A B S T R A C TIn 2011, the MOZAIC (Measurement of Ozone by AIRBUS In-Service Aircraft) successor programme IAGOS (In-service Aircraft for a Global Observing System) started to equip their long-haul passenger aircraft with the modified capacitive hygrometer Vaisala HUMICAP † of type H. The assurance of the data quality and the consistency of the data set during the transition from MOZAIC Capacitive Hygrometers to IAGOS Capacitive Hygrometers were evaluated within the CIRRUS-III and AIRTOSS-ICE field studies. During these performance tests, the capacitive hygrometers were operated aboard a Learjet 35A aircraft together with a closedcell Lyman-a fluorescence hygrometer, an open-path tunable diode laser (TDL) system and a closed-cell, direct TDL absorption hygrometer for water vapour measurement. For MOZAIC-typical operation conditions, the comparison of relative humidity (RH) data from the capacitive hygrometers and reference instruments yielded remarkably good agreement with an uncertainty of 5% RH. The temperature dependence of the sensor's response time was derived from the cross-correlation of capacitive hygrometer data and smoothed data from the fast-responding reference instruments. The resulting exponential moving average function could explain the major part of the observed deviations between the capacitive hygrometers and the reference instruments.
A B S T R A C T This paper describes the NO y plumes originating from lightning emissions based on 4 yr (2001Á2005) of MOZAIC measurements in the upper troposphere of the northern mid-latitudes, together with ground-and space-based observations of lightning flashes and clouds. This analysis is primarily for the North Atlantic region where the MOZAIC flights are the most frequent and for which the measurements are well representative in space and time. The study investigates the influence of lightning NO x (LNO x ) emissions on large-scale (300Á2000 km) plumes (LSPs) of NO y . One hundred and twenty seven LSPs (6% of the total MOZAIC NO y dataset) have been attributed to LNO x emissions. Most of these LSPs were recorded over North America and the Atlantic mainly in spring and summer during the maximum lightning activity occurrence. The majority of the LSPs (74%) is related to warm conveyor belts and extra-tropical cyclones originating from North America and entering the intercontinental transport pathway between North America and Europe, leading to a negative (positive) west to east NO y (O 3 ) zonal gradient with (0.4 ('18) ppbv difference during spring and (0.6 ('14) ppbv difference in summer. The NO y zonal gradient can correspond to the mixing of the plume with the background air. On the other hand, the O 3 gradient is associated with both mixing of background air and with photochemical production during transport. Such transatlantic LSPs may have a potential impact on the European pollution. The remaining sampled LSPs are related to mesoscale convection over Western Europe and the Mediterranean Sea (18%) and to tropical convection (8%).
, a fully automatic NO y instrument was installed on one of the five Airbus A340 aircraft used in the MOZAIC project (Measurement of Ozone and Water Vapour by Airbus in-service Aircraft) for measurements of O 3 and H 2 O since 1994. This long-range aircraft was operated by Lufthansa, mainly out of Frankfurt and Munich. After an initial testing period, regular data collection started in May 2001. Until May 2005, 1533 flights have been recorded, corresponding to 8500 flight hours of NO y measurements. Concurrent data of NO y and O 3 are available from 1433 flights and concurrent data for CO, O 3 and NO y exist from 1125 flights since 2002. The paper describes the data availability in terms of geographical, vertical and seasonal distribution and discusses the quality and limitations of the data, including interference by HCN. The vast majority of vertical profiles were measured over Frankfurt, followed by Munich and North American airports. While most of the data were collected in the upper troposphere and lower stratosphere over the North Atlantic, significant data sets exist also from flights to Far and Middle East, whereas data from the tropics and the Southern Hemisphere are relatively sparse.
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