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Arctic Cloud Macrophysical Characteristics from Cloudsat and CALIPSO

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Arctic Cloud Macrophysical Characteristics from Cloudsat and CALIPSO University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Publications, Agencies and Staff of the U.S. Department of Commerce U.S. Department of Commerce 2012 Arctic cloud macrophysical characteristics from CloudSat and CALIPSO Yinghui Liu University of Wisconsin, [email protected] Jeffrey R. Key Center for Satellite Applications and Research Steven A. Ackerman University of Wisconsin Gerald G. Mace University of Utah Qiuqing Zhang University of Utah Follow this and additional works at: https://digitalcommons.unl.edu/usdeptcommercepub Part of the Environmental Sciences Commons Liu, Yinghui; Key, Jeffrey R.; Ackerman, Steven A.; Mace, Gerald G.; and Zhang, Qiuqing, "Arctic cloud macrophysical characteristics from CloudSat and CALIPSO" (2012). Publications, Agencies and Staff of the U.S. Department of Commerce. 344. https://digitalcommons.unl.edu/usdeptcommercepub/344 This Article is brought to you for free and open access by the U.S. Department of Commerce at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Publications, Agencies and Staff of the U.S. Department of Commerce by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Remote Sensing of Environment 124 (2012) 159–173 Contents lists available at SciVerse ScienceDirect Remote Sensing of Environment journal homepage: www.elsevier.com/locate/rse Arctic cloud macrophysical characteristics from CloudSat and CALIPSO Yinghui Liu a,⁎, Jeffrey R. Key b, Steven A. Ackerman a,c, Gerald G. Mace d, Qiuqing Zhang d a Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin, Madison, WI, United States b Center for Satellite Applications and Research, NOAA/NESDIS, Madison, WI, United States c Department of Atmospheric and Oceanic Sciences, University of Wisconsin at Madison, Madison, WI, United States d Department of Atmospheric Sciences, University of Utah, Salt Lake City, UT, United States article info abstract Article history: The lidar and radar profiling capabilities of the CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Received 22 October 2011 (CALIPSO) satellites provide opportunities to improve the characterization of cloud properties. An Arctic cloud Received in revised form 6 May 2012 climatology based on their observations may be fundamentally different from earlier Arctic cloud climatologies Accepted 8 May 2012 based on passive satellite observations, which have limited contrast between the cloud and underlying surface. Available online xxxx Specifically, the Radar–Lidar Geometrical Profile product (RL-GEOPROF) provides cloud vertical profiles from the combination of active lidar and radar. Based on this data product for the period July 2006 to March 2011, this Keywords: Arctic paper presents a new cloud macrophysical property characteristic analysis for the Arctic, including cloud occur- Cloud rence fraction (COF), vertical distributions, and probability density functions (PDF) of cloud base and top heights. Remote sensing Seasonal mean COF shows maximum values in autumn, minimum values in winter, and moderate values in CloudSat spring and summer; this seasonality is more prominent over the Arctic Ocean on the Pacific side. The mean ratios CALIPSO of multi-layer cloud to total cloud over the ocean and land are between 24% and 28%. Low-level COFs are higher over ocean than over land. The ratio of low-level cloud to total cloud is also higher over ocean. Middle-level and high-level COFs are smaller over ocean than over land except in summer, and the ratios of middle-level and high- level clouds to total cloud are also smaller over ocean. Over the central Arctic Ocean, PDFs of cloud top height and cloud bottom height show (1) two cloud top height PDF peaks, one for cloud top heights lower than 1200 m and another between 7 and 9 km; and (2) high frequency for cloud base below 1000 m with the majority of cloud base heights lower than 2000 m. © 2012 Elsevier Inc. All rights reserved. 