of cloud and aerosol discrimination (CAD). CAD, together with the aerosol sub-typing and cloud sub-typing algorithms, consists of the CALIOP scene classification algorithm (SCA) module, which is a critical part of the level-2 data processing to help correctly interpret the CALIOP measurements and do quantitative analyses. The theoretical basis and architecture of these algorithms can be found in the CALIPSO Scene Classification ATBD and also in the papers published in JGR-Atmosphere (Liu et al, 2004) and JTECH (Liu et al, 2009; Omar et al, 2009, and Hu et al, 2009).
I and my colleagues at the NASA Langley Research Center have also performed studies to characterize the random noises contained in the backscatter lidar measurements (Liu et al, 2006). Based on these studies, we have developed an algorithm to compute the so-called noise scale factor (NSF) used to estimate uncertainties due to random measure noise in the CALIOP level 1 and 2 data products. We have demonstrated the possibility using the background radiation scattered from ice clouds to validate the calibration of depolarization measurements based on the NASA Goddard Space Flight Center’s airborne Cloud Physics Lidar (CPL) measurements (Liu et al, 2004). In addition, I also led finalization of the initial release of the CALIOP Level 1 ATBD.
A full list of the CALIPSO project documentation and publications can be found at the CALIPSO website http://www-calipso.larc.nasa.gov/resources/project_documentation.php and http://www-calipso.larc.nasa.gov/resources/publications.php.
· I also provide support to scientific applications of the CALIOP data and conduct researches in collaboration with the atmospheric scientists and researchers from Japan, China, India, and in the US. A focus is on the airborne dust generation and long-range transport. With the capability of depolarization measurement, the CALIOP measurement can identify dust aerosol from other types of aerosols (Liu et al., 2008a) and therefore provides a unique data set to study the dust generation and transport on a global scale. We have derived unprecedented, vertical-resolved, regional (Liu et al., 2008b) and global (D. Liu et al., 2008) dust distributions from the CALIOP measurements. Combining dust transport models and the CALIOP measurements, an extraordinary long distance transport of Asian dust for more than one full circuit around the globe was directly observed and tracked for the first time (Uno et al., 2009). Read (in Japanese) introducing the research activities to study the aerosol generation and transport in the East Asia using the NIES ground-based lidar network and the CALIOP measurements.NIES Research Booklet No. 29
· Measurement of tropospheric winds for weather forecasting and pollution transport using Doppler lidar is recommended for launch in a time frame of 2016-2020 in the national decadal survey report (Earth Science and Applications from Space – National Imperatives for the Next Decade and Beyond, 2007). I currently participate in a research in collaboration with scientists at the Langley Research Center and the Goddard Space Flight Center. This research attempts to develop a tool to simulate the performance of wind measurements using spaceborne coherent Doppler lidars based on the CALIOP observed aerosol distributions and optical properties.
Publications
· Z. Liu, A. Omar, M. Vaughan, et al., “CALIPSO Lidar Observations of the Optical Properties of Saharan Dust: A Case Study of Long Range Transport”, J. Geophys. Res., 113, D07207, doi:10.1029/2007JD008878, 2008a.
· Z. Liu, D. Liu, J. Huang, et al., “Airborne dust distributions over the Tibetan Plateau and surrounding areas derived from the first year of CALIPSO lidar observations,” Atmos. Chem. Phys., 8, 5045-5060, 2008b.
· I. Uno, K. Eguchi, K. Yumimoto, T. Takemura, A. Shimizu, M. Uematsu, Z. Liu, Z. Wang, Y. Hara, and N. Sugimoto, “Asian dust transported one full circuit around the globe,” Nature Geoscience, 2, 557-560, 2009.
· R. Gautam, Z. Liu, R. Singh, and N. Hsu, “Two contrasting dust-dominant periods over India observed from MODIS and CALIPSO data,” Geophys. Res. Lett., 36, L06813, doi:10.1029/2008GL036967, 2009.
· Z. Liu, M. Vaughan, D. Winker, et al., “The CALIPSO lidar cloud and aerosol discrimination: Version 2 altorithm and initial assessment of performance,” J. Atmos. Oceanic Technol., 26, 1198–1213, 2009.
· A. Omar, D. Winker, C. Kittaka, M. Vaughan, Z. Liu, Y. Hu, R. Kuehn, R. Rogers, C. Hostetler, R. Ferrare, and C. Trepte, “An automated aerosol classification and lidar ratio selection algorithm,” J. Atmos. Oceanic Technol., 26, 1994-2014, 2009.
· K. Powell, C. Hostetler, Z. Liu, et al., “CALIOP calibration algorithms: Part I – 532 nm and 1064 nm calibration algorithm overview with details of calibration algorithms for nighttime 532 nm parallel channel and 532 nm perpendicular channel,” J. Atmos. Oceanic Technol., 26, 2015-2033, 2009.
· M. Vaughan, K. Powell, R. Kuehn, S. Young, D. Winker, C. Hostetler, W. Hunt, Z. Liu, M. McGill, B. Getzewich, “Fully Automated Detection of Cloud and Aerosol Layers in the CALIPSO Lidar Measurements,” J. Atmos. Oceanic Technol., 26, 2034-2050, 2009.
· Y. Hu., D. Winker, M. Vaughan, B. Lin, A. Omar, C. Trepte, D. Flittner, P. Yang, W. Sun, Z. Liu, Z. Wang, S. Young, K. Stamnes, J. Huang, R. Kuehn, B. Baum, and R. Holz, “CALIPSO Cloud Phase Discrimination Algorithm,” J. Atmos. Oceanic Technol., 26, 2293-2309, 2009.
· J. Su, M. McCormick, Z. Liu, K. Leavor, R. Lee, J. Levis, and M. Hill, “Obtaining a ground-based lidar geometric forma factor using coincident spaceborne lidar measurements,” Appl. Opt., 49, 108-113, 2010.