Instrument : Doppler Lidar (DL)

Instrument Categories
Cloud Properties

Picture of the Doppler Lidar
Picture of the Doppler Lidar

General Overview

The Doppler Lidar (DL) is an active remote sensing instrument that provides range- and time-resolved measurements of radial velocity and attenuated backscatter. The principle of operation is similar to radar in that pulses of energy are transmitted into the atmosphere; the energy scattered back to the transceiver is collected and measured as a time-resolved signal. From the time delay between each outgoing transmitted pulse and the backscattered signal, the distance to the scatterer is inferred. The radial or line-of-sight velocity of the scatterers is determined from the Doppler frequency shift of the backscattered radiation. The DL uses a heterodyne detection technique in which the return signal is mixed with a reference laser beam (i.e. local ocsillator) of known frequency. An on-board signal processing computer then determines the Doppler frequency shift from the spectra of the heterodyne signal. The energy content of the Doppler spectra can also be used to determine attenuated backscatter.

The DL operates in the near-IR (1.5 microns) and is sensitive to backscatter from micron-sized aerosols. Aerosols are ubiquitous in the low troposphere and are ideal tracers of atmospheric winds. Thus, in contrast to radar, the DL is capable of measuring wind velocities under clear-sky conditions with very good precision (typically ~10 cm/sec). The DL also has full upper-hemispheric scanning capability, enabling the three-dimensional mapping of turbulent flows in the atmospheric boundary layer. When the scanner is pointed vertically, the DL provides height- and time-resolved measurements of vertical velocity.

Output Datastreams

  • dlcal1 : Doppler Lidar - calibration scan 1
  • dlcal2 : Doppler Lidar - calibration scan 2
  • dlfpt : Doppler Lidar - Fixed Pointing mode
  • dlppi : Doppler Lidar - Full Plan-Position-Indicator
  • dlrhi : Doppler Lidar - Full Range-Height-Indicator scan
  • dlrhi2 : Doppler Lidar - Patrial Range-Height-Indicator scan
  • dlusr : Reserved for any user-defined scans

Primary Measurements

The following measurements are those considered scientifically relevant.

Locations

North Slope Alaska
NSAC1Browse DataCentral Facility, Barrow AK
Southern Great Plains
SGPC1Browse DataCentral Facility, Lamont, OK
SGPS01Browse DataSupplemental 1, Lamont, OK
Tropical Western Pacific
TWPC3Browse DataCentral Facility, Darwin, Australia
ARM Mobile Facility
MAOM1Browse DataManacapuru, Amazonas, Brazil; AMF1
OLIM1Browse DataOliktok Point, Alaska
PGHM1Browse DataARIES Observatory, Nainital, Uttarkhand, India
PVCM1Browse DataHighland Center, Cape Cod MA; AMF 1

Contact(s)

Rob Newsom
(509) 372-6020
rob.newsom@pnnl.gov