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Observations of subtropical air in the european mid‐latitude lower stratosphere
Author(s) -
O'Connor F. M.,
Vaughan G.,
De Backer H.
Publication year - 1999
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49712556009
Subject(s) - stratosphere , tropopause , subtropics , potential vorticity , middle latitudes , atmospheric sciences , climatology , latitude , environmental science , vorticity , air mass (solar energy) , ozone , mixing ratio , meteorology , geology , geography , physics , vortex , geodesy , boundary layer , fishery , biology , thermodynamics
Evidence of two wave‐breaking events, during which subtropical air was transported into the northern mid latitudes, is presented. the first event took place in January 1997 when ozone mixing ratios of the order of 120 parts per billion (10 9 ) by volume (p.p.b.v.) were measured in the lower stratosphere above Aberystwyth (52.4°N, 4.1°W). the amount of subtropical air involved was 13 × 10 14 kg. A second, more dramatic, wavebreaking event took place in March 1997 involving 36 × 10 14 kg of air. This case contained a region with potential vorticity ⩽ 2 potential vorticity units (1 PVU=1 × 10 ‐6 K kg‐1m 2 s‐1 ), consistent with ozone mixing ratios of 80 p.p.b.v. observed at Aberystwyth at 365 K. Trajectory analysis showed that this air was advected northwards from near the subtropical tropopause. the extent to which irreversible transport into the mid‐latitude lower stratosphere followed both events is evaluated using trajectory analysis and potential‐vorticity evolution.