Instrument : Doppler Lidar (DL)
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 Value-Added Products
This instrument is an input to the following value-added products, which provide improved measurements or derived quantities.
- dlcal1 : Doppler Lidar - calibration scan 1
- dlcal2 : Doppler Lidar - calibration scan 2
- dlfpt : Doppler Lidar - Fixed Pointing mode
- dlppi : Doppler Lidar - Plan Position Indicator
- dlrhi : Doppler LIDAR Range-Height Indicator scan
- dlrhi2 : Doppler Lidar - Patrial Range-Height-Indicator scan
- dlusr : Doppler Lidar -- ? user information ?
The following measurements are those considered scientifically relevant.
|Eastern North Atlantic|
|ENA||C1||Browse Data||Browse Plots||Graciosa Island, Azores, Portugal|
|North Slope Alaska|
|NSA||C1||Browse Data||Central Facility, Barrow AK|
|Southern Great Plains|
|SGP||C1||Browse Data||Central Facility, Lamont, OK|
|SGP||S01||Browse Data||Supplemental 1, Lamont, OK||retired|
|Tropical Western Pacific|
|TWP||C3||Browse Data||Central Facility, Darwin, Australia||retired|
|ARM Mobile Facility|
|MAO||M1||Browse Data||Manacapuru, Amazonas, Brazil; AMF1|
|OLI||M1||Browse Data||Oliktok Point, Alaska|
|PGH||M1||Browse Data||ARIES Observatory, Nainital, Uttarkhand, India||retired|
|PVC||M1||Browse Data||Highland Center, Cape Cod MA; AMF 1||retired|