Measurements of total odd nitrogen (NO<sub>y</sub>) aboard MOZAIC in-service aircraft: instrument design, operation and performance

Abstract

Abstract.A small system for the unattended measurement of total odd nitrogen (NO y , i.e., the sum of NO and its atmospheric oxidation products) aboard civil in-service aircraft in the framework of MOZAIC is described. The instrument employs the detection of NO by its chemiluminescence with O 3 in combination with catalytic conversion of the other NO y compounds to NO at 300 • C on a gold surface in the presence of H 2 . The instrument has a sensitivity of 0.4-0.7 cps/ppt and is designed for unattended operation during 1-2 service cycles of the aircraft (400-800 flight hours). The total weight is 50 kg, including calibration system, compressed gases, mounting, and safety measures. The layout and inlet configuration are governed by requirements due to the certification for passenger aircraft. Laboratory tests are described regarding the conversion efficiency for NO 2 and HNO 3 (both >98%). Interference by non-NO y species is <1% for CH 3 CN and NH 3 , <5×10 −5 % for N 2 O (corresponding to <0.2 ppt fake NO y from ambient N 2 O) and 100% for HCN. The time response of the instrument is <1 s (90% change) for NO 2 . The response for HNO 3 is nonlinear: 20 s for 67%, 60 s for 80%, and 150 s for 90% response, respectively.

The IAGOS NO&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; instrument – design, operation and first results from deployment aboard passenger aircraft

“…The three zero-air types showed no differences in zero mode within measurement errors, which is in agreement with the finding of Volz- Thomas et al (2005) for the MOZAIC NO y instrument. However, the difference between measuring mode and zero mode of instrument background signal is not equal to zero and has to be subtracted from the ambient measured signal (see Sect.…”

“…The pressure in the discharge tube is kept constant between 1 and 1.2 bar and is monitored by a pressure transducer. More details are described by Volz- Thomas et al (2005).…”

“…The chemiluminescence detector mounted in the NOD unit is similar to that described by Volz- Thomas et al (2005). The PMT is cooled by four Peltier elements to temperatures below −10 • C at an instrument temperature (T Instrument ) of 20 • C. The reaction cell is separated from the PMT housing by a 1 mm thick window and a low-pass red-light filter.…”

“…The design of the IAGOS NO x instrument Package 2b (P2b) is based on the former MOZAIC NO y instrument described by Volz- Thomas et al (2005) and Pätz et al (2006), using the CLD method for NO with a photolytic converter to convert NO 2 into NO. When using passenger aircraft as platform, many conflicting needs have to be fulfilled: the instrument has to be fully automated, small and lightweight, with limited power consumption, and fulfill high safety standards (mechanical stability, electromagnetic interference and flammability specifications).…”

“…IAGOS builds on the former EU framework projects MOZAIC (Measurement of Ozone and Water Vapour by Airbus In-service Aircraft; Marenco et al, 1998) and CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container; Brenninkmeijer et al, 2007). Between 2001 and 2005, total odd nitrogen (NO y = NO and its atmospheric oxidation products, such as nitrogen dioxide, NO 2 ; nitric acid, HNO 3 ; and peroxyacetyl nitrate, PAN) was measured on MOZAIC (Volz- Thomas et al, 2005;Pätz et al, 2006), and since 2005 it has been measured on CARIBIC (Stratmann et al, 2016).…”