Balloon-borne in situ measurements of total reactive nitrogen (NO,), nitric
oxide (NO), nitric acid (HNO3), ozone (O-3), and aerosols were conducted o
ver Are sur l'Adour, France (44 degrees N), between October 11 and 12, 1994
, NO, and NO were measured by chemiluminescence NO detectors combined with
a gold catalytic converter, and HNO3, was measured by ion mass spectrometry
. Two independent box models (Goddard Space Flight Center and Atmospheric a
nd Environment Inc.) run on isentropic trajectories were used to interpret
the observed partitioning of reactive nitrogen. The NO partitioning calcula
ted by the two models agreed within 10% of each other. The model-calculated
NO/ NO ratios increase by similar to 25% when the updated reaction rates o
f NO2 + OH, HNO3 + OH, and NO2 + O [Portpnann et al., 1999] were used inste
ad of those given by DeMore ei al. [1997], leading to a better agreement wi
th the observations by the same amount. At 21-25 km the calculated NO/NOy,
ratios depended sensitively on the estimate of aerosol surface area. Within
the uncertainty of the estimate of aerosol surface area the NO/NOy, and HN
O3/NOy ratios calculated by the models reproduced those observed within 20%
. The same trajectory models also reproduced the NO/NOy ratios measured bel
ow 25 km under high aerosol loading in October and November 1992 within +/-
20%, which is the accuracy level of the measurements.