Measurements of CO2
concentration are carried out on a weekly basis since 1992 on the island of Lampedusa
(35.5°N, 12.6°E), in the Mediterranean.
Measurements are based at the Station for Climate Observations, which rests on
a rocky plateau (45 m asl) on the North-Eastern coast of the island, and are
made with a NDIR analyzer. World Meteorological Organization (WMO) reference standards are used for
calibrations. Continuous measurements
were started in 1998; they were interrupted in early 2003, and activated again
in 2005. The continuous observations show evidence of a small daily cycle
(amplitude < ±1 ppm) only during the months of June, July, and August. Mean
annual cycles derived from weekly flask measurements show a dependency on the
wind origin: the annual cycle and the annual CO2 mean are smaller
for winds originating from the Southern sectors, than for winds from Northern
sectors. The continuous measurements were combined with daily backward airmass
trajectories to identify the dependency of the CO2 amount on the
airmass origin. Trajectories provided by National Oceanic and Atmospheric
Administration / Air Resources Laboratory (Hysplit) are used. During winter,
low CO2 is generally connected to Southern/South-Eastern airmasses.
In summer airmasses from North often display lower CO2 content, due
to the influence of the European sink.
Author: A. di Sarra, P. Chamard, S. Piacentino, et al (disarra at casaccia dot enea dot it)
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