MicroPulse DIAL (MPD)

Science motivation

MPD01 Deployed near Córdorba Argentina (Nov 2018)

Water vapor is one of the fundamental thermodynamic variables that define the state of the atmosphere. It is highly variable in space and time and influences many important processes related to weather and climate. The ability to continuously measure water vapor 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. National Research Council Studies list continuous, high-vertical-resolution, profiles of water vapor as one of the highest priority observations. Plus, these observations are of high importance to the National Weather Service and other Federal agencies for improvement of both severe weather forecasts and quantitative precipitation forecasts.

Radiosondes, combined with satellite-based measurements, form the backbone of observations used for weather forecasting. However the limited spatial and temporal observations prohibit forecasting of mesoscale high-impact weather events like thunderstorms. Passive sensors -- e.g., infrared and microwave radiometers -- are useful at low ranges close to the surface but only provide coarse vertical resolutions and are unable to detect elevated water vapor layers. GPS receivers only provide the integrated column measurements of precipitable water vapor. Raman lidars, and high-power water vapor Differential Absorption Lidar or DIAL (e.g., injection seeded Ti:sapphire laser systems) provide the high spatial and temporal measurements of water vapor that are desired, however they are inherently large and expensive instruments to build, operate, and maintain.

Development of the MPD testbed

Researchers at Montana State University MSU and NCAR have pioneered, demonstrated, and validated a micropulse, diode-laser-based, differential absorption lidar for water vapor profiling in the lower troposphere.  This development effort was initally just called by the name of the technique: Water Vapor Differential Absorption Lidar (WV-DIAL). Building on the proven design, we have developed five compact field deployable units, now called MicroPulse DIAL (MPD).  These instruments are capable of measuring water vapor in the lower troposphere with the appropriate vertical range, resolution, and measurement time needed for monitoring, verification, and data assimilation.  The five unit testbed is enabling the first tests of larger scale ground-based water vapor profiling networks.

Example data from the RELAMPAGO field campaign