Ground‐based infrared measurements of HNO₃ total column abundances: Long‐term trend and variability

Abstract

The long-term trend and variability of the total column amount of atmospheric nitric acid (HNO3) have been investigated based on time series of infrared solar absorption spectra recorded at two remote high-altitude sites, the International Scientific Station of the Jungfraujoch (ISSJ) in the Swiss Alps (altitude 3.6 km, latitude 46.5øN, longitude 8.0øE) and the National Solar Observatory McMath solar telescope facility on Kitt Peak (altitude 2.1 km, latitude 31.9øN, longitude 111.6øW), southwest of Tucson, Arizona. The HNO 3 v5 band Q branch at 879.1 cm -1 and three P branch manifolds near 869 cm-1 were analyzed using a nonlinear least squares spectral fitting technique and a consistent set of spectroscopic line parameters. The ISSJ measurements evaluated in the present work consist of two solar spectra recorded with a grating spectrometer in June 1951 and a set of observations obtained with a high-resolution Foiltier transform spectrometer between June 1986 and June 1990. The modern ISSJ measurements show a -•20% peak-to-peak amplitude seasonal cycle with a winter maximum superimposed on significant variability and a summer minimum; the June results from 1986 to 1990 are both higher and lower than the two retrieved June 1951 HNO 3 total column amounts. The fitted trend, (-0.16 + 0.50)% yr -1, 2tr, indicates that there has been no detectable change in the HNO3 total column over the last 4 decades. The Kitt Peak measurements, recorded with a high-resolution Fourier transform spectrometer between December 1980 and June 1990, also show marked variability in the HNO3 total column, but in contrast to the ISSJ measurements, no obvious seasonal cycle is observed.The deduced trend in the total column above Kitt Peak, (-0.8 + 1.6)% yr -1 , 2tr, is consistent with the ISSJ time series of measurements, in that no significant HNO3 long-term trend has been found. The sets of measurements from the two sites are compared with each other and with previously published results, with emphasis on the reported variability of HNO3 and the changes in the HNO3 total column with season and latitude.

Global distributions of nitric acid from IASI/MetOP measurements

“…Values of potential vorticity (PV) at the potential temperature of 520 K (∼50 hPa) gathered from the Met Office fields 1 for MLS analyses have further been used to represent the size, the shape and the strength of the polar vortex and are superim-1 available at: https://mls.jpl.nasa.gov/dmp/ chosen mid-latitude (Moshiri,44 • N, 142.3 • E) and polar sites (Ny Alesund,78.9 • N 11.9 • E) in the Northern Hemisphere vary on average between 2.50×10 16 molecules cm −2 in January to 1.35×10 16 molecules cm −2 in July and between 3.15×10 16 molecules cm −2 in January to 1.89×10 16 molecules cm −2 in July, respectively. These large-scale spatial and seasonal variations in the HNO 3 total columns are fully consistent with the photochemical processes occurring in the stratosphere (Austin et al, 1986;Rinsland et al, 1991;Santee at al., 1999 andreferences therein, Santee et al, 2004;Urban et al, 2008, among others).…”

A review of atmospheric chemistry observations at mountain sites

“…The site has been shown to be excellent for studies on new particle formation (Bianchi et al 2016) or aerosol-cloud interaction, including mixed-phase and glaciated clouds Verheggen et al 2007). In addition, remote sensing investigations have been performed by FTIR spectroscopy, which allows for quasisimultaneous investigation of total column concentrations of a large number of gaseous constituents (e.g., Barret et al 2002Barret et al , 2003aDe Mazière et al 1999;Dils et al 2011;Duchatelet et al 2009Duchatelet et al , 2010Krieg et al 2005;Mahieu et al 1997;Melen et al 1998;Rinsland et al 1991Rinsland et al , 1992Rinsland et al , 1996Rinsland et al , 2000Rinsland et al , 2008Vigouroux et al 2007;Zander et al 2008Zander et al , 2010. JFJ is exposed mostly to FT air masses in autumn and winter.…”

Balloon-borne radiometer measurements of Northern Hemisphere mid-latitude stratospheric HNO<sub>3</sub> profiles spanning 12 years

“…Long-term changes in HNO 3 have been studied by use of ground-based observations of total columns, and spacebased, vertically resolved HNO 3 profiles. In an analysis of data comprised of solar spectra recorded with a grating spectrometer in June 1951 and a set of observations obtained with a Fourier transform spectrometer between June 1986 and June 1990, all from the International Scientific Station of the Jungfraujoch in Swiss Alps, Rinsland et al (1991) found no significant change in the June HNO 3 total column over this time span. Randel et al (1999) (Rinsland et al, 2003).…”