Balloon profiles of stratospheric NO 2 and HNO 3 for testing the heterogeneous hydrolysis of N 2 O 5 on sulfate aerosols

Simultaneous in situ measurements of stratospheric NO 2 , HNO 3 , HCl, and CH 4 from 34 to 24 km were made in August 1992 from Palestine, Texas, using the Balloon‐borne Laser In‐Situ Sensor (BLISS) tunable diode laser spectrometer. Although the measurements of NO 2 , HNO 3 , and NO 2 /HNO 3 agree well with gas‐phase model calculations near 34 km where SAGE II data show little sulfate aerosol, this is not true at the lower altitudes where SAGE II shows high aerosol loadings. At 24 km the BLISS NO 2 and HNO 3 measurements are 70% lower, and 50% higher, respectively, than the gas phase model predictions, with a measured NO 2 /HNO 3 ratio 5 times smaller. When the heterogeneous hydrolysis of N 2 O 5 and ClONO 2 on sulfate aerosol of surface area densities matching the SAGE II measurements is added to the model, good agreement with the BLISS measurements is found over the whole altitude range.