The AOS Carbon Monoxide Analyzer (AOSCO) instrument system measures two primary atmospheric trace gases - namely, carbon monoxide (CO) and nitrous oxide (N2O). These two trace gases are of importance to the study of atmospheric chemistry. Common sources of CO include the burning of fossil fuels and either natural or man-made fires. N2O, an atmospheric greenhouse gas, is produced naturally by bacteria and fungi in soils and in the oceans; anthropogenic sources include fertilized soils, among others.
Please monitor the b1-level aosco datastreams for all AOSCO instrument systems. When submitting DQPRs for the AOSCO, please use the CO-ANALYZER instrument class under the AOS Group.
For more information, please see the AOSCO Instrument web page.
The AOSCO is a component instrument within the Aerosol Observing System (AOS). For a more complete overview the AOS system and its general backing measurement theory, please see the AOS DQ Wiki page.
In the metrics table below, there are four primary measurements outlined; all other measurements are diagnostic in nature. Those primary fields are:
The primary carbon monoxide (CO) and nitrous oxide (N2O) mixing ratios are plotted on both daily and weekly timescales. Note that for both CO and N2O, the water-vapor-corrected fields are plotted alongside the non-corrected fields for comparison. The water vapor measurement - which is used to perform this water vapor correction - is plotted in the bottom panel; it is diagnostic in nature.
In addition to the primary trace gas mixing ratio fields, a number of CO diagnostic fields are also plotted to better monitor the "health" of the instrument. These diagnostic fields include cell pump pressures, instrument temperatures, and flow rates of sample air through the instrument system.
The AOSCO is currently deployed at ENA C1, AMF2 and AMF3. All systems operate in a similar manner.
Known behaviors do not require DQPRs or mentions in DQAs.
On a daily basis a ~10-20 sccm standard addition is introduced into the instrument flow and on a weekly basis, a 1 SLPM replacement calibration is done with the same standard. This means the instrument will display a spike between 00:00:00 and 00:05:00 UTC each day with the spike being larger once a week. This spike is associated with a calibration and should not be reported. If there are no spikes in a weekly plot an email should be sent to mentor asking if calibration should be performed but is not.
The following problems do need to be mentioned in DQAs and/or DQPRs.
Sometimes the pump that draws sample air through the instrument can fail. In these cases, large changes should be apparent in the cell pressure field. These pressure deviations will be flagged by a QC test in the metrics.
The Carbon Monoxide Analyzer is sensitive to temperature swings within its immediate surrounding environment. In the case below, there was a leak in the sample air line to the instrument that resulted in the instrument sampling cabin air that was cooled by air conditioners. The air conditioning cycles are evident in the instrument temperature time series (blue curve in bottom panel); the same cyclic signature is also evident in the primary mixing ratio data (top plot panels). See DQPR 5331 for more information.
If you see this behavior, please submit a DQPR.