UTLS Workshop, NCAR – 20/10/ STT and Tropopause Changes from Radar Windprofilers and Ozonesondes David W. Tarasick Air Quality Research Division, Environment Canada W.K. Hocking (UWO) T. Carey-Smith (NIWA)

UTLS Workshop, NCAR – 20/10/ Walsingham

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UTLS Workshop, NCAR – 20/10/ Radar signal power from the first Montreal campaign. Solid line shows the tropopause height derived from this data.

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UTLS Workshop, NCAR – 20/10/ Ozonesonde profiles from this campaign. White solid line = radar tropopause. The dashed lines indicate times when the tropopause undergoes rapid ascent.

UTLS Workshop, NCAR – 20/10/ FLEXPART modeling seems to show good correspondence with apparent intrusions Driven by wind fields from the Canadian operational NWP model: GEM v North American regional grid, 0.5° x 0.5°, hourly, 58 levels.

UTLS Workshop, NCAR – 20/10/ Almost every ozone intrusion follows a level 2 or 3 (0.3 – 0.4 km/hr) tropopause excursion. Every level 2 or 3 tropopause excursion is associated with an intrusion.

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UTLS Workshop, NCAR – 20/10/ The vertical gradient of the refractive index 2 nd term in square brackets is generally ignored, as q is small above the lower troposphere. But, where there are sharp negative gradients of water vapour, can be much larger than and the term in q can dominate.

UTLS Workshop, NCAR – 20/10/ Successive ozone and water vapor pressure profiles taken four hours apart on 19 August, Movement can be seen, as peak A moves to peak B.

UTLS Workshop, NCAR – 20/10/ Conclusions  Stratospheric intrusions generally preceded by rapid changes in tropopause height  Quite common at midlatitudes (every 2-5 days)  Success of FLEXPART modeling suggests that GEM dynamics are quite good  Radar appears to be a particularly good intrusion detector  May be possible to follow the descent of layers of low humidity  Can we transfer this to Brewer total ozone changes?

UTLS Workshop, NCAR – 20/10/ EXTRAS

UTLS Workshop, NCAR – 20/10/ Continuing work… CFCAS project GR-7042, "Impact of Large-Scale Stratospheric Ozone Intrusions on Operational Air Quality Forecast Model Applications” (Bourqui, Moran, McConnell, Jones, He, Osman)  New radars at Egbert, Sudbury, Eureka  Ozone data from Tropospheric Emission Spectrometer (TES) on the NASA Aura satellite  Several more ozonesonde campaigns with coordinated launches  Use of GEM-MACH  Operational GEM-based post-processing package for diagnosis of STE (Bourqui, Neary, Moran)

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UTLS Workshop, NCAR – 20/10/ Radar signal power from the first Walsingham campaign. Dashed line shows the tropopause height derived from this data.

UTLS Workshop, NCAR – 20/10/ Ozonesonde profiles from this campaign..

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UTLS Workshop, NCAR – 20/10/ Modelling the intrusions With FLEXPART - Written by Andreas Stohl  A Lagrangian particle dispersion model  The model domain is filled with (millions of) particles.  Particles initially in the stratosphere are given an ozone concentration calculated using potential vorticity.  Ozone "parcels" are then advected with the model winds. Wind fields from Canadian forecast model: GEM version  North American regional grid.  0.5 x 0.5 degrees, 58 levels, hourly.