Comparison of BrO Diurnal Variations as Measured by Ground Based Long-Path DOAS and Remotely by Satellite (GOME-2)

Halogen activation processes in the lower polar troposphere play an important role in ozone destruction events (ODEs) during polar spring. Several studies in the past investigated halogen oxide radicals (BrO, ClO, IO) as indicators for halogen activation. Similar amounts of BrO are detected in both the Arctic and the Antarctic, while IO concentrations appear to be much lower in the Arctic. In comparison to bromine compounds, which are released by inorganic heterogeneous chemistry (bromine explosion), reactive iodine probably originates mainly from organic precursors. Halogen activation is thought to take place on widely different scales ranging from hundreds of kilometers down to centimeters. In particular, the origin of precursors triggering the process and the actual conditions that may result in a bromine explosion are poorly understood. Thus combining studies by satellite (several hundreds of km) to the resolution of ground based instrumentation (order of meters) should provide further insight. Within the OASIS framework in the scope of the International Polar Year (IPY), active long-path differential optical absorption spectroscopy (LP-DOAS) measurements were carried out on board the Amundsen research vessel in the Amundsen Gulf in March and April 2008. These LP-DOAS measurements clearly reveal high BrO concentrations in the air above the surface during daylight and during periods of low ozone mixing ratios. Instruments on polar orbiting satellites (e.g. GOME, SCIAMACHY, OMI, and GOME-2) usually observe a given site once per day, however at high latitudes each location is scanned several times a day thus allowing to record diurnal profiles. For the first time, active DOAS measurements of BrO are compared with diurnal profiles measured by the GOME-2 instrument on board the MetOp satellite. Implications on the understanding of the underlying chemical mechanisms are discussed.