Midlatitude and high-latitude N2O distributions in the Northern Hemisphere in early and late Arctic polar vortex breakup years

• Published in: Journal of Geophysical Research - Atmospheres Vol. 112; no. D18; pp. D18305 - n/a
• Main Authors: Akiyoshi, H., Zhou, L. B.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Geophysical Union 27-09-2007; Blackwell Publishing Ltd
• Subjects: Arctic; Atmospheric Composition and Structure; Atmospheric Processes; chemical transport model; composition and chemistry; constituent transport and chemistry; Earth sciences; Earth, ocean, space; Exact sciences and technology; Middle atmosphere; Middle atmosphere dynamics; N2O; polar vortex; probability distribution function; vortex breakup; Arctic region; probability distribution function; vortex breakup; chemical transport model; Arctic; N 2 O; polar vortex; High latitude; altitude; Mid latitude; Divergence; springs; Summer; Probability distribution; air; Meridional circulation; Winter; Northern Hemisphere; Spring(season); Distribution function; polar regions; heat flux; stratosphere; advection; models; Polar vortex; tracers; concentration; climate; transport; lead; heat transfer
• ISSN: 0148-0227; 2156-2202
• DOI: 10.1029/2007JD008491

Simulated N2O distributions at midlatitudes and high latitudes in the Northern Hemisphere are analyzed in early and late vortex breakup years with the probability distribution function (PDF) technique. The data are from a Center for Climate System Research/National Institute for Environmental Studies (CCSR/NIES) nudging chemical transport model (CTM) for 24 years from 1979 to 2002. Results show that there is a large difference in midlatitude and high‐latitude N2O concentrations on the 600 K isentrope between early and late vortex breakup years. In the early breakup years, the N2O concentration with the maximum area shows low values in the lower stratosphere in the springtime after the vortex breakup. In the late breakup years, the maximum area concentration shows constant high values from the winter to the summer. Our analyses show that the winter and springtime meridional circulation is a main factor for these differences in N2O concentration. In the early breakup years, a larger eddy heat flux causes a stronger winter meridional circulation and a stronger downward advection of low‐N2O concentration air at higher altitudes to the lower stratosphere, which leads to the low values of N2O concentration in the lower stratosphere in late winter and early spring. Inside the Arctic vortex, however, the importance of vertical advection is smaller than or comparable to other processes such as horizontal divergence and subgrid‐scale motions. These results are consistent with the previous studies on tracer distribution, which showed that not only the vertical advection but also the horizontal eddy transport are important for tracer concentration tendency in the polar vortex.