Identification

Title

Airborne measurements of oxygen concentration from the surface to the lower stratosphere and pole to pole

Abstract

We have developed in situ and flask sampling systems for airborne measurements of variations in the O-2/N-2 ratio at the part per million level. We have deployed these instruments on a series of aircraft campaigns to measure the distribution of atmospheric O-2 from 0-14 km and 87 degrees N to 86 degrees S throughout the seasonal cycle. The National Center for Atmospheric Research (NCAR) airborne oxygen instrument (AO(2)) uses a vacuum ultraviolet (VUV) absorption detector for O-2 and also includes an infrared CO2 sensor. The VUV detector has a precision in 5 s of +/- 1:25 per meg (1 sigma) delta(O-2/N-2), but thermal fractionation and motion effects increase this to +/- 2:5-4.0 per meg when sampling ambient air in flight. The NCAR/Scripps airborne flask sampler (Medusa) collects 32 cryogenically dried air samples per flight under actively controlled flow and pressure conditions. For in situ or flask O-2 measurements, fractionation and surface effects can be important at the required high levels of relative precision. We describe our sampling and measurement techniques and efforts to reduce potential biases. We also present a selection of observational results highlighting the individual and combined instrument performance. These include vertical profiles, O-2 : CO2 correlations, and latitudinal cross sections reflecting the distinct influences of terrestrial photosynthesis, air-sea gas exchange, burning of various fuels, and stratospheric dynamics. When present, we have corrected the flask delta(O-2/N-2) measurements for fractionation during sampling or analysis with the use of the concurrent delta(Ar/N-2) measurements. We have also corrected the in situ delta(O-2 /N-2) measurements for inlet fractionation and hu- midity effects by comparison to the corrected flask values. A comparison of Ar/N-2-corrected Medusa flask delta(O-2/N-2) measurements to regional Scripps O-2 Program station observations shows no systematic biases over 10 recent campaigns (+0 :2 +/- 8 :2 per meg, mean and standard deviation, n = 86). For AO2, after resolving sample drying and inlet fractionation biases previously on the order of 10-100 per meg, independent AO2 delta(O-2/N-2) measurements over six more recent campaigns differ from coincident Medusa flask measurements by -0:3 +/- 7:2 per meg (mean and standard deviation, n = 1361) with campaign-specific means ranging from -5 to +5 per meg.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d7gb27gv

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

Text

originating controlled vocabulary

title

Resource Type

reference date

date type

publication

effective date

2016-01-01T00:00:00Z

Geographic location

West bounding longitude

East bounding longitude

North bounding latitude

South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

publication

effective date

2021-04-01T00:00:00Z

Frequency of update

Quality and validity

Lineage

Conformity

Data format

name of format

version of format

Constraints related to access and use

Constraint set

Use constraints

Limitations on public access

None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact