Patrick Neis

Quality assessment of MOZAIC and IAGOS capacitive hygrometers: insights from airborne field studies

In 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 closed-cell Lyman-α 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 sensors 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.

The first regular measurements of ozone, carbon monoxide and water vapour in the Pacific UTLS by IAGOS

We present the features seen in the first 2 months (July and August 2012) of data collected over the Pacific by IAGOS (In-service Aircraft for a Global Observing System)-equipped aircraft. IAGOS is the continuation and development of the well-known MOZAIC (Measurement of Ozone and Water Vapour on Airbus in-service Aircraft) project where scientific instruments were carried on commercially operated A340 aircraft to make measurements of chemical species in the atmosphere. Here, we show data from an aircraft operated by China Airlines on routes from Taipei to Vancouver, which provided the first trans-Pacific measurements by an IAGOS-equipped aircraft. We describe the chemical composition of the extratropical upper troposphere/lower stratosphere (Ex-UTLS) across the Pacific basin in the Northern Hemisphere. The observed concentrations of ozone span a range from 18 to 500 ppbv indicating sources in the marine boundary layer and lowermost stratosphere, respectively. Concentrations of carbon monoxide (CO) greater than 400 ppbv are observed in the Ex-UTLS suggesting that plumes of pollution have been exported from the continent. These low concentrations of ozone and high concentrations of CO were rarely recorded in 8 yr of MOZAIC observations over the Atlantic.