Forecast, Modeling, And Satellite And Lidar Measurements, Of A Rare Polar Ozone Filament Event Over Mauna Loa Observatory, Hawaii

In mid-March 2005, the Northern lower stratospheric polar vortex experienced a severe stretching episode, bringing a large polar filament far South of Alaska towards the Hawaiian Islands. This meridional intrusion of rare extent was immediately followed by a zonal stretching of the filament in the wake of the Easterly propagating main flow, causing lower stratospheric polar air to pass over Hawaii during several days, then dilute into the subtropics. After being successfully forecasted to pass over Hawaii by the forecast version of the high resolution PV advection model MIMOSA, the filament was identified between 415 K and 455 K on the 16th and 17th of March by the Jet Propulsion Laboratory stratospheric ozone lidar located at Mauna Loa Observatory, Hawaii. It has been also detected by the MLS and HIRDLS instruments onboard EOS/AURA. The filament was materialized on the lidar profile by a thin layer of enhanced ozone peaking at 2 ppmv in a region where the climatological values usually run around 1 ppmv. Ozone mixing ratio calculated from the three-dimensional Chemistry-Transport Model MIMOSA-CHIM will be compared to the ozone mixing ratio measured by lidar and MLS and HIRDLS. The qualitative agreement turns to be excellent, in particular with the emergence of the 2 ppmv ozone peak at around 435 K on March 16, and the persistence of this layer at higher isentropic levels (450 K) for the following 3 days. Quantitatively, the 2 ppmv ozone values measured by lidar imply significant chemical polar ozone depletion within the filament (as reproduced by the model), instead of the 4 ppmv values that should have been observed if ozone had been advected as a passive tracer. The ozone Lagrangian evolution within the air mass sampled by lidar was investigated along the filament's journey from the polar regions to the subtropics. Inspection of the high resolution advected PV fields on the few days/weeks after this event showed that, after passing over Hawaii, the severely stretched filament separated from the main vortex and never reconnected. In less than ten days, the filament eroded entirely in the subtropics (equatorward of 40°N).