WAIL was deployed as a part of multi-instrument campaign in March 2002 at the ARM Climate Research Facility in Oklahoma. A more recent analysis [Polonsky et al., 2005] of the collected data demonstrated good accuracy for the retrieved cloud parameters, presently, geometrical and optical thicknesses as well as the classic laser ceilometry product, cloud base height. Using the WAIL data, we find: cloud top and bottom altitudes at ±20%, and the cloud extinction coefficient at ±6%. This makes WAIL an efficient and cost-effective solution for probing optically thick clouds. In view of certain suboptimal settings during the 2002 campaign, this is a worse-case accuracy for nighttime operation. We have investigated mitigating strategies for the solar background noise that complicates daytime operation [Love et al., 2002]. We are currently upgrading the photon diffusion model to incorporate, hence access in retrieval mode, the in-cloud stratification of the extinction coefficient. We thus plan to restore full profiling capability for lidar remote sensing in the presence of a dense cloud layer, a situation where it was previously reduced to an active ceilometry method.
Finally, the imaging capabilities of WAIL offer the possibility to explore the aerosol layer situated between the probed cloud and the sensor, or even under clear skies. Similarly to how it has been exploited in Multiple Field of View (MFoV) lidar [Bissonnette et al., 2002], the angular dependence of the signal allows us to determine aerosol characteristics such as extinction coefficient and phase function as a function of altitude. In the case of WAIL however, much larger zenith angles can also be accessed and the analytical small-angle approximation is replaced by a numerical model.
Bissonnette, L., G. Roy, L. Poutier, S. Cober, and G. Isaac, 2002: Multiple-Scattering Lidar Retrieval Method: Tests on Monte Carlo Simulations and Comparisons with in situ Measurements, Appl. Opt., 41, 6307-6324.
Davis, A. B., R. F. Cahalan, J. D. Spinhirne, M. J. McGill, and S. P. Love, 1999: Off-beam lidar: An Emerging Technique in Cloud Remote Sensing Based on Radiative Green-Function Theory in the Diffusion Domain, Phys. Chem. Earth (B), 24, 177-185 (Erratum 757-765).
Love, S. P., A. B. Davis, C. A. Rohde, L. Tellier, and C. Ho, 2002: Active Probing of Cloud Multiple Scattering, Optical Depth, Vertical Thickness, and Liquid Water Content using Wide-Angle Imaging Lidar, S.P.I.E. Proceedings, vol. 4815: "Atmospheric Radiation Measurements and Applications in Climate," J. A. Shaw (ed.), pp. 129-138.
Polonsky, I. N., S. P. Love, and A. B. Davis, 2005: The Wide-Angle Imaging Lidar (WAIL) Deployment at the ARM Southern Great Plains Site: Intercomparison of Cloud Property Retrievals, J. Atmos. and Oceanic Techn., 22, 628-648.