Macrophysical and optical properties of midlatitude cirrus clouds from four ground‐based lidars and collocated CALIOP observations

Abstract

[1] Ground-based lidar and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) data sets gathered over four midlatitude sites, two U.S. and two French sites, are used to evaluate the consistency of cloud macrophysical and optical property climatologies that can be derived by such data sets. The consistency in average cloud height (both base and top height) between the CALIOP and ground data sets ranges from −0.4 km to +0.5 km. The cloud geometrical thickness distributions vary significantly between the different data sets, due in part to the original vertical resolutions of the lidar profiles. Average cloud geometrical thicknesses vary from 1.2 to 1.9 km, i.e., by more than 50%. Cloud optical thickness distributions in subvisible, semitransparent, and moderate intervals differ by more than 50% between ground-and space-based data sets. The cirrus clouds with optical thickness below 0.1 (not included in historical cloud climatologies) represent 30-50% of the nonopaque cirrus class. An important part of this work consists in quantifying the different possible causes of discrepancies between CALIOP and surface lidar. The differences in average cloud base altitude between ground and CALIOP data sets can be attributed to (1) irregular sampling of seasonal variations in the ground-based data, (2) daynight differences in detection capabilities by CALIOP, and (3) the restriction to situations without low-level clouds in ground-based data. Cloud geometrical thicknesses are not affected by irregular sampling of seasonal variations in the ground-based data but by the day-night differences in detection capabilities of CALIOP and by the restriction to situations without low-level clouds in ground-based data.

Comparison of CALIPSO aerosol optical depth retrievals to AERONET measurements, and a climatology for the lidar ratio of dust

“…The CALIOP 532 nm channel is known to be accurately calibrated (Rogers et al, 2011), and a number of previous studies have shown that the performance of the CALIPSO layer detection scheme is consistent with the predictions and limitations described in the project's algorithm theoretical basis document (Vaughan et al, 2005;McGill et al, 2007;Dupont et al, 2010;Thorsen et al, 2011;Yorks et al, 2011). Although there are few systematic studies of CALIOP's aerosol subtyping reported in the literature, the available comparisons suggest that the CALIOP scheme is successful ∼70 % of the time; the best agreement occurs for dust, and the least agreement occurs for aerosol layers dominated by the fine mode (Mielonen et al, 2009).…”

A decadal cirrus clouds climatology from ground-based and spaceborne lidars above the south of France (43.9° N–5.7° E)

“…The fundamental sampling resolution of the lidar is 30 m vertical and 335 m horizontal. The high quality of processed CALIPSO data products has been demonstrated through validation campaigns (Winker et al, 2007;Vaughan et al, 2008) and comparisons studies with ground-based instruments (Plana-Fattori et al, 2009;Dupont et al, 2010;Thorsen et al, 2011). In this study, we compare the regional quality of climatological cirrus cloud properties from CALIOP to those observed from the ground-based lidar at the OHP.…”

“…In an area 100 km wide, CALIOP will only sample twice per 16 day repeat cycle, providing 45 sampling opportunities per year. Extending the domain to a 2 • × 6 • latitude-longitude box yields 300 (day + night) overpasses with about 45 samples each, resulting in about 14 000 samples (as in Dupont et al, 2010). Temperature used through the paper in relation with CALIOP data come from the GEOS-5 general circulation model reanalyses, which are included in CALIOP data files.…”

Satellite observations of cirrus clouds in the Northern Hemisphere lowermost stratosphere

“…There are a couple of recent studies on the properties of cirrus clouds at midlatitudes based on ground-based lidar observations (Dupont et al, 2010;Hoareau et al, 2013;Dionisi et al, 2013). The analyses show a significant and large proportion of optically thin cirrus clouds in the upper troposphere (42 % of all profiles, Hoareau et al, 2013), in the tropopause region (30 % of all and 9 % of the cloudy profiles, Dionisi et al, 2013), or, even more precisely localised, above the tropopause (up 10 % of all cloudy profiles, Rolf, 2013 , the cloud measurements show 5 % cross-tropopause cirrus (cloud base below and cloud top above the tropopause) and 2 % inter-tropopause (cloud base above tropopause) events.…”