Home » Emerging Technologies » Wide-Angle Imaging Lidar (WAIL)
Wide-Angle Imaging Lidar (WAIL)
Research Prototype
The current version of WAIL is an engineering prototype that can be deployed to remote locations. At present it needs to be attended to by its builder, Steve Love, from LANL.
Contact Steven P. Love: +1 (505) 667-0067, splove@lanl.gov
Emerging Technologies
WAIL, a ground-based cloud probing system, is cross between atmospheric lidar and the emerging technique of optical diffuse tomography in non-invasive medical diagnostics. It uses a pulsed laser beam against a cloud of any optical thickness and, in sharp contrast with standard “on-beam” lidar, the in-cloud flight time is interpreted in terms of multiple scattering. In “off-beam” lidar such as WAIL, horizontal transport away from the beam on the order of physical cloud thickness, and total in-cloud paths several more, are measurable and useful. As in optical tomography, the analytical theory of photon diffusion is a useful approximation for the return signal: a time-sequence of images---in effect, a movie---of the radiance emerging from cloud base built with a sufficient number of pulses. The main remote sensing products, beyond cloud base height (obtained from the on-beam part of the WAIL signal), are cloud thickness and volume-averaged extinction. The next generation of data analysis algorithm will also target the mean extinction profile and a statistical measure of internal optical variability. The current technology and analysis methodology is mature for nighttime boundary-layer clouds. Hardware evolution is being investigated to enable practical daytime observations. Data analysis techniques under consideration will extend WAIL to clouds with low optical depth, including cirrus, and even aerosol layers. Finally, particle size (at least near cloud base) can be retrieved by applying established techniques for near-beam multiple scattering returns; see MFOV lidar.
Anthony B. Davis
Jet propulsion Lab /California Institute of Technology
4800 Oak Grove Drive Mail Stop 169-237 Pasadena, CA 91109, USA
(818) 354-0450
DeveloperAnthony Davis
Development SectorFed/State Gov
R&D ProgramYes
Years Till Available3-5
Investment Required$100k-$1M
Projected ApplicationActive remote sensing of clouds of all optical depths
Unit Cost<$100k
Key RisksDaytime capability is the current technological challenge. Could however work in tandem with a high-resolution oxygen A-band spectrometer for daytime dense cloud remote sensing. Automated/remote operation not yet implemented.
Ease of Usesingle operator
Davis, A. B., Multiple-scattering lidar from both sides of the clouds: Addressing internal structure. J. Geophys. Res., vol. 113, D14S10, doi:10.1029/2007JD009666 (2008). Polonsky, I. N., S. P. Love, and A. B. Davis, The Wide-Angle Imaging Lidar (WAIL) Deployment at the ARM Southern Great Plains Site: Intercomparison of Cloud Property Retrievals, J. Atmos. and Oceanic Techn., vol. 22, 628-648 (2005). Love, S. P., A. B. Davis, C. Ho, and C. A. Rohde, Remote Sensing of Cloud Thickness and Liquid Water Content with Wide-Angle Imaging Lidar (WAIL), Atm. Res., vols. 59-60, 295-312 (2001). Davis, A. B., R. F. Cahalan, J. D. Spinhirne, M. J. McGill, and S. P. Love, Off-Beam Lidar: An Emerging Technique in Cloud Remote Sensing Based on Radiative Green-Function Theory in the Diffusion Domain, Phys. Chem. Earth (B), vol. 24, 177-185, Erratum 757-765 (1999).
The same physical principles as used for this remote measurement can be applied to any dense optical medium in the environment that is dominated by scattering (snow, sea-/land-ice, turbid coastal water, etc.); only field-of-view and other instrument parameters need to be adapted. WAIL may be of interest in aviation and maritime safety (cloud and visibility characterization).
6 Apr 2011 14:07