Validation of aerosol and cloud layer structures from the space-borne lidar CALIOP using a ground-based lidar in Seoul, Korea

Abstract

Abstract. We present initial validation results of the space-borne lidar CALIOP onboard CALIPSO satellite using coincidental observations from a ground-based lidar in Seoul National University (SNU), Seoul, Korea (37.46 • N, 126.95 • E). We analyze six selected cases between September 2006 and February 2007, including 3 daytime and 3 night-time observations and covering different types of clear and cloudy atmospheric conditions. Apparent scattering ratios calculated from the two lidar measurements of total attenuated backscatter at 532 nm show similar aerosol and cloud layer structures both under cloud-free conditions and in cases of multiple aerosol layers underlying semitransparent cirrus clouds. Agreement on top and base heights of cloud and aerosol layers is generally within 0.10 km, particularly during night-time. This result confirms that the CALIPSO science team algorithms for the discrimination of cloud and aerosol as well as for the detection of layer top and base altitude provide reliable information in such atmospheric conditions. This accuracy of the planetary boundary layer top height under cirrus cloud appears, however, limited during daytime. Under thick cloud conditions, however, information on the cloud top (bottom) height only is reliable from CALIOP (ground-based lidar) due to strong signal attenuations. However, simultaneous space-borne CALIOP and ground-based SNU lidar (SNU-L) measurements complement each other and can be combined to provide full information on the vertical distribution of aerosols and clouds. An aerosol backscatter-to-extinction ratio (BER) estimated from lidar and sunphotometer synergy at the SNU site during the CALIOP overpass is assessed to be 0.023±0.004 sr −1 (i.e. a lidar ratio of 43.2±6.2 sr) fromCorrespondence to: S.-W. Kim (sang-woo.kim@cea.fr) CALIOP and 0.027±0.006 sr −1 (37.4±7.2 sr) from SNU-L. For aerosols within the planetary boundary layer under cloud-free conditions, the aerosol extinction profiles from both lidars are in agreement within about 0.02 km −1 . Under semi-transparent cirrus clouds, such profiles also show good agreement for the night-time CALIOP flight, but large discrepancies are found for the daytime flights due to a small signal-to-noise ratio of the CALIOP data.

Assessment of the CALIPSO Lidar 532 nm attenuated backscatter calibration using the NASA LaRC airborne High Spectral Resolution Lidar

“…In addition to aircraft studies previously discussed , ground based lidars have also offered an assessment of CALIOP attenuated backscatter profiles. Kim et al (2008) qualitatively show good agreement between an elastic backscatter lidar and CALIOP attenuated backscatter. In another study, Mamouri et al, 2009 used a ground based Raman lidar for nighttime validation and an elastic backscatter lidar for daytime validation of the CALIOP 532 nm total attenuated backscatter.…”

“…Since the launch of CALIPSO, several studies have been conducted validating the CALIOP data products (Mona et al, 2009;Mamouri et al, 2009;Kim et al, 2008). Some promising results were also published by McGill et al (2007) qualitatively comparing measurements from CALIOP to the Cloud Profiling Lidar (CPL) deployed on the ER-2 aircraft.…”

Detection of dust aerosol by combining CALIPSO active lidar and passive IIR measurements

“…Huang et al, 2008), the height-resolved global distribution of dust aerosols (D. , long-distance dust aerosol vertical distribution over Shanghai, China, (Chen et al, 2008), the Saharan dust outflow (Generoso et al, 2008), and Taklamakan dust aerosol radiative heating ). Kim et al (2008) confirmed that the CALIPSO algorithms discriminate clouds and aerosols and detect the layer top and base altitudes reliably by comparing CALIOP and ground-based lidar data at a site far from the dust source, in Seoul, Korea. However, as pointed out by Z.…”

Cirrus cloud macrophysical and optical properties over North China from CALIOP measurements

“…Synergy of these nadir-viewing sensors allows for a complete representation of physical cirrus cloud properties. The high quality of processed CALIPSO data products has been demonstrated through validation campaigns Winker et al, 2007;Vaughan et al, 2008;Kahn et al, 2008;Kim et al, 2008).…”