Balloon-borne radiometer measurements of Northern Hemisphere mid-latitude stratospheric HNO3 profiles spanning 12 years
Low-resolution atmospheric thermal emission spectra collected by balloon-borne radiometers over the time span of 1990-2002 are used to retrieve vertical profiles of HNO3, CFC-11 and CFC-12 volume mixing ratios between approximately 10 and 35 km altitude. All of the data analyzed have been collected from launches from a Northern Hemisphere mid-latitude site, during late summer, when stratospheric dynamic variability is at a minimum. The retrieval technique incorporates detailed forward modeling of the instrument and the radiative properties of the atmosphere, and obtains a best fit between modeled and measured spectra through a combination of onion-peeling and optimization steps. The retrieved HNO3 profiles are consistent over the 12-year period, and are consistent with recent measurements by the Atmospheric Chemistry Experiment-Fourier transform spectrometer satellite instrument. We therefore find no evidence of long-term changes in the HNO3 summer mid-latitude profile, although the uncertainty of our measurements precludes a conclusive trend analysis.