The temporal evolution of the ratio HNO₃/NO_y in the Arctic lower stratosphere from January to March 1997

Abstract

In late winter/early spring, sunrise after the polar night, followed by photodissociation oI HNO3 leads to formation o• Nt) x and, via reaction (1), of C1ONO 2. This is expected to shift the partitioning within NOy towards NOx and C1ONO 2 and to a decrease of the HNO3 fraction within NOy. This paper reports on measurements of HNO 3, NOy, N20 , and 03 during two aircraft campaigns in winter 1997 in the Arctic lower stratosphere. We focus on a strong reduction of the ratio HNO3/NOy observed from January to March.

Analysis of ozone and nitric acid in spring and summer Arctic pollution using aircraft, ground-based, satellite observations and MOZART-4 model: source attribution and partitioning

“…3. This is consistent with earlier studies which point to different HNO 3 vs. O 3 relationships in the troposphere and in the stratosphere (Bregman et al, 1995;Talbot et al, 1997;Schneider et al, 1999;Neuman et al, 2001;Popp et al, 2009) and which show lower ozone production for air masses with fresh emissions from biomass burning and urban sources than in the free troposphere (Shon et al, 2008). For each specific air mass (fresh pollution, free troposphere or stratosphere-contaminated air mass) and for each data set, we find that O 3 /HNO 3 ratios and the scatter values are of comparable magnitude between the aircraft observations and the model results.…”

“…Correlations between NO x , NO y (the sum of all reactive nitrogen species) and O 3 have frequently been used as a probe of chemistry and transport in the lower atmosphere (Murphy et al, 1993;Trainer et al, 1993;Ridley, et al, 1994;Singh et al, 1996;Fischer et al, 2000, Zellweger et al, 2003. Strong correlations between HNO 3 and O 3 were established in the lower stratosphere/upper troposphere and have been used previously to characterize air masses in the Arctic and midlatitude regions (Bregman et al, 1995;Talbot et al, 1997;Schneider et al, 1999;Neuman et al, 2001;Popp et al, 2009), to validate satellite HNO 3 profiles (Irie et al, 2006;Popp et al, 2009), or to infer the efficiency of ozone production . Study of the correlation of HNO 3 and O 3 in the lower/middle troposphere is less common, despite its importance in quantifying the dependence of ozone on nitrogen compounds.…”

“…It provides profiles on 39 layers from the surface up to 39 km, relying on a fast radiative transfer and retrieval methodology, based on the Optimal Estimation Method (Rodgers, 2000), which has been developed initially for the retrieval of HNO 3 from IASI . As described in Scannell et al (2011), the a priori information (a priori profile and a priori covariance matrix) used for the retrieval of O 3 is built from the Logan/Labow/McPeters climatology (McPeters et al, 2007) which is a combination of data from the Stratospheric Aerosol and Gas Experiment II (SAGE II;1988, the Microwave Limb Sounder (MLS;1991-1999 and data from balloon sondes (1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002) to represent the best approximation of the atmospheric state. Note that a single O 3 a priori profile and variance-covariance matrix are used.…”

Global distributions of nitric acid from IASI/MetOP measurements

“…We also note that, except for the denitrification period, the HNO 3 /O 3 ratio increases on average with latitude, pointing to the larger latitudinal gradient of HNO 3 as compared to that of ozone. The HNO 3 /O 3 ratios obtained from IASI measurements are in agreement with previous studies which report values ranging from 1.8×10 −3 to 9×10 −3 in the lower stratosphere (Trainer et al, 1993;Bregman et al, 1995;Talbot et al, 1997;Schneider et al, 1999;Neuman et al, 2001). …”

Intercomparison of stratospheric HNO3 measurements over Antarctica: Ground‐based millimeter‐wave versus UARS/MLS Version 5 retrievals

“…In the polar darkness, conversion of NO and NO 2 to N 2 O 5 takes place rapidly, followed by hydrolysis of N 2 O 5 to HNO 3 on sulfate aerosols [e.g., Garcia and Solomon , 1994; Santee et al , 1999; de Zafra and Smyshlyaev , 2001]. We thus expect HNO 3 to represent almost 100% of NO y in the polar stratosphere during late fall and winter at altitudes up to ∼23 km [ Garcia and Solomon , 1994; Schneider et al , 1999; Michelsen et al , 1999]. In Figure 5 we have plotted the NO y ‐N 2 O correlation curve obtained at midlatitudes (44°–55°S) by ATMOS/ATLAS‐2 in April 1993 [e.g., Michelsen et al , 1998], together with the HNO 3 ‐N 2 O correlation obtained using GBMS profiles at 90°S (for GBMS N 2 O retrievals see Crewell et al [1995]) from 15 April 1993 (day 105), which is during our fall pseudo‐season and more than 3 weeks after sunset at the South Pole.…”