Abstract
Abstract. We derive tropospheric column BrO during the ARCTAS and ARCPAC field campaigns in spring 2008 using retrievals of total column BrO from the satellite UV nadir sensors OMI and GOME-2 using a radiative transfer model and stratospheric column BrO from a photochemical simulation. We conduct a comprehensive comparison of satellite-derived tropospheric BrO column to aircraft in-situ observations of BrO and related species. The aircraft profiles reveal that tropospheric BrO, when present during April 2008, was distributed over a broad range of altitudes rather than being confined to the planetary boundary layer (PBL). Perturbations to the total column resulting from tropospheric BrO are the same magnitude as perturbations due to longitudinal variations in the stratospheric component, so proper accounting of the stratospheric signal is essential for accurate determination of satellite-derived tropospheric BrO. We find reasonably good agreement between satellite-derived tropospheric BrO and columns found using aircraft in-situ BrO profiles, particularly when satellite radiances were obtained over bright surfaces (albedo >0.7), for solar zenith angle <80° and clear sky conditions. The rapid activation of BrO due to surface processes (the bromine explosion) is apparent in both the OMI and GOME-2 based tropospheric columns. The wide orbital swath of OMI allows examination of the evolution of tropospheric BrO on about hourly time intervals near the pole. Low surface pressure, strong wind, and high PBL height are associated with an observed BrO activation event, supporting the notion of bromine activation by high winds over snow.
Highlights
Bromine plays an important role in tropospheric ozone chemistry and the resulting oxidation capacity of the polar boundary layer
We present a series of figures for various Aircraft and Satellite (ARCTAS) and ARCPAC flights
We show plots of various parameters that affect the sensitivity of the satellite measurements to tropospheric Bromine monoxide (BrO) and note times and places where satellite observing conditions are not ideal for inferring reliable tropospheric BrO amounts
Summary
Bromine plays an important role in tropospheric ozone chemistry and the resulting oxidation capacity of the polar boundary layer. Wagner and Platt (1998) and Richter et al (1998) estimated tropospheric VCD of BrO using this approach from GOME observations, based on simple assumptions for stratospheric BrO These studies and many others assumed that stratospheric BrO is zonally symmetric and that bromine was supplied to the stratosphere solely by the decomposition of long-lived organic compounds. Salawitch et al (2010) provided an initial analysis of BrO observations obtained by instruments aboard the NASA and NOAA aircraft (Neuman et al, 2010; Liao et al, 2011b) and the OMI satellite instrument (Kurosu and Chance, 2011) during spring 2008 They simulated the stratospheric BrO column assuming VSL bromocarbons supply between 5 and 10 ppt of Bry to the stratosphere in the form of product gas injection (PGI), in addition to the ∼2 ppt of Bry supplied by source gas injection (SGI) of the VSL species CH2Br2. 2.1 Aircraft in-situ measurements (a) NASA DC-8 aircraft during ARCTAS and (b) NOAA WP-3D aircraft during ARC
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