Micropulse Lidars Get Boost from Recovery Act

Published: 15 August 2010

Shown here during installation on the aft deck of the RV Connecticut, the upgraded MPL includes a sleek new computer that can fit into smaller spaces. The laser window at the top is covered by a cone until the instrument is turned on.
Through funding from the American Recovery and Reinvestment Act of 2009, ARM is upgrading the micropulse lidars (MPL) throughout the user facility. Similar to a radar, the MPL sends pulses of energy into the atmosphere. Signals scattered back to the transceiver are used to characterize the extent and properties of aerosol, clouds, or other particulates in the lowest 15 kilometers of the atmosphere. On July 19, the first official data ingest from the upgraded instrument began arriving at the ARM Data Archive.

The original MPLs transmit in a single polarization state for one averaging period (about 3 seconds) and then the other state for the next averaging period. This separates the data by several seconds, which can lead to ambiguity in the interpretation of the data. As each MPL is refurbished, it will be able to switch polarity with each pulse, essentially recording data simultaneously (separated by .0004 seconds) in separate channels. This reduces much of the uncertainty in the interpretation of the data.

A hybrid system was deployed at the ARM Southern Great Plains (SGP) site in December 2009 for a testing and evaluation period. Based on successful side-by-side operations with the existing MPL and data analysis, plans were implemented to move forward with upgrades to all the MPLs throughout the user facility using funds from the Recovery Act. The first refurbished MPL was shipped to Greenland in May to support the ICECAPS field campaign. On June 1, the hybrid MPL replaced the operational system to collect routine data from the SGP site. Another upgraded MPL was deployed during ship testing for the second ARM Mobile Facility in late June.

In late June, an upgraded MPL (inside the silver casing) underwent ship testing.The new data ingest provides the data in much the same format as the original MPL data ingest. Watch this video for an explanation of the data by Rich Coulter, a scientist at Argonne National Laboratory, who supervised the instrument upgrades and ship test.