We present observations of the 2010-2011 Arc- tic winter stratosphere from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard ENVISAT. Limb sounding infrared measurements were taken by MIPAS during the Northern polar winter and into the subsequent spring, giving a continuous vertically resolved view of the Arctic dynamics, chemistry and polar stratospheric clouds (PSCs). We adopted a 2-D tomographic retrieval approach to account for the strong horizontal inhomogeneity of the at- mosphere present under vortex conditions, self-consistently comparing 2011 to the 2-D analysis of 2003-2010. Unlike most Arctic winters, 2011 was characterized by a strong stratospheric vortex lasting until early April. Lower strato- spheric temperatures persistently remained below the thresh- old for PSC formation, extending the PSC season up to mid- March, resulting in significant chlorine activation leading to ozone destruction. On 3 January 2011, PSCs were detected up to 30.5 ± 0.9 km altitude, representing the highest PSCs ever reported in the Arctic. Through inspection of MIPAS spectra, 83 % of PSCs were identified as supercooled ternary solution (STS) or STS mixed with nitric acid trihydrate (NAT), 17 % formed mostly by NAT particles, and only two cases by ice. In the lower stratosphere at potential tempera- ture 450 K, vortex average ozone showed a daily depletion rate reaching 100 ppbv day-1 . In early April at 18 km alti- tude, 10 % of vortex measurements displayed total depletion of ozone, and vortex average values dropped to 0.6 ppmv. This corresponds to a chemical loss from early winter greater than 80 %. Ozone loss was accompanied by activation of ClO, associated depletion of its reservoir ClONO2 , and sig- nificant denitrification, which further delayed the recovery of ozone in spring. Once the PSC season halted, ClO was re- converted primarily into ClONO2 . Compared to MIPAS ob- served 2003-2010 Arctic average values, the 2010-2011 vor- tex in late winter had 15 K lower temperatures, 40 % lower HNO3 and 50 % lower ozone, reaching the largest ozone de- pletion ever observed in the Arctic. The overall picture of this Arctic winter was remarkably closer to conditions typically found in the Antarctic vortex than ever observed before.
Extreme ozone depletion in the 2010-2011 Arctic winter stratosphere as observed by MIPAS/ENVISAT using a 2-D tomographic approach
E Arnone;E Castelli;E Papandrea;B M Dinelli
2012
Abstract
We present observations of the 2010-2011 Arc- tic winter stratosphere from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard ENVISAT. Limb sounding infrared measurements were taken by MIPAS during the Northern polar winter and into the subsequent spring, giving a continuous vertically resolved view of the Arctic dynamics, chemistry and polar stratospheric clouds (PSCs). We adopted a 2-D tomographic retrieval approach to account for the strong horizontal inhomogeneity of the at- mosphere present under vortex conditions, self-consistently comparing 2011 to the 2-D analysis of 2003-2010. Unlike most Arctic winters, 2011 was characterized by a strong stratospheric vortex lasting until early April. Lower strato- spheric temperatures persistently remained below the thresh- old for PSC formation, extending the PSC season up to mid- March, resulting in significant chlorine activation leading to ozone destruction. On 3 January 2011, PSCs were detected up to 30.5 ± 0.9 km altitude, representing the highest PSCs ever reported in the Arctic. Through inspection of MIPAS spectra, 83 % of PSCs were identified as supercooled ternary solution (STS) or STS mixed with nitric acid trihydrate (NAT), 17 % formed mostly by NAT particles, and only two cases by ice. In the lower stratosphere at potential tempera- ture 450 K, vortex average ozone showed a daily depletion rate reaching 100 ppbv day-1 . In early April at 18 km alti- tude, 10 % of vortex measurements displayed total depletion of ozone, and vortex average values dropped to 0.6 ppmv. This corresponds to a chemical loss from early winter greater than 80 %. Ozone loss was accompanied by activation of ClO, associated depletion of its reservoir ClONO2 , and sig- nificant denitrification, which further delayed the recovery of ozone in spring. Once the PSC season halted, ClO was re- converted primarily into ClONO2 . Compared to MIPAS ob- served 2003-2010 Arctic average values, the 2010-2011 vor- tex in late winter had 15 K lower temperatures, 40 % lower HNO3 and 50 % lower ozone, reaching the largest ozone de- pletion ever observed in the Arctic. The overall picture of this Arctic winter was remarkably closer to conditions typically found in the Antarctic vortex than ever observed before.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.