Observations and analysis of polar stratospheric clouds detected by POAM III and SAGE III during the SOLVE II/VINTERSOL campaign in the 2002/2003 Northern Hemisphere winter

Abstract

Abstract. The Polar Ozone and Aerosol Measurement and Stratospheric Aerosol and Gas Experiment instruments both observed high numbers of polar stratospheric clouds (PSCs) in the polar region during the second SAGE Ozone Loss and Validation (SOLVE II) and Validation of INTERnational Satellites and Study of Ozone Loss (VINTERSOL) campaign, conducted during the 2002/2003 Northern Hemisphere winter. Between 15 November 2002 (14 November 2002) and 18 March 2003 (21 March 2003) SAGE (POAM) observed 122 (151) aerosol extinction profiles containing PSCs. PSCs were observed on an almost daily basis, from early December through 15 January, in both instruments. No PSCs were observed from either instrument from 15 January until 4 February, and from then only sparingly in three periods in mid- and late February and mid-March. In early December, PSCs were observed in the potential temperature range from roughly 375 K to 750 K. Throughout December the top of this range decreases to near 600 K. In February and March, PSC observations were primarily constrained to potential temperatures below 500 K. The PSC observation frequency as a function of ambient temperature relative to the nitric acid-trihydrate saturation point (using a nitric acid profile prior to denitrification) was used to infer irreversible denitrification. By late December 38% denitrification was inferred at both the 400–475 K and 475–550 K potential temperature ranges. By early January extensive levels of denitrification near 80% were inferred at both potential temperature ranges, and the air remained denitrified at least through early March.

Can gravity waves significantly impact PSC occurrence in the Antarctic?

“…It should be noted that the temperature thresholds determined account for variations in the water vapour mixing ratio based on POAM III observations, but that the nitric acid is held constant at 10 ppbv. Previous studies suggest that the difference between the occurrence probability based on POAM III observations and those based on temperature thresholds later in the season is due to denitrification and dehydration (Nedoluha et al, 2003;Alfred et al, 2007). Thus, the fixed nitric acid concentrations used in Fig.…”

“…Uncertainties on the probabilities displayed later in this study are derived assuming a binomial distribution in a similar manner to that utilized in Alfred et al (2007). The standard deviation of a binomial distribution, σ , can be written as:…”

Validation of GOMOS‐Envisat vertical profiles of O3, NO2, NO3, and aerosol extinction using balloon‐borne instruments and analysis of the retrievals

“…At mid latitudes balloons were launched from Aire sur l'Adour, France (latitude 42°43′N, longitude 0°15′W), and at high latitude from Kiruna, Northern Sweden (latitude 67°53′N, longitude 21°05′E); details are given in Table 1. Validation was conducted in March 2003 during a Polar Stratospheric Cloud event (PSC) [ Alfred et al , 2006] located at altitudes between 21 and 26 km, and in March 2004 just outside the polar vortex.…”

Inclusion of mountain-wave-induced cooling for the formation of PSCs over the Antarctic Peninsula in a chemistry–climate model

“…for type Ib (supercooled ternary solution droplets), and 188 K for type II (water ice particles) (Pawson et al, 1995;Alfred et al, 2007). Within the centre of the Antarctic stratospheric vortex in winter, the atmosphere is so cold that temperatures are regularly below these thresholds, i.e.…”