Measurement of chlorine nitrate in the stratosphere using the ν₄ and ν₅ bands

Abstract

We present laboratory measurements of the absorption cross sections of the ν5 band (540–580 cm−1) of chlorine nitrate made under stratospheric conditions of temperature and pressure. We use the measured cross sections and observed mid‐infrared stratospheric emission spectra to retrieve mid‐latitude vertical mixing ratio profiles for both day and night in the altitude range 20–34 km, and compare the results with a sunset profile obtained simultaneously from solar absorption measurements of the ν4 Q branch at 780 cm−1. The profiles obtained using these two methods are shown to be in excellent agreement, validating retrievals using the ν4 band. We also find good agreement in this altitude range between the observed day/night ratio and the results of a 1‐D photochemical model

Stratospheric and mesospheric HO<sub>2</sub> observations from the Aura Microwave Limb Sounder

“…It retrieves HO 2 from 43 rotational transitions between 110 and 220 cm −1 (Jucks et al, 1998). The retrieval algorithm first estimates slant columns and then, in an onion-peeling fashion, a singular value decomposition routine is used to retrieve mixing ratios on a 1 km vertical grid (Johnson et al, 1996). The total systematic errors for the retrieved HO 2 are estimated to be 3 %.…”

Validation of MIPAS ClONO<sub>2</sub> measurements

“…This is followed by a summary of the mean difference profiles per instrument. Johnson et al (1996) no no no yes no no Wagner and Birk (2003) yes yes yes yes yes yes 3.1 MIPAS-B MIPAS-B (Table 2) is a balloon-borne limb emission sounder with a similar spectral coverage (4-14 µm), a slightly lower spectral resolution (14.5 cm OPD) and a slightly better vertical resolution (2-3 km below the flight level) compared to MIPAS (Friedl-Vallon et al, 2004 . This flight was part of the Envisat validation activities and perfectly coincident in time and location to MIPAS measurements of Envisat orbit 2975.…”

“…(Johnson et al, 1995). Vertical profiles of ClONO 2 volume mixing ratios with an altitude resolution of about 3 km have been derived from FIRS observations using the ν 5 Q-branch at 563 cm −1 (Johnson et al, 1996) and the ν 4 Q-branch at 780.2 cm −1 (spectroscopic data by Wagner and Birk (2003) Table 5 and plotted in the top row of Fig. 8.…”

The ν2 Bands of BrNO2 around 787 cm−1 (12.7 μm)

“…Meanwhile, to the best of our knowledge, there is no experimental detection of atmospheric BrNO 2 . The Q branches of the ν 2 bands should be most suitable for this purpose due to their high intensity in an atmospheric "window," similar to the feature around 780.2 cm −1 currently used for atmospheric ClONO 2 detection (30,31).…”