The extreme complexity, diversity and variability of atmospheric particles involved both in air quality and climate forcing require observations of aerosols
and clouds in their natural medium. Passive ground-based remote sensing measurements such as those performed by sunphotometer networks like AERONET although
highly relevant for the total column can not be used to derive information on aerosols vertical distribution.
However, active systems like LIDAR provide the aerosols as well as the thin clouds vertical profiles.
The last eruption of Eyjafjöll volcanoe during spring 2010 demonstrated the deficiency of present monitoring system,
which strongly impacted the human activities such as air traffic. Today, simple and automatic LIDAR systems are operated
by more and more research laboratories. Since 2006, LOA started developping the basis of small LIDAR network composed of single
wavelength (532 nm) elastic backscatter CIMEL micro-LIDAR (T. Podvin & D. Tanré).
Thanks to his expertize in instrumentation,
data processing and visualization tools acquired in the framework of the « Service d'Observation PHOTONS/AERONET »
LOA is now maintaining a couple of routinely (24h per day/7days a week) operating LIDAR in Lille (France),
M'Bour (Dakar, Senegal).
Real Time time series (day & night) of backscatter LIDAR power (Level 1) as well as daily variation of AOD and Angström exponent
plots derived from sunphotometer Level 1.5 data are publically available. The overall system (data acquisition, transfer and processing),
is quite evolutive (C. Deroo). For example, one additionnal Cimel LIDAR operated by LPAT from La Guadeloupe University was included in the system
in 2010 as well as short time observations periods at several locations.
Technical parameters of each system are also monitored and warning messages sent automatically if instrumental failures or data transfer problems occur.
An automatic inversion code for LIDAR data processing has been developped and is operating for Lille and Dakar sites (version 1).
Basically, during daytime only, LIDAR inversion is constrained using accurate sunphotometer AOD to derive aerosol extinction coefficient profile,
σext(z), as well as an average aerosol extinction-to-backsactter ratio, Sa, (Level 1.5a).
During night time, prescribed average Sa can be used to derive σext(z).
The entire archive (Level 1 and 1.5b) from 2006 to present time, for Lille and M'Bour sites have been processed with this LOA inversion code (P. Goloub & A. Mortier).
Version 2, in preparation, includes improvements on Level 1 Data Quality (update of instrument corrections), level 1.5a processing, estimate of boundary layer height, high altitude cloud detection.
Copyright : P. Goloub, Update from 10th november 2010