CALIOP high resolution IRF modeling based on in-situ observations and application to AOD retrieval.

Abstract:

The CALIOP Lidar system onboard the CALIPSO satellite delivers daily atmospheric cloud and aerosol data that is widely used throughout the Atmospheric Science community.
However, the lidar atmospheric returns suffer a number of modifications before downlinking which result in narrow-bandwidth signals. Additionally, the 532nm channel photomultiplier tube (PMT) detector introduces an artifact described in previous literature as “after-pulsing” or “tail effect” that has a direct impact on the received energy measurement.
We present here a technique that allows for the full characterization of the detection channel’s impulse response function (IRF) and the recovery of high-resolution signals. Emphasis is laid on the tail part of the 532nm channel’s IRF caused by the PMT. The technique involves the use of multiple surface return (SR) signals to derive a super-resolution model of the IRF. We then demonstrate the use of this model for ocean SR data fitting and the application to aerosol optical depth (AOD) retrieval and to the 1064nm channel calibration.