Airborne Observations of Atmospheric O2 and CO2 on Regional to Global Scales

Britton Stephens (NCAR, Boulder, USA and NIWA, Wellington, New Zealand)

Coauthors: Steve Shertz and Andrew Watt (NCAR), Jonathan Bent and Ralph Keeling (SIO), Steve Wofsy, Bruce Daube, Rodrigo Jimenez and Eric Kort (Harvard), Sara Mikaloff-Fletcher (NIWA)

Can be measured with:

1.Interferometer2.Mass-spectrometer3.Paramagnetic analyzer4.Fuel-cell analyzer5.Gas chromatograph6.VUV absorption analyzer

Atmospheric O2 Measurements

Provide insight into:

1.Global land-ocean carbon flux partitioning2.Oceanic transport and exchange of O2 and CO2

3.Seasonal ocean productivity4.Air-sea gas-exchange5.Plant physiology6.Fossil-fuel emission signals7.Atmospheric transport

O2/N2 (per meg) =

[(O2/N2)sample/(O2/N2)reference -1]x 106

NCAR Airborne Oxygen Instrument (AO2)

• Vacuum ultraviolet absorption technique

• Xe lamp (147 nm) and CsI detector

• Adapted from shipboard design (Stephens et al., 2003)

• Active pressure and flow control to 10-6

• Switches every 2.5 seconds between sample and WT gas

• 5-second 1-sigma precision of ± 2 per meg

• Factor of 2-5 motion degradation is correctable

O2 sensor

Flow control:

NCAR Airborne Oxygen Instrument (AO2)

System components:

NCAR Airborne Oxygen Instrument (AO2)

8-hour flight

3-min cal

Stratosphere-Troposphere Analyses of Regional Transport

START-08

• PIs: Laura Pan (NCAR), Elliot Atlas (U. Miami), Ken Bowman (TAMU)

•NSF / NCAR Gulfstream V•April – June, 2008•Physical and chemical studies of the UTLS region•20 flights for a total of 111 hours

June 23, 2008 at 1600 LT

Descent into Grand Forks, ND

Boundary-layer transition

HIPPO

• PIs: Harvard, NCAR, Scripps, NOAA

• Global and seasonal survey of CO2, O2, CH4, CO, N2O,

H2, SF6, COS, CFCs, HCFCs,

O3, H2O, black carbon, and

hydrocarbons

• NSF / NCAR Gulfstream V

• 5 campaigns over 4 years

• HIPPO1 in January of 2009, with 13 flights for 85 hours

• Continuous profiling from surface to 10 km and to 15 km twice per flight

HIAPER Pole-to-Pole Observations of Atmospheric Tracers

HIPPO Flight tracks January 2009

January 12, 2009

HIPPO Profile at 80 N

January 20, 2009

HIPPO Profile at 65 S

Southern Ocean O2 outgassing

Comparison to HIPPO flask samples

• Possibly related to temperature gradients in reference cylinders• Temperatures were measured at 6 points in the cylinder box• Options exist for back-correcting and revising procedures to minimize effect

O2 Cross Section, January, 2009

per meg

CO2 Cross Section, January, 2009

AO2 Instrument

ppm

APO Cross Section, January, 2009

Atmospheric Potential Oxygen:APO = O2 + 1.1*CO2

per meg

Preliminary model comparisons

Fluxes:

Mean ocean O2: Gruber et al., 2001Seasonal ocean O2 and N2: Garcia and Keeling, 2001Mean ocean N2: Gloor et al., 2001Seasonal + mean ocean CO2: Takahashi et al., 2009Fossil-fuel CO2 and O2: CDIAC

January Mean APO from Climatological fluxes in TM3HIPPO1 APO Observations

per meg

Looking ahead:• Laboratory experiments to isolate source of in situ – flask offset

• Software improvements to reduce remaining motion sensitivity

• 4 more HIPPO campaigns: Oct/Nov 2009, Apr 2010, Jun 2011, Sep 2011

• We welcome collaboration with atmospheric, oceanic, and terrestrial modelers