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 semi-transparent 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) from 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.
Highlights
Space-borne active remote sensing (e.g. LITE (Lidar Inspace Technology Experiment; McCormick et al, 1993), GLAS (Geoscience Laser Altimeter System; Spinhirne et al, 2005) and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations; Winker et al, 2004, 2006, 2007)) of atmospheric aerosols and clouds is the key to providing global vertically resolved observations that are needed to better understand a variety of aerosol-cloudradiation-climate feedback processes (e.g. Spinhirne et al, 2005; Berthier et al, 2006)
This study presents initial validation results of space-borne lidar Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) profiles by comparing space and time coincidental measurements collected by a ground-based lidar at Seoul National University (SNU; 37.4579◦ N, 126.9520◦ E, 116 m a.m.s.l), Seoul, South Korea, hereafter denoted SNU lidar (SNUL)
4.1 Case 1: planetary boundary layer (PBL) aerosols under clear sky Figure 2a and b shows color coded time-height images of the daytime level-1 data at 532 nm acquired by CALIOP and SNU lidar (SNU-L) on 24 October 2006
Summary
Space-borne active remote sensing (e.g. LITE (Lidar Inspace Technology Experiment; McCormick et al, 1993), GLAS (Geoscience Laser Altimeter System; Spinhirne et al, 2005) and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations; Winker et al, 2004, 2006, 2007)) of atmospheric aerosols and clouds is the key to providing global vertically resolved observations that are needed to better understand a variety of aerosol-cloudradiation-climate feedback processes (e.g. Spinhirne et al, 2005; Berthier et al, 2006). This study presents initial validation results of space-borne lidar CALIOP profiles by comparing space and time coincidental measurements collected by a ground-based lidar at Seoul National University (SNU; 37.4579◦ N, 126.9520◦ E, 116 m a.m.s.l), Seoul, South Korea, hereafter denoted SNUL. We compare the CALIOP level-2 products of height and thickness of aerosol and cloud layers This validation is made for 3 different types of atmospheric scenes: (1) boundary aerosol layer under cloud-free conditions, (2) multiple aerosol layers underlying semi-transparent cirrus clouds, and (3) aerosol layer under thick tropospheric clouds. A comparison of aerosol extinction profile between CALIOP and SNU-L measurements both under cloud-free conditions and in cases of multiple aerosol layers underlying semi-transparent cirrus clouds is presented. For the CALIPSO mission, validation is defined as an assessment of the accuracy and precision of the derived science products by independent airborne or ground-based measurements (Kovacs and McCormick, 2006). Signal attenuation by atmospheric constituents such as air molecules, aerosols and clouds need to be explicitly taken into account
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
