Sigma Space MPL (Micropulse LIDAR) measures the amount and vertical distribution of volcanic ash, clouds, and other aerosols above Bariloche, Argentina airport. View Map

See below for HOW TO INTERPRET THE DATA. 

HOW TO INTERPRET THE DATA

Based on the same principles as radar, the MPL transmits laser pulses into the atmosphere and receives the backscattered light.

The laser light transmitted by the MPL is polarized light. The MPL receiver measures the light scattered back from the atmosphere in two separate channels. One channel looks at the scattered light that has the same polarization as the transmitted light. This is the co-pol or co-polarization signal. The other channel looks at the scattered light whose polarization has changed, or rotated by 90 degrees, from the transmitted light. This is cross-pol or cross-polarization signal.

We are displaying two separate graphs of real-time data. The top one shows the co-polarized backscatter and the bottom one shows the ratio of the cross- and co-polarized backscatter, known as the depolarization ratio. The large depolarization ratio indicates the presence of volcanic ash (asymmetrical particles)—and gives the vertical distribution of volcanic ash above the airport. These lidar measurements are proportional to the amount of volcanic ash at a given height.