| 1. |
- Randall, C. E., et al.
(författare)
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Stratospheric effects of energetic particle precipitation in 2003-2004
- 2005
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Ingår i: Geophysical Research Letters. - 1944-8007 .- 0094-8276. ; 32:5, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- Upper stratospheric enhancements in NOx (NO and NO2) were observed at high northern latitudes from March through at least July of 2004. Multi-satellite data analysis is used to examine the temporal evolution of the enhancements, to place them in historical context, and to investigate their origin. The enhancements were a factor of 4 higher than nominal at some locations, and are unprecedented in the northern hemisphere since at least 1985. They were accompanied by reductions in O-3 of more than 60% in some cases. The analysis suggests that energetic particle precipitation led to substantial NOx production in the upper atmosphere beginning with the remarkable solar storms in late October 2003 and possibly persisting through January. Downward transport of the excess NOx, facilitated by unique meteorological conditions in 2004 that led to an unusually strong upper stratospheric vortex from late January through March, caused the enhancements.
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| 2. |
- Ricaud, P., et al.
(författare)
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Polar Vortex Evolution during the 2002 Antarctic Major Warming as Observed by the Odin Satellite
- 2005
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 110:D5, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- In September 2002 the Antarctic polar vortex split in two under the influence of a sudden warming. During this event, the Odin satellite was able to measure both ozone (O(3)) and chlorine monoxide (ClO), a key constituent responsible for the so-called "ozone hole'', together with nitrous oxide (N(2)O), a dynamical tracer, and nitric acid (HNO(3)) and nitrogen dioxide (NO(2)), tracers of denitrification. The submillimeter radiometer (SMR) microwave instrument and the Optical Spectrograph and Infrared Imager System (OSIRIS) UV-visible light spectrometer (VIS) and IR instrument on board Odin have sounded the polar vortex during three different periods: before (19-20 September), during (24-25 September), and after (1-2 and 4-5 October) the vortex split. Odin observations coupled with the Reactive Processes Ruling the Ozone Budget in the Stratosphere (REPROBUS) chemical transport model at and above 500 K isentropic surfaces (heights above 18 km) reveal that on 19-20 September the Antarctic vortex was dynamically stable and chemically nominal: denitrified, with a nearly complete chlorine activation, and a 70% O(3) loss at 500 K. On 25-26 September the unusual morphology of the vortex is monitored by the N(2)O observations. The measured ClO decay is consistent with other observations performed in 2002 and in the past. The vortex split episode is followed by a nearly complete deactivation of the ClO radicals on 1-2 October, leading to the end of the chemical O(3) loss, while HNO(3) and NO(2) fields start increasing. This acceleration of the chlorine deactivation results from the warming of the Antarctic vortex in 2002, putting an early end to the polar stratospheric cloud season. The model simulation suggests that the vortex elongation toward regions of strong solar irradiance also favored the rapid reformation of ClONO(2). The observed dynamical and chemical evolution of the 2002 polar vortex is qualitatively well reproduced by REPROBUS. Quantitative differences are mainly attributable to the too weak amounts of HNO(3) in the model, which do not produce enough NO(2) in presence of sunlight to deactivate chlorine as fast as observed by Odin.
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