NCAR / Scripps Airborne Flask Sampler

Short Name or Variable Name:

Medusa

HAIS Instrument:

Manufacturer or Builder:

Britton Stephens

TABS

Description

Model:

32 (Medusa-32 superseded Medusa-16 when expanded from 16 to 32 flask capacity)

Measurements Provided:

Whole air samples collected under constant pressure and flow and cryogenically dried conditions. Typically measured for d(O2/N2), CO2, d(Ar/N2), and isotopologues of CO2

Typical Sampling Rates:

32 samples per flight

General Description:

Medusa provides the capability for collecting samples of air integrated over 30-s (1 e-fold) sample periods. 32 cryogenically dried 1.5 l air samples can be collected in glass flasks by an automated sampler that controls the flow and pressure to the flasks. As used for example in the HIPPO campaigns, Medusa provided discretely-sampled comparisons for onboard in situ O₂/N₂ ratio and CO₂ measurements and unique measurements of Ar/N₂ and ¹³C, ¹⁴C, and ¹⁸O isotopologues of CO₂. The complementary O₂ and CO₂ measurements allow ground-truthing of onboard instrument measurements in a laboratory setting, where analysis conditions can often be more stringently controlled and carefully monitored. Isotopologue and Ar/N2 measurements provide additional information about land and ocean controls over the carbon cycle, and other influences on the sampled air.
Medusa consists of an onboard computer, two pressure controllers, two pumps, three multi-position selector valves, and a host of other hardware that control and direct the air samples. All air is dried by passing it through traps immersed in a -78 C dry ice bath, adjusted to match atmospheric pressure at sea level, and then automatically isolated in a flask. HIPPO, ORCAS, and ATom flasks were later analyzed on a sector-magnet mass spectrometer and a LI-COR non-dispersive infrared CO₂ analyzer by the Atmospheric Oxygen Research Group at Scripps Institution of Oceanography.
EOL supports the sampler and its airborne operation. The 1.5 l glass flasks and their laboratory analysis must be provided by the requestor.