MicroPulse DIAL (MPD)
The Micro-pulse Differential Absorption Lidar (MicroPulse DIAL, or MPD) is a compact, field-deployable, eye-safe lidar that offers continuous unattended monitoring of water vapor, temperature, and quantitative cloud/aerosol properties in the lower troposphere. A network of five water vapor MPD units has been constructed with four currently available to the research community. These instruments can be used to advance knowledge in a variety of areas, including the temporal and spatial distribution of boundary layer temperature and water vapor, convection initiation, and land-atmosphere exchange.
The multi-system MPD network can provide continuous high-vertical resolution water vapor and temperature profiling across a user-defined area of observations. Water vapor and temperature are the fundamental thermodynamic variables that define the state of the atmosphere. Water vapor is highly variable in space and time and influences many important processes related to weather and climate. The ability to continuously measure these thermodynamic variables in the lower troposphere with high vertical resolution has been identified as a priority observation needed by the weather forecasting, atmospheric science, and climate science communities.
MPD is a combination of three lidars in one unit. A water vapor Differential Absorption Lidar (DIAL) measures absolute humidity, a High Spectral Resolution Lidar (HSRL) measures calibrated aerosol backscatter coefficient, and an oxygen DIAL measures temperature. These techniques provide accurate and calibration-free measurements requiring a minimal set of assumptions.
The use of a diode laser (semiconductor active medium) in a lidar has distinct benefits. The lasers are considerably more compact, reliable, and less expensive than typical lasers used for lidar instrumentation. The diode-laser-based lidar architecture uses continuous wave seed lasers that are amplified into pulses at high repetition rates. For high-quality daytime operation, suppression of the solar background is achieved with a narrow receiver field-of-view and extremely narrow-band optical filters. The transmitted laser beam is eye-safe and invisible (Class 1M) and the receiver uses single photon counting detectors.
|Nominal Wavelengths||828.2 nm, 770 nm|
|Pulse length||0.6 μs to 1.0 μs|
|Nominal Pulse Energy||5 µJ|
|Pulse repetition rate||7-9 kHz|
|Receiver Field of View||100 µrad|
|Receiver bandpass||10-20 pm full-width half max)|
|Vertical resolution||150 m|
|Vertical range||250-4000 m|
2-sec sample resolution
5-10 minute actual resolution
NCAR/EOL MPD Team. (2018). MicroPulse DIAL (MPD). UCAR/NCAR - Earth Observing Laboratory.