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Picarro G2401 gas analyzer

The instrument is measuring CO2, CH4, CO and H2O at Hyytiälä SMEAR II site (61 51'N 24 17'E, 181 m a.s.l).
Three levels are measured (16.8m, 67.2m and 125m), each 10 minutes at a time. Buffer volumes (5.6 l) are used to average out the high frequency variation in the concentrations allowing simultaneous measurements from all levels with one instrument.
For more information about the measurements, contact Petri Keronen (petri.keronen (at) helsinki.fi)

The figures are updated several times in a day.

In case the plots produced by ATC are not up to date you might find more recent versions here.

Data from last 10 days (ICOS ATC):

Data from last 3 days (ICOS ATC):

Data from the past week (local processing)

Time series of 10 min averaged concentrations from the three levels.


Time series of 10 min standard deviations of concentrations from the three levels. In principle, if buffer volumes average out succesfully all high frequency variation from the data, the standard deviations should relate only to instrument precision and thus should be relatively constant. For CO2, CH4, CO and H2O the values should mainly be around < 0.05 ppm, < 0.0005 ppm,  < 0.01 ppm and 0.003 %, respectively. Intermittent higher values of standard deviation occur, but continous increase in any of the signals is a sign of error (e.g. buffer volumes do not average enough or analyser is faulty).

Diagnostic data from the last month (ICOS ATC):

Top: Flow through the instrument (aka sample flow), The in-situ sample flow rate should be around 200 ml/min (+/- 10 ml/min). The daily runs of the target gas have a higher flow rate and
this causes the seemingly peaks in the data. Likewise the bi-monthly calibration runs causes the highest sample flow rates in the data.
Middle: temperature inside the cottage. Bottom: flushing (aka F-Main) flows in the sample lines .

Data from the past week (local processing)


Top upper: flows through the buffer volumes in mV. Top lower: flows through the buffer volumes in ml/min. Middle: flows in the main sampling lines in l/min (F-main1=16.8 m level, F-main2=67.2 m level, F-main3=125 m level). Bottow upper: flow through the instrument in mV. Bottom lower: flow through the instrument in ml/min. In order to get correct averaging with the buffer volumes the flow through the volumes should ideally be the same for all levels with approximate value 350 ml/min (acceptable interval between 320 ml/min and 390 ml/min). The sample flow should be around 200 ml/min (+/- 10 ml/min) for the in-situ measurement levels. Occasional deflections from the acceptable levels may occur due un-synchronous valve operation or electronic signal logging errors.




The internal temperature of the Picarro analyser. It should be < 40 C.

Data from today

Diagnostic data

Calibration and target gases

Previous succesful calibration.


Previous successfull sampling periods of calibration gases L, M and H. Bold dots show 1 min means. For each of the 30 min sampling period, 20 min is reserved for flushing of the sample lines and the analyser, and then the last 10 min of the data are used to estimate the concentrations. The vertical dashded line indicates the 20 min time line.



Previous successfull sampling periods of target gases T1 and T2. Bold dots show 1 min means. For each of the 30 min sampling period, 20 min is reserved for flushing of the sample lines and the analyser, and then the last 10 min of the data are used to estimate the concentrations. The vertical dashded line indicates the 20 min time line.


Time series of target gas T1 and T2 measurements.



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