Extinction coefficients retrieved in deep tropical ice clouds from lidar observations using a CALIPSO-like algorithm compared to in-situ measurements from the cloud integrating nephelometer during CRYSTAL-FACE1Laboratoire de Météorologie Dynamique, Palaiseau, France
2NASA Langley Research Center, VA, USA
3Univ. of Utah, UT, USA
4NASA Goddard Space Flight Center, Greenbelt, ML, USA
Abstract. This paper presents a comparison of lidar ratios and volume extinction
coefficients in tropical ice clouds, retrieved using observations from two
instruments: the 532-nm Cloud Physics Lidar (CPL), and the in-situ Cloud Integrating Nephelometer (CIN) probe. Both instruments
were mounted on airborne platforms during the CRYSTAL-FACE campaign and took
measurements up to 17 km. Coincident observations from two cases of ice
clouds located on top of deep convective systems are compared. First, lidar
ratios are retrieved from CPL observations of attenuated backscatter, using
a retrieval algorithm for opaque cloud similar to one used in the recently
launched CALIPSO mission, and compared to results from the regular CPL
algorithm. These lidar ratios are used to retrieve extinction coefficient
profiles, which are compared to actual observations from the CIN in-situ
probe, putting the emphasis on their vertical variability. When observations
coincide, retrievals from both instruments are very similar, in the limits
of colocation. Differences are generally variations around the average
profiles, and general trends on larger spatial scales are well reproduced.
The two instruments agree well, with an average difference of less than
11% on optical depth retrievals. Results suggest the CALIPSO Deep
Convection algorithm can be trusted to deliver realistic estimates of the
lidar ratio, leading to good retrievals of extinction coefficients.
Citation: Noel, V., Winker, D. M., Garrett, T. J., and McGill, M.: Extinction coefficients retrieved in deep tropical ice clouds from lidar observations using a CALIPSO-like algorithm compared to in-situ measurements from the cloud integrating nephelometer during CRYSTAL-FACE, Atmos. Chem. Phys., 7, 1415-1422, doi:10.5194/acp-7-1415-2007, 2007.