1. Introduction a decreased warming/increased cooling effect of clouds on the surface. Wang and Key (2003) concluded that the surface temperature would An accurate determination of cloud amount and height is critical to have risen even higher than observed if cloud cover had not changed studying the Arctic climate system and its changes. There are complex the way it did. Furthermore, cloud amount and cloud vertical structure interactions between clouds and other processes in the Arctic climate change with the retreat of the sea ice cover (Kay and Gettelman, 2009; system (Curry et al., 1996; Francis et al., 2009; Liu et al., 2009), and an Schweiger et al., 2008b; Vavrus et al., 2011) and with changes in mois- accurate description of cloud macrophysical properties is important to ture convergence (Liu et al., 2007). understand and model these interactions. Arctic clouds are a key factor Cloud feedback is the primary source of uncertainty in projecting fu- in determining the energy budget at the top of the atmosphere and at ture climate change, especially in the Polar Regions (Solomon et al., the surface by modulating the longwave and shortwave radiation fluxes 2007). Uncertainties result from limitations in scientific understanding (Intrieri et al., 2002; Tjernström et al., 2008), which affect the surface of the cloud formation and dissipation processes (Beesley and Moritz, temperature and may regulate the growth or retreat of sea ice extent 1999; Vavrus and Waliser, 2008) and the lack of detailed observations and thickness (Kay et al., 2008; Schweiger et al., 2008a). Liu et al. of these processes. A better understanding of the Arctic climate system (2008, 2009) show that changes in cloud amount play a key role in and forecasting of the Arctic climate require accurate observations of the surface temperature changes in the Arctic. Wang and Key (2003) Arctic clouds. found that changes in Arctic cloud cover over the period 1982–1999, Previous work made good progress in developing Arctic cloud detec- generally less cloud in winter and more in spring/summer, resulted in tion algorithms and in deriving an Arctic cloud macrophysical property climatology from multiple observation platforms. Visual cloud reports from weather stations on land and ocean in the Arctic have been collected ⁎ Corresponding author at: Cooperative Institute of Meteorological Satellite Studies, and processed to study the global cloud climatology (Hahn and Warren, University of Wisconsin, 1225 West Dayton Street, Madison, WI 53706, United States. Tel.: +1 6088901893; fax: +1 6082625974. 2003, 2007), and Arctic cloud inter-annual variability (Eastman and E-mail address: [email protected] (Y. Liu). Warren, 2010). Dong et al. (2010) generated a 10-year climatology of 0034-4257/$ – see front matter © 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.rse.2012.05.006 160 Y. Liu et al. / Remote Sensing of Environment 124 (2012) 159–173 Arctic cloud fraction and radiative forcing at Barrow, Alaska from radar– cirrus (Stephens et al., 2002, 2008), and has been used to study the ver- lidar and ceilometer observations at the Atmospheric Radiation tical structure in the tropics (Yuan et al., 2011). The Cloud-Aerosol LIdar Measurement North Slope of Alaska site and the nearby NOAA Barrow with Orthogonal Polarization (CALIOP) instrument onboard the Cloud- Observatory from June 1998 to May 2008. Intrieri et al. (2002) reported Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) is the temporal distributions of cloudiness, and the vertical distribution of sensitive to optically thin clouds (Winker et al., 2003) and has been cloud boundary heights from combined radar and lidar observations on- used to determine probability density functions of cloud base and top board a ship from October 1997 to October 1998 during the Surface Heat heights and geometrical thickness of optically thin clouds (Devasthale Budget of the Arctic Ocean (SHEBA). Shupe et al. (2011) described cloud et al., 2011). CloudSat and CALIPSO data complement each other, and occurrence fraction, vertical distribution, boundary statistics, etc. based a combination of both observations provides an opportunity of a de- on combined observations of radar and lidar at six Arctic atmospheric ob- scription of cloud extent and distribution. These observations provide servatories. The surface-based cloud observations have relatively low a reference for model simulations of Arctic clouds. spatial resolutions and inhomogeneous observation locations, especially This study presents a description of the Arctic cloud occurrence frac- over the Arctic Ocean. tion (COF), vertical distributions, and probability density functions Observing clouds from satellites with passive sensors utilizes the dif- (PDF) of cloud base and top heights based on combined observations ferences in spectral signatures of clouds from surfaces in the visible, of CloudSat and CALIPSO from July 2006 to March 2011. The data and near-infrared, and thermal infrared channels, using the single- and mul- the method to process the data are described in Section 2. Results and tispectral threshold methods (Ackerman et al., 1998; Gao et al., 1998; comparisons to some of the studies mentioned above are presented in Inoune, 1987; Minnis et al., 2001; Rossow and Schiffer, 1999; Section 3. Conclusions and a discussion of the limitations and potential Schweiger et al., 1999; Spangenberg et al., 2001, 2002; Yamanouchi et applications of this study are detailed in Section 4. al., 1987) and statistical
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