What is Lidar?
Lidar is similar to radar, but employs light. Pulses of light, produced by a powerful laser, are fired upward throught the atmopshere. These pulses excite sodium atoms in the mesosphere, about 90 kilometers above the Earth's surface. The excited sodium atoms re-emit the photons that they absorb, some of which propagate downward towards a receiving telescope. Each photon collected by the telescope is measured, and its time of arrival is recorded. From the time difference between the reception of the photon, and the firing of the laser pulse, the distance to the sodium atom can be determined. In this way, it is possible to determine the number of sodium atoms as a function of altitude.
Recent Results
This image shows sodium density above the facility as a function of altitude (75 to 105 km) and time (horizontal direction, covering about 5 hours) on the night of August 5, 2008.
Here we see a layer of sodium atoms becoming unstable and developing vortices. The vertical extent is 5 km and the elapsed time is 20 min.
The LZT lidar facility is the Ph.D. project of UBC graduate student Thomas Pfrommer.