Summertime stratospheric processes at northern mid-latitudes: comparisons between MANTRA balloon measurements and the Canadian Middle Atmosphere Model

[摘要] In this paper we report on a study conducted using the Middle AtmosphericNitrogen TRend Assessment (MANTRA) balloon measurements of stratosphericconstituents and temperature and the Canadian Middle Atmosphere Model(CMAM). Three different kinds of data are used to assess theinter-consistency of the combined dataset: single profiles of long-livedspecies from MANTRA 1998, sparse climatologies from the ozonesondemeasurements during the four MANTRA campaigns and from HALOE satellitemeasurements, and the CMAM climatology. In doing so, we evaluate the abilityof the model to reproduce the measured fields and to thereby test ourability to describe mid-latitude summertime stratospheric processes. TheMANTRA campaigns were conducted at Vanscoy, Saskatchewan, Canada (52° N,107° W) in late August and early September of 1998, 2000, 2002 and 2004.During late summer at mid-latitudes, the stratosphere is close tophotochemical control, providing an ideal scenario for the study reportedhere. From this analysis we find that: (1) reducing the value for thevertical diffusion coefficient in CMAM to a more physically reasonable valueresults in the model better reproducing the measured profiles of long-livedspecies; (2) the existence of compact correlations among the constituents,as expected from independent measurements in the literature and from models,confirms the self-consistency of the MANTRA measurements; and (3) the 1998measurements show structures in the chemical species profiles that can beassociated with transport, adding to the growing evidence that thesummertime stratosphere can be much more disturbed than anticipated. Themechanisms responsible for such disturbances need to be understood in orderto assess the representativeness of the measurements and to isolatelong-term trends.

[学科分类] 大气科学