Measurements of total odd nitrogen (NOy) aboard MOZAIC in-service aircraft: instrument design, operation and performance

[摘要] A small system for the unattended measurement of total oddnitrogen (NO_y, i.e., the sum of NO and its atmosphericoxidation products) aboard civil in-service aircraft in theframework of MOZAIC is described. The instrument employs thedetection of NO by its chemiluminescence with O₃ incombination with catalytic conversion of the other NO_ycompounds to NO at 300°C on a gold surface in the presenceof H₂. The instrument has a sensitivity of 0.4-0.7cps/pptand is designed for unattended operation during 1-2 servicecycles of the aircraft (400-800 flight hours). The total weightis 50kg, including calibration system, compressed gases,mounting, and safety measures. The layout and inlet configurationare governed by requirements due to the certification forpassenger aircraft. Laboratory tests are described regarding theconversion efficiency for NO₂ and HNO₃ (both>98%). Interference by non-NO_y species is<1% for CH₃CN and NH₃, <5x10^-5% forN₂O (corresponding to <0.2ppt fake NO_y fromambient N₂O)and 100% for HCN. The time response of theinstrument is <1s (90% change) for NO₂. The responsefor HNO₃ is nonlinear: 20s for 67%, 60s for 80%,and 150s for 90% response, respectively.

[学科分类] 大气科学