Net ozone production and its relationship to nitrogen oxides and volatile organic compounds in the marine boundary layer around the Arabian Peninsula

Abstract

Abstract. Strongly enhanced tropospheric ozone (O3) mixing ratios have been reported in the Arabian Basin, a region with intense solar radiation and high concentrations of O3 precursors such as nitrogen oxides (NOx) and volatile organic compounds (VOCs). To analyze photochemical O3 production in the marine boundary layer (MBL) around the Arabian Peninsula, we use shipborne observations of NO, NO2, O3, OH, HO2, HCHO, the actinic flux, water vapor, pressure and temperature obtained during the summer 2017 Air Quality and Climate in the Arabian Basin (AQABA) campaign, and we compare them to simulation results from the ECHAM-MESSy Atmospheric Chemistry (EMAC) general circulation model. Net O3 production rates (NOPRs) were greatest over both the Gulf of Oman and the northern Red Sea (16 ppbv d−1) and over the Arabian Gulf (32 ppbv d−1). The NOPR over the Mediterranean, the southern Red Sea and the Arabian Sea did not significantly deviate from zero; however, the results for the Arabian Sea indicated weak net O3 production of 5 ppbv d−1 as well as net O3 destruction over the Mediterranean and the southern Red Sea with values of −1 and −4 ppbv d−1, respectively. Constrained by HCHO∕NO2 ratios, our photochemistry calculations show that net O3 production in the MBL around the Arabian Peninsula mostly occurs in NOx-limited regimes with a significant share of O3 production occurring in the transition regime between NOx limitation and VOC limitation over the Mediterranean and more significantly over the northern Red Sea and Oman Gulf.

Reactive nitrogen around the Arabian Peninsula and in the Mediterranean Sea during the 2017 AQABA ship campaign

“…induced oxidation of NO to NO2 resulted in a median (over the diel cycle) value of NOPR = 32 ppbv per day which was driven by high noon-time mixing ratios of RO2 (73 pptv in the Arabian Gulf) (Tadic et al, 2020). In the other two regions, the correlation coefficients are notably smaller, due to the lower span in O3 and NOz, resulting in increased relative errors for the derived OPE values.…”

“…Ozone was measured by optical absorption at 253.65 nm in a commercial ozone monitor (2B Technologies Model 202) with total measurement uncertainty of 2 % ± 1 ppbv and a detection limit of 3 ppbv (at 10 s integration time). NO and NO2 were measured with a chemiluminescence detector (CLD 790 SR, ECO Physics, 5 s time resolution) as described in Tadic et al (2020), with total measurement uncertainties of 6 % (NO) and 23 % (NO2) and detection limits of 22 pptv for NO and 52 pptv for NO2, both calculated at a time resolution of 5 s and a confidence interval of 2σ. HONO mixing ratios were measured by a long path absorption photometer (LOPAP; Heland et al (2001)) with a 3-5 pptv detection limit and a measurement uncertainty of 20 %.…”

Central role of nitric oxide in ozone production in the upper tropical troposphere over the Atlantic Ocean and West Africa

“…In the US, ambient ozone was designated a criteria air pollutant already in the 1970s (Jaffe et al, 2018). Since then and especially in the last decades, increasing effort has been put in the understanding and mitigation of tropospheric ozone pollution (Fiore et al, 2002;Dentener et al, 2005;West and Fiore, 2005;Lelieveld et al, 2009, Pusede et al, 2015Jaffe et al, 2018;Nussbaumer and Cohen, 2020;Tadic et al, 2020). To further resolve the complexity of scientific and policy-related issues of the NOx-O3-VOCs relationship, careful evaluation of model simulations against in situ measurement data is required (Sillman et al, 1995).…”

“…Note that the deactivation of O( 1 D) to O( 3 P) via collisions with N2 and O2 will result in the reformation of O3 (Bozem et al, 2017;Tadic et al, 2020). We express the portion of O3 that is effectively lost via photolysis by (see section 2.2).…”

Measurement report: In situ observations of deep convection without lightning during the tropical cyclone Florence 2018

“…The research aircraft carried multiple instruments for the measurement of various atmospheric trace gases including NO, O 3 , CO, H 2 O 2 , CH 3 I and DMS. NO was measured via chemiluminescence (detector from ECO Physics CLD 790 SR, Dürnten, Switzerland) with a relative uncertainty of 6 % and a detection limit of 5 ppt v (Tadic et al, 2020). O 3 mixing ratios were analyzed by UV absorption and chemiluminescence with the FAIRO instrument (chemiluminesence data with a total uncertainty of 2.5 %, Zahn et al (2012)).…”