Airborne measurements of the nitric acid partitioning in persistent contrails

Abstract

Abstract. This study reports the first systematic measurements of nitric acid (HNO 3 ) uptake in contrail ice particles at typical aircraft cruise altitudes. During the CIRRUS-III campaign cirrus clouds and almost 40 persistent contrails were probed with in situ instruments over Germany and Northern Europe in November 2006. Besides reactive nitrogen, water vapor, cloud ice water content, ice particle size distributions, and condensation nuclei were measured during 6 flights. Contrails with ages up to 12 h were detected at altitudes 10-11.5 km and temperatures 211-220 K. These contrails had a larger ice phase fraction of total nitric acid (HNO ice 3 /HNO tot 3 = 6%) than the ambient cirrus layers (3%). On average, the contrails contained twice as much HNO ice 3 as the cirrus clouds, 14 pmol/mol and 6 pmol/mol, respectively. Young contrails with ages below 1 h had a mean HNO ice 3 of 21 pmol/mol. The contrails had higher nitric acid to water molar ratios in ice and slightly higher ice water contents than the cirrus clouds under similar meteorological conditions. The differences in ice phase fractions and molar ratios between developing contrails and cirrus are likely caused by high plume concentrations of HNO 3 prior to contrail formation. The location of the measurements in the upper region of frontal cirrus layers might account for slight differences in the ice water content between contrails and adjacent cirrus clouds. The observed dependence of molar ratios as a function of the mean ice particle diameter suggests that icebound HNO 3 concentrations are controlled by uptake of exhaust HNO 3 in the freezing plume aerosols in young contrails and subsequent trapping of ambient HNO 3 in growing ice particles in older (age > 1 h) contrails.

In-situ observations of young contrails – overview and selected results from the CONCERT campaign

“…Initial ice crystal concentrations larger than 1000 cm −3 have been detected in a few seconds old contrails decreasing by dilution to concentrations of less than 100 cm −3 within the first minutes (Poellot et al, 1999;Febvre et al, 2009). In persistent contrails with ages of few hours, ice crystal concentrations of less than 20 cm −3 have been observed Schäuble et al, 2009). Contrail widths of 100-300 m have been derived from in situ measurements (Poellot et al, 1999) for less than 15 minutes old contrails increasing to 1-3 km for less than 30 min old contrails (Freudenthaler et al, 1995).…”

Dimension of aircraft exhaust plumes at cruise conditions: effect of wake vortices

“…Primarily, the campaign aimed at probing contrails. In aircraft plumes of ages smaller than 3 min NO y is dominated by NO and NO 2 , and to a much lesser amount gas phase HONO and HNO 3 (Tremmel et al, 1998) from which only a small portion may be lost to the particulate phase at this early stage (Schäuble et al, 2009). For our purpose it may therefore be treated as passive tracer to a good approximation.…”

The evolution of microphysical and optical properties of an A380 contrail in the vortex phase

“…The technique has extensively been used in previous campaigns for the identification of aircraft exhaust plumes and for the detection of NO and NO y in contrails and cirrus clouds (Schlager et al, 1997;Ziereis et al, 2000;Voigt et al, 2006Voigt et al, , 2007Schäuble et al, 2009). Sample air passes through a backward facing inlet with a fluoropolymer (PFA) tube to sample reactive nitrogen compounds from outside the aircraft.…”