Probing the subtropical lowermost stratosphere and the tropical upper troposphere and tropopause layer for inorganic bromine

Abstract

Abstract. We report measurements of CH 4 (measured in situ by the Harvard University Picarro Cavity Ringdown Spectrometer (HUPCRS) and NOAA Unmanned Aircraft System Chromatograph for Atmospheric Trace Species (UCATS) instruments), O 3 (measured in situ by the NOAA dual-beam ultraviolet (UV) photometer), NO 2 , BrO (remotely detected by spectroscopic UV-visible (UV-vis) limb observations; see the companion paper of Stutz et al., 2016), and of some key brominated source gases in whole-air samples of the Global Hawk Whole Air Sampler (GWAS) instrument within the subtropical lowermost stratosphere (LS) and the tropical upper troposphere (UT) and tropopause layer (TTL). The measurements were performed within the framework of the NASA-ATTREX (National Aeronautics and Space Administration -Airborne Tropical Tropopause Experiment) project from aboard the Global Hawk (GH) during six deployments over the eastern Pacific in early 2013. These measurements are compared with TOMCAT/SLIMCAT (Toulouse Off-line Model of Chemistry And Transport/Single Layer Isentropic Model of Chemistry And Transport) 3-D model simulations, aiming at improvements of our understanding of the bromine budget and photochemistry in the LS, UT, and TTL.Changes in local O 3 (and NO 2 and BrO) due to transport processes are separated from photochemical processes in intercomparisons of measured and modeled CH 4 and O 3 . After excellent agreement is achieved among measured and simulated CH 4 and O 3 , measured and modeled [NO 2 ] are found to closely agree with ≤ 15 ppt in the TTL (which is the detection limit) and within a typical range of 70 to 170 ppt in the subtropical LS during the daytime. Measured [BrO] ranges between 3 and 9 ppt in the subtropical LS. In the TTL, [BrO] ] is found to increase from a mean of 2.63 ± 1.04 ppt for potential temperatures (θ ) in the range of 350-360 K to 5.11 ± 1.57 ppt for θ = 390 − 400 K, whereas in the subtropical LS (i.e., when [CH 4 ] ≤ 1790 ppb), it reaches 7.66 ± 2.95 ppt for θ in the range of 390-400 K. Finally, for the eastern Pacific (170-90 • W), the TOMCAT/SLIMCAT simulations indicate a net loss of ozone of −0.3 ppbv day −1 at the base of the TTL (θ = 355 K) and a net production of +1.8 ppbv day −1 in the upper part (θ = 383 K).

The novel HALO mini-DOAS instrument: inferring trace gas concentrations from airborne UV/visible limb spectroscopy under all skies using the scaling method

“…4.2). These concentrations are on the higher end of comparable BrO measurements in the same altitude range (12-13 km) reported in the literature (Harder et al, 1998;Dorf et al, 2006;Hendrick et al, 2007;Werner et al, 2017), which could be caused by the subsidence of stratospheric air from higher altitudes discussed above. Panel (e) of Fig.…”

“…The scaling method makes use of the information on the relevant RT gained from a simultaneously in situ and remotely (line-of-sight) measured scaling gas P and the remotely measured absorption of the target gas X to infer the absolute concentration [X] (Raecke, 2013;Großmann, 2014;Werner et al, 2017;Stutz et al, 2017). Ideally, the absorption bands of X (e.g.…”

“…the DLR Falcon, Geophysica, NASA Global Hawk, NSF/NCAR C-130) and high-flying balloon (LPMA/DOAS and MIPAS/TELIS/mini-DOAS payload) observations (Ferlemann et al, 2000;Weidner et al, 2005;Kritten et al, 2010;Prados-Roman et al, 2011;Kreycy et al, 2013;Gratz et al, 2015;Ye et al, 2016;Stutz et al, 2017;Werner et al, 2017). The major design criteria for airborne measurements are a small weight (several to tens of kilograms), a small power consumption (200 W), multiple channels of moderate spectral resolution (i.e.…”

“…The airborne limb measurements of scattered skylight continued with the aircraft studies of Prados-Roman et al (2011) made from aboard the DLR Falcon and more recently from the American High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) aircraft , the NSF/NCAR C-130 (Gratz et al, 2015;Ye et al, 2016), the NASA Global Hawk Werner et al, 2017), and those reported here from HALO, an aircraft based on a Gulfstream G550 jet (http://www.halo.dlr.de/). For first results from measurement campaigns involving the HALO mini-DOAS instrument, the reader is referred to e.g.…”

“…In order to render the interpretation of airborne UV/vis limb measurements more tractable for all kind of skies, in particular for measurements in partly cloudy skies, we recently developed the so-called scaling method (Raecke, 2013;Großmann, 2014;Werner, 2015;Hüneke, 2016;Stutz et al, 2017;Werner et al, 2017). The scaling method makes use of the concentration of a scaling gas, either in situ measured (e.g.…”