No.8

Introduction
Data Policy
Data
Documentation
Contact Information



Cape Point

-CO-

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Observation
Category : Air sampling observation
Situation : ongoing
Time zone : UTC


Sampling
Sampling height : 30
Description : continuous
Sampling and analysis frequency : 12-minute
Sampling environment :
Description for sampling analysis : GC in combination with AAS

The height of the ambient air intake is 260 m above sea level from the top of a 30 m high mast.
Two freezing units (-4 and -45 °C respectively) are used in series to dry the ambient air prior to analysis.
30-metre 1/4 inch stainless steel air intake


Instrument and Analysis
Measurement method : Gas Chromatography (other)
Current status and history of instrument : GC-Mercuric Oxide Detector (RGA 3)
Description of instrument : RGA3 Trace Analytical


Calibration
Current scale employed in the measurement : 1978-2002:CPT scale, 2003-present:NOAA scale
Measurement calibration : Calibrations are automatically performed every two hours and the target gas once daily.
Scale and calibration(treasability) : 1978 - 2002 (CPT scale)
2003 - present (NOAA scale)


Data Processing
Measurement unit : ppb
Data processing : All data with obvious sampling or analytical error are rejected. Furthermore, a statistical filter (moving percentiles) is applied for the selection of background concentrations. Data selection applied to the "all data set" (based on statistical filtering)are done as follows:
Two 11-day moving percentiles are applied to the data. The two freely selectable percentiles, each tuneable by a factor, serve as upper and lower cut-off limits for background concentration selection.
Calibration data are omitted from final reported data set.
Processing for averaging :

Data flag : All data reported a valid. Calibration data are removed from final reported data set.
Data remarks :


Other Information
Scientific aim : Long-term measurements of tropospheric CO representative of air masses advected from the SW Atlantic ocean.
Reference :


submitted by South African Weather Service

The WDCGG is operated by the Japan Meteorological Agency
in collaboration with the World Meteorological Organization