05/16/2017

Cloud Vertical Distribution from Combined Surface and Space Radar-Lidar Observations at Two Arctic Atmospheric Observatories

Blending observations from the surface and space provides more information about Arctic clouds.

The Science

Clouds play a critical role in the Arctic climate system, yet a comprehensive set of cloud observations is lacking due to condition-specific limitations of the available observing systems. These difficulties have in turn led to substantial deficiencies in how models represent Arctic clouds and cloud phase. Observations from ground-based and space-based radar and lidar are compared at two Arctic sites to assess the relative strengths and weaknesses of these observational approaches for characterizing the vertical distribution and phase of Arctic clouds.

The Impact

This study increases the value and clarifies the interpretation of both ground-based and space-based observations of clouds, helping the community to better understand the limitations of these observations and ultimately to better understand the role of clouds in the Arctic system. Moreover, a combined cloud product, drawing upon the strengths of both ground- and space-based measurements, is developed to offer a more complete data set for assessing model representations of clouds at these Arctic sites.

Summary

Ground-based remote sensors provide continuous, long-term observations, yet are limited to specific locations. On the other hand, space-based remote sensors cover wide spatial domains, yet cannot resolve diurnal processes at a given location. Both approaches face distinct observational challenges depending on cloud type, microphysical parameters, and the environment. In this study, multiple years of ground-based measurements from zenith-pointing Ka-band cloud radar and depolarization lidar are compared with similar observations from the space-based CloudSat radar and CALIPSO lidar at two sites in the Arctic: the DOE ARM North Slope of Alaska site in Barrow and the NOAA/Canadian Network for the Detection of Arctic Change site in Eureka, Canada. In the Arctic, where low clouds are frequent, ground-based sensors observe 25-40% more clouds (primarily ice and mixed-phase clouds) below 1 km than satellite sensors due to CloudSat ground-contamination issues and CALIPSO signal attenuation. The two perspectives show comparable observations between 1-2 km. Space-based sensors observe an annual average of 1-6% more cloudiness at most heights above 2-3 km than surface-based sensors due to diminishing sensitivity of surface sensors with height and lidar attenuation. In summer, the space-based measurements observe a higher fraction of liquid-containing clouds at these heights relative to the ground-based observations, while in winter they observe a higher fraction of ice clouds. A blended, monthly average product based on observations from these two perspectives provides the most comprehensive cloud occurrence and phase data set at these Arctic sites to date.

Principal Investigator(s)

Matthew Shupe
Cooperative Institute for Research in Environmental Sciences, University of Colorado and NOAA Earth System Research Laboratory
matthew.shupe@noaa.gov

Funding

Matthew D. Shupe acknowledges support from the US Department of Energy (DOE) Atmospheric System Research Program (DE-SC0011918) and the National Science Foundation (ARC-0632187). The authors thank Norm Wood, Ralph Kuehn, and Mark Vaughan for their valuable comments on the paper. Yinghui Liu thanks Leanne Avila for editing the paper. Ground-based observations from Barrow were obtained from the DOE Atmospheric Radiation Measurement Program. Ground-based observations at Eureka were obtained from the NOAA Earth System Research Laboratory and the Canadian Network for the Detection of Arctic Change (CANDAC). The CALIPSO products from June 2006 to December 2010 were obtained from the Atmospheric Science Data Center at NASA Langley Research Center. The 2B-GEOPROF, 2B-GEOPROF-lidar, 2B-CLDCLASS-lidar, and 2B-CWC-RO products from June 2006 to December 2010 were obtained from the CloudSat Data Processing Center at the Colorado State University.

References

Liu, Y., M. D. Shupe, Z. Wang, and G. Mace. “Cloud vertical distribution from combined surface and space radar-lidar observations at two Arctic atmospheric observatories.” Atmospheric Chemistry and Physics, 17, 9 (2017). [DOI: 10.5194/acp-17-5973-2017].