Instrument : High Spectral Resolution Lidar (HSRL)
The High Spectral Resolution Lidar (HSRL ) provides calibrated measurements of aerosol optical depth, volume backscatter coefficient, cross section, and depolarization. Measurements are computed from ratios of the particulate scattering to the measured molecular scattering. This provides absolute calibration and makes the calibration insensitive to dirt or precipitation on the output window. A very narrow, angular field-of-view reduces multiple scattering contributions. The small field-of-view, coupled with a narrow optical bandwidth, nearly eliminates noise due to scattered sunlight.
Description of Raw Data
The raw HSRL data are in NetCDF format and include four backscatter channels:
|molecular||=||molecular signal only|
These data are uncalibrated, but can be used to obtain a qualitative view of the atmospheric column. The file does not include a height variable, but the height can be calculated using the following expression:
delta_z (in meters) = binwidth_ns*(1.0e-9)*(3.0e8)/2.0
z (in meters) = ([0,1,2,3,...,bincount-1]-pulse_index)*delta_z
Where "binwidth_ns" and "pulse_index" are attributes of the four backscatter variables and bincount is the vertical dimension.
Note: the first several z values will be negative because the system records background data for a few nanoseconds before sending out the pulse.
To derive physical properties like optical extinction, the high and low gain channels will be merged to provide a unified aerosol+molecular profile and combined with the other channels. These higher order products will be available soon.
Shipley, ST, DH Tracy, EW Eloranta, JT Trauger, JT Sroga, FL Roesler and JA Weinman, "A High Spectral Resolution Lidar to measure optical scattering properties of atmospheric aersols, Part I: Instrumentation and theory" Applied Optics, 23, 3716 – 3724, 1983.
Piironen, P, and EW Eloranta, "Demonstration of a high spectral resolution lidar based on an iodine absorption filter," OL 19, 234 – 236, 1994.
Piironen, P, "A High Spectral Resolution Lidar Based on an Iodine Absorption Filter", Ph.D. Thesis, University of Joensuu, Department of Physics, 1994.
- hsrl : High Spectral Resolution Lidar
The following measurements are those considered scientifically relevant.