Le concentrazioni di CO, CO2, CH4 e la percentuale di H2O sono misurate utilizzando l’analizzatore PICARRO G2401; tale strumento si basa sulla tecnologia Cavity-Ring-Down Spectroscopy (CRDS) che, dall’analisi dell’attenuazione di un segnale laser su un cammino ottico di 20 km, permette di valutare in modo accurato e selettivo le concentrazione dei gas. Lo strumento è stato tarato sulla base di miscele di taratura fornite dal World Calibration Center (NOAA-GMDL) della rete WMO/GAW. Ogni 48 ore vengono eseguite tarature di routine utilizzando working standard commerciali.

Instrument (Picarro G2401) is connected by a Synflex 1300 (OD: ¼”) to the air intake manifold. Antiparticulate filter (Svagelock) are present at the instrument inlet.

Scale and calibration: WMO-CH4-X2004, WMO-CO-X2014, WMO-CO2-X2007.

CALIBRATION STANDARDS: A set composed by n.3 calibration standards from NOAA-GMDL is available at the Lamezia Terme station: CB11039, CB11164, CB10928. They represent the I-AMICA network laboratory primary standards. These calibration standards will be compared every 6 months against the station working standards for evaluating possible working standard drifts and directly to the instrument to evaluate the stability of calibration factors.

WORKING STANDARD: For each gas, two working standards (6 cylinders in total) with CO2,CH4 and CO representing upper and lower ranges of the expected ambient variability are used to perform automatic calibration every 48 h. Working standard are provided by SOL S.p.A. 48h calibration are performed at different time from one day to another. Avoiding to perform routinely calibrations at the same hour of day, helps in increasing the representativeness of the measurements at daily scales and allows to determine possible problems occurring at different time of day (e.g. related with laboratory ambient conditions). Two-stage stainless steel pressure regulators for high purity gas are used (HARRIS Calorific mod. LHP 742 N2).

Data are recorded on a 5sec basis by the Picarro internal PC and mirrored to a station server, then delivered in NRT mode to ISAC-CNR HQs in Lamezia Terme, where 1-minute averages are calculated. Final aggregation to hourly average will be executed by using validated 1-min data. On hourly basis data will be flagged to identify “background” observations. This can be done both by considering wind sector (with the aim of selecting observations under sea breeze conditions, thus neglecting influence from in-land contributions) as well as by using de-spiking procedures as proposed by Thoning et al. [1989]

Information about instrument functioning and intervention are stored within an e-logbook. Instrument manual are present at the station.

SOP are extracted by the: GAW Report No. 185 “Guidelines for the Measurement of Methane and Nitrous Oxide and their Quality Assurance”, GAW Report No. 192 “Guidelines for the Measurement of Atmospheric Carbon Monoxide”; GAW Report No. 213 “17th WMO/IAEA Meeting on Carbon Dioxide, Other Greenhouse Gases and Related Tracers Measurement Techniques”.