Intercomparison of aircraft instruments on board the C-130 and Falcon 20 over southern Germany during EXPORT 2000

Abstract

Abstract. In the summer 2000 EXPORT aircraft campaign (European eXport of Precursors and Ozone by long-Range Transport), two comprehensively instrumented research aircraft measuring a variety of chemical species flew wing tip to wing tip for a period of one and a quarter hours. During this interval a comparison was undertaken of the measurements of nitrogen oxide (NO), odd nitrogen species (NO y ), carbon monoxide (CO) and ozone (O 3 ). The comparison was performed at two different flight levels, which provided a 10-fold variation in the concentrations of both NO (10 to 1000 parts per trillion by volume (pptv)) and NO y (200 to over 2500 pptv). Large peaks of NO and NO y observed from the Falcon 20, which were at first thought to be from the exhaust of the C-130, were also detected on the 4 channel NO xy instrument aboard the C-130. These peaks were a good indication that both aircraft were in the same air mass and that the Falcon 20 was not in the exhaust plume of the C-130. Correlations and statistical analysis are presented between the instruments used on the two separate aircraft platforms. These were found to be in good agreement giving a high degree of correlation for the ambient air studied. Any deviations from the correlations are accounted for in the estimated inaccuracies of the instruments. These results help to establish that the instruments aboard the separate aircraft are reliably able to measure the corresponding chemical species in the range of conditions sampled and that data collected by both aircraft can be co-ordinated for purposes of interpretation.

Radical chemistry at night: comparisons between observed and modelled HO<sub>x</sub>, NO<sub>3</sub> and N<sub>2</sub>O<sub>5</sub> during the RONOCO project

“…Decreases in the optimised values for γ N 2 O 5 are found with increasing nitrate fraction of the aerosol and ammonium to sulfate ratio, with smaller decreases observed with increasing ammonium and organic fractions. Such behaviour has been observed previously in a number of laboratory and field studies (see, for example, Brown et al, 2006;Chang et al, 2011;Brown and Stutz, 2012;Riedel et al, 2012Riedel et al, , 2013Wagner et al, 2013;and Gaston et al, 2013), and optimisation of γ N 2 O 5 through use of model simulations to reach agreement between ambient gas phase measured and modelled N 2 O 5 has been reported in previous work .…”

“…Given the high modelled RO 2 to HO 2 ratios, a measurement of RO 2 concentrations would provide a significant constraint on the chemistry. The N 2 O 5 uptake coefficient has been shown to display a complex dependence on aerosol composition, humidity and temperature (see for example, Brown et al, 2006;Brown and Stutz, 2012;Riedel et al, 2012;Wagner et al, 2013;Gaston et al, 2013), and further laboratory studies of γ N 2 O 5 leading to improved parameterisations of these effects would significantly reduce the model uncertainty. Measurements of RO 2 + NO 3 rate coefficients for a variety of RO 2 radicals and under a range of temperatures and pressures would also improve our understanding of this system.…”

“…During the day, NO 3 is rapidly photolysed, leading to low daytime concentrations (Wayne et al, 1991;Brown and Stutz, 2012). However, during the night, NO 3 can accumulate, and a rapid equilibrium with N 2 O 5 is established through the production of N 2 O 5 via NO 3 + NO 2 followed by rapid thermal decomposition of N 2 O 5 back to NO 3 and NO 2 (Wayne et al, 1991;Brown and Stutz, 2012).…”

“…During the day, NO 3 is rapidly photolysed, leading to low daytime concentrations (Wayne et al, 1991;Brown and Stutz, 2012). However, during the night, NO 3 can accumulate, and a rapid equilibrium with N 2 O 5 is established through the production of N 2 O 5 via NO 3 + NO 2 followed by rapid thermal decomposition of N 2 O 5 back to NO 3 and NO 2 (Wayne et al, 1991;Brown and Stutz, 2012). Losses of N 2 O 5 are primarily due to reactions on aerosol surfaces, and there is thus much interest in determination of the aerosol uptake coefficient for N 2 O 5 on atmospheric aerosols Escoreia et al, 2010;Tang et al, 2010;Badger et al, 2006;Thornton and Abbatt, 2005;Hallquist et al, 2003;Thornton et al, 2003;Kane et al, 2001;Hu and Abbatt, 1997;Fried et al, 1994;Van Doren et al, 1991;Hanson and Ravishankara, 1991;Mozurkewich and Calvert, 1998).…”

“…Losses of N 2 O 5 are primarily due to reactions on aerosol surfaces, and there is thus much interest in determination of the aerosol uptake coefficient for N 2 O 5 on atmospheric aerosols Escoreia et al, 2010;Tang et al, 2010;Badger et al, 2006;Thornton and Abbatt, 2005;Hallquist et al, 2003;Thornton et al, 2003;Kane et al, 2001;Hu and Abbatt, 1997;Fried et al, 1994;Van Doren et al, 1991;Hanson and Ravishankara, 1991;Mozurkewich and Calvert, 1998). NO 3 radicals can react with a range of species, including alkenes, aldehydes and RO x radicals (Wayne et al, 1991;Brown and Stutz, 2012).…”